TWebCanvas.cxx

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// Author: Sergey Linev, GSI   7/12/2016
 
/*************************************************************************
 * Copyright (C) 1995-2023, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
 
#include "TWebCanvas.h"
 
#include "TWebSnapshot.h"
#include "TWebPadPainter.h"
#include "TWebPS.h"
#include "TWebMenuItem.h"
#include "ROOT/RWebWindowsManager.hxx"
#include "THttpServer.h"
 
#include "TSystem.h"
#include "TStyle.h"
#include "TCanvas.h"
#include "TButton.h"
#include "TFrame.h"
#include "TPaveText.h"
#include "TPaveStats.h"
#include "TText.h"
#include "TROOT.h"
#include "TClass.h"
#include "TColor.h"
#include "TObjArray.h"
#include "TArrayI.h"
#include "TList.h"
#include "TF1.h"
#include "TF2.h"
#include "TH1.h"
#include "TH2.h"
#include "TH1K.h"
#include "THStack.h"
#include "TMultiGraph.h"
#include "TEnv.h"
#include "TError.h"
#include "TGraph.h"
#include "TGraphPolar.h"
#include "TGraphPolargram.h"
#include "TGraph2D.h"
#include "TGaxis.h"
#include "TScatter.h"
#include "TCutG.h"
#include "TBufferJSON.h"
#include "TBase64.h"
#include "TAtt3D.h"
#include "TView.h"
#include "TExec.h"
#include "TVirtualX.h"
#include "TMath.h"
#include "TTimer.h"
#include "TThread.h"
 
#include <cstdio>
#include <cstring>
#include <fstream>
#include <iostream>
#include <memory>
#include <sstream>
#include <vector>
 
 
class TWebCanvasTimer : public TTimer {
   TWebCanvas &fCanv;
   Bool_t fProcessing{kFALSE};
   Bool_t fSlow{kFALSE};
   Int_t fSlowCnt{0};
public:
   TWebCanvasTimer(TWebCanvas &canv) : TTimer(10, kTRUE), fCanv(canv) {}
 
   Bool_t IsSlow() const { return fSlow; }
   void SetSlow(Bool_t slow = kTRUE)
   {
      fSlow = slow;
      fSlowCnt = 0;
      SetTime(slow ? 1000 : 10);
   }
 
   /// used to send control messages to clients
   void Timeout() override
   {
      if (fProcessing || fCanv.fProcessingData) return;
      fProcessing = kTRUE;
      Bool_t res = fCanv.CheckDataToSend();
      fProcessing = kFALSE;
      if (res) {
         fSlowCnt = 0;
      } else if (++fSlowCnt > 10 && !IsSlow()) {
         SetSlow(kTRUE);
      }
   }
};
 
 
/** \class TWebCanvas
\ingroup webgui6
\ingroup webwidgets
 
Basic TCanvasImp ABI implementation for Web-based Graphics
Provides painting of main ROOT classes in web browsers using [JSROOT](https://root.cern/js/)
 
Following settings parameters can be useful for TWebCanvas:
 
     WebGui.FullCanvas:       1     read-only mode (0), full-functional canvas (1) (default - 1)
     WebGui.StyleDelivery:    1     provide gStyle object to JSROOT client (default - 1)
     WebGui.PaletteDelivery:  1     provide color palette to JSROOT client (default - 1)
     WebGui.TF1UseSave:       1     used saved values for function drawing: 0 - off, 1 - if client fail to evaluate function, 2 - always (default - 1)
 
TWebCanvas is used by default in interactive ROOT session. To use web-based canvas in batch mode for image
generation, one should explicitly specify `--web` option when starting ROOT:
 
    [shell] root -b --web tutorials/hsimple.root -e 'hpxpy->Draw("colz"); c1->SaveAs("image.png");'
 
If for any reasons TWebCanvas does not provide required functionality, one always can disable it.
Either by specifying `root --web=off` when starting ROOT or by setting `Canvas.Name: TRootCanvas` in rootrc file.
 
*/
 
using namespace std::string_literals;
 
static const std::string sid_pad_histogram = "__pad_histogram__";
 
 
struct WebFont_t {
   Int_t fIndx{0};
   TString fName;
   TString fFormat;
   TString fData;
   WebFont_t() = default;
   WebFont_t(Int_t indx, const TString &name, const TString &fmt, const TString &data) : fIndx(indx), fName(name), fFormat(fmt), fData(data) {}
};
 
static std::vector<WebFont_t> gWebFonts;
 
std::string TWebCanvas::gCustomScripts = {};
std::vector<std::string> TWebCanvas::gCustomClasses = {};
 
UInt_t TWebCanvas::gBatchImageMode = 0;
std::string TWebCanvas::gBatchMultiPdf;
std::vector<std::string> TWebCanvas::gBatchFiles;
std::vector<std::string> TWebCanvas::gBatchJsons;
std::vector<int> TWebCanvas::gBatchWidths;
std::vector<int> TWebCanvas::gBatchHeights;
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Configure batch image mode for web graphics.
/// Allows to process many images with single headless browser invocation and increase performance of image production.
/// When many canvases are stored as image in difference places, they first collected in batch and then processed when at least `n`
/// images are prepared. Only then headless browser invoked and create all these images at once.
/// This allows to significantly increase performance of image production in web mode
 
void TWebCanvas::BatchImageMode(UInt_t n)
{
   gBatchImageMode = n;
   if (gBatchImageMode <= gBatchJsons.size())
      FlushBatchImages();
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Flush batch images
 
bool TWebCanvas::FlushBatchImages()
{
   bool res = true;
 
   if (gBatchJsons.size() > 0)
      res = ROOT::RWebDisplayHandle::ProduceImages(gBatchFiles, gBatchJsons, gBatchWidths, gBatchHeights);
 
   gBatchFiles.clear();
   gBatchJsons.clear();
   gBatchWidths.clear();
   gBatchHeights.clear();
 
   return res;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Constructor
 
TWebCanvas::TWebCanvas(TCanvas *c, const char *name, Int_t x, Int_t y, UInt_t width, UInt_t height, Bool_t readonly)
   : TCanvasImp(c, name, x, y, width, height)
{
   // Workaround for multi-threaded environment
   // Ensure main thread id picked when canvas implementation is created -
   // otherwise it may be assigned in other thread and screw-up gPad access.
   // Workaround may not work if main thread id was wrongly initialized before
   // This resolves issue https://github.com/root-project/root/issues/15498
   TThread::SelfId();
 
   fTimer = new TWebCanvasTimer(*this);
 
   fReadOnly = readonly;
   fStyleDelivery = gEnv->GetValue("WebGui.StyleDelivery", 1);
   fPaletteDelivery = gEnv->GetValue("WebGui.PaletteDelivery", 1);
   fPrimitivesMerge = gEnv->GetValue("WebGui.PrimitivesMerge", 100);
   fTF1UseSave = gEnv->GetValue("WebGui.TF1UseSave", (Int_t) 1);
   fJsonComp = gEnv->GetValue("WebGui.JsonComp", TBufferJSON::kSameSuppression + TBufferJSON::kNoSpaces);
 
   fWebConn.emplace_back(0); // add special connection which only used to perform updates
 
   fTimer->TurnOn();
 
   // fAsyncMode = kTRUE;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Destructor
 
TWebCanvas::~TWebCanvas()
{
   delete fTimer;
}
 
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Add font to static list of fonts supported by the canvas
/// Name specifies name of the font, second is font file with .ttf or .woff2 extension
/// Only True Type Fonts (ttf) are supported by PDF
/// Returns font index which can be used in
///   auto font_indx = TWebCanvas::AddFont("test", "test.ttf", 2);
///   gStyle->SetStatFont(font_indx);
 
Font_t TWebCanvas::AddFont(const char *name, const char *fontfile, Int_t precision)
{
   Font_t maxindx = 22;
   for (auto &entry : gWebFonts) {
      if (entry.fName == name)
         return precision > 0 ? entry.fIndx*10 + precision : entry.fIndx;
      if (entry.fIndx > maxindx)
         maxindx = entry.fIndx;
   }
 
   TString fullname = fontfile, fmt = "ttf";
   auto pos = fullname.Last('.');
   if (pos != kNPOS) {
      fmt = fullname(pos+1, fullname.Length() - pos);
      fmt.ToLower();
      if ((fmt != "ttf") && (fmt != "woff2")) {
         ::Error("TWebCanvas::AddFont", "Unsupported font file extension %s", fmt.Data());
         return (Font_t) -1;
      }
   }
 
   gSystem->ExpandPathName(fullname);
 
   if (gSystem->AccessPathName(fullname.Data(), kReadPermission)) {
      ::Error("TWebCanvas::AddFont", "Not possible to read font file %s", fullname.Data());
      return (Font_t) -1;
   }
 
   std::ifstream is(fullname.Data(), std::ios::in | std::ios::binary);
   std::string res;
   if (is) {
      is.seekg(0, std::ios::end);
      res.resize(is.tellg());
      is.seekg(0, std::ios::beg);
      is.read((char *)res.data(), res.length());
      if (!is)
         res.clear();
   }
 
   if (res.empty()) {
      ::Error("TWebCanvas::AddFont", "Fail to read font file %s", fullname.Data());
      return (Font_t) -1;
   }
 
   TString base64 = TBase64::Encode(res.c_str(), res.length());
 
   maxindx++;
 
   gWebFonts.emplace_back(maxindx, name, fmt, base64);
 
   return precision > 0 ? maxindx*10 + precision : maxindx;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Initialize window for the web canvas
/// At this place canvas is not yet register to the list of canvases - one cannot call RWebWindow::Show()
 
Int_t TWebCanvas::InitWindow()
{
   return 111222333; // should not be used at all
}
 
////////////////////////////////////////////////////////////////////////////////
/// Creates web-based pad painter
 
TVirtualPadPainter *TWebCanvas::CreatePadPainter()
{
   return new TWebPadPainter();
}
 
////////////////////////////////////////////////////////////////////////////////
/// Returns kTRUE when object is fully supported on JSROOT side
/// In ROOT7 Paint function will just return appropriate flag that object can be displayed on JSROOT side
 
Bool_t TWebCanvas::IsJSSupportedClass(TObject *obj, Bool_t many_primitives)
{
   if (!obj)
      return kTRUE;
 
   static const struct {
      const char *name{nullptr};
      bool with_derived{false};
      bool reduse_by_many{false};
   } supported_classes[] = {{"TH1", true},
                            {"TF1", true},
                            {"TGraph", true},
                            {"TScatter"},
                            {"TFrame"},
                            {"THStack"},
                            {"TMultiGraph"},
                            {"TGraphPolargram", true},
                            {"TPave", true},
                            {"TGaxis"},
                            {"TPave", true},
                            {"TArrow"},
                            {"TBox", false, true},  // can be handled via TWebPainter, disable for large number of primitives (like in greyscale.C)
                            {"TWbox"}, // some extra calls which cannot be handled via TWebPainter
                            {"TLine", false, true}, // can be handler via TWebPainter, disable for large number of primitives (like in greyscale.C)
                            {"TEllipse", true, true},  // can be handled via TWebPainter, disable for large number of primitives (like in greyscale.C)
                            {"TText"},
                            {"TLatex"},
                            {"TAnnotation"},
                            {"TMathText"},
                            {"TMarker"},
                            {"TPolyMarker"},
                            {"TPolyLine", true, true}, // can be handled via TWebPainter, simplify colors handling
                            {"TPolyMarker3D"},
                            {"TPolyLine3D"},
                            {"TGraphTime"},
                            {"TGraph2D"},
                            {"TGraph2DErrors"},
                            {"TGraphTime"},
                            {"TASImage"},
                            {"TRatioPlot"},
                            {"TSpline"},
                            {"TSpline3"},
                            {"TSpline5"},
                            {"TGeoManager"},
                            {"TGeoVolume"},
                            {}};
 
   // fast check of class name
   for (int i = 0; supported_classes[i].name != nullptr; ++i)
      if ((!many_primitives || !supported_classes[i].reduse_by_many) && (strcmp(supported_classes[i].name, obj->ClassName()) == 0))
         return kTRUE;
 
   // now check inheritance only for configured classes
   for (int i = 0; supported_classes[i].name != nullptr; ++i)
      if (supported_classes[i].with_derived && (!many_primitives || !supported_classes[i].reduse_by_many))
         if (obj->InheritsFrom(supported_classes[i].name))
            return kTRUE;
 
   return IsCustomClass(obj->IsA());
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Configures custom script for canvas.
/// If started with "modules:" prefix, module(s) will be imported with `loadModules` function of JSROOT.
/// If custom path was configured in RWebWindowsManager::AddServerLocation, it can be used in module paths.
/// If started with "load:" prefix, code will be loaded with `loadScript` function of JSROOT (old, deprecated way)
/// Script also can be a plain JavaScript code which imports JSROOT and provides draw function for custom classes
/// See tutorials/webgui/custom/custom.mjs demonstrating such example
 
void TWebCanvas::SetCustomScripts(const std::string &src)
{
   gCustomScripts = src;
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Returns configured custom script
 
const std::string &TWebCanvas::GetCustomScripts()
{
   return gCustomScripts;
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// For batch mode special handling of scripts are required
/// Headless browser not able to load modules from the file system
/// Therefore custom web-canvas modules and scripts has to be loaded in advance and processed
 
std::string TWebCanvas::ProcessCustomScripts(bool batch)
{
   if (!batch || gCustomScripts.empty() || (gCustomScripts.find("modules:") != 0))
      return gCustomScripts;
 
   auto loc = ROOT::RWebWindowsManager::GetServerLocations();
 
   std::string content;
 
   std::string modules_names = gCustomScripts.substr(8);
 
   std::map<std::string, bool> mapped_funcs;
 
   while (!modules_names.empty()) {
      std::string modname;
      auto p = modules_names.find(";");
      if (p == std::string::npos) {
         modname = modules_names;
         modules_names.clear();
      } else {
         modname = modules_names.substr(0, p);
         modules_names = modules_names.substr(p+1);
      }
 
      p = modname.find("/");
      if ((p == std::string::npos) || modname.empty())
         continue;
 
      std::string pathname = modname.substr(0, p+1);
      std::string filename = modname.substr(p+1);
 
      auto fpath = loc[pathname];
 
      if (fpath.empty())
         continue;
 
      auto cont = THttpServer::ReadFileContent(fpath + filename);
      if (cont.empty())
         continue;
 
      // check that special mark is in the script
      auto pmark = cont.find("$$jsroot_batch_conform$$");
      if (pmark == std::string::npos)
         continue;
 
      // process line like this
      // import { ObjectPainter, addMoveHandler, addDrawFunc, ensureTCanvas } from 'jsroot';
 
      static const std::string str1 = "import {";
      static const std::string str2 = "} from 'jsroot';";
 
      auto p1 = cont.find(str1);
      auto p2 = cont.find(str2, p1);
      if ((p1 == std::string::npos) || (p2 == std::string::npos) || (p2 > pmark))
         continue;
 
      TString globs;
 
      TString funcs = cont.substr(p1 + 8, p2 - p1 - 8).c_str();
      auto arr = funcs.Tokenize(",");
 
      TIter next(arr);
      while (auto obj = next()) {
         TString name = obj->GetName();
         name = name.Strip(TString::kBoth);
         if (!mapped_funcs[name.Data()]) {
            globs.Append(TString::Format("globalThis.%s = JSROOT.%s;\n", name.Data(), name.Data()));
            mapped_funcs[name.Data()] = true;
         }
      }
      delete arr;
 
      cont.erase(p1, p2 + str2.length() - p1);
 
      cont.insert(p1, globs.Data());
 
      content.append(cont);
   }
 
   return content;
}
 
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Assign custom class
 
void TWebCanvas::AddCustomClass(const std::string &clname, bool with_derived)
{
   if (with_derived)
      gCustomClasses.emplace_back("+"s + clname);
   else
      gCustomClasses.emplace_back(clname);
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Checks if class belongs to custom
 
bool TWebCanvas::IsCustomClass(const TClass *cl)
{
   for (auto &name : gCustomClasses) {
      if (name[0] == '+') {
         if (cl->InheritsFrom(name.substr(1).c_str()))
            return true;
      } else if (name.compare(cl->GetName()) == 0) {
         return true;
      }
   }
   return false;
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Creates representation of the object for painting in web browser
 
void TWebCanvas::CreateObjectSnapshot(TPadWebSnapshot &master, TPad *pad, TObject *obj, const char *opt, TWebPS *masterps)
{
   if (IsJSSupportedClass(obj, masterps != nullptr)) {
      master.NewPrimitive(obj, opt).SetSnapshot(TWebSnapshot::kObject, obj);
      return;
   }
 
   // painter is not necessary for batch canvas, but keep configuring it for a while
   auto *painter = dynamic_cast<TWebPadPainter *>(Canvas()->GetCanvasPainter());
 
   TView *view = nullptr;
 
   TVirtualPad::TContext ctxt;
 
   gPad = pad;
 
   if (obj->InheritsFrom(TAtt3D::Class()) && !pad->GetView()) {
      pad->GetViewer3D("pad");
      view = TView::CreateView(1, 0, 0); // Cartesian view by default
      pad->SetView(view);
 
      // Set view to perform first auto-range (scaling) pass
      view->SetAutoRange(kTRUE);
   }
 
   TVirtualPS *saveps = gVirtualPS;
 
   TWebPS ps;
   gVirtualPS = masterps ? masterps : &ps;
   if (painter)
      painter->SetPainting(ps.GetPainting());
 
   // calling Paint function for the object
   obj->Paint(opt);
 
   if (view) {
      view->SetAutoRange(kFALSE);
      // call 3D paint once again to make real drawing
      obj->Paint(opt);
      pad->SetView(nullptr);
   }
 
   if (painter)
      painter->SetPainting(nullptr);
 
   gVirtualPS = saveps;
 
   fPadsStatus[pad]._has_specials = true;
 
   // if there are master PS, do not create separate entries
   if (!masterps && !ps.IsEmptyPainting())
      master.NewPrimitive(obj, opt).SetSnapshot(TWebSnapshot::kSVG, ps.TakePainting(), kTRUE);
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Calculate hash function for all colors and palette
 
UInt_t TWebCanvas::CalculateColorsHash()
{
   UInt_t hash = 0;
 
   TObjArray *colors = (TObjArray *)gROOT->GetListOfColors();
 
   if (colors) {
      for (Int_t n = 0; n <= colors->GetLast(); ++n)
         if (colors->At(n))
            hash += TString::Hash(colors->At(n), TColor::Class()->Size());
   }
 
   TArrayI pal = TColor::GetPalette();
 
   hash += TString::Hash(pal.GetArray(), pal.GetSize() * sizeof(Int_t));
 
   return hash;
}
 
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Add special canvas objects with list of colors and color palette
 
void TWebCanvas::AddColorsPalette(TPadWebSnapshot &master)
{
   TObjArray *colors = (TObjArray *)gROOT->GetListOfColors();
 
   if (!colors)
      return;
 
   //Int_t cnt = 0;
   //for (Int_t n = 0; n <= colors->GetLast(); ++n)
   //   if (colors->At(n))
   //      cnt++;
   //if (cnt <= 598)
   //   return; // normally there are 598 colors defined
 
   TArrayI pal = TColor::GetPalette();
 
   auto listofcols = new TWebPainting;
   for (Int_t n = 0; n <= colors->GetLast(); ++n)
      listofcols->AddColor(n, (TColor *)colors->At(n));
 
   // store palette in the buffer
   auto *tgt = listofcols->Reserve(pal.GetSize());
   for (Int_t i = 0; i < pal.GetSize(); i++)
      tgt[i] = pal[i];
   listofcols->FixSize();
 
   master.NewSpecials().SetSnapshot(TWebSnapshot::kColors, listofcols, kTRUE);
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Add special canvas objects with custom fonts
 
void TWebCanvas::AddCustomFonts(TPadWebSnapshot &master)
{
   for (auto &entry : gWebFonts) {
      TString code = TString::Format("%d:%s:%s:%s", entry.fIndx, entry.fName.Data(), entry.fFormat.Data(), entry.fData.Data());
      auto custom_font = new TWebPainting;
      custom_font->AddOper(code.Data());
      master.NewSpecials().SetSnapshot(TWebSnapshot::kFont, custom_font, kTRUE);
   }
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Create snapshot for pad and all primitives
/// Callback function is used to create JSON in the middle of data processing -
/// when all misc objects removed from canvas list of primitives or histogram list of functions
/// After that objects are moved back to their places
 
void TWebCanvas::CreatePadSnapshot(TPadWebSnapshot &paddata, TPad *pad, Long64_t version, PadPaintingReady_t resfunc)
{
   auto &pad_status = fPadsStatus[pad];
 
   // send primitives if version 0 or actual pad version grater than already send version
   bool process_primitives = (version == 0) || (pad_status.fVersion > version);
 
   if (paddata.IsSetObjectIds()) {
      paddata.SetActive(pad == gPad);
      paddata.SetObjectIDAsPtr(pad);
   }
   paddata.SetSnapshot(TWebSnapshot::kSubPad, pad); // add ref to the pad
   paddata.SetWithoutPrimitives(!process_primitives);
   paddata.SetHasExecs(pad->GetListOfExecs()); // if pad execs are there provide more events from client
 
   // check style changes every time when creating canvas snapshot
   if (resfunc && (GetStyleDelivery() > 0)) {
 
      if (fStyleVersion != fCanvVersion) {
         auto hash = TString::Hash(gStyle, TStyle::Class()->Size());
         if ((hash != fStyleHash) || (fStyleVersion == 0)) {
            fStyleHash = hash;
            fStyleVersion = fCanvVersion;
         }
      }
 
      if (fStyleVersion > version)
         paddata.NewPrimitive().SetSnapshot(TWebSnapshot::kStyle, gStyle);
   }
 
   // for the first time add custom fonts to the canvas snapshot
   if (resfunc && (version == 0))
      AddCustomFonts(paddata);
 
   fAllPads.emplace_back(pad);
 
   TList *primitives = pad->GetListOfPrimitives();
 
   TWebPS masterps;
   bool usemaster = primitives ? (primitives->GetSize() > fPrimitivesMerge) : false;
 
   TIter iter(primitives);
   TObject *obj = nullptr;
   TFrame *frame = nullptr;
   TPaveText *title = nullptr;
   TGraphPolar *first_polar = nullptr;
   TGraphPolargram *polargram = nullptr;
   TString polargram_drawopt = "-";
   bool need_frame = false, has_histo = false, need_palette = false;
   std::string need_title;
 
   auto checkNeedPalette = [](TH1* hist, const TString &opt) {
      auto check = [&opt](const TString &arg) {
         return opt.Contains(arg + "Z") || opt.Contains(arg + "HZ");
      };
 
      return ((hist->GetDimension() == 2) && (check("COL") || check("LEGO") || check("LEGO4") || check("SURF2"))) ||
             ((hist->GetDimension() == 3) && (check("BOX2") || check("BOX3")));
   };
 
   while (process_primitives && ((obj = iter()) != nullptr)) {
      TString opt = iter.GetOption();
      opt.ToUpper();
 
      if (obj->InheritsFrom(THStack::Class())) {
         // workaround for THStack, create extra components before sending to client
         if (!opt.Contains("PADS") && !opt.Contains("SAME")) {
            Bool_t do_rebuild_stack = kFALSE;
 
            auto hs = static_cast<THStack *>(obj);
 
            if (!opt.Contains("NOSTACK") && !opt.Contains("CANDLE") && !opt.Contains("VIOLIN") && !IsReadOnly() && !fUsedObjs[hs]) {
               do_rebuild_stack = kTRUE;
               fUsedObjs[hs] = true;
            }
 
            if (strlen(obj->GetTitle()) > 0)
               need_title = obj->GetTitle();
            TVirtualPad::TContext ctxt(pad, kFALSE);
            hs->BuildPrimitives(iter.GetOption(), do_rebuild_stack);
            has_histo = true;
            need_frame = true;
         }
      } else if (obj->InheritsFrom(TMultiGraph::Class())) {
         // workaround for TMultiGraph
         if (opt.Contains("A")) {
            auto mg = static_cast<TMultiGraph *>(obj);
            TVirtualPad::TContext ctxt(kFALSE);
            mg->GetHistogram(); // force creation of histogram without any drawings
            has_histo = true;
            if (strlen(obj->GetTitle()) > 0)
               need_title = obj->GetTitle();
            need_frame = true;
         }
      } else if (obj->InheritsFrom(TFrame::Class())) {
         if (!frame)
            frame = static_cast<TFrame *>(obj);
      } else if (obj->InheritsFrom(TH1::Class())) {
         need_frame = true;
         has_histo = true;
         if (!obj->TestBit(TH1::kNoTitle) && !opt.Contains("SAME") && !opt.Contains("AXIS") && !opt.Contains("AXIG") && (strlen(obj->GetTitle()) > 0))
            need_title = obj->GetTitle();
         if (checkNeedPalette(static_cast<TH1*>(obj), opt))
            need_palette = true;
      } else if (obj->InheritsFrom(TGraphPolar::Class())) {
         auto polar = static_cast<TGraphPolar *> (obj);
         if (!first_polar) {
            first_polar = polar;
            need_title = first_polar->GetTitle();
            polargram = first_polar->GetPolargram();
            if (!polargram) {
               polargram = first_polar->CreatePolargram(opt);
               polargram_drawopt = opt.Contains("N") ? "N" : "";
               if (opt.Contains("O")) polargram_drawopt.Append("O");
            }
         }
         polar->SetPolargram(polargram);
      } else if (obj->InheritsFrom(TGraph::Class())) {
         if (opt.Contains("A")) {
            need_frame = true;
            if (!has_histo && (strlen(obj->GetTitle()) > 0) && !obj->TestBit(TH1::kNoTitle))
               need_title = obj->GetTitle();
         }
      } else if (obj->InheritsFrom(TGraph2D::Class())) {
         if (!has_histo && (strlen(obj->GetTitle()) > 0))
            need_title = obj->GetTitle();
      } else if (obj->InheritsFrom(TScatter::Class())) {
         need_frame = need_palette = true;
         if (strlen(obj->GetTitle()) > 0)
            need_title = obj->GetTitle();
      } else if (obj->InheritsFrom(TF1::Class())) {
         if (!opt.Contains("SAME")) {
            need_frame = !obj->InheritsFrom(TF2::Class());
            if (!has_histo && (strlen(obj->GetTitle()) > 0))
               need_title = obj->GetTitle();
         }
      } else if (obj->InheritsFrom(TPaveText::Class())) {
         if (strcmp(obj->GetName(), "title") == 0)
            title = static_cast<TPaveText *>(obj);
      }
   }
 
   if (need_frame && !frame && primitives && CanCreateObject("TFrame")) {
      if (!IsReadOnly() && need_palette && (pad->GetRightMargin() < 0.12) && (pad->GetRightMargin() == gStyle->GetPadRightMargin()))
         pad->SetRightMargin(0.12);
 
      frame = pad->GetFrame();
      if(frame)
         primitives->AddFirst(frame);
   }
 
   if (!need_title.empty() && gStyle->GetOptTitle()) {
      if (title) {
         auto line0 = title->GetLine(0);
         if (line0 && !IsReadOnly()) line0->SetTitle(need_title.c_str());
      } else if (primitives && CanCreateObject("TPaveText")) {
         title = new TPaveText(0, 0, 0, 0, "blNDC");
         title->SetFillColor(gStyle->GetTitleFillColor());
         title->SetFillStyle(gStyle->GetTitleStyle());
         title->SetName("title");
         title->SetBorderSize(gStyle->GetTitleBorderSize());
         title->SetTextColor(gStyle->GetTitleTextColor());
         title->SetTextFont(gStyle->GetTitleFont(""));
         if (gStyle->GetTitleFont("") % 10 > 2)
            title->SetTextSize(gStyle->GetTitleFontSize());
         title->AddText(need_title.c_str());
         title->SetBit(kCanDelete);
         primitives->Add(title);
      }
   }
 
   if (polargram && (polargram_drawopt != "-"))
      primitives->Add(polargram, polargram_drawopt);
 
   auto flush_master = [&]() {
      if (!usemaster || masterps.IsEmptyPainting()) return;
 
      paddata.NewPrimitive(pad).SetSnapshot(TWebSnapshot::kSVG, masterps.TakePainting(), kTRUE);
      masterps.CreatePainting(); // create for next operations
   };
 
   auto check_cutg_in_options = [&](const TString &opt) {
      auto p1 = opt.Index("["), p2 = opt.Index("]");
      if ((p1 != kNPOS) && (p2 != kNPOS) && p2 > p1 + 1) {
         TString cutname = opt(p1 + 1, p2 - p1 - 1);
         TObject *cutg = primitives->FindObject(cutname.Data());
         if (!cutg || (cutg->IsA() != TCutG::Class())) {
            cutg = gROOT->GetListOfSpecials()->FindObject(cutname.Data());
            if (cutg && cutg->IsA() == TCutG::Class())
               paddata.NewPrimitive(cutg, "__ignore_drawing__").SetSnapshot(TWebSnapshot::kObject, cutg);
         }
      }
   };
 
   auto check_save_tf1 = [&](TObject *fobj, bool ignore_nodraw = false) {
      if (!paddata.IsBatchMode() && (fTF1UseSave <= 0))
         return;
      if (!ignore_nodraw && fobj->TestBit(TF1::kNotDraw))
         return;
 
      auto f1 = static_cast<TF1 *>(fobj);
      // check if TF1 can be used
      if (!f1->IsValid())
         return;
 
      // in default case save buffer used as is
      if ((fTF1UseSave == 1) && f1->HasSave())
         return;
 
      f1->Save(0, 0, 0, 0, 0, 0);
   };
 
   auto create_stats = [&]() {
      TPaveStats *stats = nullptr;
      if (CanCreateObject("TPaveStats")) {
         stats = new TPaveStats(
                        gStyle->GetStatX() - gStyle->GetStatW(),
                        gStyle->GetStatY() - gStyle->GetStatH(),
                        gStyle->GetStatX(),
                        gStyle->GetStatY(), "brNDC");
 
          // do not set optfit and optstat, they calling pad->Update,
          // values correctly set already in TPaveStats constructor
          // stats->SetOptFit(gStyle->GetOptFit());
          // stats->SetOptStat(gStyle->GetOptStat());
          stats->SetFillColor(gStyle->GetStatColor());
          stats->SetFillStyle(gStyle->GetStatStyle());
          stats->SetBorderSize(gStyle->GetStatBorderSize());
          stats->SetTextFont(gStyle->GetStatFont());
          if (gStyle->GetStatFont()%10 > 2)
             stats->SetTextSize(gStyle->GetStatFontSize());
          stats->SetFitFormat(gStyle->GetFitFormat());
          stats->SetStatFormat(gStyle->GetStatFormat());
          stats->SetName("stats");
 
          stats->SetTextColor(gStyle->GetStatTextColor());
          stats->SetTextAlign(12);
          stats->SetBit(kCanDelete);
          stats->SetBit(kMustCleanup);
      }
 
      return stats;
   };
 
   auto check_graph_funcs = [&](TGraph *gr, TList *funcs = nullptr) {
      if (!funcs && gr)
         funcs = gr->GetListOfFunctions();
      if (!funcs)
         return;
 
      TIter fiter(funcs);
      TPaveStats *stats = nullptr;
      bool has_tf1 = false;
 
      while (auto fobj = fiter()) {
        if (fobj->InheritsFrom(TPaveStats::Class()))
            stats = dynamic_cast<TPaveStats *> (fobj);
        else if (fobj->InheritsFrom(TF1::Class())) {
           check_save_tf1(fobj);
           has_tf1 = true;
        }
      }
 
      if (!stats && has_tf1 && gr && !gr->TestBit(TGraph::kNoStats) && (gStyle->GetOptFit() > 0)) {
         stats = create_stats();
         if (stats) {
            stats->SetOptStat(0);
            stats->SetOptFit(gStyle->GetOptFit());
            stats->SetParent(funcs);
            funcs->Add(stats);
         }
      }
   };
 
   iter.Reset();
 
   bool first_obj = true;
 
   if (process_primitives)
      pad_status._has_specials = false;
 
   while ((obj = iter()) != nullptr) {
      if (obj->InheritsFrom(TPad::Class())) {
         flush_master();
         CreatePadSnapshot(paddata.NewSubPad(), (TPad *)obj, version, nullptr);
      } else if (!process_primitives) {
         continue;
      } else if (obj->InheritsFrom(TH1K::Class())) {
         flush_master();
         TH1K *hist = static_cast<TH1K *>(obj);
 
         Int_t nbins = hist->GetXaxis()->GetNbins();
 
         TH1D *h1 = new TH1D("__dummy_name__", hist->GetTitle(), nbins, hist->GetXaxis()->GetXmin(), hist->GetXaxis()->GetXmax());
         h1->SetDirectory(nullptr);
         h1->SetName(hist->GetName());
         hist->TAttLine::Copy(*h1);
         hist->TAttFill::Copy(*h1);
         hist->TAttMarker::Copy(*h1);
         for (Int_t n = 1; n <= nbins; ++n)
             h1->SetBinContent(n, hist->GetBinContent(n));
 
         TIter fiter(hist->GetListOfFunctions());
         while (auto fobj = fiter())
            h1->GetListOfFunctions()->Add(fobj->Clone());
 
         paddata.NewPrimitive(obj, iter.GetOption()).SetSnapshot(TWebSnapshot::kObject, h1, kTRUE);
 
      } else if (obj->InheritsFrom(TH1::Class())) {
         flush_master();
 
         TH1 *hist = static_cast<TH1 *>(obj);
         hist->BufferEmpty();
 
         TPaveStats *stats = nullptr;
         TObject *palette = nullptr;
 
         TIter fiter(hist->GetListOfFunctions());
         while (auto fobj = fiter()) {
            if (fobj->InheritsFrom(TPaveStats::Class()))
               stats = dynamic_cast<TPaveStats *> (fobj);
            else if (fobj->InheritsFrom("TPaletteAxis"))
               palette = fobj;
            else if (fobj->InheritsFrom(TF1::Class()))
               check_save_tf1(fobj);
         }
 
         TString hopt = iter.GetOption();
         TString o = hopt;
         o.ToUpper();
 
         if (!stats && (first_obj || o.Contains("SAMES")) && (gStyle->GetOptStat() > 0)) {
            stats = create_stats();
            if (stats) {
                stats->SetParent(hist);
                hist->GetListOfFunctions()->Add(stats);
            }
         }
 
         if (!palette && CanCreateObject("TPaletteAxis") && checkNeedPalette(hist, o)) {
            std::stringstream exec;
            exec << "new TPaletteAxis(0,0,0,0, (TH1*)" << std::hex << std::showbase << (size_t)hist << ");";
            palette = (TObject *)gROOT->ProcessLine(exec.str().c_str());
            if (palette)
               hist->GetListOfFunctions()->AddFirst(palette);
         }
 
         paddata.NewPrimitive(obj, hopt.Data()).SetSnapshot(TWebSnapshot::kObject, obj);
 
         if (hist->GetDimension() == 2)
            check_cutg_in_options(iter.GetOption());
 
         first_obj = false;
      } else if (obj->InheritsFrom(TGraphPolar::Class())) {
         flush_master();
 
         auto polar = static_cast<TGraphPolar *>(obj);
 
         check_graph_funcs(polar);
 
         paddata.NewPrimitive(obj, iter.GetOption()).SetSnapshot(TWebSnapshot::kObject, obj);
 
         first_obj = false;
      } else if (obj->InheritsFrom(TGraphPolargram::Class())) {
         // do nothing, object must be streamed with graphpolar
      } else if (obj->InheritsFrom(TGraph::Class())) {
         flush_master();
 
         TGraph *gr = static_cast<TGraph *>(obj);
 
         check_graph_funcs(gr);
 
         TString gropt = iter.GetOption();
 
         // ensure histogram exists on server to draw it properly on clients side
         if (!IsReadOnly() && (first_obj || gropt.Index("A", 0, TString::kIgnoreCase) != kNPOS ||
               (gropt.Index("X+", 0, TString::kIgnoreCase) != kNPOS) || (gropt.Index("Y+", 0, TString::kIgnoreCase) != kNPOS)))
            gr->GetHistogram();
 
         paddata.NewPrimitive(obj, gropt.Data()).SetSnapshot(TWebSnapshot::kObject, obj);
 
         first_obj = false;
      } else if (obj->InheritsFrom(TGraph2D::Class())) {
         flush_master();
 
         TGraph2D *gr2d = static_cast<TGraph2D *>(obj);
 
         check_graph_funcs(nullptr, gr2d->GetListOfFunctions());
 
         // ensure correct range of histogram
         if (!IsReadOnly() && first_obj) {
            TString gropt = iter.GetOption();
            gropt.ToUpper();
            Bool_t zscale = gropt.Contains("TRI1") || gropt.Contains("TRI2") || gropt.Contains("COL");
            Bool_t cont5_draw = gropt.Contains("CONT5");
            Bool_t real_draw = gropt.Contains("TRI") || gropt.Contains("LINE") || gropt.Contains("ERR") || gropt.Contains("P") || cont5_draw;
 
            TString hopt = !real_draw ? iter.GetOption() : (cont5_draw ? "" : (zscale ? "lego2z" : "lego2"));
            if (title) hopt.Append(";;use_pad_title");
 
            // if gr2d not draw - let create histogram with correspondent content
            auto hist = gr2d->GetHistogram(real_draw ? "empty" : "");
 
            paddata.NewPrimitive(gr2d, hopt.Data(), "#hist").SetSnapshot(TWebSnapshot::kObject, hist);
         }
 
         paddata.NewPrimitive(obj, iter.GetOption()).SetSnapshot(TWebSnapshot::kObject, obj);
         first_obj = false;
      } else if (obj->InheritsFrom(TMultiGraph::Class())) {
         flush_master();
 
         TMultiGraph *mgr = static_cast<TMultiGraph *>(obj);
         TIter fiter(mgr->GetListOfFunctions());
         while (auto fobj = fiter()) {
            if (fobj->InheritsFrom(TF1::Class()))
               check_save_tf1(fobj);
         }
 
         TIter giter(mgr->GetListOfGraphs());
         while (auto gobj = giter())
            check_graph_funcs(static_cast<TGraph *>(gobj));
 
         paddata.NewPrimitive(obj, iter.GetOption()).SetSnapshot(TWebSnapshot::kObject, obj);
 
         first_obj = false;
      } else if (obj->InheritsFrom(THStack::Class())) {
         flush_master();
 
         THStack *hs = static_cast<THStack *>(obj);
 
         TString hopt = iter.GetOption();
         hopt.ToLower();
         if (!hopt.Contains("nostack") && !hopt.Contains("candle") && !hopt.Contains("violin") && !hopt.Contains("pads")) {
            auto arr = hs->GetStack();
            arr->SetName(hs->GetName()); // mark list for JS
            paddata.NewPrimitive(arr, "__ignore_drawing__").SetSnapshot(TWebSnapshot::kObject, arr);
         }
 
         paddata.NewPrimitive(obj, iter.GetOption()).SetSnapshot(TWebSnapshot::kObject, obj);
 
         first_obj = hs->GetNhists() > 0; // real drawing only if there are histograms
      } else if (obj->InheritsFrom(TScatter::Class())) {
         flush_master();
 
         TScatter *scatter = static_cast<TScatter *>(obj);
 
         TObject *palette = nullptr;
 
         TIter fiter(scatter->GetGraph()->GetListOfFunctions());
         while (auto fobj = fiter()) {
            if (fobj->InheritsFrom("TPaletteAxis"))
               palette = fobj;
         }
 
         // ensure histogram exists on server to draw it properly on clients side
         if (!IsReadOnly() && first_obj)
            scatter->GetHistogram();
 
         if (!palette && CanCreateObject("TPaletteAxis")) {
            std::stringstream exec;
            exec << "new TPaletteAxis(0,0,0,0,0,0);";
            palette = (TObject *)gROOT->ProcessLine(exec.str().c_str());
            if (palette)
               scatter->GetGraph()->GetListOfFunctions()->AddFirst(palette);
         }
 
         paddata.NewPrimitive(obj, iter.GetOption()).SetSnapshot(TWebSnapshot::kObject, obj);
 
         first_obj = false;
      } else if (obj->InheritsFrom(TF1::Class())) {
         flush_master();
         auto f1 = static_cast<TF1 *> (obj);
 
         TString f1opt = iter.GetOption();
 
         check_save_tf1(obj, true);
         if (fTF1UseSave > 1)
            f1opt.Append(";force_saved");
         else if (fTF1UseSave == 1)
            f1opt.Append(";prefer_saved");
 
         if (first_obj) {
            auto hist = f1->GetHistogram();
            paddata.NewPrimitive(hist, "__ignore_drawing__").SetSnapshot(TWebSnapshot::kObject, hist);
            f1opt.Append(";webcanv_hist");
         }
 
         if (f1->IsA() == TF2::Class())
            check_cutg_in_options(iter.GetOption());
 
         paddata.NewPrimitive(f1, f1opt.Data()).SetSnapshot(TWebSnapshot::kObject, f1);
 
         first_obj = false;
 
      } else if (obj->InheritsFrom(TGaxis::Class())) {
         flush_master();
         auto gaxis = static_cast<TGaxis *> (obj);
         auto func = gaxis->GetFunction();
         if (func)
            paddata.NewPrimitive(func, "__ignore_drawing__").SetSnapshot(TWebSnapshot::kObject, func);
 
         paddata.NewPrimitive(obj, iter.GetOption()).SetSnapshot(TWebSnapshot::kObject, obj);
      } else if (obj->InheritsFrom(TFrame::Class())) {
         flush_master();
         if (frame && (obj == frame)) {
            paddata.NewPrimitive(obj, iter.GetOption()).SetSnapshot(TWebSnapshot::kObject, obj);
            frame = nullptr; // add frame only once
         }
      } else if (IsJSSupportedClass(obj, usemaster)) {
         flush_master();
         paddata.NewPrimitive(obj, iter.GetOption()).SetSnapshot(TWebSnapshot::kObject, obj);
      } else {
         CreateObjectSnapshot(paddata, pad, obj, iter.GetOption(), usemaster ? &masterps : nullptr);
      }
   }
 
   flush_master();
 
   bool provide_colors = false;
 
   if ((GetPaletteDelivery() > 2) || ((GetPaletteDelivery() == 2) && resfunc)) {
      // provide colors: either for each subpad (> 2) or only for canvas (== 2)
      provide_colors = process_primitives;
   } else if ((GetPaletteDelivery() == 1) && resfunc) {
      // check that colors really changing, using hash
 
      if (fColorsVersion != fCanvVersion) {
         auto hash = CalculateColorsHash();
         if ((hash != fColorsHash) || (fColorsVersion == 0)) {
            fColorsHash = hash;
            fColorsVersion = fCanvVersion;
         }
      }
 
      provide_colors = fColorsVersion > version;
   }
 
   // add colors after painting is performed - new colors may be generated only during painting
   if (provide_colors)
      AddColorsPalette(paddata);
 
   if (!resfunc)
      return;
 
   // now hide all primitives to perform I/O
   std::vector<TList *> all_primitives(fAllPads.size());
   for (unsigned n = 0; n < fAllPads.size(); ++n) {
      all_primitives[n] = fAllPads[n]->fPrimitives;
      fAllPads[n]->fPrimitives = nullptr;
   }
 
   // execute function to prevent storing of colors with custom TCanvas streamer
   TColor::DefinedColors();
 
   // invoke callback for streaming
   resfunc(&paddata);
 
   // and restore back primitives - delete any temporary if necessary
   for (unsigned n = 0; n < fAllPads.size(); ++n) {
      if (fAllPads[n]->fPrimitives)
         delete fAllPads[n]->fPrimitives;
      fAllPads[n]->fPrimitives = all_primitives[n];
   }
   fAllPads.clear();
   fUsedObjs.clear();
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Add control message for specified connection
/// Same control message can be overwritten many time before it really sends to the client
/// If connid == 0, message will be add to all connections
/// After ctrl message is add to the output, short timer is activated and message send afterwards
 
void TWebCanvas::AddCtrlMsg(unsigned connid, const std::string &key, const std::string &value)
{
   Bool_t new_ctrl = kFALSE;
 
   for (auto &conn : fWebConn) {
      if (conn.match(connid)) {
         conn.fCtrl[key] = value;
         new_ctrl = kTRUE;
      }
   }
 
   if (new_ctrl && fTimer->IsSlow())
      fTimer->SetSlow(kFALSE);
}
 
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Add message to send queue for specified connection
/// If connid == 0, message will be add to all connections
 
void TWebCanvas::AddSendQueue(unsigned connid, const std::string &msg)
{
   for (auto &conn : fWebConn) {
      if (conn.match(connid))
         conn.fSend.emplace(msg);
   }
}
 
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Check if any data should be send to client
/// If connid != 0, only selected connection will be checked
 
Bool_t TWebCanvas::CheckDataToSend(unsigned connid)
{
   if (!Canvas())
      return kFALSE;
 
   bool isMoreData = false, isAnySend = false;
 
   for (auto &conn : fWebConn) {
 
      bool isConnData = !conn.fCtrl.empty() || !conn.fSend.empty() ||
                        ((conn.fCheckedVersion < fCanvVersion) && (conn.fSendVersion == conn.fDrawVersion));
 
      while ((conn.is_batch() && !connid) || (conn.match(connid) && fWindow && fWindow->CanSend(conn.fConnId, true))) {
         // check if any control messages still there to keep timer running
 
         std::string buf;
 
         if (!conn.fCtrl.empty()) {
            buf = "CTRL:"s + TBufferJSON::ToJSON(&conn.fCtrl, TBufferJSON::kMapAsObject + TBufferJSON::kNoSpaces);
            conn.fCtrl.clear();
         } else if (!conn.fSend.empty()) {
            std::swap(buf, conn.fSend.front());
            conn.fSend.pop();
         } else if ((conn.fCheckedVersion < fCanvVersion) && (conn.fSendVersion == conn.fDrawVersion)) {
 
            buf = "SNAP6:"s + std::to_string(fCanvVersion) + ":"s;
 
            TCanvasWebSnapshot holder(IsReadOnly(), true, false); // readonly, set ids, batchmode
 
            holder.SetFixedSize(fFixedSize); // set fixed size flag
 
            // scripts send only when canvas drawn for the first time
            if (!conn.fSendVersion)
               holder.SetScripts(ProcessCustomScripts(false));
 
            holder.SetHighlightConnect(Canvas()->HasConnection("Highlighted(TVirtualPad*,TObject*,Int_t,Int_t)"));
 
            CreatePadSnapshot(holder, Canvas(), conn.fSendVersion, [&buf, &conn, this](TPadWebSnapshot *snap) {
               if (conn.is_batch()) {
                  // for batch connection only calling of CreatePadSnapshot is important
                  buf.clear();
                  return;
               }
 
               auto json = TBufferJSON::ToJSON(snap, fJsonComp);
               auto hash = json.Hash();
               if (conn.fLastSendHash && (conn.fLastSendHash == hash) && conn.fSendVersion) {
                  // prevent looping when same data send many times
                  buf.clear();
               } else {
                  buf.append(json.Data());
                  conn.fLastSendHash = hash;
               }
            });
 
            conn.fCheckedVersion = fCanvVersion;
 
            conn.fSendVersion = fCanvVersion;
 
            if (buf.empty())
               conn.fDrawVersion = fCanvVersion;
         } else {
            isConnData = false;
            break;
         }
 
         if (!buf.empty() && !conn.is_batch()) {
            fWindow->Send(conn.fConnId, buf);
            isAnySend = true;
         }
      }
 
      if (isConnData)
         isMoreData = true;
   }
 
   if (fTimer->IsSlow() && isMoreData)
      fTimer->SetSlow(kFALSE);
 
   return isAnySend;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Close web canvas - not implemented
 
void TWebCanvas::Close()
{
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Show canvas in specified place.
/// If parameter args not specified, default ROOT web display will be used
 
void TWebCanvas::ShowWebWindow(const ROOT::RWebDisplayArgs &args)
{
   if (!fWindow) {
      fWindow = ROOT::RWebWindow::Create();
 
      fWindow->SetConnLimit(0); // configure connections limit
 
      fWindow->SetDefaultPage("file:rootui5sys/canv/canvas6.html");
 
      fWindow->SetCallBacks(
         // connection
         [this](unsigned connid) {
            if (fWindow->GetConnectionId(0) == connid)
               fWebConn.emplace(fWebConn.begin() + 1, connid);
            else
               fWebConn.emplace_back(connid);
            CheckDataToSend(connid);
         },
         // data
         [this](unsigned connid, const std::string &arg) {
            ProcessData(connid, arg);
            CheckDataToSend();
         },
         // disconnect
         [this](unsigned connid) {
            unsigned indx = 0;
            for (auto &c : fWebConn) {
               if (c.fConnId == connid) {
                  fWebConn.erase(fWebConn.begin() + indx);
                  break;
               }
               indx++;
            }
         });
   }
 
   auto w = Canvas()->GetWindowWidth(), h = Canvas()->GetWindowHeight();
   if ((w > 0) && (w < 50000) && (h > 0) && (h < 30000))
      fWindow->SetGeometry(w, h);
 
   if ((args.GetBrowserKind() == ROOT::RWebDisplayArgs::kQt5) ||
       (args.GetBrowserKind() == ROOT::RWebDisplayArgs::kQt6) ||
       (args.GetBrowserKind() == ROOT::RWebDisplayArgs::kCEF))
      SetLongerPolling(kTRUE);
 
   fWindow->Show(args);
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Show canvas in browser window
 
void TWebCanvas::Show()
{
   if (gROOT->IsWebDisplayBatch())
      return;
 
   ROOT::RWebDisplayArgs args;
   args.SetWidgetKind("TCanvas");
   args.SetSize(Canvas()->GetWindowWidth(), Canvas()->GetWindowHeight());
   args.SetPos(Canvas()->GetWindowTopX(), Canvas()->GetWindowTopY());
 
   ShowWebWindow(args);
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Function used to send command to browser to toggle menu, toolbar, editors, ...
 
void TWebCanvas::ShowCmd(const std::string &arg, Bool_t show)
{
   AddCtrlMsg(0, arg, show ? "1"s : "0"s);
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Activate object in editor in web browser
 
void TWebCanvas::ActivateInEditor(TPad *pad, TObject *obj)
{
   if (!pad || !obj) return;
 
   UInt_t hash = TString::Hash(&obj, sizeof(obj));
 
   AddCtrlMsg(0, "edit"s, std::to_string(hash));
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Returns kTRUE if web canvas has graphical editor
 
Bool_t TWebCanvas::HasEditor() const
{
   return (fClientBits & TCanvas::kShowEditor) != 0;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Returns kTRUE if web canvas has menu bar
 
Bool_t TWebCanvas::HasMenuBar() const
{
   return (fClientBits & TCanvas::kMenuBar) != 0;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Returns kTRUE if web canvas has status bar
 
Bool_t TWebCanvas::HasStatusBar() const
{
   return (fClientBits & TCanvas::kShowEventStatus) != 0;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Returns kTRUE if tooltips are activated in web canvas
 
Bool_t TWebCanvas::HasToolTips() const
{
   return (fClientBits & TCanvas::kShowToolTips) != 0;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Set window position of web canvas
 
void TWebCanvas::SetWindowPosition(Int_t x, Int_t y)
{
   AddCtrlMsg(0, "x"s, std::to_string(x));
   AddCtrlMsg(0, "y"s, std::to_string(y));
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Set window size of web canvas
 
void TWebCanvas::SetWindowSize(UInt_t w, UInt_t h)
{
   AddCtrlMsg(0, "w"s, std::to_string(w));
   AddCtrlMsg(0, "h"s, std::to_string(h));
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Set window title of web canvas
 
void TWebCanvas::SetWindowTitle(const char *newTitle)
{
   AddCtrlMsg(0, "title"s, newTitle);
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Set canvas size of web canvas
 
void TWebCanvas::SetCanvasSize(UInt_t cw, UInt_t ch)
{
   fFixedSize = kTRUE;
   AddCtrlMsg(0, "cw"s, std::to_string(cw));
   AddCtrlMsg(0, "ch"s, std::to_string(ch));
   if ((cw > 0) && (ch > 0)) {
      Canvas()->fCw = cw;
      Canvas()->fCh = ch;
   } else {
      // temporary value, will be reported back from client
      Canvas()->fCw = Canvas()->fWindowWidth;
      Canvas()->fCh = Canvas()->fWindowHeight;
   }
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Iconify browser window
 
void TWebCanvas::Iconify()
{
   AddCtrlMsg(0, "winstate"s, "iconify"s);
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Raise browser window
 
void TWebCanvas::RaiseWindow()
{
   AddCtrlMsg(0, "winstate"s, "raise"s);
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Assign clients bits
 
void TWebCanvas::AssignStatusBits(UInt_t bits)
{
   fClientBits = bits;
   Canvas()->SetBit(TCanvas::kShowEventStatus, bits & TCanvas::kShowEventStatus);
   Canvas()->SetBit(TCanvas::kShowEditor, bits & TCanvas::kShowEditor);
   Canvas()->SetBit(TCanvas::kShowToolTips, bits & TCanvas::kShowToolTips);
   Canvas()->SetBit(TCanvas::kMenuBar, bits & TCanvas::kMenuBar);
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Decode all pad options, which includes ranges plus objects options
 
Bool_t TWebCanvas::DecodePadOptions(const std::string &msg, bool process_execs)
{
   if (IsReadOnly() || msg.empty())
      return kFALSE;
 
   auto arr = TBufferJSON::FromJSON<std::vector<TWebPadOptions>>(msg);
 
   if (!arr)
      return kFALSE;
 
   Bool_t need_update = kFALSE;
 
   TPad *pad_with_execs = nullptr;
   TExec *hist_exec = nullptr;
 
   for (unsigned n = 0; n < arr->size(); ++n) {
      auto &r = arr->at(n);
 
      TPad *pad = dynamic_cast<TPad *>(FindPrimitive(r.snapid));
 
      if (!pad)
         continue;
 
      if (pad == Canvas()) {
         AssignStatusBits(r.bits);
         Canvas()->fCw = r.cw;
         Canvas()->fCh = r.ch;
         if (r.w.size() == 4)
            SetWindowGeometry(r.w);
      }
 
      // only if get OPTIONS message from client allow to change gPad
      if (r.active && (pad != gPad) && process_execs)
         gPad = pad;
 
      if ((pad->GetTickx() != r.tickx) || (pad->GetTicky() != r.ticky))
         pad->SetTicks(r.tickx, r.ticky);
      if ((pad->GetGridx() != (r.gridx > 0)) || (pad->GetGridy() != (r.gridy > 0)))
         pad->SetGrid(r.gridx, r.gridy);
      pad->fLogx = r.logx;
      pad->fLogy = r.logy;
      pad->fLogz = r.logz;
 
      pad->SetLeftMargin(r.mleft);
      pad->SetRightMargin(r.mright);
      pad->SetTopMargin(r.mtop);
      pad->SetBottomMargin(r.mbottom);
 
      if (r.ranges) {
         // avoid call of original methods, set members directly
         // pad->Range(r.px1, r.py1, r.px2, r.py2);
         // pad->RangeAxis(r.ux1, r.uy1, r.ux2, r.uy2);
 
         pad->fX1 = r.px1;
         pad->fX2 = r.px2;
         pad->fY1 = r.py1;
         pad->fY2 = r.py2;
 
         pad->fUxmin = r.ux1;
         pad->fUxmax = r.ux2;
         pad->fUymin = r.uy1;
         pad->fUymax = r.uy2;
      }
 
      // pad->SetPad(r.mleft, r.mbottom, 1-r.mright, 1-r.mtop);
 
      pad->fAbsXlowNDC = r.xlow;
      pad->fAbsYlowNDC = r.ylow;
      pad->fAbsWNDC = r.xup - r.xlow;
      pad->fAbsHNDC = r.yup - r.ylow;
 
      if (pad == Canvas()) {
         pad->fXlowNDC = r.xlow;
         pad->fYlowNDC = r.ylow;
         pad->fXUpNDC = r.xup;
         pad->fYUpNDC = r.yup;
         pad->fWNDC = r.xup - r.xlow;
         pad->fHNDC = r.yup - r.ylow;
      } else {
         auto mother = pad->GetMother();
         if (mother->GetAbsWNDC() > 0. && mother->GetAbsHNDC() > 0.) {
            pad->fXlowNDC = (r.xlow - mother->GetAbsXlowNDC()) / mother->GetAbsWNDC();
            pad->fYlowNDC = (r.ylow - mother->GetAbsYlowNDC()) / mother->GetAbsHNDC();
            pad->fXUpNDC = (r.xup - mother->GetAbsXlowNDC()) / mother->GetAbsWNDC();
            pad->fYUpNDC = (r.yup - mother->GetAbsYlowNDC()) / mother->GetAbsHNDC();
            pad->fWNDC = (r.xup - r.xlow) / mother->GetAbsWNDC();
            pad->fHNDC = (r.yup - r.ylow) / mother->GetAbsHNDC();
         }
      }
 
      if (r.phi || r.theta) {
         pad->fPhi = r.phi;
         pad->fTheta = r.theta;
      }
 
      // copy of code from TPad::ResizePad()
 
      Double_t pxlow   = r.xlow * r.cw;
      Double_t pylow   = (1-r.ylow) * r.ch;
      Double_t pxrange = (r.xup - r.xlow) * r.cw;
      Double_t pyrange = -1*(r.yup - r.ylow) * r.ch;
 
      Double_t rounding = 0.00005;
      Double_t xrange  = r.px2 - r.px1;
      Double_t yrange  = r.py2 - r.py1;
 
      if ((xrange != 0.) && (pxrange != 0)) {
         // Linear X axis
         pad->fXtoAbsPixelk = rounding + pxlow - pxrange*r.px1/xrange;      //origin at left
         pad->fXtoPixelk = rounding +  -pxrange*r.px1/xrange;
         pad->fXtoPixel = pxrange/xrange;
         pad->fAbsPixeltoXk = r.px1 - pxlow*xrange/pxrange;
         pad->fPixeltoXk = r.px1;
         pad->fPixeltoX = xrange/pxrange;
      }
 
      if ((yrange != 0.) && (pyrange != 0.)) {
         // Linear Y axis
         pad->fYtoAbsPixelk = rounding + pylow - pyrange*r.py1/yrange;      //origin at top
         pad->fYtoPixelk = rounding +  -pyrange - pyrange*r.py1/yrange;
         pad->fYtoPixel = pyrange/yrange;
         pad->fAbsPixeltoYk = r.py1 - pylow*yrange/pyrange;
         pad->fPixeltoYk = r.py1;
         pad->fPixeltoY = yrange/pyrange;
      }
 
      pad->SetFixedAspectRatio(kFALSE);
 
      TObjLink *objlnk = nullptr;
 
      TH1 *hist = static_cast<TH1 *>(FindPrimitive(sid_pad_histogram, 1, pad, &objlnk));
 
      if (hist) {
 
         TObject *hist_holder = objlnk ? objlnk->GetObject() : nullptr;
         if (hist_holder == hist)
            hist_holder = nullptr;
 
         Bool_t no_entries = hist->GetEntries();
         Bool_t is_stack = hist_holder && (hist_holder->IsA() == THStack::Class());
 
         Double_t hmin = 0., hmax = 0.;
 
         if (r.zx1 == r.zx2)
            hist->GetXaxis()->SetRange(0, 0);
         else
            hist->GetXaxis()->SetRangeUser(r.zx1, r.zx2);
 
         if (hist->GetDimension() == 1) {
            hmin = r.zy1;
            hmax = r.zy2;
            if ((hmin == hmax) && !no_entries && !is_stack) {
               // if there are no zooming on Y and histogram has no entries, hmin/hmax should be set to full range
               hmin = pad->fLogy ? TMath::Power(pad->fLogy < 2 ? 10 : pad->fLogy, r.uy1) : r.uy1;
               hmax = pad->fLogy ? TMath::Power(pad->fLogy < 2 ? 10 : pad->fLogy, r.uy2) : r.uy2;
            }
         } else if (r.zy1 == r.zy2) {
            hist->GetYaxis()->SetRange(0, 0);
         } else {
            hist->GetYaxis()->SetRangeUser(r.zy1, r.zy2);
         }
 
         if (hist->GetDimension() == 2) {
            hmin = r.zz1;
            hmax = r.zz2;
            if ((hmin == hmax) && !no_entries) {
               // z scale is not transformed
               hmin = r.uz1;
               hmax = r.uz2;
            }
         } else if (hist->GetDimension() == 3) {
            if (r.zz1 == r.zz2) {
               hist->GetZaxis()->SetRange(0, 0);
            } else {
              hist->GetZaxis()->SetRangeUser(r.zz1, r.zz2);
            }
         }
 
         if (hmin == hmax)
            hmin = hmax = -1111;
 
         if (is_stack) {
            hist->SetMinimum(hmin);
            hist->SetMaximum(hmax);
            hist->SetBit(TH1::kIsZoomed, hmin != hmax);
         } else if (!hist_holder || (hist_holder->IsA() == TScatter::Class())) {
            hist->SetMinimum(hmin);
            hist->SetMaximum(hmax);
         } else {
            auto SetMember = [hist_holder](const char *name, Double_t value) {
               auto offset = hist_holder->IsA()->GetDataMemberOffset(name);
               if (offset > 0)
                  *((Double_t *)((char*) hist_holder + offset)) = value;
               else
                  ::Error("SetMember", "Cannot find %s data member in %s", name, hist_holder->ClassName());
            };
 
            // directly set min/max in classes like THStack, TGraph, TMultiGraph
            SetMember("fMinimum", hmin);
            SetMember("fMaximum", hmax);
         }
 
         TIter next(hist->GetListOfFunctions());
         while (auto fobj = next())
            if (!hist_exec && fobj->InheritsFrom(TExec::Class())) {
               hist_exec = (TExec *) fobj;
               need_update = kTRUE;
            }
      }
 
      std::map<std::string, int> idmap;
 
      for (auto &item : r.primitives) {
         auto iter = idmap.find(item.snapid);
         int idcnt = 1;
         if (iter == idmap.end())
            idmap[item.snapid] = 1;
         else
            idcnt = ++iter->second;
 
         ProcessObjectOptions(item, pad, idcnt);
      }
 
      // without special objects no need for explicit update of the pad
      if (fPadsStatus[pad]._has_specials) {
         pad->Modified(kTRUE);
         need_update = kTRUE;
      }
 
      if (process_execs && (gPad == pad))
         pad_with_execs = pad;
   }
 
   ProcessExecs(pad_with_execs, hist_exec);
 
   if (fUpdatedSignal) fUpdatedSignal(); // invoke signal
 
   return need_update;
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Process TExec objects in the pad
 
void TWebCanvas::ProcessExecs(TPad *pad, TExec *extra)
{
   auto execs = pad ? pad->GetListOfExecs() : nullptr;
 
   if ((!execs || !execs->GetSize()) && !extra)
      return;
 
   auto saveps = gVirtualPS;
   TWebPS ps;
   gVirtualPS = &ps;
 
   auto savex = gVirtualX;
   TVirtualX x;
   gVirtualX = &x;
 
   TIter next(execs);
   while (auto obj = next()) {
      auto exec = dynamic_cast<TExec *>(obj);
      if (exec)
         exec->Exec();
   }
 
   if (extra)
      extra->Exec();
 
   gVirtualPS = saveps;
   gVirtualX = savex;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Execute one or several methods for selected object
/// String can be separated by ";;" to let execute several methods at once
void TWebCanvas::ProcessLinesForObject(TObject *obj, const std::string &lines)
{
   std::string buf = lines;
 
   Int_t indx = 0;
 
   while (obj && !buf.empty()) {
      std::string sub = buf;
      auto pos = buf.find(";;");
      if (pos == std::string::npos) {
         sub = buf;
         buf.clear();
      } else {
         sub = buf.substr(0,pos);
         buf = buf.substr(pos+2);
      }
      if (sub.empty()) continue;
 
      std::stringstream exec;
      exec << "((" << obj->ClassName() << " *) " << std::hex << std::showbase << (size_t)obj << ")->" << sub << ";";
      if (indx < 3 || gDebug > 0)
         Info("ProcessLinesForObject", "Obj %s Execute %s", obj->GetName(), exec.str().c_str());
      gROOT->ProcessLine(exec.str().c_str());
      indx++;
   }
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Handle data from web browser
/// Returns kFALSE if message was not processed
 
Bool_t TWebCanvas::ProcessData(unsigned connid, const std::string &arg)
{
   if (arg.empty())
      return kTRUE;
 
   // try to identify connection for given WS request
   unsigned indx = 0; // first connection is batch and excluded
   while(++indx < fWebConn.size()) {
      if (fWebConn[indx].fConnId == connid)
         break;
   }
   if (indx >= fWebConn.size())
      return kTRUE;
 
   Bool_t is_main_connection = indx == 1; // first connection allow to make changes
 
   struct FlagGuard {
      Bool_t &flag;
      FlagGuard(Bool_t &_flag) : flag(_flag) { flag = true; }
      ~FlagGuard() { flag = false; }
   };
 
   FlagGuard guard(fProcessingData);
 
   const char *cdata = arg.c_str();
 
   if (arg == "KEEPALIVE") {
      // do nothing
 
   } else if (arg == "QUIT") {
 
      // use window manager to correctly terminate http server
      fWindow->TerminateROOT();
 
   } else if (arg.compare(0, 7, "READY6:") == 0) {
 
      // this is reply on drawing of ROOT6 snapshot
      // it confirms when drawing of specific canvas version is completed
 
      cdata += 7;
 
      const char *separ = strchr(cdata, ':');
      if (!separ) {
         fWebConn[indx].fDrawVersion = std::stoll(cdata);
      } else {
         fWebConn[indx].fDrawVersion = std::stoll(std::string(cdata, separ - cdata));
         if (is_main_connection && !IsReadOnly())
            if (DecodePadOptions(separ+1, false))
               CheckCanvasModified();
      }
 
   } else if (arg == "RELOAD") {
 
      // trigger reload of canvas data
      fWebConn[indx].reset();
 
   } else if (arg.compare(0, 5, "SAVE:") == 0) {
 
      // save image produced by the client side - like png or svg
      const char *img = cdata + 5;
 
      const char *separ = strchr(img, ':');
      if (separ) {
         TString filename(img, separ - img);
         img = separ + 1;
 
         std::ofstream ofs(filename.Data());
 
         int filelen = -1;
 
         if (filename.Index(".svg") != kNPOS) {
            // ofs << "<?xml version=\"1.0\" standalone=\"no\"?>";
            ofs << img;
            filelen = strlen(img);
         } else {
            TString binary = TBase64::Decode(img);
            ofs.write(binary.Data(), binary.Length());
            filelen = binary.Length();
         }
         ofs.close();
 
         Info("ProcessData", "File %s size %d has been created", filename.Data(), filelen);
      }
 
   } else if (arg.compare(0, 8, "PRODUCE:") == 0) {
 
      // create ROOT, PDF, ... files using native ROOT functionality
      Canvas()->Print(arg.c_str() + 8);
 
   } else if (arg.compare(0, 8, "GETMENU:") == 0) {
 
      TObject *obj = FindPrimitive(arg.substr(8));
      if (!obj)
         obj = Canvas();
 
      TWebMenuItems items(arg.c_str() + 8);
      items.PopulateObjectMenu(obj, obj->IsA());
      std::string buf = "MENU:";
      buf.append(TBufferJSON::ToJSON(&items, 103).Data());
 
      AddSendQueue(connid, buf);
 
   } else if (arg.compare(0, 11, "STATUSBITS:") == 0) {
 
      if (is_main_connection) {
         AssignStatusBits(std::stoul(arg.substr(11)));
         if (fUpdatedSignal) fUpdatedSignal(); // invoke signal
      }
 
   } else if (arg.compare(0, 10, "HIGHLIGHT:") == 0) {
 
      if (is_main_connection) {
         auto arr = TBufferJSON::FromJSON<std::vector<std::string>>(arg.substr(10));
         if (!arr || (arr->size() != 4)) {
            Error("ProcessData", "Wrong arguments count %d in highlight message", (int)(arr ? arr->size() : -1));
         } else {
            auto pad = dynamic_cast<TVirtualPad *>(FindPrimitive(arr->at(0)));
            auto obj = FindPrimitive(arr->at(1));
            int argx = std::stoi(arr->at(2));
            int argy = std::stoi(arr->at(3));
            if (pad && obj) {
              Canvas()->Highlighted(pad, obj, argx, argy);
              CheckCanvasModified();
            }
         }
      }
 
   } else if (ROOT::RWebWindow::IsFileDialogMessage(arg)) {
 
      ROOT::RWebWindow::EmbedFileDialog(fWindow, connid, arg);
 
   } else if (IsReadOnly() || !is_main_connection) {
 
      ///////////////////////////////////////////////////////////////////////////////////////
      // all following messages are not allowed in readonly mode or for secondary connections
 
      return kFALSE;
 
   } else if (arg.compare(0, 9, "OPTIONS6:") == 0) {
 
      if (DecodePadOptions(arg.substr(9), true))
         CheckCanvasModified();
 
   } else if (arg.compare(0, 9, "FITPANEL:") == 0) {
 
      std::string chid = arg.substr(9);
 
      TH1 *hist = nullptr;
      TIter iter(Canvas()->GetListOfPrimitives());
      while (auto obj = iter()) {
         hist = dynamic_cast<TH1 *>(obj);
         if (hist) break;
      }
 
      TString showcmd;
      if (chid == "standalone")
         showcmd = "panel->Show()";
      else
         showcmd = TString::Format("auto wptr = (std::shared_ptr<ROOT::RWebWindow>*)0x%zx;"
                                   "panel->Show({*wptr, %u, %s})",
                                   (size_t) &fWindow, connid, chid.c_str());
 
      auto cmd = TString::Format("auto panel = std::make_shared<ROOT::Experimental::RFitPanel>(\"FitPanel\");"
                                 "panel->AssignCanvas(\"%s\");"
                                 "panel->AssignHistogram((TH1 *)0x%zx);"
                                 "%s;panel->ClearOnClose(panel);",
                                 Canvas()->GetName(), (size_t) hist, showcmd.Data());
      gROOT->ProcessLine(cmd.Data());
   } else if (arg == "START_BROWSER"s) {
 
      gROOT->ProcessLine("new TBrowser;");
 
   } else if (arg.compare(0, 6, "EVENT:") == 0) {
      auto arr = TBufferJSON::FromJSON<std::vector<std::string>>(arg.substr(6));
      if (!arr || (arr->size() != 5)) {
         Error("ProcessData", "Wrong arguments count %d in event message", (int)(arr ? arr->size() : -1));
      } else {
         auto pad = dynamic_cast<TPad *>(FindPrimitive(arr->at(0)));
         std::string kind = arr->at(1);
         int event = -1;
         if (kind == "move"s) event = kMouseMotion;
         int argx = std::stoi(arr->at(2));
         int argy = std::stoi(arr->at(3));
         auto selobj = FindPrimitive(arr->at(4));
 
         if ((event >= 0) && pad && (pad == gPad)) {
            Canvas()->fEvent = event;
            Canvas()->fEventX = argx;
            Canvas()->fEventY = argy;
 
            Canvas()->fSelected = selobj;
 
            ProcessExecs(pad);
         }
      }
 
   } else if (arg.compare(0, 8, "PRIMIT6:") == 0) {
 
      auto opt = TBufferJSON::FromJSON<TWebObjectOptions>(arg.c_str() + 8);
 
      if (opt) {
         TPad *modpad = ProcessObjectOptions(*opt, nullptr);
 
         // indicate that pad was modified
         if (modpad)
            modpad->Modified();
      }
 
   } else if (arg.compare(0, 11, "PADCLICKED:") == 0) {
 
      auto click = TBufferJSON::FromJSON<TWebPadClick>(arg.c_str() + 11);
 
      if (click) {
 
         TPad *pad = dynamic_cast<TPad *>(FindPrimitive(click->padid));
 
         if (pad && pad->InheritsFrom(TButton::Class())) {
            auto btn = (TButton *) pad;
            const char *mthd = btn->GetMethod();
            if (mthd && *mthd) {
               TVirtualPad::TContext ctxt(gROOT->GetSelectedPad(), kTRUE, kTRUE);
               gROOT->ProcessLine(mthd);
            }
            return kTRUE;
         }
 
         if (pad && (pad != gPad)) {
            gPad = pad;
            Canvas()->SetClickSelectedPad(pad);
            if (fActivePadChangedSignal)
               fActivePadChangedSignal(pad);
         }
 
         if (!click->objid.empty()) {
            auto selobj = FindPrimitive(click->objid);
            Canvas()->SetClickSelected(selobj);
            Canvas()->fSelected = selobj;
            if (pad && selobj && fObjSelectSignal)
               fObjSelectSignal(pad, selobj);
         }
 
         if ((click->x >= 0) && (click->y >= 0)) {
            Canvas()->fEvent = click->dbl ? kButton1Double : kButton1Up;
            Canvas()->fEventX = click->x;
            Canvas()->fEventY = click->y;
            if (click->dbl && fPadDblClickedSignal)
               fPadDblClickedSignal(pad, click->x, click->y);
            else if (!click->dbl && fPadClickedSignal)
               fPadClickedSignal(pad, click->x, click->y);
         }
 
         ProcessExecs(pad);
      }
 
   } else if (arg.compare(0, 8, "OBJEXEC:") == 0) {
 
     auto buf = arg.substr(8);
     auto pos = buf.find(":");
 
     if ((pos > 0) && (pos != std::string::npos)) {
        auto sid = buf.substr(0, pos);
        buf.erase(0, pos + 1);
 
        TObjLink *lnk = nullptr;
        TPad *objpad = nullptr;
 
        TObject *obj = FindPrimitive(sid, 1, nullptr, &lnk, &objpad);
 
        if (obj && !buf.empty()) {
 
           ProcessLinesForObject(obj, buf);
 
           if (objpad)
              objpad->Modified();
           else
              Canvas()->Modified();
 
           CheckCanvasModified();
        }
     }
 
   } else if (arg.compare(0, 12, "EXECANDSEND:") == 0) {
 
      // execute method and send data, used by drawing projections
 
      std::string buf = arg.substr(12);
      std::string reply;
      TObject *obj = nullptr;
 
      auto pos = buf.find(":");
 
      if (pos > 0) {
         // only first client can execute commands
         reply = buf.substr(0, pos);
         buf.erase(0, pos + 1);
         pos = buf.find(":");
         if (pos > 0) {
            auto sid = buf.substr(0, pos);
            buf.erase(0, pos + 1);
            obj = FindPrimitive(sid);
         }
      }
 
      if (obj && !buf.empty() && !reply.empty()) {
         std::stringstream exec;
         exec << "((" << obj->ClassName() << " *) " << std::hex << std::showbase << (size_t)obj
              << ")->" << buf << ";";
         if (gDebug > 0)
            Info("ProcessData", "Obj %s Exec %s", obj->GetName(), exec.str().c_str());
 
         auto res = gROOT->ProcessLine(exec.str().c_str());
         TObject *resobj = (TObject *)(res);
         if (resobj) {
            std::string send = reply;
            send.append(":");
            send.append(TBufferJSON::ToJSON(resobj, 23).Data());
            AddSendQueue(connid, send);
            if (reply[0] == 'D')
               delete resobj; // delete object if first symbol in reply is D
         }
      }
 
   } else if (arg.compare(0, 6, "CLEAR:") == 0) {
      std::string snapid = arg.substr(6);
 
      TPad *pad = dynamic_cast<TPad *>(FindPrimitive(snapid));
 
      if (pad) {
         pad->Clear();
         pad->Modified();
         CheckCanvasModified();
      } else {
         Error("ProcessData", "Not found pad with id %s to clear\n", snapid.c_str());
      }
   } else if (arg.compare(0, 7, "DIVIDE:") == 0) {
      auto arr = TBufferJSON::FromJSON<std::vector<std::string>>(arg.substr(7));
      if (arr && arr->size() == 2) {
         TPad *pad = dynamic_cast<TPad *>(FindPrimitive(arr->at(0)));
         int nn = 0, n1 = 0, n2 = 0;
 
         std::string divide = arr->at(1);
         auto p = divide.find('x');
         if (p == std::string::npos)
            p = divide.find('X');
 
         if (p != std::string::npos) {
            n1 = std::stoi(divide.substr(0,p));
            n2 = std::stoi(divide.substr(p+1));
         } else {
            nn = std::stoi(divide);
         }
 
         if (pad && ((nn > 1) || (n1*n2 > 1))) {
            pad->Clear();
            pad->Modified();
            if (nn > 1)
               pad->DivideSquare(nn);
            else
               pad->Divide(n1, n2);
            pad->cd(1);
            CheckCanvasModified();
         }
      }
 
   } else if (arg.compare(0, 8, "DRAWOPT:") == 0) {
 
      auto arr = TBufferJSON::FromJSON<std::vector<std::string>>(arg.substr(8));
      if (arr && arr->size() == 2) {
         TObjLink *objlnk = nullptr;
         FindPrimitive(arr->at(0), 1, nullptr, &objlnk);
         if (objlnk)
            objlnk->SetOption(arr->at(1).c_str());
      }
 
   } else if (arg.compare(0, 8, "RESIZED:") == 0) {
 
      auto arr = TBufferJSON::FromJSON<std::vector<int>>(arg.substr(8));
      if (arr && arr->size() == 7) {
         // set members directly to avoid redrawing of the client again
         Canvas()->fCw = arr->at(4);
         Canvas()->fCh = arr->at(5);
         fFixedSize = arr->at(6) > 0;
         arr->resize(4);
         SetWindowGeometry(*arr);
      }
 
   } else if (arg.compare(0, 7, "POPOBJ:") == 0) {
 
      auto arr = TBufferJSON::FromJSON<std::vector<std::string>>(arg.substr(7));
      if (arr && arr->size() == 2) {
         TPad *pad = dynamic_cast<TPad *>(FindPrimitive(arr->at(0)));
         TObject *obj = FindPrimitive(arr->at(1), 0, pad);
         if (pad && obj && (obj != pad->GetListOfPrimitives()->Last())) {
            TIter next(pad->GetListOfPrimitives());
            while (auto o = next())
               if (obj == o) {
                  TString opt = next.GetOption();
                  pad->Remove(obj, kFALSE);
                  pad->Add(obj, opt.Data());
                  break;
               }
         }
      }
 
   } else if (arg.compare(0, 8, "SHOWURL:") == 0) {
 
      ROOT::RWebDisplayArgs args;
      args.SetUrl(arg.substr(8));
      args.SetStandalone(false);
 
      fHelpHandles.emplace_back(ROOT::RWebDisplayHandle::Display(args));
 
   } else if (arg == "INTERRUPT"s) {
 
      gROOT->SetInterrupt();
 
   } else {
 
      // unknown message, probably should be processed by other implementation
      return kFALSE;
 
   }
 
   return kTRUE;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Returns true if any pad in the canvas were modified
/// Reset modified flags, increment canvas version (if inc_version is true)
 
void TWebCanvas::CheckPadModified(TPad *pad)
{
   if (fPadsStatus.find(pad) == fPadsStatus.end())
      fPadsStatus[pad] = PadStatus{0, true, true};
 
   auto &entry = fPadsStatus[pad];
   entry._detected = true;
   if (pad->IsModified()) {
      pad->Modified(kFALSE);
      entry._modified = true;
   }
 
   TIter iter(pad->GetListOfPrimitives());
   while (auto obj = iter()) {
      if (obj->InheritsFrom(TPad::Class()))
         CheckPadModified(static_cast<TPad *>(obj));
   }
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Check if any pad on the canvas was modified
/// If yes, increment version of correspondent pad
/// Returns true when canvas really modified
 
Bool_t TWebCanvas::CheckCanvasModified(bool force_modified)
{
   // clear temporary flags
   for (auto &entry : fPadsStatus) {
      entry.second._detected = false;
      entry.second._modified = force_modified;
   }
 
   // scan sub-pads
   CheckPadModified(Canvas());
 
   // remove no-longer existing pads
   bool is_any_modified = false;
   for(auto iter = fPadsStatus.begin(); iter != fPadsStatus.end(); ) {
      if (iter->second._modified)
         is_any_modified = true;
      if (!iter->second._detected)
         fPadsStatus.erase(iter++);
      else
         iter++;
   }
 
   // if any pad modified, increment canvas version and set version of modified pads
   if (is_any_modified) {
      fCanvVersion++;
      for(auto &entry : fPadsStatus)
         if (entry.second._modified)
            entry.second.fVersion = fCanvVersion;
   }
 
   return is_any_modified;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Set window geometry as array with coordinates and dimensions
 
void TWebCanvas::SetWindowGeometry(const std::vector<int> &arr)
{
   fWindowGeometry = arr;
   Canvas()->fWindowTopX = arr[0];
   Canvas()->fWindowTopY = arr[1];
   Canvas()->fWindowWidth = arr[2];
   Canvas()->fWindowHeight = arr[3];
   if (fWindow) {
      // position is unreliable and cannot be used
      // fWindow->SetPosition(arr[0], arr[1]);
      fWindow->SetGeometry(arr[2], arr[3]);
   }
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Returns window geometry including borders and menus
 
UInt_t TWebCanvas::GetWindowGeometry(Int_t &x, Int_t &y, UInt_t &w, UInt_t &h)
{
   if (fWindowGeometry.size() == 4) {
      x = fWindowGeometry[0];
      y = fWindowGeometry[1];
      w = fWindowGeometry[2];
      h = fWindowGeometry[3];
   } else {
      x = Canvas()->fWindowTopX;
      y = Canvas()->fWindowTopY;
      w = Canvas()->fWindowWidth;
      h = Canvas()->fWindowHeight;
   }
   return 0;
}
 
 
//////////////////////////////////////////////////////////////////////////////////////////
/// if canvas or any subpad was modified,
/// scan all primitives in the TCanvas and subpads and convert them into
/// the structure which will be delivered to JSROOT client
 
Bool_t TWebCanvas::PerformUpdate(Bool_t async)
{
   CheckCanvasModified();
 
   CheckDataToSend();
 
   if (!fProcessingData && !IsAsyncMode() && !async)
      WaitWhenCanvasPainted(fCanvVersion);
 
   return kTRUE;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Increment canvas version and force sending data to client - do not wait for reply
 
void TWebCanvas::ForceUpdate()
{
   CheckCanvasModified(true);
 
   if (!fWindow) {
      TCanvasWebSnapshot holder(IsReadOnly(), false, true); // readonly, set ids, batchmode
 
      holder.SetScripts(ProcessCustomScripts(true));
 
      CreatePadSnapshot(holder, Canvas(), 0, nullptr);
   } else {
      CheckDataToSend();
   }
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Wait when specified version of canvas was painted and confirmed by browser
 
Bool_t TWebCanvas::WaitWhenCanvasPainted(Long64_t ver)
{
   if (!fWindow)
      return kTRUE;
 
   // simple polling loop until specified version delivered to the clients
   // first 500 loops done without sleep, then with 1ms sleep and last 500 with 100 ms sleep
 
   long cnt = 0, cnt_limit = GetLongerPolling() ? 5500 : 1500;
 
   if (gDebug > 2)
      Info("WaitWhenCanvasPainted", "version %ld", (long)ver);
 
   while (cnt++ < cnt_limit) {
 
      if (!fWindow->HasConnection(0, false)) {
         if (gDebug > 2)
            Info("WaitWhenCanvasPainted", "no connections - abort");
         return kFALSE; // wait ~1 min if no new connection established
      }
 
      if ((fWebConn.size() > 1) && (fWebConn[1].fDrawVersion >= ver)) {
         if (gDebug > 2)
            Info("WaitWhenCanvasPainted", "ver %ld got painted", (long)ver);
         return kTRUE;
      }
 
      gSystem->ProcessEvents();
      if (cnt > 500)
         gSystem->Sleep((cnt < cnt_limit - 500) ? 1 : 100); // increase sleep interval when do very often
   }
 
   if (gDebug > 2)
      Info("WaitWhenCanvasPainted", "timeout");
 
   return kFALSE;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Create JSON painting output for given pad
/// Produce JSON can be used for offline drawing with JSROOT
 
TString TWebCanvas::CreatePadJSON(TPad *pad, Int_t json_compression, Bool_t batchmode)
{
   TString res;
   if (!pad)
      return res;
 
   TCanvas *c = dynamic_cast<TCanvas *>(pad);
   if (c) {
      res = CreateCanvasJSON(c, json_compression, batchmode);
   } else {
      auto imp = std::make_unique<TWebCanvas>(pad->GetCanvas(), pad->GetName(), 0, 0, pad->GetWw(), pad->GetWh(), kTRUE);
 
      TPadWebSnapshot holder(true, false, batchmode); // readonly, no ids, batchmode
 
      imp->CreatePadSnapshot(holder, pad, 0, [&res, json_compression](TPadWebSnapshot *snap) {
         res = TBufferJSON::ToJSON(snap, json_compression);
      });
   }
 
   return res;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Create JSON painting output for given canvas
/// Produce JSON can be used for offline drawing with JSROOT
 
TString TWebCanvas::CreateCanvasJSON(TCanvas *c, Int_t json_compression, Bool_t batchmode)
{
   TString res;
 
   if (!c)
      return res;
 
   {
      auto imp = std::make_unique<TWebCanvas>(c, c->GetName(), 0, 0, c->GetWw(), c->GetWh(), kTRUE);
 
      TCanvasWebSnapshot holder(true, false, batchmode); // readonly, no ids, batchmode
 
      holder.SetScripts(ProcessCustomScripts(batchmode));
 
      imp->CreatePadSnapshot(holder, c, 0, [&res, json_compression](TPadWebSnapshot *snap) {
         res = TBufferJSON::ToJSON(snap, json_compression);
      });
   }
 
   return res;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Create JSON painting output for given canvas and store into the file
/// See TBufferJSON::ExportToFile() method for more details about option
/// If option string starts with symbol 'b', JSON for batch mode will be generated (default)
/// If option string starts with symbol 'i', JSON for interactive mode will be generated
 
Int_t TWebCanvas::StoreCanvasJSON(TCanvas *c, const char *filename, const char *option)
{
   Int_t res = 0;
   Bool_t batchmode = kTRUE;
   if (option) {
      if (*option == 'b') {
         batchmode = kTRUE;
         ++option;
      } else if (*option == 'i') {
         batchmode = kFALSE;
         ++option;
      }
   }
 
   if (!c)
      return res;
 
   {
      auto imp = std::make_unique<TWebCanvas>(c, c->GetName(), 0, 0, c->GetWw(), c->GetWh(), kTRUE);
 
      TCanvasWebSnapshot holder(true, false, batchmode); // readonly, no ids, batchmode
 
      holder.SetScripts(ProcessCustomScripts(batchmode));
 
      imp->CreatePadSnapshot(holder, c, 0, [&res, filename, option](TPadWebSnapshot *snap) {
         res = TBufferJSON::ExportToFile(filename, snap, option);
      });
   }
 
   return res;
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Create image using batch (headless) capability of Chrome or Firefox browsers
/// Supported png, jpeg, svg, pdf formats
 
bool TWebCanvas::ProduceImage(TPad *pad, const char *fileName, Int_t width, Int_t height)
{
   if (!pad)
      return false;
 
   auto json = CreatePadJSON(pad, TBufferJSON::kNoSpaces + TBufferJSON::kSameSuppression, kTRUE);
   if (!json.Length())
      return false;
 
   TString fname = fileName;
   const char *endings[4] = {"(", "[", "]", ")"};
   const char *suffix = nullptr;
   for (int n = 0; (n < 4) && !suffix; ++n) {
      if (fname.EndsWith(endings[n])) {
         fname.Resize(fname.Length() - 1);
         suffix = endings[n];
      }
   }
 
   Bool_t append_batch = kTRUE, flush_batch = kTRUE;
 
   std::string fmt = ROOT::RWebDisplayHandle::GetImageFormat(fname.Data());
   if (fmt.empty())
      return false;
 
   if (suffix) {
      if (fmt != "pdf")
         return false;
      switch (*suffix) {
         case '(': gBatchMultiPdf = fname.Data(); flush_batch = kFALSE; break;
         case '[': gBatchMultiPdf = fname.Data(); append_batch = kFALSE; flush_batch = kFALSE; break;
         case ']': gBatchMultiPdf.clear(); append_batch = kFALSE; break;
         case ')': gBatchMultiPdf.clear(); fname.Append("+"); break;
      }
   } else if (fmt == "pdf") {
      if (!gBatchMultiPdf.empty()) {
         if (gBatchMultiPdf.compare(fileName) == 0) {
            append_batch = kTRUE;
            flush_batch = kFALSE;
            suffix = "+"; // to let append to the batch
            if ((gBatchFiles.size() > 0) && (gBatchFiles.back().compare(0, fname.Length(), fname.Data()) == 0))
               fname.Append("+"); // .pdf+ means appending image to previous
         } else {
            ::Error("TWebCanvas::ProduceImage", "Cannot change PDF name when multi-page PDF active");
            return false;
         }
      }
   } else if (!gBatchMultiPdf.empty()) {
      ::Error("TWebCanvas::ProduceImage", "Cannot produce other images when multi-page PDF active");
      return false;
   }
 
   if (!width && !height) {
      if ((pad->GetCanvas() == pad) || (pad->IsA() == TCanvas::Class())) {
         width = pad->GetWw();
         height = pad->GetWh();
      } else {
         width = (Int_t) (pad->GetAbsWNDC() * pad->GetCanvas()->GetWw());
         height = (Int_t) (pad->GetAbsHNDC() * pad->GetCanvas()->GetWh());
      }
   }
 
   if (!suffix && (!gBatchImageMode || (fmt == "s.pdf") || (fmt == "json") || (fmt == "s.png")))
      return ROOT::RWebDisplayHandle::ProduceImage(fname.Data(), json.Data(), width, height);
 
   if (append_batch) {
      gBatchFiles.emplace_back(fname.Data());
      gBatchJsons.emplace_back(json);
      gBatchWidths.emplace_back(width);
      gBatchHeights.emplace_back(height);
   }
 
   if (!flush_batch || (gBatchJsons.size() < gBatchImageMode))
      return true;
 
   return FlushBatchImages();
}
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Create images for several pads using batch (headless) capability of Chrome or Firefox browsers
/// Supported png, jpeg, svg, pdf, webp formats
/// One can include %d qualifier which will be replaced by image index using printf functionality.
/// If for pdf format %d qualifier not specified, all images will be stored in single PDF file.
/// For all other formats %d qualifier will be add before extension automatically
 
bool TWebCanvas::ProduceImages(std::vector<TPad *> pads, const char *filename, Int_t width, Int_t height)
{
   if (pads.empty())
      return false;
 
   std::vector<std::string> jsons;
   std::vector<Int_t> widths, heights;
 
   for (unsigned n = 0; n < pads.size(); ++n) {
      auto pad = pads[n];
 
      auto json = CreatePadJSON(pad, TBufferJSON::kNoSpaces + TBufferJSON::kSameSuppression, kTRUE);
      if (!json.Length())
         continue;
 
      Int_t w = width, h = height;
 
      if (!w && !h) {
         if ((pad->GetCanvas() == pad) || (pad->IsA() == TCanvas::Class())) {
            w = pad->GetWw();
            h = pad->GetWh();
         } else {
            w = (Int_t) (pad->GetAbsWNDC() * pad->GetCanvas()->GetWw());
            h = (Int_t) (pad->GetAbsHNDC() * pad->GetCanvas()->GetWh());
         }
      }
 
      jsons.emplace_back(json.Data());
      widths.emplace_back(w);
      heights.emplace_back(h);
   }
 
   std::string fmt = ROOT::RWebDisplayHandle::GetImageFormat(filename);
 
   if (!gBatchImageMode || (fmt == "json") || (fmt == "s.png") || (fmt == "s.pdf"))
      return ROOT::RWebDisplayHandle::ProduceImages(filename, jsons, widths, heights);
 
   auto fnames = ROOT::RWebDisplayHandle::ProduceImagesNames(filename, jsons.size());
 
   gBatchFiles.insert(gBatchFiles.end(), fnames.begin(), fnames.end());
   gBatchJsons.insert(gBatchJsons.end(), jsons.begin(), jsons.end());
   gBatchWidths.insert(gBatchWidths.end(), widths.begin(), widths.end());
   gBatchHeights.insert(gBatchHeights.end(), heights.begin(), heights.end());
   if (gBatchJsons.size() < gBatchImageMode)
      return true;
 
   return FlushBatchImages();
}
 
 
//////////////////////////////////////////////////////////////////////////////////////////
/// Process data for single primitive
/// Returns object pad if object was modified
 
TPad *TWebCanvas::ProcessObjectOptions(TWebObjectOptions &item, TPad *pad, int idcnt)
{
   TObjLink *lnk = nullptr;
   TPad *objpad = nullptr;
   TObject *obj = FindPrimitive(item.snapid, idcnt, pad, &lnk, &objpad);
 
   if (item.fcust.compare("exec") == 0) {
      auto pos = item.opt.find("(");
      if (obj && (pos != std::string::npos) && obj->IsA()->GetMethodAllAny(item.opt.substr(0,pos).c_str())) {
         std::stringstream exec;
         exec << "((" << obj->ClassName() << " *) " << std::hex << std::showbase
                      << (size_t)obj << ")->" << item.opt << ";";
         if (gDebug > 0)
            Info("ProcessObjectOptions", "Obj %s Execute %s", obj->GetName(), exec.str().c_str());
         gROOT->ProcessLine(exec.str().c_str());
      } else {
         Error("ProcessObjectOptions", "Fail to execute %s for object %p %s", item.opt.c_str(), obj, obj ? obj->ClassName() : "---");
         objpad = nullptr;
      }
      return objpad;
   }
 
   bool modified = false;
 
   if (obj && lnk) {
      auto pos = item.opt.find(";;use_"); // special coding of extra options
      if (pos != std::string::npos) item.opt.resize(pos);
 
      if (gDebug > 0)
         Info("ProcessObjectOptions", "Set draw option %s for object %s %s", item.opt.c_str(),
               obj->ClassName(), obj->GetName());
 
      lnk->SetOption(item.opt.c_str());
 
      modified = true;
   }
 
   if (item.fcust.compare(0,10,"auto_exec:") == 0) {
      ProcessLinesForObject(obj, item.fcust.substr(10));
   } else if (item.fcust.compare("frame") == 0) {
      if (obj && obj->InheritsFrom(TFrame::Class())) {
         TFrame *frame = static_cast<TFrame *>(obj);
         if (item.fopt.size() >= 4) {
            frame->SetX1(item.fopt[0]);
            frame->SetY1(item.fopt[1]);
            frame->SetX2(item.fopt[2]);
            frame->SetY2(item.fopt[3]);
            modified = true;
         }
      }
   } else if (item.fcust.compare(0,4,"pave") == 0) {
      if (obj && obj->InheritsFrom(TPave::Class())) {
         TPave *pave = static_cast<TPave *>(obj);
         if ((item.fopt.size() >= 4) && objpad) {
            TVirtualPad::TContext ctxt(objpad, kFALSE);
 
            // first time need to overcome init problem
            pave->ConvertNDCtoPad();
 
            pave->SetX1NDC(item.fopt[0]);
            pave->SetY1NDC(item.fopt[1]);
            pave->SetX2NDC(item.fopt[2]);
            pave->SetY2NDC(item.fopt[3]);
            modified = true;
 
            pave->ConvertNDCtoPad();
         }
         if ((item.fcust.length() > 4) && pave->InheritsFrom(TPaveStats::Class())) {
            // add text lines for statsbox
            auto stats = static_cast<TPaveStats *>(pave);
            stats->Clear();
            size_t pos_start = 6, pos_end;
            while ((pos_end = item.fcust.find(";;", pos_start)) != std::string::npos) {
               stats->AddText(item.fcust.substr(pos_start, pos_end - pos_start).c_str());
               pos_start = pos_end + 2;
            }
            stats->AddText(item.fcust.substr(pos_start).c_str());
         }
      }
   } else if (item.fcust.compare(0,9,"func_fail") == 0) {
      if (fTF1UseSave <= 0) {
         fTF1UseSave = 1;
         modified = true;
      }
   }
 
   return modified ? objpad : nullptr;
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Search of object with given id in list of primitives
/// One could specify pad where search could be start
/// Also if object is in list of primitives, one could ask for entry link for such object,
/// This can allow to change draw option
 
TObject *TWebCanvas::FindPrimitive(const std::string &sid, int idcnt, TPad *pad, TObjLink **objlnk, TPad **objpad)
{
   if (sid.empty() || (sid == "0"s))
      return nullptr;
 
   if (!pad)
      pad = Canvas();
 
   std::string subelement;
   long unsigned id = 0;
   bool search_hist = (sid == sid_pad_histogram);
   if (!search_hist) {
      auto separ = sid.find("#");
 
      if (separ == std::string::npos) {
         id = std::stoul(sid);
      } else {
         subelement = sid.substr(separ + 1);
         id = std::stoul(sid.substr(0, separ));
      }
      if (TString::Hash(&pad, sizeof(pad)) == id)
         return pad;
   }
 
   for (auto lnk = pad->GetListOfPrimitives()->FirstLink(); lnk != nullptr; lnk = lnk->Next()) {
      TObject *obj = lnk->GetObject();
      if (!obj) continue;
 
      if (!search_hist && (TString::Hash(&obj, sizeof(obj)) != id)) {
         if (obj->InheritsFrom(TPad::Class())) {
            obj = FindPrimitive(sid, idcnt, (TPad *)obj, objlnk, objpad);
            if (objpad && !*objpad)
               *objpad = pad;
             if (obj)
                return obj;
         }
         continue;
      }
 
      // one may require to access n-th object
      if (!search_hist && --idcnt > 0)
         continue;
 
      if (objpad)
         *objpad = pad;
 
      if (objlnk)
         *objlnk = lnk;
 
      if (search_hist)
         subelement = "hist";
 
      auto getHistogram = [](TObject *container) -> TH1* {
         auto offset = container->IsA()->GetDataMemberOffset("fHistogram");
         if (offset > 0)
            return *((TH1 **)((char *)container + offset));
         ::Error("getHistogram", "Cannot access fHistogram data member in %s", container->ClassName());
         return nullptr;
      };
 
      while(!subelement.empty() && obj) {
         // do not return link if sub-selement is searched - except for histogram
         if (!search_hist && objlnk)
            *objlnk = nullptr;
 
         std::string kind = subelement;
         auto separ = kind.find("#");
         if (separ == std::string::npos) {
            subelement.clear();
         } else {
            kind.resize(separ);
            subelement = subelement.substr(separ + 1);
         }
 
         TH1 *h1 = obj->InheritsFrom(TH1::Class()) ? static_cast<TH1 *>(obj) : nullptr;
         TGraph *gr = obj->InheritsFrom(TGraph::Class()) ? static_cast<TGraph *>(obj) : nullptr;
         TGraph2D *gr2d = obj->InheritsFrom(TGraph2D::Class()) ? static_cast<TGraph2D *>(obj) : nullptr;
         TScatter *scatter = obj->InheritsFrom(TScatter::Class()) ? static_cast<TScatter *>(obj) : nullptr;
         TMultiGraph *mg = obj->InheritsFrom(TMultiGraph::Class()) ? static_cast<TMultiGraph *>(obj) : nullptr;
         THStack *hs = obj->InheritsFrom(THStack::Class()) ? static_cast<THStack *>(obj) : nullptr;
         TF1 *f1 = obj->InheritsFrom(TF1::Class()) ? static_cast<TF1 *>(obj) : nullptr;
 
         if (kind.compare("hist") == 0) {
            if (h1)
               obj = h1;
            else if (gr)
               obj = getHistogram(gr);
            else if (mg)
               obj = getHistogram(mg);
            else if (hs && (hs->GetNhists() > 0))
               obj = getHistogram(hs);
            else if (scatter)
               obj = getHistogram(scatter);
            else if (f1)
               obj = getHistogram(f1);
            else if (gr2d)
               obj = getHistogram(gr2d);
            else
               obj = nullptr;
         } else if (kind.compare("x") == 0) {
            obj = h1 ? h1->GetXaxis() : nullptr;
         } else if (kind.compare("y") == 0) {
            obj = h1 ? h1->GetYaxis() : nullptr;
         } else if (kind.compare("z") == 0) {
            obj = h1 ? h1->GetZaxis() : nullptr;
         } else if ((kind.compare(0,5,"func_") == 0) || (kind.compare(0,5,"indx_") == 0)) {
            auto funcname = kind.substr(5);
            TList *col = nullptr;
            if (h1)
               col = h1->GetListOfFunctions();
            else if (gr)
               col = gr->GetListOfFunctions();
            else if (mg)
               col = mg->GetListOfFunctions();
            else if (scatter->GetGraph())
               col = scatter->GetGraph()->GetListOfFunctions();
            if (!col)
               obj = nullptr;
            else if (kind.compare(0,5,"func_") == 0)
               obj = col->FindObject(funcname.c_str());
            else
               obj = col->At(std::stoi(funcname));
         } else if (kind.compare("polargram") == 0) {
            auto polar = dynamic_cast<TGraphPolar *>(obj);
            obj = polar ? polar->GetPolargram() : nullptr;
         } else if (kind.compare(0,7,"graphs_") == 0) {
            TList *graphs = mg ? mg->GetListOfGraphs() : nullptr;
            obj = graphs ? graphs->At(std::stoi(kind.substr(7))) : nullptr;
         } else if (kind.compare(0,6,"hists_") == 0) {
            TList *hists = hs ? hs->GetHists() : nullptr;
            obj = hists ? hists->At(std::stoi(kind.substr(6))) : nullptr;
         } else if (kind.compare(0,6,"stack_") == 0) {
            auto stack = hs ? hs->GetStack() : nullptr;
            obj = stack ? stack->At(std::stoi(kind.substr(6))) : nullptr;
         } else if (kind.compare(0,7,"member_") == 0) {
            auto member = kind.substr(7);
            auto offset = obj->IsA() ? obj->IsA()->GetDataMemberOffset(member.c_str()) : 0;
            obj = (offset > 0) ? *((TObject **)((char *) obj + offset)) : nullptr;
         } else {
             obj = nullptr;
         }
      }
 
      if (!search_hist || obj)
         return obj;
   }
 
   return nullptr;
}
 
//////////////////////////////////////////////////////////////////////////////////////////////////
/// Static method to create TWebCanvas instance
/// Used by plugin manager
 
TCanvasImp *TWebCanvas::NewCanvas(TCanvas *c, const char *name, Int_t x, Int_t y, UInt_t width, UInt_t height)
{
   Bool_t readonly = gEnv->GetValue("WebGui.FullCanvas", (Int_t) 1) == 0;
 
   auto imp = new TWebCanvas(c, name, x, y, width, height, readonly);
 
   c->fWindowTopX = x;
   c->fWindowTopY = y;
   c->fWindowWidth = width;
   c->fWindowHeight = height;
   if (!gROOT->IsBatch() && (height > 25))
      height -= 25;
   c->fCw = width;
   c->fCh = height;
 
   return imp;
}