RCanvasPainter.cxx

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// Author: Axel Naumann <axel@cern.ch>
// Date: 2017-05-31
// Warning: This is part of the ROOT 7 prototype! It will change without notice. It might trigger earthquakes. Feedback is welcome!
 
/*************************************************************************
 * Copyright (C) 1995-2017, 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 "ROOT/RVirtualCanvasPainter.hxx"
#include "ROOT/RCanvas.hxx"
#include <ROOT/RLogger.hxx>
#include <ROOT/RDisplayItem.hxx>
#include <ROOT/RPadDisplayItem.hxx>
#include <ROOT/RMenuItems.hxx>
#include <ROOT/RWebDisplayArgs.hxx>
#include <ROOT/RWebDisplayHandle.hxx>
#include <ROOT/RWebWindow.hxx>
 
#include <memory>
#include <string>
#include <vector>
#include <list>
#include <thread>
#include <chrono>
#include <fstream>
#include <algorithm>
#include <cstdlib>
#include <regex>
 
#include "TList.h"
#include "TEnv.h"
#include "TROOT.h"
#include "TFile.h"
#include "TClass.h"
#include "TBufferJSON.h"
#include "TBase64.h"
 
using namespace std::string_literals;
using namespace ROOT::Experimental;
 
namespace {
RLogChannel &CanvasPainerLog() {
   static RLogChannel sLog("ROOT.CanvasPainer");
   return sLog;
}
}
 
/** \class RCanvasPainter
\ingroup webdisplay
New implementation of canvas painter, using RWebWindow
*/
 
namespace ROOT {
namespace Experimental {
 
class RCanvasPainter : public Internal::RVirtualCanvasPainter {
private:
   struct WebConn {
      unsigned fConnId{0};                 ///<! connection id
      std::list<std::string> fSendQueue;   ///<! send queue for the connection
      RDrawable::Version_t fSend{0};       ///<! indicates version send to connection
      RDrawable::Version_t fDelivered{0};  ///<! indicates version confirmed from canvas
      WebConn() = default;
      WebConn(unsigned connid) : fConnId(connid) {}
   };
 
   struct WebCommand {
      std::string fId;                                ///<! command identifier
      std::string fName;                              ///<! command name
      std::string fArg;                               ///<! command arguments
      enum { sInit, sRunning, sReady } fState{sInit}; ///<! true when command submitted
      bool fResult{false};                            ///<! result of command execution
      CanvasCallback_t fCallback{nullptr};            ///<! callback function associated with command
      unsigned fConnId{0};                            ///<! connection id for the command, when 0 specified command will be submitted to any available connection
      WebCommand() = default;
      WebCommand(const std::string &id, const std::string &name, const std::string &arg, CanvasCallback_t callback,
                 unsigned connid)
         : fId(id), fName(name), fArg(arg), fCallback(callback), fConnId(connid)
      {
      }
      void CallBack(bool res)
      {
         if (fCallback)
            fCallback(res);
         fCallback = nullptr;
      }
   };
 
   struct WebUpdate {
      uint64_t fVersion{0};                ///<! canvas version
      CanvasCallback_t fCallback{nullptr}; ///<! callback function associated with the update
      WebUpdate() = default;
      WebUpdate(uint64_t ver, CanvasCallback_t callback) : fVersion(ver), fCallback(callback) {}
      void CallBack(bool res)
      {
         if (fCallback)
            fCallback(res);
         fCallback = nullptr;
      }
   };
 
   typedef std::vector<Detail::RMenuItem> MenuItemsVector;
 
   RCanvas &fCanvas; ///<!  Canvas we are painting, *this will be owned by canvas
 
   std::shared_ptr<ROOT::RWebWindow> fWindow; ///!< configured display
 
   std::list<WebConn> fWebConn;                  ///<! connections list
   std::list<std::shared_ptr<WebCommand>> fCmds; ///<! list of submitted commands
   uint64_t fCmdsCnt{0};                         ///<! commands counter
 
   uint64_t fSnapshotDelivered{0};   ///<! minimal version delivered to all connections
   std::list<WebUpdate> fUpdatesLst; ///<! list of callbacks for canvas update
 
   int fJsonComp{23};                ///<! json compression for data send to client
 
   /// Disable copy construction.
   RCanvasPainter(const RCanvasPainter &) = delete;
 
   /// Disable assignment.
   RCanvasPainter &operator=(const RCanvasPainter &) = delete;
 
   void CancelUpdates();
 
   void CancelCommands(unsigned connid = 0);
 
   void CheckDataToSend();
 
   void ProcessData(unsigned connid, const std::string &arg);
 
   std::string CreateSnapshot(RDrawable::RDisplayContext &ctxt);
 
   std::shared_ptr<RDrawable> FindPrimitive(const RCanvas &can, const std::string &id, const RPadBase **subpad = nullptr);
 
   void CreateWindow();
 
   void SaveCreatedFile(std::string &reply);
 
   void FrontCommandReplied(const std::string &reply);
 
public:
   RCanvasPainter(RCanvas &canv);
 
   virtual ~RCanvasPainter();
 
   void CanvasUpdated(uint64_t ver, bool async, CanvasCallback_t callback) final;
 
   /// return true if canvas modified since last painting
   bool IsCanvasModified(uint64_t id) const final { return fSnapshotDelivered != id; }
 
   /// perform special action when drawing is ready
   void DoWhenReady(const std::string &name, const std::string &arg, bool async, CanvasCallback_t callback) final;
 
   bool ProduceBatchOutput(const std::string &fname, int width, int height) final;
 
   std::string ProduceJSON() final;
 
   void NewDisplay(const std::string &where) final;
 
   int NumDisplays() const final;
 
   std::string GetWindowAddr() const final;
 
   std::string GetWindowUrl(bool remote) final;
 
   void Run(double tm = 0.) final;
 
   bool AddPanel(std::shared_ptr<ROOT::RWebWindow>) final;
 
   void SetClearOnClose(const std::shared_ptr<void> &) final;
 
   /** \class CanvasPainterGenerator
          Creates RCanvasPainter objects.
        */
 
   class GeneratorImpl : public Generator {
   public:
      /// Create a new RCanvasPainter to paint the given RCanvas.
      std::unique_ptr<RVirtualCanvasPainter> Create(RCanvas &canv) const override
      {
         return std::make_unique<RCanvasPainter>(canv);
      }
      ~GeneratorImpl() = default;
 
      /// Set RVirtualCanvasPainter::fgGenerator to a new GeneratorImpl object.
      static void SetGlobalPainter()
      {
         if (GetGenerator()) {
            R__LOG_ERROR(CanvasPainerLog()) << "Generator is already set! Skipping second initialization.";
            return;
         }
         GetGenerator().reset(new GeneratorImpl());
      }
 
      /// Release the GeneratorImpl object.
      static void ResetGlobalPainter() { GetGenerator().reset(); }
   };
};
 
} // namespace Experimental
} // namespace ROOT
 
struct TNewCanvasPainterReg {
   TNewCanvasPainterReg() { RCanvasPainter::GeneratorImpl::SetGlobalPainter(); }
   ~TNewCanvasPainterReg() { RCanvasPainter::GeneratorImpl::ResetGlobalPainter(); }
} newCanvasPainterReg;
 
 
////////////////////////////////////////////////////////////////////////////////
/// Constructor
 
RCanvasPainter::RCanvasPainter(RCanvas &canv) : fCanvas(canv)
{
   auto comp = gEnv->GetValue("WebGui.JsonComp", -1);
   if (comp >= 0) fJsonComp = comp;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Destructor
 
RCanvasPainter::~RCanvasPainter()
{
   CancelCommands();
   CancelUpdates();
   if (fWindow)
      fWindow->CloseConnections();
}
 
////////////////////////////////////////////////////////////////////////////////
/// Cancel all pending Canvas::Update()
 
void RCanvasPainter::CancelUpdates()
{
   fSnapshotDelivered = 0;
   for (auto &item: fUpdatesLst)
      item.fCallback(false);
   fUpdatesLst.clear();
}
 
////////////////////////////////////////////////////////////////////////////////
/// Cancel command execution on provided connection
/// All commands are cancelled, when connid === 0
 
void RCanvasPainter::CancelCommands(unsigned connid)
{
   std::list<std::shared_ptr<WebCommand>> remainingCmds;
 
   for (auto &&cmd : fCmds) {
      if (!connid || (cmd->fConnId == connid)) {
         cmd->CallBack(false);
         cmd->fState = WebCommand::sReady;
      } else {
         remainingCmds.emplace_back(std::move(cmd));
      }
   }
 
   std::swap(fCmds, remainingCmds);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Check if canvas need to send data to the clients
 
void RCanvasPainter::CheckDataToSend()
{
   uint64_t min_delivered = 0;
   bool is_any_send = true;
   int loopcnt = 0;
 
   while (is_any_send && (++loopcnt < 10)) {
 
      is_any_send = false;
 
      for (auto &conn : fWebConn) {
 
         if (conn.fDelivered && (!min_delivered || (min_delivered < conn.fDelivered)))
            min_delivered = conn.fDelivered;
 
         // flag indicates that next version of canvas has to be send to that client
         bool need_send_snapshot = (conn.fSend != fCanvas.GetModified()) && (conn.fDelivered == conn.fSend);
 
         // ensure place in the queue for the send snapshot operation
         if (need_send_snapshot && (loopcnt == 0))
            if (std::find(conn.fSendQueue.begin(), conn.fSendQueue.end(), ""s) == conn.fSendQueue.end())
               conn.fSendQueue.emplace_back(""s);
 
         // check if direct data sending is possible
         if (!fWindow->CanSend(conn.fConnId, true))
            continue;
 
         TString buf;
 
         if (conn.fDelivered && !fCmds.empty() && (fCmds.front()->fState == WebCommand::sInit) &&
               ((fCmds.front()->fConnId == 0) || (fCmds.front()->fConnId == conn.fConnId))) {
 
            auto &cmd = fCmds.front();
            cmd->fState = WebCommand::sRunning;
            cmd->fConnId = conn.fConnId; // assign command to the connection
            buf = "CMD:";
            buf.Append(cmd->fId);
            buf.Append(":");
            buf.Append(cmd->fName);
 
         } else if (!conn.fSendQueue.empty()) {
 
            buf = conn.fSendQueue.front().c_str();
            conn.fSendQueue.pop_front();
 
            // empty string reserved for sending snapshot, if it no longer required process next entry
            if (!need_send_snapshot && (buf.Length() == 0) && !conn.fSendQueue.empty()) {
               buf = conn.fSendQueue.front().c_str();
               conn.fSendQueue.pop_front();
            }
         }
 
         if ((buf.Length() == 0) && need_send_snapshot) {
            buf = "SNAP:";
            buf += TString::ULLtoa(fCanvas.GetModified(), 10);
            buf += ":";
 
            RDrawable::RDisplayContext ctxt(&fCanvas, &fCanvas, conn.fSend);
            ctxt.SetConnection(conn.fConnId, (conn.fConnId == fWebConn.begin()->fConnId));
 
            buf += CreateSnapshot(ctxt);
 
            conn.fSend = fCanvas.GetModified();
         }
 
         if (buf.Length() > 0) {
            // sending of data can be moved into separate thread - not to block user code
            fWindow->Send(conn.fConnId, buf.Data());
            is_any_send = true;
         }
      }
   }
 
   // if there are updates submitted, but all connections disappeared - cancel all updates
   if (fWebConn.empty() && fSnapshotDelivered)
      return CancelUpdates();
 
   if (fSnapshotDelivered != min_delivered) {
      fSnapshotDelivered = min_delivered;
 
      if (fUpdatesLst.size() > 0)
         fUpdatesLst.erase(std::remove_if(fUpdatesLst.begin(), fUpdatesLst.end(), [this](WebUpdate &item) {
            if (item.fVersion > fSnapshotDelivered)
               return false;
            item.CallBack(true);
            return true;
         }));
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Method invoked when canvas should be updated on the client side
/// Depending from delivered status, each client will received new data
 
void RCanvasPainter::CanvasUpdated(uint64_t ver, bool async, CanvasCallback_t callback)
{
   if (fWindow)
      fWindow->Sync();
 
   if (ver && fSnapshotDelivered && (ver <= fSnapshotDelivered)) {
      // if given canvas version was already delivered to clients, can return immediately
      if (callback)
         callback(true);
      return;
   }
 
   if (!fWindow || !fWindow->HasConnection(0, false)) {
      if (callback)
         callback(false);
      return;
   }
 
   CheckDataToSend();
 
   if (callback)
      fUpdatesLst.emplace_back(ver, callback);
 
   // wait that canvas is painted
   if (!async) {
      fWindow->WaitForTimed([this, ver](double) {
 
         if (fSnapshotDelivered >= ver)
            return 1;
 
         // all connections are gone
         if (fWebConn.empty() && !fWindow->HasConnection(0, false))
            return -2;
 
         // time is not important - timeout handle before
         // if (tm > 100) return -3;
 
         // continue waiting
         return 0;
      });
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Perform special action when drawing is ready
 
void RCanvasPainter::DoWhenReady(const std::string &name, const std::string &arg, bool async,
                                                     CanvasCallback_t callback)
{
   // ensure that window exists
   CreateWindow();
 
   unsigned connid = 0;
 
   if (arg == "AddPanel") {
      // take first connection to add panel
      connid = fWindow->GetConnectionId();
   } else {
      // create batch job to execute action
      // connid = fWindow->MakeBatch();
   }
 
   if (!connid) {
      if (callback)
         callback(false);
      return;
   }
 
   auto cmd = std::make_shared<WebCommand>(std::to_string(++fCmdsCnt), name, arg, callback, connid);
   fCmds.emplace_back(cmd);
 
   CheckDataToSend();
 
   if (async) return;
 
   int res = fWindow->WaitForTimed([this, cmd](double) {
      if (cmd->fState == WebCommand::sReady) {
         R__LOG_DEBUG(0, CanvasPainerLog()) << "Command " << cmd->fName << " done";
         return cmd->fResult ? 1 : -1;
      }
 
      // connection is gone
      if (!fWindow->HasConnection(cmd->fConnId, false))
         return -2;
 
      // time is not important - timeout handle before
      // if (tm > 100.) return -3;
 
      return 0;
   });
 
   if (res <= 0)
      R__LOG_ERROR(CanvasPainerLog()) << name << " fail with " << arg << " result = " << res;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Produce batch output, using chrome headless mode with DOM dump
 
bool RCanvasPainter::ProduceBatchOutput(const std::string &fname, int width, int height)
{
   auto len = fname.length();
   bool is_json = (len > 4) && ((fname.compare(len-4,4,".json") == 0) || (fname.compare(len-4,4,".JSON") == 0));
 
   // do not try to produce image if current settings not allowing this
   if (!is_json && !RWebDisplayHandle::CanProduceImages())
      return false;
 
   RDrawable::RDisplayContext ctxt(&fCanvas, &fCanvas, 0);
   ctxt.SetConnection(1, true);
 
   auto snapshot = CreateSnapshot(ctxt);
 
   if (is_json) {
      std::ofstream f(fname);
      if (!f) {
         R__LOG_ERROR(CanvasPainerLog()) << "Fail to open file " << fname << " to store canvas snapshot";
         return false;
      }
      R__LOG_INFO(CanvasPainerLog()) << "Store canvas in " << fname;
      f << snapshot;
      return true;
   }
 
   return RWebDisplayHandle::ProduceImage(fname, snapshot, width, height);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Produce JSON for the canvas
 
std::string RCanvasPainter::ProduceJSON()
{
   RDrawable::RDisplayContext ctxt(&fCanvas, &fCanvas, 0);
   ctxt.SetConnection(1, true);
 
   return CreateSnapshot(ctxt);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Process data from the client
 
void RCanvasPainter::ProcessData(unsigned connid, const std::string &arg)
{
   auto conn =
      std::find_if(fWebConn.begin(), fWebConn.end(), [connid](WebConn &item) { return item.fConnId == connid; });
 
   if (conn == fWebConn.end())
      return; // no connection found
 
   std::string cdata;
 
   auto check_header = [&arg, &cdata](const std::string &header) {
      if (arg.compare(0, header.length(), header) != 0)
         return false;
      cdata = arg.substr(header.length());
      return true;
   };
 
   // R__LOG_DEBUG(0, CanvasPainerLog()) << "from client " << connid << " got data len:" << arg.length() << " val:" <<
   // arg.substr(0,30);
 
   if (check_header("READY")) {
 
   } else if (check_header("SNAPDONE:")) {
      conn->fDelivered = (uint64_t)std::stoll(cdata); // delivered version of the snapshot
   } else if (arg == "QUIT") {
      // use window manager to correctly terminate http server and ROOT session
      fWindow->TerminateROOT();
      return;
   } else if (arg == "START_BROWSER") {
      gROOT->ProcessLine("auto br = std::make_shared<ROOT::RBrowser>();br->ClearOnClose(br);");
 
   } else if (arg == "RELOAD") {
      conn->fSend = 0; // reset send version, causes new data sending
   } else if (arg == "INTERRUPT") {
      gROOT->SetInterrupt();
   } else if (check_header("REPLY:")) {
      const char *sid = cdata.c_str();
      const char *separ = strchr(sid, ':');
      std::string id;
      if (separ)
         id.append(sid, separ - sid);
      if (fCmds.empty()) {
         R__LOG_ERROR(CanvasPainerLog()) << "Get REPLY without command";
      } else if (fCmds.front()->fState != WebCommand::sRunning) {
         R__LOG_ERROR(CanvasPainerLog()) << "Front command is not running when get reply";
      } else if (fCmds.front()->fId != id) {
         R__LOG_ERROR(CanvasPainerLog()) << "Mismatch with front command and ID in REPLY";
      } else {
         FrontCommandReplied(separ + 1);
      }
   } else if (check_header("SAVE:")) {
      SaveCreatedFile(cdata);
   } else if (check_header("PRODUCE:")) {
      R__LOG_DEBUG(0, CanvasPainerLog()) << "Create file " << cdata;
 
      TFile *f = TFile::Open(cdata.c_str(), "RECREATE");
      f->WriteObject(&fCanvas, "Canvas");
      delete f;
   } else if (ROOT::RWebWindow::IsFileDialogMessage(arg)) {
 
      ROOT::RWebWindow::EmbedFileDialog(fWindow, connid, arg);
 
   } else if (check_header("REQ:")) {
      auto req = TBufferJSON::FromJSON<RDrawableRequest>(cdata);
      if (req) {
         std::shared_ptr<RDrawable> drawable;
         req->GetContext().SetCanvas(&fCanvas);
         if (req->GetId().empty() || (req->GetId() == "canvas")) {
            req->GetContext().SetPad(nullptr); // no subpad for the canvas
            req->GetContext().SetDrawable(&fCanvas, 0); // drawable is canvas itself
         } else {
            const RPadBase *subpad = nullptr;
            drawable = FindPrimitive(fCanvas, req->GetId(), &subpad);
            req->GetContext().SetPad(const_cast<RPadBase *>(subpad));
            req->GetContext().SetDrawable(drawable.get(), 0);
         }
 
         req->GetContext().SetConnection(connid, conn == fWebConn.begin());
 
         auto reply = req->Process();
 
         if (req->ShouldBeReplyed()) {
            if (!reply)
               reply = std::make_unique<RDrawableReply>();
 
            reply->SetRequestId(req->GetRequestId());
 
            auto json = TBufferJSON::ToJSON(reply.get(), TBufferJSON::kNoSpaces);
            conn->fSendQueue.emplace_back("REPL_REQ:"s + json.Data());
         }
 
         // real update will be performed by CheckDataToSend()
         if (req->NeedCanvasUpdate())
            fCanvas.Modified();
 
      } else {
         R__LOG_ERROR(CanvasPainerLog()) << "Fail to parse RDrawableRequest";
      }
   } else if (check_header("RESIZED:")) {
      auto sz = TBufferJSON::FromJSON<std::vector<int>>(cdata);
      if (sz && sz->size() == 2) {
         fCanvas.SetWidth(sz->at(0));
         fCanvas.SetHeight(sz->at(1));
      }
   } else if (check_header("CLEAR")) {
      fCanvas.Wipe();
      fCanvas.Modified();
   } else {
      R__LOG_ERROR(CanvasPainerLog()) << "Got not recognized message" << arg;
   }
 
   CheckDataToSend();
}
 
////////////////////////////////////////////////////////////////////////////////
/// Create web window for canvas
 
void RCanvasPainter::CreateWindow()
{
   if (fWindow) return;
 
   fWindow = ROOT::RWebWindow::Create();
   fWindow->SetConnLimit(0); // allow any number of connections
   fWindow->SetDefaultPage("file:rootui5sys/canv/canvas.html");
   fWindow->SetCallBacks(
      // connect
      [this](unsigned connid) {
         fWebConn.emplace_back(connid);
         CheckDataToSend();
      },
      // data
      [this](unsigned connid, const std::string &arg) { ProcessData(connid, arg); },
      // disconnect
      [this](unsigned connid) {
         auto conn =
            std::find_if(fWebConn.begin(), fWebConn.end(), [connid](WebConn &item) { return item.fConnId == connid; });
 
         if (conn != fWebConn.end()) {
            fWebConn.erase(conn);
            CancelCommands(connid);
         }
      });
   // fWindow->SetGeometry(500,300);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Create new display for the canvas
/// See ROOT::RWebWindowsManager::Show() docu for more info
 
void RCanvasPainter::NewDisplay(const std::string &where)
{
   CreateWindow();
 
   int width = fCanvas.GetWidth();
   int height = fCanvas.GetHeight();
 
   RWebDisplayArgs args(where);
 
   if ((width > 10) && (height > 10)) {
      // extra size of browser window header + ui5 menu
      args.SetWidth(width + 4);
      args.SetHeight(height + 36);
   }
 
   args.SetWidgetKind("RCanvas");
 
   fWindow->Show(args);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Returns number of connected displays
 
int RCanvasPainter::NumDisplays() const
{
   if (!fWindow) return 0;
 
   return fWindow->NumConnections();
}
 
////////////////////////////////////////////////////////////////////////////////
/// Returns web window name
 
std::string RCanvasPainter::GetWindowAddr() const
{
   if (!fWindow) return "";
 
   return fWindow->GetAddr();
}
 
////////////////////////////////////////////////////////////////////////////////
/// Returns connection URL for web window
 
std::string RCanvasPainter::GetWindowUrl(bool remote)
{
   if (!fWindow) return "";
 
   return fWindow->GetUrl(remote);
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Add window as panel inside canvas window
 
bool RCanvasPainter::AddPanel(std::shared_ptr<ROOT::RWebWindow> win)
{
   if (gROOT->IsWebDisplayBatch())
      return false;
 
   if (!fWindow) {
      R__LOG_ERROR(CanvasPainerLog()) << "Canvas not yet shown in AddPanel";
      return false;
   }
 
   if (!fWindow->IsShown()) {
      R__LOG_ERROR(CanvasPainerLog()) << "Canvas window was not shown to call AddPanel";
      return false;
   }
 
   std::string addr = fWindow->GetRelativeAddr(win);
 
   if (addr.length() == 0) {
      R__LOG_ERROR(CanvasPainerLog()) << "Cannot attach panel to canvas";
      return false;
   }
 
   // connection is assigned, but can be refused by the client later
   // therefore handle may be removed later
 
   std::string cmd("ADDPANEL:");
   cmd.append(addr);
 
   /// one could use async mode
   DoWhenReady(cmd, "AddPanel", true, nullptr);
 
   return true;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Set handle to window which will be cleared when connection is closed
 
void RCanvasPainter::SetClearOnClose(const std::shared_ptr<void> &handle)
{
   if (fWindow)
      fWindow->SetClearOnClose(handle);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Create JSON representation of data, which should be send to the clients
/// Here server-side painting is performed - each drawable adds own elements in
/// so-called display list, which transferred to the clients
 
std::string RCanvasPainter::CreateSnapshot(RDrawable::RDisplayContext &ctxt)
{
   auto canvitem = std::make_unique<RCanvasDisplayItem>();
 
   fCanvas.DisplayPrimitives(*canvitem, ctxt);
 
   canvitem->SetTitle(fCanvas.GetTitle());
   canvitem->SetWindowSize(fCanvas.GetWidth(), fCanvas.GetHeight());
 
   canvitem->BuildFullId(""); // create object id which unique identify it via pointer and position in subpads
   canvitem->SetObjectID("canvas"); // for canvas itself use special id
 
   TBufferJSON json;
   json.SetCompact(fJsonComp);
 
   static std::vector<const TClass *> exclude_classes = {
      TClass::GetClass<RAttrMap::NoValue_t>(),
      TClass::GetClass<RAttrMap::BoolValue_t>(),
      TClass::GetClass<RAttrMap::IntValue_t>(),
      TClass::GetClass<RAttrMap::DoubleValue_t>(),
      TClass::GetClass<RAttrMap::StringValue_t>(),
      TClass::GetClass<RAttrMap>(),
      TClass::GetClass<RStyle::Block_t>(),
      TClass::GetClass<RPadPos>(),
      TClass::GetClass<RPadLength>(),
      TClass::GetClass<RPadExtent>(),
      TClass::GetClass<std::unordered_map<std::string,RAttrMap::Value_t*>>()
   };
 
   for (auto cl : exclude_classes)
      json.SetSkipClassInfo(cl);
 
   auto res = json.StoreObject(canvitem.get(), TClass::GetClass<RCanvasDisplayItem>());
 
   return std::string(res.Data());
}
 
////////////////////////////////////////////////////////////////////////////////
/// Find drawable in the canvas with specified id
/// Used to communicate with the clients, which does not have any pointer
 
std::shared_ptr<RDrawable>
RCanvasPainter::FindPrimitive(const RCanvas &can, const std::string &id, const RPadBase **subpad)
{
   std::string search = id;
   size_t pos = search.find("#");
   // exclude extra specifier, later can be used for menu and commands execution
   if (pos != std::string::npos)
      search.resize(pos);
 
   if (subpad) *subpad = can.FindPadForPrimitiveWithDisplayId(search);
 
   return can.FindPrimitiveByDisplayId(search);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Method called when GUI sends file to save on local disk
/// File data coded with base64 coding beside SVG format
 
void RCanvasPainter::SaveCreatedFile(std::string &reply)
{
   size_t pos = reply.find(":");
   if ((pos == std::string::npos) || (pos == 0)) {
      R__LOG_ERROR(CanvasPainerLog()) << "SaveCreatedFile does not found ':' separator";
      return;
   }
 
   std::string fname(reply, 0, pos);
   reply.erase(0, pos + 1);
 
   Bool_t isSvg = (fname.length() > 4) && ((fname.rfind(".svg") == fname.length()-4) || (fname.rfind(".SVG") == fname.length()-4));
 
   int file_len = 0;
 
   std::ofstream ofs(fname, std::ios::binary);
   if (isSvg) {
      ofs << reply;
      file_len = reply.length();
   } else {
      TString binary = TBase64::Decode(reply.c_str());
      ofs.write(binary.Data(), binary.Length());
      file_len = binary.Length();
   }
   ofs.close();
 
   R__LOG_INFO(CanvasPainerLog()) << " Save file from GUI " << fname << " len " << file_len;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Process reply on the currently active command
 
void RCanvasPainter::FrontCommandReplied(const std::string &reply)
{
   auto cmd = fCmds.front();
   fCmds.pop_front();
 
   cmd->fState = WebCommand::sReady;
 
   bool result = false;
 
   if ((cmd->fName == "SVG") || (cmd->fName == "PNG") || (cmd->fName == "JPEG")) {
      if (reply.length() == 0) {
         R__LOG_ERROR(CanvasPainerLog()) << "Fail to produce image" << cmd->fArg;
      } else {
         TString content = TBase64::Decode(reply.c_str());
         std::ofstream ofs(cmd->fArg, std::ios::binary);
         ofs.write(content.Data(), content.Length());
         ofs.close();
         R__LOG_INFO(CanvasPainerLog()) << cmd->fName << " create file " << cmd->fArg << " length " << content.Length();
         result = true;
      }
   } else if (cmd->fName.find("ADDPANEL:") == 0) {
      R__LOG_DEBUG(0, CanvasPainerLog()) << "get reply for ADDPANEL " << reply;
      result = (reply == "true");
   } else {
      R__LOG_ERROR(CanvasPainerLog()) << "Unknown command " << cmd->fName;
   }
 
   cmd->fResult = result;
   cmd->CallBack(result);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Run canvas functionality for specified period of time
/// Required when canvas used not from the main thread
 
void RCanvasPainter::Run(double tm)
{
   if (fWindow) {
      fWindow->Run(tm);
   } else if (tm>0) {
      std::this_thread::sleep_for(std::chrono::milliseconds(int(tm*1000)));
   }
}