Logo ROOT  
Reference Guide
triangles.C File Reference

Detailed Description

View in nbviewer Open in SWAN Generate small triangles randomly in the canvas.

Each triangle has a unique id and a random color in the color palette

root > .x triangles.C

Then click on any triangle. A message showing the triangle number and its color will be printed.

void triangles(Int_t ntriangles=50) {
TCanvas *c1 = new TCanvas("c1","triangles",10,10,700,700);
Double_t dx = 0.2; Double_t dy = 0.2;
Double_t x[4],y[4];
Int_t ci;
for (Int_t i=0;i<ntriangles;i++) {
x[0] = r.Uniform(.05,.95); y[0] = r.Uniform(.05,.95);
x[1] = x[0] + dx*r.Rndm(); y[1] = y[0] + dy*r.Rndm();
x[2] = x[1] - dx*r.Rndm(); y[2] = y[1] - dy*r.Rndm();
x[3] = x[0]; y[3] = y[0];
TPolyLine *pl = new TPolyLine(4,x,y);
ci = ncolors*r.Rndm();
c = gROOT->GetColor(TColor::GetColorPalette(ci));
void TriangleClicked() {
//this action function is called whenever you move the mouse
//it just prints the id of the picked triangle
//you can add graphics actions instead
int event = gPad->GetEvent();
if (event != 11) return; //may be comment this line
TObject *select = gPad->GetSelected();
if (!select) return;
if (select->InheritsFrom(TPolyLine::Class())) {
TPolyLine *pl = (TPolyLine*)select;
printf("You have clicked triangle %d, color=%d\n",
#define c(i)
Definition: RSha256.hxx:101
int Int_t
Definition: RtypesCore.h:45
double Double_t
Definition: RtypesCore.h:59
Option_t Option_t TPoint TPoint const char GetTextMagnitude GetFillStyle GetLineColor GetLineWidth GetMarkerStyle GetTextAlign GetTextColor GetTextSize void char Point_t Rectangle_t WindowAttributes_t Float_t r
#define gROOT
Definition: TROOT.h:404
R__EXTERN TStyle * gStyle
Definition: TStyle.h:414
#define gPad
Definition: TVirtualPad.h:288
virtual Color_t GetFillColor() const
Return the fill area color.
Definition: TAttFill.h:30
virtual void SetFillColor(Color_t fcolor)
Set the fill area color.
Definition: TAttFill.h:37
The Canvas class.
Definition: TCanvas.h:23
The color creation and management class.
Definition: TColor.h:19
static Int_t GetColorPalette(Int_t i)
Static function returning the color number i in current palette.
Definition: TColor.cxx:1450
Mother of all ROOT objects.
Definition: TObject.h:37
virtual UInt_t GetUniqueID() const
Return the unique object id.
Definition: TObject.cxx:381
virtual Bool_t InheritsFrom(const char *classname) const
Returns kTRUE if object inherits from class "classname".
Definition: TObject.cxx:449
virtual void SetUniqueID(UInt_t uid)
Set the unique object id.
Definition: TObject.cxx:709
Defined by an array on N points in a 2-D space.
Definition: TPolyLine.h:23
void Draw(Option_t *option="") override
Draw this polyline with its current attributes.
Definition: TPolyLine.cxx:231
static TClass * Class()
This is the base class for the ROOT Random number generators.
Definition: TRandom.h:27
Int_t GetNumberOfColors() const
Return number of colors in the color palette.
Definition: TStyle.cxx:1123
Double_t y[n]
Definition: legend1.C:17
return c1
Definition: legend1.C:41
Double_t x[n]
Definition: legend1.C:17
Rene Brun

Definition in file triangles.C.