Logo ROOT   6.08/07
Reference Guide
canvas.C File Reference

Detailed Description

View in nbviewer Open in SWAN Example of primitives in a canvas.

One of the first actions in a ROOT session is the creation of a Canvas. Here we create a Canvas named "c1".

After having executed this macro, try now to point on any object on the screen: pad, text, lines, etc.

When the cursor points to sensitive areas in an object, the cursor shape changes and suggests the type of action that can be applied.

For example:

Point to an object and click the right mouse button to change attributes. Try to change the canvas size.

In the canvas "File" menu, select the option "Print" to produce a PostScript file with a copy of the canvas.

pict1_canvas.C.png
void canvas(){
TCanvas *c1 = new TCanvas("c1","Canvas Example",200,10,600,480);
gBenchmark->Start("canvas");
// Inside this canvas, we create two pads
TPad *pad1 = new TPad("pad1","This is pad1",0.05,0.52,0.95,0.97);
TPad *pad2 = new TPad("pad2","This is pad2",0.05,0.02,0.95,0.47);
pad1->SetFillColor(11);
pad2->SetFillColor(11);
pad1->Draw();
pad2->Draw();
// A pad may contain other pads and graphics objects.
// We set the current pad to pad2.
// Note that the current pad is always highlighted.
pad2->cd();
TPad *pad21 = new TPad("pad21","First subpad of pad2",0.02,0.05,0.48,0.95,17,3);
TPad *pad22 = new TPad("pad22","Second subpad of pad2",0.52,0.05,0.98,0.95,17,3);
pad21->Draw();
pad22->Draw();
// We enter some primitives in the created pads and set some attributes
pad1->cd();
float xt1 = 0.5;
float yt1 = 0.1;
TText *t1 = new TText(0.5,yt1,"ROOT");
t1->SetTextAlign(22);
t1->SetTextSize(0.05);
t1->Draw();
TLine *line1 = new TLine(0.05,0.05,0.80,0.70);
line1->SetLineWidth(8);
line1->SetLineColor(2);
line1->Draw();
line1->DrawLine(0.6,0.1,0.9,0.9);
TLine *line2 = new TLine(0.05,0.70,0.50,0.10);
line2->SetLineWidth(4);
line2->SetLineColor(5);
line2->Draw();
pad21->cd();
TText *t21 = new TText(0.05,0.8,"This is pad21");
t21->SetTextSize(0.1);
t21->Draw();
float xp2 = 0.5;
float yp2 = 0.4;
TPavesText *paves = new TPavesText(0.1,0.1,xp2,yp2);
paves->AddText("This is a PavesText");
paves->AddText("You can add new lines");
paves->AddText("Text formatting is automatic");
paves->SetFillColor(43);
paves->Draw();
pad22->cd();
TText *t22 = new TText(0.05,0.8,"This is pad22");
t22->SetTextSize(0.1);
t22->Draw();
float xlc = 0.01;
float ylc = 0.01;
TPaveLabel *label = new TPaveLabel(xlc, ylc, xlc+0.8, ylc+0.1,"This is a PaveLabel");
label->SetFillColor(24);
label->Draw();
// Modify object attributes in a loop
Int_t nloops = 50;
float dxp2 = (0.9-xp2)/nloops;
float dyp2 = (0.7-yp2)/nloops;
float dxlc = (0.1-xlc)/nloops;
float dylc = (0.4-xlc)/nloops;
float dxt1 = (0.5-xt1)/nloops;
float dyt1 = (0.8-yt1)/nloops;
float t10 = t1->GetTextSize();
float t1end = 0.3;
float t1ds = (t1end - t10)/nloops;
Int_t color = 0;
for (int i=0;i<nloops;i++) {
color++;
color %= 8;
line1->SetLineColor(color);
t1->SetTextSize(t10 + t1ds*i);
t1->SetTextColor(color);
t1->SetX(xt1+dxt1*i);
t1->SetY(yt1+dyt1*i);
pad1->Modified();
paves->SetX2NDC(xp2+dxp2*i);
paves->SetY2NDC(yp2+dyp2*i);
pad21->Modified();
label->SetX1NDC(xlc+dxlc*i);
label->SetY1NDC(ylc+dylc*i);
label->SetX2NDC(xlc+dxlc*i+0.8);
label->SetY2NDC(ylc+dylc*i+0.2);
pad22->Modified();
c1->Update();
}
gBenchmark->Show("canvas");
}
Author
Rene Brun

Definition in file canvas.C.