Canvas and Pad Management

{
//
// To see the output of this macro, click  here 
// One of the first actions in a ROOT session is the creation of a Canvas.
// Here we create a Canvas named "c1"
//
  gROOT.Reset();
  c1 = new TCanvas("c1","Canvas Example",200,10,600,480);

  gBenchmark->Start("canvas");
//
// Inside this canvas, we create two pads
//
  TPad pad1("pad1","This is pad1",0.05,0.52,0.95,0.97);
  TPad pad2("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("pad21","First subpad of pad2",0.02,0.05,0.48,0.95,17,3);
  TPad pad22("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(0.5,yt1,"ROOT");
  t1.SetTextAlign(22);
  t1.SetTextSize(0.05);
  t1.Draw();
  TLine line1(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(0.05,0.70,0.50,0.10);
  line2.SetLineWidth(4);
  line2.SetLineColor(5);
  line2.Draw();
//
  pad21.cd();
  TText t21(0.05,0.8,"This is pad21");
  t21.SetTextSize(0.1);
  t21.Draw();
  float xp2 = 0.5;
  float yp2 = 0.4;
  TPavesText paves(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(0.05,0.8,"This is pad22");
  t22.SetTextSize(0.1);
  t22.Draw();
  float xlc = 0.01;
  float ylc = 0.01;
  TPaveLabel label(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");
//
// 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, one can move, grow,shrink a pad.
// A text can be moved.
// A line can be moved or its end points can be modified.
// One can move, grow and shrink PaveLabels and PavesText.
// 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.
	
}