Update and fix documentation.

Author: rlalik

documentation/doxygen/images/canvas_divide.png

@@ -1225,13 +1225,12 @@ Int_t TPad::DistancetoPrimitive(Int_t px, Int_t py)
 /// Automatic pad generation by division.
 ///
 ///  - The current canvas is divided in nx by ny equal divisions (pads).
-///  - xmargin defines the horizontal spacing around each pad as a percentage of the canvas
-///    width. Therefore, the distance between two adjacent pads along the x-axis is equal
-///    to twice the xmargin value.
-///  - ymargin defines the vertical spacing around each pad as a percentage of the canvas
-///    height. Therefore, the distance between two adjacent pads along the y-axis is equal
-///    to twice the ymargin value.
+///  - xmargin defines the horizontal spacing between each pad as a percentage of the canvas
+///    width.
+///  - ymargin defines the vertical spacing between each pad as a percentage of the canvas
+///    height.
 ///  - color is the color of the new pads. If 0, color is the canvas color.
+///  - All pads are contained within the inner area defined by the canvas margins.
 ///
 /// Pads are automatically named `canvasname_n` where `n` is the division number
 /// starting from top left pad.
@@ -1240,6 +1239,18 @@ Int_t TPad::DistancetoPrimitive(Int_t px, Int_t py)
 ///
 /// \image html gpad_pad3.png
 ///
+/// Example if:
+/// /// ~~~ {.cpp}
+/// c->SetLeftMargin(0.30);
+/// c->SetBottomMargin(0.10);
+/// c->SetRightMargin(0.05);
+/// c->SetTopMargin(0.10);
+/// c->Divide(nx, ny, 0.03, 0.05, 46);
+/// ~~~
+/// \image html canvas_divide.png
+///
+/// More examples are in `tutorials/visualisation/graphics/canvas_divide_example.C`
+///
 /// Once a pad is divided into sub-pads, one can set the current pad
 /// to a subpad with a given division number as illustrated above
 /// with TPad::cd(subpad_number).

graf2d/gpad/src/TPad.cxx

@@ -18,20 +18,12 @@ void canvas_divide_example(int use_variant = 0)
    c->SetFillColor(19);
 
    if (use_variant == 0) {
-      c->SetLeftMargin(ml);
-      c->SetBottomMargin(mb);
-      c->SetRightMargin(mr);
-      c->SetTopMargin(mt);
-
+      c->SetMargin(ml, mr, mb, mt);
       c->Divide(nx, ny, 0.03, 0.05, 46);
    } else if (use_variant == 1) {
       c->Divide(nx, ny, 0.01, 0.01, 46);
    } else {
-      c->SetLeftMargin(0.01);
-      c->SetBottomMargin(0.01);
-      c->SetRightMargin(0.01);
-      c->SetTopMargin(0.01);
-
+      c->SetMargin(0.01, 0.01, 0.01, 0.01);
       c->Divide(nx, ny, 0.02, 0.02, 46);
    }
 
@@ -121,11 +113,6 @@ void canvas_divide_example(int use_variant = 0)
    text.SetTextFont(102);
    text.SetNDC(1);
 
-   if (use_variant == 0) {
-      text.DrawText(0.01, 0.90, "c->SetLeftMargin(ml);");
-      text.DrawText(0.01, 0.85, "c->SetBottomMargin(mb);");
-      text.DrawText(0.01, 0.80, "c->SetRightMargin(mr);");
-      text.DrawText(0.01, 0.75, "c->SetTopMargin(mt);");
-      text.DrawText(0.01, 0.70, "c->Divide(nx, ny, xm, ym);");
-   }
+   text.DrawText(0.01, 0.97, "c->SetMargin(ml, mr, mb, mt);");
+   text.DrawText(0.01, 0.94, "c->Divide(nx, ny, xm, ym);");
 }