TGraphicControl.Canvas property
A clipped window into the parent Canvas.
Declaration
property Canvas: TCanvas read FCanvas;Description
Don't paint on the entire Canvas! Instead use the dimensions of the
TGraphicControl stored in the ClientRect.
If you ask for the Canvas.Width or Canvas.Height, you
are actually getting the Canvas dimensions from the Parent control.
See also
An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.