Graphic Delphi

Title: Fast way to clear a given canvas
Question: What is the fastest way to clear a given canvas?
Answer:
Use the Windows API function PatBlt().
Example:
procedure TForm1.Button1Click(Sender: TObject);
begin
PatBlt(Form1.Canvas.Handle,
0,
0,
Form1.ClientWidth,
Form1.ClientHeight,
WHITENESS);
end;