Question

In this code I would expect a call to ReleaseDC to happen in MyCanvas.Free, but this code runs fine, how come?
And what happens to TCanvas’ own DC?

var GlobalDC: THandle;

procedure TForm1.FormCreate(Sender: TObject);
begin
   GlobalDC:= GetDC(0);
end;

function LoopMeOften(const X, Y: Integer): TColor;
var
  MyCanvas: TCanvas;
begin
  MyCanvas := TCanvas.Create;
  MyCanvas.Handle := GlobalDC;
  Result := GetPixel(MyCanvas.Handle, X, Y);
  MyCanvas.Free;
end;

Answer 1

TCanvas does not have its own DC, it neither acquires nor releases a DC. Its descendant TControlCanvas does.

From TCanvas.Handle Property

TCanvas does not own the HDC.
Applications must create an HDC and
set the Handle property. Applications
must release the HDC when the canvas
no longer needs it.