I have an application with a small status form that runs all of the time.
I made this form resizable by  using a MetaFile, and drawing the display
info on a TMetaFileCanvas.
This allows for easy resizing, and strech to fit.   The problem I am hiving
is loosing GDI resources, and finally unable to write to the canvas if the
form is covered by another form from any other application for a period of
time.  IF the form is left visible it never has any problems.  It is just
when it is covered by another form do the the problems begin to arise.    I
do test that the form is showing with "not StatForm.Showing" before I call
the display update procedure.  A timer is used to trigger the display update
about once a minute.

Code Snippit:

Procedure TStatForm.DoDisplay(Sender: TObject);

Const TMFW = 640;  // TMetaFileCanvas Width 640
      TMFH = 480;  // TMetafileCanvas Height 480

Var X,Y:Integer;
    TMFC:TMetaFileCanvas;
    TMF:TMetaFile;
    Rect:TRect;

begin
    Try
      TMF:=TMEtaFile.Create;
      TMF.Width:=TMFW;
      TMF.Height:=TMFH;
      Try
        TMFC:=TMetaFileCanvas.Create(TMF,0);
        TMFC.Font.Name:='Arial';

// build status display stuff here
// and write on the MetaFileCanvas

      Finally  // Try TMFC
        TMFC.Free;
      End;  // Try Finally

      Rect.Top:=0;
      Rect.Left:=0;
      Rect.Right:=ClientWidth;
      Rect.Bottom:=ClientHeight;
      StatForm.Canvas.FillRect(Rect);
      StatForm.Canvas.StretchDraw(Rect,TMF);
    Finally  // TRY tmf
      TMF.Free;
    End;  //Try Finally TMF