From: Renate Schaaf <renates@xmission.com>
Subject: Re: BitBlt Question - here is code
Date: 06 Feb 2000 00:00:00 GMT
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Afterthought: Why not let windows do the updating? It knows how to
paint the original form, anyways. Remembering a tip by Robert Rossmair
from last week, I tried the following, and it works (This way you don't
need the OldBG bitmap at all anymore):

procedure TForm1.RestoreBG(NewX, NewY: Integer);
var
  DC: HDC;
  R:TRect;
begin
  DC := Self.Handle;
  if NewY > OffsetY then
  begin
    R:=Rect(OffsetX, OffSetY, OffsetX+SourceW, NewY);
    InvalidateRect(DC, @R,True);
  end;
  if NewY < OffsetY then
  begin
    R:=Rect(OffsetX, NewY + SourceH, OffsetX+SourceW, OffsetY+SourceH);
    InvalidateRect(DC, @R,True);
  end;
  if NewX > OffsetX then
  begin
    R:=Rect(OffsetX, OffsetY, NewX, OffsetY+SourceH);
    InvalidateRect(DC, @R,True);
  end;
  if NewX < OffsetX then
  begin
    R:=Rect(NewX + SourceW, OffsetY, OffsetX+SourceW, OffsetY+SourceH);
    InvalidateRect(DC, @R,True);
  end;
end;

Renate