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Date Posted: 22:13:23 03/17/00 Fri
Author: Michel
Subject: Re: Help Stack Overflow
In reply to: CJ 's message, "Help" on 07:58:39 03/17/00 Fri


Hi,

There is a problem with unnecessary recursive calls to TImageScrollBox.Redraw.

What I have done is added a Boolean variable in the
TImageScrollBox protected section, FRedrawInProgress. I've have noticed that in some cases, there were a few recursive calls creating unecessary redraws. Here is the current
implementation I have:

procedure TImageScrollBox.Redraw( const GraphicChanged : Boolean );
begin
if (Self.Parent = nil) or not Self.Visible then
Exit;

if FRedrawInProgress then
Exit;

FRedrawInProgress := True;
try
if FSourceGraphic.IsEmpty then
begin
DisplayedGraphic.Clear;

Self.HorzScrollBar.Visible := False;
Self.VertScrollBar.Visible := False;

FImage.Visible := False;
Exit;
end;

if GraphicChanged then
begin
if FSourceGraphic.ImageFormat = ifBlackWhite then
FAntiAliasTransform.ApplyOnDest(FSourceGraphic, FAntiAliasedGraphic)
else
FAntiAliasedGraphic.Clear;
end;

if FSourceGraphic.ImageFormat = ifBlackWhite then
RedrawBW
else
RedrawNotBW;

if Assigned(FOnRedraw) then
FOnRedraw(FSourceGraphic);

if not FImage.Visible then
FImage.Visible := True;

finally
FRedrawInProgress := False;
end;
end;

I'm sorry for the formatting, it's hard to allign properly in the browser.

If need DCU evaluation units, please email me directly and I will send you an update.

Best regards,

Michel


> Hello Michel!
> I use ImageScrollBox component in a dynamic
> window(in the window have a StatusBar), when I Set
> ImageScrollBox.ZoomMode := zmFitHeight, the
> Application then "Stack overflow". Why?
>
> Thanks!

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