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Date Posted: 19:27:46 03/18/02 Mon
Author: Michel
Subject: Re: memory leak in TRubberBandMouseHandler
In reply to: Mark Chambers 's message, "memory leak in TRubberBandMouseHandler" on 11:07:10 03/17/02 Sun


Hi Mark,

I would check to make sure you have version 1.1. In version 1.1, the method TRubberBandMouseHandler.MouseUp is,

procedure TRubberbandMouseHandler.MouseUp(
const Button : TMouseButton;
const Shift : TShiftState;
const X, Y : Integer );
begin
if FMouseIsDown then
begin
if SelectionActive then
begin
if FX2 < FX1 then
SwapIntegers(FX2, FX1);

if FY2 < FY1 then
SwapIntegers(FY2, FY1);
end;

if FBandVisible and
(FX1 = FX2) and
(FY1 = FY2) then
FBandVisible := False;

FMouseIsDown := False;
end;
end;

I don't quite recall when this was changed. I think in version 1.1 there were major changes to the rubber band mouse handler.

Best regards,

Michel

>Hi - the method TRubberBandMouseHandler.MouseUp
>allocates a DibGraphic object in order to pass it to
>the callback method. It is then up to the callback
>method to delete it. (This isn't generally a good
>idea - responsibilty for destruction should rest with
>the creator) Unfortunately, MouseUp creates the
>DibGraphic regardless of whether or not there is a
>callback method - and if there isn't, then it never
>gets cleanedup. My suggested fix follows.
>
>Regards,
>Mark Chambers
>
>procedure TRubberBandMouseHandler.MouseUp(const
>Button: TMouseButton;
> const Shift: TShiftState; const X, Y: Integer);
>var
> DibGraphic: TDibGraphic;
> Temp: integer;
>begin
> inherited;
>
> FBottom:= Y;
> FRight:= X;
>
>
> if (FTop <> FBottom) and (FLeft <> FRight) then begin
>
> if FTop > FBottom then begin
> Temp:= FTop;
> FTop:= FBottom;
> FBottom:= Temp;
> end;
>
> if FLeft > FRight then begin
> Temp:= FLeft;
> FLeft:= FRight;
> FRight:= Temp;
> end;
>
> if Assigned(FCallback) then begin
> DibGraphic:= TDibGraphic.Create;
> try
> DibGraphic.NewImage(
> FRight - FLeft, FBottom - FTop,
> (FImageScrollBox.FImage.Picture.Graphic as
>TDibGraphic).ImageFormat,
> @(FImageScrollBox.FImage.Picture.Graphic
>as TDibGraphic).Palette,
> (FImageScrollBox.FImage.Picture.Graphic as
>TDibGraphic).XDotsPerInch,
> (FImageScrollBox.FImage.Picture.Graphic as
>TDibGraphic).YDotsPerInch
> );
>
> DibGraphic.Canvas.CopyRect(
> Rect(0, 0, FRight - FLeft - 1, FBottom -
>FTop - 1),
> (FImageScrollBox.FImage.Picture.Graphic as
>TDibGraphic).Canvas,
> Rect(FLeft, FTop, FRight, FBottom)
> );
>
> FCallback(FTop, FLeft, FBottom, FRight,
>DibGraphic);
> finally
> // DibGraphic.Free;
> // not freed as it might be kept by the
>callback routine.
> // this is not a good practice! We should free
>it ourselves (and
> // expect the CallBack method to copy it, or
>just pass the
> // FImageScrollBox.FImage.Picture.Graphic (or
>just FImageScrollBox)
> // and let the callback do what it wants.
> // I think this should be changed to at least
>free the
> // DibGraphic, but the I don't have to manage
>all
> // the complaints that will ensue!
>
> end;
> end;
> end;
> DrawRubberBand;
> Screen.Cursor:= FScreenCursor;
>end;

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