ImageEn Forum - ViewChanging event

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ViewChanging event

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Ronald Ruijs

Netherlands
24 Posts

Posted - Apr 16 2020 : 11:54:14

Hello,

I try to prevent "endless zoomout", resulting in very small image display, by limiting zoomfactor by overriding protected virtual ViewChanging(c: integer; newValue: Double) event.

From the doc, I see that c = 1 for Zoom change. but what is NewValue, and how do I stop zooming out infinitely? I expected that NewValue would be new desired zoomfactor. However, I get negative values for NewValue. Also, how should I prevent further processing? Should that be done by not calling inherited?

Best regards, Ronald

xequte

38222 Posts

Posted - Apr 20 2020 : 17:41:36

Hi Ronald

You should just use the OnZoomIn/Out events, e.g.


// Max zoom-out to 200%
Procedure Tform1.ImageEnView1ZoomOut(Sender: TObject; var NewZoom: Double);
Begin
  if NewZoom > 200 then
    NewZoom := 200;
End;

Nigel
Xequte Software
www.imageen.com

Ronald Ruijs

Netherlands
24 Posts

Posted - Apr 21 2020 : 16:51:06

Hi Nigel,

Thanks for the explanation, although using a TImageEnView descendant, I would prefer to "build-in" this behaviour by overriding protected methods, rather than using public properties.
What is the VieChanging intended use? I could not find a demo that uses it.

Regards, Ronald

xequte

38222 Posts

Posted - Apr 21 2020 : 18:03:07

Hi Ronald

I've changed the source so that NewValue is now a var parameter. This should work for you if you override the ViewChanging method. Please email me for the update.

Note: Change = 2 is for zoom changes.

Nigel
Xequte Software
www.imageen.com

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