[Lazarus] Customizing image preview in TOpenPictureDialog

[Luca Olivetti]

Hello,

in order to show animated gif, png and webp images, I subclassed the 
TOpenPictureDialog and overrode the ClearPreview and UpdatePreview methods.

Those methods are called but the picture shown isn't the one I try to 
show in my overridden UpdatePreview (e.g. I load a different picture 
that the one selected but the dialog happily shows the selected one, or 
e.g.2 I added support for webp images and under windows they don't show, 
they do with qt5 but they show also with the standard control).

What's the correct method to customize the preview?

Bye
-- 
Luca Olivetti
Wetron Automation Technology http://www.wetron.es/
Tel. +34 93 5883004 (Ext.3010)  Fax +34 93 5883007