Re: [platform-swt-dev] Images

[Carolyn MacLeod <Carolyn_MacLeod@xxxxxxxxxx>]

Are you able to boil all this down into
a snippet that shows the "images don't render the same way shapes
do" and "image instantiating performance" problems?
If so, then please open a bug against
SWT: https://bugs.eclipse.org/bugs/enter_bug.cgi?product=Platform&component=SWT

Not sure if any of the Image or ImageData
snippets are a useful starting point: http://www.eclipse.org/swt/snippets/#image
Also not sure if the GraphicsExample
has anything useful in it: http://www.eclipse.org/swt/examples.php

Thanks!
Carolyn

From:	Ed Kohlwey <ekohlwey@xxxxxxxxx>
To:	platform-swt-dev@xxxxxxxxxxx
Date:	07/29/2009 12:46 PM
Subject:	[platform-swt-dev] Images
Sent by:	platform-swt-dev-bounces@xxxxxxxxxxx

---

Hi,
I have what I would think is a usual enough problem that I was hoping someone
could help me out with it.

I'm porting a UI component from AWT/Swing to SWT . It is a canvas that
has selectable objects. The object's selection must match exactly what
is rendered on the canvas. To do this in AWT/Swing, we created a custom
composite function and rendered the alpha channel of everything as a unique
color to a background buffer. Selection is accomplished by simply seeing
what unique color the mouse was over, and then retrieving the associated
object from a map.

This doesn't seem to be readily doable in SWT. You can create a wrapper
for a GC, make it ignore changes to color, and instead use a picking color
when drawing objects. You run into problems, however, when you start rendering
images because the images don't render the same way shapes do. I've tried
a number of approaches, all of which are unsatisfactory because of the
expense in instantiating Image objects. Does anyone have an idea of how/if
someone has done this in SWT? It seems like there might be an inherent
limitation in the platform that would be worth taking a look at from a
design perspective..._______________________________________________
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