Re: [platform-swt-dev] GC operations outside paint callback

[Stef van Dijk <svandijk@xxxxxxxxxx>]

Personal Profile and Personal Configuration
(ie AWT) based on SWT also relies on this behavior. That's because in AWT
you're allowed to get a Graphics at any time, draw with it at any time
and hold the Graphics object for the entire life span of your application
if you wish. Not that I think that's a particularly good choice on the
part of AWT, but it is the way it's spec'ed.

     Stef

Knut Radloff/Raleigh/IBM@IBMUS
Sent by: platform-swt-dev-admin@xxxxxxxxxxx

07/23/2004 04:27 PM

Please respond to
platform-swt-dev

To	platform-swt-dev@xxxxxxxxxxx
cc
Subject	Re: [platform-swt-dev] GC operations outside paint callback

So if draw2d relies on it, it is probably expected to work by the users
of SWT. I'd still like to hear from the SWT team "yes, this is in
fact a supported way of using a GC" or "no". I'm thinking
the answer is yes for SWT but don't want to make assumptions since in other
toolkits the answer is no.

Randy Hudson/Raleigh/IBM@IBMUS
Sent by: platform-swt-dev-admin@xxxxxxxxxxx

07/23/2004 04:20 PM

Please respond to
platform-swt-dev

To	platform-swt-dev@xxxxxxxxxxx
cc
Subject	Re: [platform-swt-dev] GC operations outside paint callback

This works fine.  This is how draw2d paints.  The only known
issues are on GTK if you ARE inside a paint callback, and you try to create
your own GC with a bigger clip region than the one sent in the paint event,
painting will still be clipped to the region sent in the event.  The
workaround is to use the repaint mechanism always or at least when this
occurs. 

-Randy

Knut Radloff/Raleigh/IBM@IBMUS Sent by: platform-swt-dev-admin@xxxxxxxxxxx 07/23/2004 04:00 PM Please respond to platform-swt-dev

To:        platform-swt-dev@xxxxxxxxxxx       cc:               Subject:        [platform-swt-dev] GC operations outside paint callback

Is it valid for an application to render directly on a GC, outside a paint
callback? E.g., given the code below am I guaranteed to get the expected
line on all SWT implementations? I don't think this is spec'd anywhere.
Is this "implementation dependent" behavior?

shell = new Shell() 
shell.open() 
gc = new GC(shell); 
gc.drawLine(0, 0, 10, 0); 

The JUnit tests don't call GC operations inside a paint callback but they
also don't test if a call actually rendered the expected output.

Thanks, Knut