Re: [platform-swt-dev] Performance problem with owner-drawn trees on OSX

["Daniel Megert" <daniel_megert@xxxxxxxxxx>]

Thanks Thomas for the bug report and the
test case. I have targeted the bug for 4.7. If we have a fix early enough,
we might also consider to backport to 4.6.3.

Dani



From:      
 Thomas Singer <ts-swt@xxxxxxxxxxx>
To:      
 platform-swt-dev@xxxxxxxxxxx
Date:      
 10.01.2017 12:00
Subject:    
   [platform-swt-dev]
Performance problem with owner-drawn trees on OS        X
Sent by:    
   platform-swt-dev-bounces@xxxxxxxxxxx

---

Hi all,

On OS X an owner-draw tree control gets 3 SWT.MeasureItem events before
the SWT.PaintItem event occurs (instead of just 1 as on Windows). 
Because only in the 1st event the event.details are set correctly, our
caching mechanism does not work on OS X:

<https://bugs.eclipse.org/bugs/show_bug.cgi?id=510172>

The performance problem, of course, is that 3 SWT.MeasureItem events are
sent to a method that - according to 
<https://github.com/aerofs/eclipse-platform-swt/blob/master/examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet220.java>
- are performance relevant:

> Therefore it is critical for performance that these methods be as
efficient as possible.

My work-around for the above bug is to call our measure method from the
SWT.PaintItem event again (a 4th time), because the cached values are 
not correct on OS X.

This bug can cause the effect, that our applications (that make use of
a 
lot of owner-draw) feel sluggish on OS X.

--
Best regards,
Thomas Singer
=============
syntevo GmbH
http://www.syntevo.com
http://www.syntevo.com/blog
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