[Qgis-developer] Map canvas flickers

[Marco Hugentobler]

I still have the crash with the patch (Qt::WA_NativeWindow) on my 
machine (Qt 4.8.1).

Regards,
Marco

Am 27.07.2012 15:10, schrieb Matthias Kuhn:
> Hi Marco,
>
> thank you for verifying and advises on how to reproduce. I missed the
> part with "without releasing the mouse"
>
> I have created a patch that resolves the issue here. Can you please
> check the patch and commit it if it works for you as well.
>
> Thank you,
> Matthias
>
>
> On Fri, 2012-07-27 at 13:28 +0200, Marco Hugentobler wrote:
>> Hi Matthias
>>
>> I still have the resize crash with Qt 4.8.1. To reproduce, load a layer
>> with many objects. Go with the mouse to the right corner and resize
>> several times without releasing the mouse. After the mouse release, the
>> crash occures.
>> Note: this problem (and the flicker with the workaround) is X11 only.
>> But still, Linux is the most important platform.
>> Btw, the threading branch would be the clean solution for the issue. But
>> if you have another workaround in the short-term, let me know.
>>
>> Regards,
>> Marco
>>
>>
>> Am 27.07.2012 13:08, schrieb Matthias Kuhn:
>>> Hi all,
>>>
>>> there is this issue report #4011 "Map canvas flickers when content is
>>> dragged" which is actually pretty annoying and doesn't get much
>>> attention. ( http://hub.qgis.org/issues/4011 ) I think the solution
>>> would be pretty simple. Please read on.
>>>
>>> It was introduced by f4d26d6211830a866030a333236dcfbf15e077aa "Fix for
>>> resize crash, ticket #2714".
>>> This bugfix disables backbuffering, what fixes the crash but leads to
>>> the beforementioned flickering.
>>>
>>> The crash seems to be related to Qt versions (probably 4.6 and 4.7
>>> affected). When I tried to reproduce the crash in 4.8.1 (by reverting
>>> abovementioned patch) I couldn't reproduce the crash. So it is well
>>> possible that this problem has been fixed in Qt upstreams.
>>>
>>> But: I myself never could reproduce this crash (due to the lack of a
>>> system with old Qt libs). So, I would be happy if someone familiar with
>>> this problem could confirm that this is fixed with Qt 4.8.
>>>
>>> Then there are two possibilities (unless you come up with a third one):
>>>
>>> 1. Check for qVersion upon every repaint as suggested by Martin Dobias
>>> and then enable/disable the workaround accordingly.
>>>
>>> 2. Switch the workaround on/off by a pre-compiler constant. This way,
>>> any new distro with Qt>=4.8 could be shipped without the workaround-code
>>> being compiled into the binaries.
>>>
>>> Any comments on this issue are very welcome, as it makes QGIS look a lot
>>> sweeter :)
>>>
>>> Regards
>>>
>>> _______________________________________________
>>> Qgis-developer mailing list
>>> Qgis-developer at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/qgis-developer
>>
>
>
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-- 
Dr. Marco Hugentobler
Sourcepole -  Linux & Open Source Solutions
Weberstrasse 5, CH-8004 Zürich, Switzerland
marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee

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