[Qgis-developer] Map canvas flickers

Andreas Neumann a.neumann at carto.net
Fri Jul 27 05:04:08 PDT 2012


 Hi,

 I can also confirm that I have this very annoying flickering in Linux 
 Ubuntu / KDE - and it is really embarrassing when showing QGIS to 
 someone. The work on the threading branch should hopefully be done by 
 Martin (and others for the providers) until the end of the year. Then we 
 should have a good solution to fix the problem.

 Andreas

 On Fri, 27 Jul 2012 13:28:15 +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

-- 
 --
 Andreas Neumann
 Böschacherstrasse 10A
 8624 Grüt (Gossau ZH)
 Switzerland


More information about the Qgis-developer mailing list