[QGIS-trac] Re: [Quantum GIS] #1171: Layers disappear and require restart after first time selection of anti-aliased rendering

[Quantum GIS]

#1171: Layers disappear and require restart after first time selection of anti-
aliased rendering
-----------------------------------------------------+----------------------
        Reporter:  springmeyer                       |         Owner:  nobody       
            Type:  patch                             |        Status:  new          
        Priority:  major: does not work as expected  |     Milestone:  Version 1.0.1
       Component:  MapCanvas                         |       Version:  HEAD         
      Resolution:                                    |      Keywords:               
Platform_version:                                    |      Platform:  All          
        Must_fix:  Yes                               |   Status_info:  0            
-----------------------------------------------------+----------------------
Comment (by smizuno):

 This is a very subtle issue - the problem originally described occurs once
 after start up. However, resizing the map canvas causes the map size and
 extent to jump when switching from QPixmap to QImage. The map is drawn at
 the previous QImage size, then is drawn correctly on subsequent resize. I
 have since found that the Render toggle isn't a factor - it just may show
 the effects more readily.

 My recollection is that the QImage has a size of 0,0 initially, which is
 why the map goes blank. After that the object is at its previous size and
 hasn't been resized when QPixmap is the rendering object. The key factors
 are first use or that the map canvas has been resized.

 It is not Qt version related - the problem exists with either 4.3.x series
 or 4.4.x.

 For what it's worth (I admit, I am biased) I have been applying the patch
 each time I obtain the latest svn copy and have not found any other
 problem that could be attributed to the patch. I remove the patch and test
 without it when I believe there may be a problem related to it.

-- 
Ticket URL: <https://trac.osgeo.org/qgis/ticket/1171#comment:5>
Quantum GIS <http://qgis.org>
Quantum GIS is an Open Source GIS viewer/editor supporting OGR, PostGIS, and GRASS formats