[QGIS-trac] Re: [Quantum GIS] #1081: Old .qgs project causes GUI mess

[Quantum GIS]

#1081: Old .qgs project causes GUI mess
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        Reporter:  mloskot                          |         Owner:  telwertowski       
            Type:  defect                           |        Status:  closed             
        Priority:  minor: annoyance or enhancement  |     Milestone:  Version 1.0.0      
       Component:  Project Loading / Saving         |       Version:  HEAD               
      Resolution:  wontfix                          |      Keywords:  postgis qgs project
Platform_version:  10.5 (Leopard)                   |      Platform:  OS X               
        Must_fix:  No                               |   Status_info:  0                  
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Changes (by telwertowski):

  * priority:  critical: causes crash or data corruption => minor:
               annoyance or enhancement
  * status:  new => closed
  * resolution:  => wontfix

Comment:

 I consider the priority of this bug to be minor. Although it results in
 visual corruption, it does not cause a crash or corrupt data. Since the
 visual corruption is caused by attempting to open a project for which no
 layers are present, a workaround is to quit, restart and don't open the
 project again until the layers are available.

 For qgis 1.0, I consider this bug 'wontfix.' The fix is to redesign the
 render code. This could be a task for the next major release (2.0) but not
 sooner.

 This type of visual corruption occurs because Mac paint events are not
 interruptible. Interrupts are caused by calls to processEvents() inside
 paint events; removing them requires a redesign.

 I suspect there are also Mac problems using a QGraphicsScene with an
 offscreen bitmap. Mac rendering has been unstable ever since
 QGraphicsScene came into use for map rendering. The conflict is that
 QGraphicsScene tries to do visual optimizations and qgis render code also
 tries to do visual optimizations. I recommend using either QGraphicsScene
 or an offscreen bitmap but not both. Mixing the two seems to confuse
 Qt/Mac.

 One final comment. I encounter some sort of visual corruption almost every
 time I use qgis (on a Mac). Usually the window title, window controls and
 toolbar buttons get drawn inside the map canvas. Doing additional work
 redraws the items correctly. Doing yet more work causes more visual
 corruption again. The details of the corruption change with each Qt
 release but will continue until map rendering becomes Mac 'event safe.'

-- 
Ticket URL: <https://trac.osgeo.org/qgis/ticket/1081#comment:3>
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