[XaraXtreme-dev] Strange rendering problem

[Martin Wuerthner <lists@xxxxxxxxxxxxxxx>]

Is it just me or do others see this rendering problem, too? This is on 
x86, SuSE 10.0, wxWidgets 2.6.3-rc2, source revision 731 without any 
changes, debug build.

At certain zoom percentages a spurious black background appears that 
is of the size of the bounding box of all objects on the page. The 
background can be wiped away by moving an object over it but reappears 
when the area is scrolled into view again.

This is how I can provoke the problem reliably:

1. Start XaraLX
2. Create a new file - it will be displayed at 100% zoom
3. Draw an ellipse in the middle of the page and set its size to 500
   by 300 pixels.
4. Give it a red fill (not necessary to trigger the problem but it
   shows more clearly what is going on later)
5. Select the magnifier tool and change to 202% zoom.

Here, this causes a black background the size of the ellipse's 
bounding box to appear underneath the ellipse. If additional objects 
are drawn the background extends to encompass their bounding boxes. If 
the zoom percentage is changed to 200%, the problem goes away, but it 
occurs at many other zoom levels, too, though usually "even" levels 
like 500% work fine.

For instance:
310%     works fine
311%       goes wrong
312%-314%  go wrong
315%     works fine
316%-318%  go wrong
319%     works fine
320%       goes wrong

The Double buffering and Background rendering entries in the Debug 
menu do not have any effect, by the way.

I have an old revision around (609), which works fine in this respect, 
so the error has been introduced somewhere inbetween.

Martin