[vtkusers] [vtk-developers] Renderization issues with Qt/VTK on Windows 7 platform

[Clinton Stimpson]

On Tuesday, January 04, 2011 09:56:06 am Wagner Sales wrote:
> Hi all,
> Recently I've ported an application from Linux to Windows 7. This
> application basically uses Qt and VTK ( both are latest version ). In
> X11 ( Linux ), the application works like a charm. In Windows, some
> strange behaviors occurs especially on QVTKWidget: when I hide one or
> more QVTKWidget ( a quad view in a DICOM exam, for example ) and show
> a QVTKWidget with a volume, for example, the widget are shown simply
> are transparent, showing the contents of the windows that are behind,
> for example a WordPad windowuntil it is completely rendered.
> In other cases, when I go back to quadview, not all widgets are
> rendered, and in other cases, the content of these can be rendered
> inanother: for example, the content of the widget that shows a
> sagittal view can be rendered on coronal widget, or appears two axial
> contents and one sagittal. If I have some Qt control designed on the
> render window, for example to calls a popup menu, and the application
> are busy, if I move the window, this controls will not be repainted
> properly.
> All of this problems occurs on the same machine with I run the
> application on X11 without problems. If I change the machine for a
> more and more powerful machine, the problems tends to minimize until
> disappears on the more powerfull machine.
> I think may be are some dirty cache in some place, but I don't have any
> idea. I know may be the information present in this mail will not be
> sufficient to help, then just ask. I'll be very proud to help. I can
> simply change the machine, but I think this will not the solution for
> others users if fall in the same problem.
> 

Is this the Window Ghosting feature of Windows you are seeing?
You can look at the docs for the Windows api GetMessage() and it has comments 
about ghost windows.  When an application doesn't respond, its contents are 
copied and put into a ghost window that has interaction enabled.  So this 
could be the caching you are seeing.

I've seen this appear to freeze animations and subsequent Render() calls do 
nothing to change the image unless the event queue is peeked at periodically 
to prevent Windows from ghosting it.

-- 
Clinton Stimpson
Elemental Technologies, Inc
Computational Simulation Software, LLC
www.csimsoft.com