Mapper bug - sort of.

[Bill Lorensen]

John,
  A bug is a bug... don't stop,

Bill

At 10:01 PM 12/5/99 +0000, John Biddiscombe wrote:
>Dear vtk,
>
>Please stop me if I'm posting too many bug reports.
>
>vtkMapper and sub classes can get munged if you do this...
>
>This is bad
>-----------
>render->RemoveProp(prop);
>Renderwindow->Delete()
>prop->Delete()
>
>this is good
>------------
>Renderwindow->Delete()
>prop->Delete()
>
>
>The problem is that when you call RemoveProp(), the renderer doesn't call
>ReleaseGraphicsResources() on the mapper - (this may be sensible if you're
>about to put the prop into another window and may have to redo a massive
>displaylist).
>However, the mapper keeps its renderwindow pointer and when the window is
>deleted, the pointer is left hanging. Subsequent deletion of the prop
>causes a pointer violation during the destructor cleaning up.
>
>The solution is for users to call ReleaseGraphicsResources themselves when
>deleting a prop if they think the window may disappear ...
>
>My own solution is to add a flag to removeprop (in my code) which says
>whether the window is being deleted or left. If deleted, then
>ReleaseGrraphicsResources should be called.
>
>This may not be a good solution because the prop may be removed without a
>window deletion occuring, then later the window is really deleted, and now
>the pointer is left hanging. The only safe solution is to call
>ReleaseGraphicsResources every time. - if an alternative ReplaceProp
>routine were used, then one could safely pass the display lists from one
>renderer to another without worrying but there are no doubt other reasons
>why this wouldn't work. (not least opengl display contexts anyway).
>
>ttfn
>
>John B




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