[vtkusers] vtkFreeType in a multi-threading application

[David Lonie]

On Wed, Mar 11, 2015 at 8:26 AM, Butterfly <ninarock at list.ru> wrote:

> After start both render windows show normally, I see the data update in
> both
> windows several times (about 10 times or more..) and then the application
> crashes with "corruption of the heap" error "HEAP: Free Heap block 12e58b20
> modified at 12e58b78 after it was freed". The call stack is not the same at
> each start, but the error is always inside the vtkFreeType.dll (please see
> 2
> examples of the call stack below).
>
> As I understand the error appears while drawing text in the chart (drawing
> axis labels and chart legend). I tried to read about FreeType project, and
> I
> found the following:
> *    For multi-threading applications each thread should have its own
> FT_Library object.*
> http://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html
> <http://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html>
>
> But if I understand right, VTK creates only one instance of
> vtkFreeTypeTools
> (in the code is said that it is a singleton), and consequently we have only
> one FT_Library object.
>

This is indeed the problem -- thanks for the report. As of right now, we
don't have a workaround, but I've created an bug report to keep track of
the issue:

 http://vtk.org/Bug/view.php?id=15376

Dave
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