[vtkusers] Offscreen rendering and text mapper.

[Jeff Lee]

Why wouldn't vtkWindowToImageFilter work in this case?
-Jeff

Berk Geveci wrote:

>Hiho,
>
>This is a known problem (or feature, if you wish :-). Currently,
>accessing font information on X requires a connection to a server.
>I don't know if there is anybody with a solution out there but
>if there is, I will be more than happy to help incorporate it
>into VTK.
>
>-Berk
>
>On Wed, 2002-04-24 at 00:57, JL wrote:
>
>>Hi,
>>
>>I'm running into a minor problem while using off-screen rendering.
>>
>>Here's the scenario:
>>vtk version: 3.2
>>OS: Linux 2.4 (Red-Hat 7.1).
>>Mesa version: 4.0.1
>>
>>I have a very simple program that uses off-screen rendering (i.e.,
>>it calls renWin->OffScreenRenderingOn()).  It works fine (no window
>>pops-up, no X server connection is required, etc).
>>
>>I have a second program that is slightly more elaborated.  For
>>instance, it creates and uses vtkScalarBarActor and
>>vtkCubeAxesActor2D objects.
>>
>>When I execute the second program it prints the following message:
>>
>>ERROR: In ../../src/graphics/vtkXRenderWindow.cxx, line 176
>>vtkMesaRenderWindow (0x8057dd8): bad X server connection.
>>
>>after that the program 'seg faults'.
>>
>>After exploring a little bit here and there, it seems to me that
>>the problem is caused by the vtkXTextMapper which is used by
>>both vtkScalarBarActor and vtkCubeAxesActor2D.
>>
>>My questions are:
>>1. Does this problem occur only with vtkXTextMapper, or does it
>>   occur with other 2D actors/mappers?
>>2. More important, is there a way I can use off-screen rendering
>>   with these actors / mappers? or
>>3. is this a well known 'feature'?  (I skimmed the mailing list
>>   and didn't find anything relevant).
>>4. If so, do I have to use a different off-screen rendering
>>   approach, like use vtkOpenGLOffscreenRenderWindow?
>>5. Or is this a 'bug' that has been fixed in the CVS version or
>>   in a later release (i.e. 4.x)?
>>
>>Thanks in advance for any information you can provide,
>>
>>-- Julio
>>
>>P.S.:  If it is of any help, I've included additional details about how and
>>where the problem occurs.
>>
>>
>>
>>----------------------------------------------------------------------
>>
>>I tracked the problem down to:
>>
>>vtkXTextMapper::DetermineSize(vtkViewport* viewport, int* size)
>>
>>near the beginning, this method tries to get the display id ->
>>
>>Display* displayId = (Display*) window->GetGenericDisplayId();
>>this in turns calls vtkXRenderWindow::GetDisplayId(), which in turn
>>calls XOpenDisplay((char *)NULL);
>>
>>XOpenDisplay returns NULL since there's no X server running (i.e.,
>>the DISPLAY variable is not set), but that's intended since the goal
>>is to do off-screen rendering.  And here is where the error message
>>gets printed, and a NULL display is returned.
>>
>>later vtkXTextMapper::DetermineSize(...) calls
>>XLoadFont(displayId,  fontname );  with a NULL display and this is
>>where the program crashes.
>>
>>Here's a trace of the stack when the program crashes.
>>
>>#0  0x414c5cbe in XListFonts () from /usr/X11R6/lib/libX11.so.6
>>#1  0x40f9789c in vtkXTextMapper::DetermineSize(vtkViewport*, int*) ()
>>    at eval.c:41
>>#2  0x40f97426 in vtkXTextMapper::GetSize(vtkViewport*, int*) () at
>>eval.c:41
>>#3  0x40f79e13 in vtkScalarBarActor::SizeTitle(int*, int*, vtkViewport*) ()
>>    at eval.c:41
>>#4  0x40f786ef in vtkScalarBarActor::RenderOpaqueGeometry(vtkViewport*) ()
>>    at eval.c:41
>>#5  0x4044e4be in vtkRenderer::UpdateGeometry() () at eval.c:41
>>#6  0x404f2cdd in vtkMesaRenderer::DeviceRender() () at eval.c:41
>>#7  0x4044d882 in vtkRenderer::Render() () at eval.c:41
>>#8  0x40451e10 in vtkRendererCollection::Render() () at eval.c:41
>>#9  0x40449657 in vtkRenderWindow::DoStereoRender() () at eval.c:41
>>#10 0x404495f4 in vtkRenderWindow::DoFDRender() () at eval.c:41
>>#11 0x40449174 in vtkRenderWindow::DoAARender() () at eval.c:41
>>#12 0x4044891c in vtkRenderWindow::Render() () at eval.c:41
>>#13 0x4050b1e9 in vtkXRenderWindow::Render() () at eval.c:41
>>#14 0x0804ac33 in ?? () at eval.c:41
>>#15 0x0804b1bc in ?? () at eval.c:41
>>#16 0x411b6306 in __libc_start_main (main=0x804b170, argc=10,
>>
>>
>>
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>
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-- 
Jeff Lee 
Software Engineer jeff at cdnorthamerica.com
CD North America
21 Lafayette Street, Suite 230
Lebanon, NH 03766
Tel:    (603) 643-9993 ext. 109
Fax:    (603) 643-9994