[vtkusers] drawing with OpenGL primitives within Paint() in a sub-class of vtkContextItem

[Allie Vacanti]

There's nothing stopping you from doing this, but it is generally
considered bad design. The ContextItems are expected to go through the
Context2D painter interface, since that can draw to a variety of backends
(PDF, SVG, etc) that aren't OpenGL. You'll lose the ability to have this
flexibility when you bypass the painter.

But if it's for a one-off application that doesn't care about other
backends, it should be fine. Your best bet is have a look at the
vtkOpenGLContextDevice2D source code and see the conventions it uses and
try to match them within your item's Paint() method.

HTH,
Allie

On Wed, Nov 14, 2018 at 6:09 AM Paul Douglas Hahn <pdhahn at compintensehpc.com>
wrote:

> Does anyone know if it is feasible to call OpenGL2 primitives directly
> within the overridden Paint() method of a sub-class of vtkContextItem
> (i.e., as found in Rendering/Context2D)? I am using VTK 8.1 specifically.
>
> If so, is there an example somewhere?
>
> Thanks!
>
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>
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