Re: The best way to draw a GL texture from a different process

[Emmanuele Bassi <ebassi gmail com>]

On 25 May 2018 at 10:23, Jiří Janoušek <janousek jiri gmail com> wrote:

> Hello,
>
> My app consists of the main process, where the GTK+ main loop and widgetry
> live, and the GPU process, which does OpenGL kung-fu and provides GL
> texture and dirty/invalidated rectangles as a result. I have little control
> over the GPU process - I can patch it a bit, but I cannot merge the main
> and GPU process, for example.
>
> If I understand it correctly, I cannot simply share GL textures between the
> processes and use e.g. gdk_cairo_draw_from_gl(). I can transfer the pixel
> buffer via IPC, store it in the main process, call
> gtk_widget_queue_draw_area(), and finally paint it in the draw signal
> handler, but that is slow and involves a lot of copying.
>
> Do you have any suggestions what could be a better way to draw the GL
> texture from a different process? With GTK 3.22 and under Xorg.

You can store the texture data as an X11 Pixmap object, and use the
GLX_EXT_texture_from_pixmap extension to get a GL texture object out of a
Pixmap XID.

Ciao,
 Emmanuele.

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