Drawing CSD on EGL apps

[Bill Spitzak]

Giulio Camuffo wrote:

> I don't see how that would help drawing client side decorations. Or are 
> you talking about a different problem?

The problem I am talking about is that on X and Windows, if you have a 
window created for OpenGL rendering, the method used to get a "normal 
drawing context" (an HDC on Windows and a GC on X) does not work! You 
therefore cannot use existing drawing functions (ie toolkits) to draw 
into the same window as OpenGL.

I suspect this is about 99% of the reason for people using subwindows to 
render OpenGL under X and Windows. It certainly is the reason I do it. 
The fact that you have to account for the subwindow in your OpenGL code 
is minor in comparison, though I agree it would be nice to add this to 
the OpenGL/EGL api. In the same application we make subrectangles out of 
the OpenGL window (for dividing the viewer into 4 views) without any 
trouble.

Under wayland if you assume the "normal drawing context" is a cairo_t, 
and you can make a cairo_t from an OpenGL/EGL buffer, then this does 
seem like it would work. The current status of the Cairo OpenGL backend 
however worries me.