scaling rendering is broken with opengl

[Antoine Martin]

Not sure when this started, tested with vpx. (found thanks to #692)

The opengl window renders the update only on the top-left portion of the screen which corresponds to the downscaled dimensions.
The non-opengl rendering works fine.

[Antoine Martin]

Good news: v0.14.x is not affected by this, but trunk r7803 is.

Bisecting by visual inspection (..) using a server running like this:

XPRA_SCALING_HARDCODED=1:3 xpra start :10 --start-child=glxspheres --no-mmap

Hardcoding the scaling to ensure it is enabled, and disabling mmap which bypasses encodings.

• r7500 good
• r7600 bad (with some other opengl errors thrown in..)
• r7550 good
• r7575 good
• r7587 good
• r7594 good
• r7597 good
• r7599 good
• r7600 bad!

So this was caused by #679.

[Antoine Martin]

Fixed in r7804: we must paint the screen using the unscaled dimensions!