GUI blend layering artifacts

[einarf]

We seem to get some blending artifacts when drawing the framebuffer to the screen. Especially when doing text rendering.

Text rendered on top of an opaque brown surface. It should not cause the blended pixels to make transparent holes in the surface making the window background visible through the surface once rendered to the screen.

This is the raw pixel dump from the surface itself: shown in gimp to identify the transparency

[einarf]

Possibly we move this to 3.0.x if there is no time.

[einarf]

The only reasonable way to solve this is actually doing the math. I have a blending simulator we can use for this.

• Simulate blending opaque, semi-transparent and fully transparent objects to the surface (no top of each other)
• Simulate drawing this to the window with blending