604469 - ReadPixels from cx/FBO without alpha must return 0xff for alpha values

Status: RESOLVED FIXED

(Core :: Graphics: CanvasWebGL, defect)

Description

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

According to the GL/ES specs, calling ReadPixels with GL_ALPHA or GL_RGBA when the read source (either cx or FBO) doesn't have an alpha channel must return a 1.0 value for alpha (thus 0xff).  At least on nvidia on Windows and OSX, it returns whatever was written to the alpha channel (even though it's ignored when compositing or being used as a source).

We need to fix this up after the readpixels call, and I started writing the trivial patch, but then I realized that we'd need to track whether the current FBO has alpha or not.  That would've required more lines of code, so I didn't do this yet.

Needed for a webgl conformance test.

Comment 1

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

this was fixed and I created a test; should be a dup of something else