[Webkit-unassigned] [Bug 166489] REGRESSION(r208997): [GLX] Google maps labels broken when using glXCreateContextAttribsARB

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=166489

--- Comment #8 from Miguel Gomez <magomez at igalia.com> ---
I've finally found the problem. It happens because WebGL is passing some parameters to OpenGL calls that have been deprecated and are not present in a core profile. That's why it works with a compatibility profile (those parameters are supported in Mesa compatibility) and not with a core profile.

In this concrete case, the problem happens when using glTexImage2D and glTexSubImage2D using GL_ALPHA as the format parameter. GL_ALPHA is a valid parameter in WebGL but not in OpenGL core, so the call fails in core profile and the labels are not rendered.

In order to fix this, GL_ALPHA has to be replaced, using GL_RED (which is the only single component format available in core), and then swizzle the red and alpha components when accessing the texture data.

I'll attach a patch in a while with the fix.

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