<html>
<head>
<base href="https://bugs.webkit.org/" />
</head>
<body>
<p>
<div>
<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - REGRESSION(r208997): [GLX] Google maps labels broken when using glXCreateContextAttribsARB"
href="https://bugs.webkit.org/show_bug.cgi?id=166489#c8">Comment # 8</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - REGRESSION(r208997): [GLX] Google maps labels broken when using glXCreateContextAttribsARB"
href="https://bugs.webkit.org/show_bug.cgi?id=166489">bug 166489</a>
from <span class="vcard"><a class="email" href="mailto:magomez@igalia.com" title="Miguel Gomez <magomez@igalia.com>"> <span class="fn">Miguel Gomez</span></a>
</span></b>
<pre>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.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are the assignee for the bug.</li>
</ul>
</body>
</html>