Comment 23 for bug 1277905

I did some bit of uneducated debugging.

It seems there is something going on with the GL/GLX and alpha bits.

The LWJGL code is creating a GLX window for its content.

I noticed that the screen displaying the logo on startup was entirely translucent, without the 256x256 block in the lower left corner that is not translucent later on.

Changing a "glClearColor(0, 0, 0, 0);" to "glClearColor(0, 0, 0, 1);" makes the logo screen not translucent (and any value between 0 and 1 for the alpha value makes it somewhere in-between). - i.e. using glClearColor(0, 0, 0, 1); makes at least the logo screen look the way it should be!

Now, it seems Minecraft is only using that code path for the logo and not for the rest of the game. Now I am wondering if "0" for the alpha means translucend and "1" means solid or if it's supposed to be the other way around.

Also, I am wondering if the game is expecting that the alpha value on the window has any meaning at all or if there is some hidden flag somewhere that tells the compositing manager what to do with that alpha bit and something is wrong in there. (?)

Maybe Minecraft/LWJGL is selecting a visual where it expects the alpha bit to be ignored and chooses the wrong one - but this is a random guess as I really don't know much about GLX and the setup procedure of windows/visuals and how the alpha information is passed down to the compositor.

Maybe someone with more knowledge could point me into the right direction...