Affects Version/s: Minecraft 1.7.9, Minecraft 14w19a, Minecraft 14w25b, Minecraft 1.7.10, Minecraft 14w28b, Minecraft 14w29a, Minecraft 14w29b, Minecraft 14w30a, Minecraft 14w30b, Minecraft 14w30c, Minecraft 14w31a, Minecraft 14w32a, Minecraft 14w32b, Minecraft 14w34a, Minecraft 14w34b, Minecraft 14w34c
Fix Version/s: Minecraft 14w34d
Environment:Most (all?) Linux desktops affected
LWJGL dev/contributor here.
This is about Minecraft cannot reliably enter fullscreen on linux, and about LWJGL being blamed for it.
I tried to fix this issue in LWJGL once and for all only to discover that it is in fact a Minecraft issue
You are calling Display.setFullscreen(true) when the user presses F11 (which is correct), but shortly after this you check if the window lost its focus. If Display.isActive() return false you disable fullscreen.
The problem is that switching to fullscreen can take a while and LWJGL returns false on Display.isActive() while the switching happens (during which the window is destroyed and re-created, so this is technically correct).
This leads to a race-condition where sometimes LWJGL is fast enough and the game enters fullscreen as expected and sometimes Minecraft decides the game lost focus before fullscreen is reached and switches back to window mode.
Related ticket in LWJGL bug tracker: