What pixel format does X server use?

Question

What pixel format (RGBA, ARBG, BGRA) does the X server use? If any specific format at all.

Update: I'm specifically looking for information about the color component order and bit patterns.

Answer 1

That's a difficult question to answer as you don't say explicitly what kind of a graphical interface you are running on, since X is the bare-bones X driver behind the GUI such as GNOME, KDE, WindowMaker, fluxbox, NextStep to name a few, I know for certain that KDE's interface uses compiz to communicate with the X driver interface to draw on the screen and perform eye-candy movements...but the resolution of X is still the same regardless..8 bits, 16 bits, 24 bits, 32 bits pixel format depending on your screen resolution and how X is configured.

To clue you in on the graphics display, look for /etc/X11/xorg.conf or similar to find out .... you can usually, hit 'Ctrl', 'Alt', '+' to increase resolution or use a '-' to decrease resolution (bear in mind that you need to hold down the Ctrl+Alt and hit either the + or - key to achieve the resolution where warranted...)

Answer 2

Use xdpyinfo to find information about an X server.

Answer 3

You mean the framebuffer format? Or all the supported pixmap formats? Whichever it is, it depends on your graphics hardware, driver and configuration.

To see all the formats supported on your X server (they're called "visuals" in X lingo), try the xdpyinfo utility. You will probably see lots of separate, but identically looking visuals. They differ in additional data associated with each pixel besides the RGB values (alpha, depth, stencil, multisample, etc.). This can be shown by the glxinfo utility.

That all being said, the most popular format on contemporary PC hardware is the windowsish 8-bit per channel, 32-bit per pixel BGRX or BGRA (X stands for unused). Note that this is byte order, not "logical word" order, which on a little-endian architecture like x86 would be the opposite (XRGB, ARGB).