## GTK for the X Window System

On UNIX, the X backend is enabled by default, so you don’t need to do anything special when compiling it, and everything should “just work.”

To mix low-level Xlib routines into a GTK program, see GDK X Window System interaction in the GDK manual.

## X11-specific environment variables

: The X11 GDK backend can be influenced with some additional environment variables.

### GDK_SYNCHRONIZE

If set, GDK makes all X requests synchronously. This is a useful option for debugging, but it will slow down the performance considerably.

### GDK_SCALE

Must be set to an integer, typically 2. If set, GDK will scale all windows by the specified factor. Scaled output is meant to be used on high-dpi displays. Normally, GDK will pick up a suitable scale factor for each monitor from the display system. This environment variable allows to override that.