Introduction
~~~~~~~~~~~~

Windowing support means the caller sets a window rectangle in screen coords
then sends a pixel stream to it. This lets the caller do partial screen updates.
The standard API is:

void set_window(unsigned char x, unsigned char y, unsigned char w, unsigned char h);
void write_window(const void *data, unsigned int len);

Pixel data format is driver-specific and shall be specified in the driver's
comments. Len may be restricted (as described in the driver's comments).


Example
~~~~~~~

TODO