Function 13 - draw a rectangle in the window.
Parameters:
- eax = 13 - function number
- ebx = [coordinate on axis x]*65536 + [size on axis x]
- ecx = [coordinate on axis y]*65536 + [size on axis y]
- edx = color 0xRRGGBB or 0x80RRGGBB for gradient fill
Returned value:
- function does not return value
Remarks:
- Coordinates are understood as coordinates of the left upper corner
of a rectangle relative to the window.