pattern parameter does not allow to manage the thickness of the drawing, but only the hatch pattern.
Basically each bit set of pattern means there is a point drawn, while 0 means no point is drawn.
Usual patterns :
0xFFFFFFFF : all bits set so the line is plain (this is the default)
0xAAAAAAAA : one pixel drawn for two pixels considered.
0xCCCCCCCC : two consecutive pixels drawn for four pixels considered.
If you need thick lines, you have to use a trick, like
-dilate 2 on your drawing afterwards, or drawing multiple primitives with shifted coordinates.