Comment 8 for bug 1266308

the class SPCtrlRect is used for drawing live borders while dragging the mouse. Previously this was done using XOR drawing, the XOR command showing up in the macro INK_COMPOSE. This has been disabled previously in trunk since it belonged to libnr. In addition to this, cairo does not appear to support this kind of bitwise xor operation, see:

http://comments.gmane.org/gmane.comp.lib.cairo/1320

for this reason, and since it is essential that this rendering be done very quickly since it is occurring during a drag event, it was decided to do the outline using a very simple method of drawing two lines, one light, one dark. This appears to be somewhat similar to what Gimp does, but much simpler than their rubberband designs.

committed to rev 12936