looking up the color in the pattern, this is needed because before,
patterns were always drawn with the virtual origin in screen coordinate
space, but they need to be drawn with view coordinate origin taken into
account (will be implemented in a forthcomming commit)
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@21639 a95241bf-73f2-0310-859d-f6bbb57e9c96