Fix cursor rendering for multi-head.

Before putting anything on the screen, check if the GC was made for the
ScreenRec we want to render to. If not, toss the GC and create a new one. This
is not the best solution but it does the job for now. Same thing for ARGB
cursors except that it's even uglier.

Also remember the screen the cursor was rendered to and check for the right
screen in the BlockHandler, SourceValidate and a few others. Only remove or
restore the cursor if we are rendering to the same screen, otherwise we get
artefacts that are both funky and really annoying.

0 files changed, 0 insertions, 0 deletions