Erase the cursor before drawing.
Must call unblock when finished.
Normally, you don't need to call this function manually, but it can be more efficient to do so if there is a long sequence of drawing functions.
context |
the target content for null for the global context |
x1 |
the left x coordinate |
y1 |
the top y coordinate |
x2 |
the right x coordinate |
y2 |
the bottom y coordinate |
state flags that need to be passed to unblock |