[matplotlib-devel] wx draw_idle

Hi,

The attached patch has a couple of changes to the wx backend that I
want people to test before I commit.

1) implement draw_idle.  Rather than using the wx IdleEvent which seemed
to be triggered too often I used a timer which is delayed and possibly
reset if a new draw request comes within a certain time period (5 ms),
or if there are pending wx events.  The scheme isn't perfect since wx
doesn't see all the native events, but it seems to work well enough.

2) Don't draw bitmap on the screen if the graph isn't shown.  Otherwise
a plot inside of a wx aui notebook bleeds through even if the graph
notebook is not on top.

3) Don't regenerate entire plot for each PaintEvent.  Instead, only
draw the graph if this is the first time the window is exposed, otherwise
work from the bitmap.  I've only tested this for wxagg on the mac.  I don't
know if it breaks wx, or if anyone cares about wx anymore.

Let me know if it works for you.

	- Paul