def _on_expose(self, drawing, event):
# just mark lock as callbacks are already inside gtk thread
with self._gooey.lock_marker:
# get a new cairo context from the drawing area
context = self._drawing_area.window.cairo_create()
# set a clip region for the expose event
context.rectangle(event.area.x, event.area.y,
event.area.width, event.area.height)
context.clip()
# zoom and scroll
context.scale(self.zoom, self.zoom)
context.translate(*self.scroll)
# call draw handler to draw contents of canvas to cairo context
self.handle_draw(Brush(context, self.size))
return False
