inhibiting x_scroll_run for a window?

[joakim]

I spent a little time on the xwidget branch, and noticed that sometimes
widgets get "stuck" on a coordinate when scrolling. This only happens
sometimes.

I think this is because Emacs sometimes decide to scroll the window by
blitting rather than redrawing. I would like to understand how to get
more control over scrolling.

- is it possible to disable blit-scrolling and instead force redraw
  scrolling for a particular window?

- is it possible to know where a glyp is supposed to be on-screen after
  a redisplay? Currently I solve this for xwidgets by assuming that
  after a redisplay has finished, my drawing routine has been called
  with valid coordinates sometime during redisplay. This doesnt seem to
  happen always and thats why I suspect the scrolling routine, but
  perhaps my basic aproach is flawed.

-- 
Joakim Verona