Drawing widget parts off-screen

[Olivier Guilyardi <ml xung org>]

Hi,

For a specialized (audio pattern) editor I'm currently drawing everything on a
off screen pixmap, and calling gdk_draw_drawable() to copy the needed areas on
expose events into a drawing area's GdkWindow.

I would like to draw some widget parts (a ruler actually) using the
gtk_paint_*() methods into this editor. However, since the whole drawing process
is made off screen using some sort of layers, I can't draw directly on the
GdkWindow. I would prefer to draw the widget parts on the off-screen pixmap.

However, all the gtk_paint_*() functions need a GdkWindow to draw on. Funny
thing, I've tried to pass my GdkPixmap to gtk_paint_box(), it issued an "invalid
cast from `GdkPixmap' to `GdkWindow'", but it did draw ;)

Anyway, I sense this isn't the right thing to do. I also thought about having an
"off-screen" (never shown) GdkWindow instead of my GdkPixmap. This should work,
since all the gdk drawing functions I use expect a GdkDrawable. Is it the right
way to do this? Isn't drawing on a GdkWindow heavier, because it implies
interactions with X11 (or Quartz, whatever)?

Regards,

-- 
  Olivier Guilyardi / Samalyse