[cairo] cairo_surface_write_to_png and 32-bit visuals in 1.10.0
Ross.Alexander at EU.NEC.COM
Tue Sep 28 02:36:09 PDT 2010
Background: I was tired of using xwd, especially as it does not support RGBA 32 bit visuals. I hacked together a program from the latest xwininfo (based on XCB) to get the Window ID using a pointer selection and then created a surface based on that ID.
cairo_surface_t *surface = cairo_xlib_surface_create(dpy, target_win, vinfos.visual, geom->width, geom->height);
cairo_surface_t *surface = cairo_xcb_surface_create(conn, target_win, v, geom->width, geom->height);
This works fine for 24-bit visual windows but with 32-bit visuals (eg gnome-terminal) I get the following error.
xwd: cairo-xcb-surface.c:504: _get_image: Assertion `reply->depth == surface->depth' failed.
Using xlib on 32-bit visuals doesn’t fail but instead produces a zero sized PNG file.
I understand this may be an abuse of cairo for which it wasn’t designed and I maybe should use XImage or Xrender (I haven’t actually looked at render for image transfers) but as cairo has most of this code already I was hoping for some pointers.
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