[cairo] Screen* must be known in Xlib backend
otaylor at redhat.com
Tue Jul 19 17:35:49 PDT 2005
On Tue, 2005-07-19 at 17:55 -0400, Keith Packard wrote:
> On Tue, 2005-07-19 at 14:38 -0400, Owen Taylor wrote:
> > An obvious question is whether we should be using a Screen * here or a
> > screen number.
> I used Screen * because it can be statically typechecked.
> > So a using a screen number (just like Xft) would have been my expectation.
> I can change this if you're really adamant, but I do like to encourage
> type-safe interfaces where possible...
Since my instinct to order the arguments
display, screen, drawable
display, drawable, screen
The static type check is probably good :-). I'll trust your judgment in
terms of Xlib-related API taste ... you've been doing it longer than I
> > So the right check is:
> > - if (src->dpy == dst->dpy && !_surfaces_compatible (src, dst))
> > + /* If the source and destination are for the same screen,
> > + * then we can go ahead and check for compatibility now. Otherwise,
> > + * we have to wait until _cairo_xlib_surface_clone_similar() does
> > + * its work */
> > + if (src->dpy == dst->dpy && src->screen == dst->screen &&
> > + !_surfaces_compatible (src, dst))
> I've changed this to use:
> /* If these are on the same screen but otherwise incompatible,
> * make a copy as core drawing can't cross depths and doesn't
> * work rightacross visuals of the same depth
> if (_cairo_xlib_surface_same_screen (dst, src) &&
> !_surfaces_compatible (dst, src))
> return DO_UNSUPPORTED;
Hmm, the comment there doesn't strike me as accurate ... we aren't
making a copy ... we are doing a GetImage/PutImage fallback. I might
also prefer a comment that hints as to why surfaces on different screens
are (possibly) OK. But I can certainly go in and improve comments
afterwords if so inspired...
> With _cairo_xlib_surface_same_screen implemented as:
> * Return whether two xlib surfaces share the same
> * screen. Both core and Render drawing require this
> * when using multiple drawables in an operation.
> static cairo_bool_t
> _cairo_xlib_surface_same_screen (cairo_xlib_surface_t *dst,
> cairo_xlib_surface_t *src)
> return dst->dpy == src->dpy && dst->screen == src->screen;
Otherwise looks OK.
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