Re: GTK pixmap background support?

[Jan D.]

> This means that calls to XClear*, and exposures, will start out with 
> the
> correct background color, and emacs need only worry about changing 
> other
> things.  When using the GTK toolkit, GTK itself apparently uses
> XSetWindowBackground for its own purposes, but the xg_set_background 
> gives
> GTK enough info to keep things basically how emacs likes.

Yes, since the display engine in Emacs uses X calls, GTK must be kept
in sync so it doesn't mess things up.

> However, with pixmap backgrounds, I want to use 
> `XSetWindowBackgroundPixmap'
> instead -- but there doesn't appear to be any equivalent call to
> `gtk_widget_modify_bg' that takes a pixmap instead of a color!  So you 
> can
> see the problem:  even though I've done a XSetWindowBackgroundPixmap, 
> GTK
> will at some point set the window background to a color, and there 
> doesn't
> seem to be any way to tell it not to, so clears/exposures come out
> incorrectly.
>
> As it happens, I think I have to support more complete redrawing modes 
> in
> emacs anyway (for more complicated background tiling than just simple
> frame-relative pixmaps), but it would be nice to be able to use the 
> native X
> calls when possible, as it's more efficient, and probably going to be 
> less
> buggy for a while... :-)
>
> So can you see any possible GTK solution to this qunadary?  I thought 
> maybe
> it would possible to do something tricky by consing up a theme or 
> something,
> but that seems rather hairy and certainly beyond my limited experience.

I have no solution to this.  I disabled setting of a background pixmap
by GTK themes because of the problems you are seeing.  I suspect you
need to look at the GTK (or rather GDK) code to see exactly what it
is doing, and how Emacs can work with it.

In general you set a background pixmap with styles.  If you look at
xg_create_frame_widgets (near the end) in gtkutil.c, you can see how
it is disabled.  By setting bg_pixmap in a GtkStyle to a suitable
GdkPixmap, and the apply the style to the widget, you can set a 
background
pixmap for the GTK widget.

        Jan D.