Re: parent_relative questions

[Brett Granger <bdgranger alum mit edu>]

Replying to myself (having gdb and source code is nice, but it takes a 
while to slog through!) --

It's the double-buffering that's initing the pixmap to black.  Since the 
TOPLEVEL window has no parent gdk window, gdk_window_get_bg_gc returns 
the window's bgcolor to initialize the pixmap with in 
gdk_window_begin_paint_region.  If I 
gtk_widget_set_double_buffered(widget, FALSE), then I no longer get 
black.  Double buffering sure is a nice feature, though.  Is there any 
way to wrap the root window in such a way that it could be a workable 
GdkWindow parent for the TOPLEVEL windows? Barring that, is there a way 
to set the parent window for a GdkWindow correctly so that I could 
create a window with the desired background and use it as a parent for 
multiple windows?  gtk_window_new either makes a frame a parent or NULL 
the parent...

Thanks again,
--Brett


Brett Granger wrote:
> Adding a little to my previous post, I have written a very simple X-only 
> app that creates a 200x200 window and sets the background pixmap to 
> ParentRelative and can see that it works as expected (well, almost.  It 
> actually sets the window background to be whatever's already on screen 
> as opposed to refreshing with the root window's bg pixmap, but that's 
> okay for what I'm doing).  When I use gtk for the simple test program 
> (code attached), I get a solid black window instead.
>
> So something in GTK2.0 must be drawing black into the rectangle that's 
> about to be occupied by the window even though it's "app paintable", and 
> then that black is getting picked up by the window's background, 
> defeating the purpose of the ParentRelative setting.  That's assuming 
> that the ParentRelative setting even took and the black isn't just X 
> clearing the background to black because it thinks the window has no 
> pixmap...
>
> Anybody ever worked with this or have any thoughts as to how I avoid the 
> black?  GTK+-2.0.2 on XFree86 4.2.0.
>
> Thanks again,
> --Brett
>
>
> Brett Granger wrote:
>
> > I've been experimenting with gdk_window_set_back_pixmap and the 
> > parent_relative flag under X.  According to the X docs, setting a bg 
> > pixmap of ParentRelative should indicate that the background of this 
> > window is the appropriately offset pixmap of whatever's in the bg of 
> > the parent window.  This seems like it might be yet another way to 
> > pretend to have transparent top level windows, since the background 
> > pixmaps should be tiled in such a way as to make the child fit right 
> > in over the parent.
> >
> > The first thing I learned is that if I don't 
> > "gtk_widget_set_app_paintable" I still get the default gray background 
> > fill.  However, when I set the window to be "app paintable" I would 
> > expect that I should see the bg pixmap that I have set in my root 
> > window (since the windows I am playing with are TOPLEVEL).  Instead I 
> > get a solid black background, regardless of what's in the root window.
> >
> > Has anybody else had any success with parent_relative windows and can 
> > anyone comment on whether I really can achieve a fake transparency 
> > with toplevel windows in this way?  I'm using GTK2.0.
> >
> > Thanks in advance!
> > --Brett
> >
> > ps. directfb is not an option for us, which is why I thought I'd try 
> > it this way...
> >
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