Re: Pixmap oddity

[Owen Taylor <otaylor redhat com>]

"Scott A. Barron" <sbarron@abalonesoft.com> writes:

> Hello all,
> 
> I am having trouble with some pixmaps.  Here are my scenarios:
> 
> Scenario 1:
> I have a button into which I put a pixmap created with
> gdk_pixmap_create_from_xpm_d.  I then insert this button into a table and show
> everything.  This scenario works as expected, no problems here.
> 
> But, Scenario 2:
> I have the same button with the same pixmap, but this time I insert the button
> into an hbox, then put the hbox in the table.  When I do this I get:
> Gdk-WARNING **: Creating pixmap from xpm with NULL window and colormap
> 
> Can anyone help me understand why I'm getting this error?  Is there a way
> around it?  Everything displays fine, and the pixmaps are all seemingly
> correct, so I'm not sure why I get this error.

I'll see if I can quickly summarize the situation with
pixmaps and colormaps/visuals.

 gdk_pixmap_create_from_xpm_d()

requires a non-NULL window parameter, to get a colormap
for the pixmap. (At one point, GTK+ would silently use
the default colormap if the window was NULL, but using
that colormap is not correct.)

Typically, people do this by doing:

 gdk_pixmap_create_from_xpm_d (widget->window, ...)

Which works only if 'widget' is realized. To be realized
a widget must first be added into a widget heirarchy
that includes a toplevel window at the top; you
may also need to explicitely call gtk_widget_realize()
on the widget.

However, this is not the best way to handle the
problem. Instead, you should use:

  GdkPixmap* gdk_pixmap_colormap_create_from_xpm 
                                        (GdkWindow   *window,
					 GdkColormap *colormap,
					 GdkBitmap  **mask,
					 GdkColor    *transparent_color,
					 const gchar *filename);

Which takes, in addition to the window parameter,
a colormap parameter. If you pass in a non-null
colormap, then you can pass in a null window parameter.

Where do you get the colormap from? You can 
get the colormap for any widget using 
gtk_widget_get_colormap(); this does not
require the widget to be realized.

Regards,
                                        Owen