[gtkada] Putting an XMP graphic on a button

[Grein, Christoph]

This is generated Ada code from glade. The main window holds just one button 
without text, which I want to adorn with an XPM pixmap.

So I edited the generated Fsms_Gui procedure by adding Set_Button_Pixmap to it.
If I call Set_Button_Pixmap at the place (1) I get the message "Gdk-WARNING **: 
Creating pixmap from xpm with NULL window and colormap", but the button is 
adorned with the graphic.
At position (2), I get no warning and also no graphic on the button.

What is wrong/missing?

with Gtk; use Gtk;
with Gtk.Main;
with Gtk.Widget; use Gtk.Widget;
with F_Smedit_Pkg; use F_Smedit_Pkg;

with Gdk.Bitmap, Gdk.Pixmap, Gdk.Color, Gtk.Button, Gtk.Pixmap;  -- added

procedure Fsms_Gui is

  procedure Set_Button_Pixmap is
    Pixmap : Gdk.Pixmap.Gdk_Pixmap;
    Mask   : Gdk.Bitmap.Gdk_Bitmap;
    Graphic: Gtk.Pixmap.Gtk_Pixmap;
  begin
    Gdk.Pixmap.Create_From_Xpm (Pixmap,
                                Gtk.Button.Get_Window
                                  (F_Smedit.Current_State_Scroll_Up),
                                Mask,
                                Transparent => Gdk.Color.Null_Color,
                                Filename    => "Up.xpm");
    Gtk.Pixmap.Gtk_New (Graphic, Pixmap, Mask);
    Gtk.Button.Add (F_Smedit.Current_State_Scroll_Up, Graphic);
  end Set_Button_Pixmap;

begin

  Gtk.Main.Set_Locale;
  Gtk.Main.Init;

  Gtk_New (F_Smedit);
  -- Set_Button_Pixmap;  -- (1)
  Show_All (F_Smedit);
  -- Set_Button_Pixmap;  -- (2)

  Gtk.Main.Main;

end Fsms_Gui;