[gnome-control-center] wacom: Allow button mapping if the stylus has one button too

[Bastien Nocera <hadess src gnome org>]

commit 5fcf43a135fabc0fe6c9c35e33adbd9ff64e6407
Author: Benjamin Tissoires <benjamin tissoires redhat com>
Date:   Sun Mar 15 20:55:07 2015 -0400

    wacom: Allow button mapping if the stylus has one button too
    
    The airbrush tool has only one button, and the button mapping combo box
    does not work.
    We should not bail out if the widget has been removed, that means that
    the stylus does not support the second button.
    
    Check upfront the number of buttons to know if the top button parameter
    is available.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=746263

 panels/wacom/cc-wacom-stylus-page.c |   14 +++++++++-----
 1 files changed, 9 insertions(+), 5 deletions(-)
---
diff --git a/panels/wacom/cc-wacom-stylus-page.c b/panels/wacom/cc-wacom-stylus-page.c
index d7378b6..fe7e059 100644
--- a/panels/wacom/cc-wacom-stylus-page.c
+++ b/panels/wacom/cc-wacom-stylus-page.c
@@ -202,12 +202,16 @@ button_changed_cb (GtkComboBox *combo, gpointer user_data)
                            BUTTONNUMBER_COLUMN, &mapping_b2,
                            -1);
 
-       if (!gtk_combo_box_get_active_iter (GTK_COMBO_BOX (WID ("combo-topbutton")), &iter))
-               return;
+       if (gsd_wacom_stylus_get_num_buttons (priv->stylus) > 1) {
+               if (!gtk_combo_box_get_active_iter (GTK_COMBO_BOX (WID ("combo-topbutton")), &iter))
+                       return;
 
-       gtk_tree_model_get (GTK_TREE_MODEL (liststore), &iter,
-                           BUTTONNUMBER_COLUMN, &mapping_b3,
-                           -1);
+               gtk_tree_model_get (GTK_TREE_MODEL (liststore), &iter,
+                                   BUTTONNUMBER_COLUMN, &mapping_b3,
+                                   -1);
+       } else {
+               mapping_b3 = 0;
+       }
 
        map_button (priv->stylus_settings, mapping_b2, mapping_b3);
 }