[gcalctool] Make backspace button work

[Robert Ancell <rancell src gnome org>]

commit b84f79538df8950aa67adb8f69f1376e9748ff8c
Author: Robert Ancell <robert ancell gmail com>
Date:   Thu Apr 15 17:17:49 2010 +0800

    Make backspace button work

 data/buttons-advanced.ui |    1 +
 src/math-buttons.c       |   17 +++++++++++++++++
 2 files changed, 18 insertions(+), 0 deletions(-)
---
diff --git a/data/buttons-advanced.ui b/data/buttons-advanced.ui
index f2d61e3..f8e35aa 100644
--- a/data/buttons-advanced.ui
+++ b/data/buttons-advanced.ui
@@ -943,6 +943,7 @@
             <property name="border_width">3</property>
             <property name="use_underline">True</property>
             <property name="focus_on_click">False</property>
+            <signal name="clicked" handler="backspace_cb"/>            
           </object>
           <packing>
             <property name="left_attach">5</property>
diff --git a/src/math-buttons.c b/src/math-buttons.c
index 2e07216..99d3558 100644
--- a/src/math-buttons.c
+++ b/src/math-buttons.c
@@ -390,6 +390,7 @@ load_mode(MathButtons *buttons, ButtonMode mode)
     set_tint(GET_WIDGET(builder, "calc_factor_button"), &buttons->priv->colour_action, 2);
     set_tint(GET_WIDGET(builder, "calc_clear_button"), &buttons->priv->colour_action, 1); // Different colour
     set_tint(GET_WIDGET(builder, "calc_backspace_button"), &buttons->priv->colour_action, 1); // Different colour?
+    set_tint(GET_WIDGET(builder, "calc_delete_button"), &buttons->priv->colour_action, 1); // Different colour?
     set_tint(GET_WIDGET(builder, "calc_shift_left_button"), &buttons->priv->colour_action, 1);
     set_tint(GET_WIDGET(builder, "calc_shift_right_button"), &buttons->priv->colour_action, 1);
   
@@ -583,6 +584,22 @@ clear_cb(GtkWidget *widget, MathButtons *buttons)
 }
 
 
+G_MODULE_EXPORT
+void
+delete_cb(GtkWidget *widget, MathButtons *buttons)
+{
+    math_equation_delete(buttons->priv->equation);
+}
+
+
+G_MODULE_EXPORT
+void
+backspace_cb(GtkWidget *widget, MathButtons *buttons)
+{
+    math_equation_backspace(buttons->priv->equation);
+}
+
+
 static void
 shift_cb(GtkWidget *widget, MathButtons *buttons)
 {