[gnome-calculator] Added shortcut to clear history (bgo#792814)

[Robert Roth <robertroth src gnome org>]

commit a95e2e5896fbfceaa5d5dc9110e798bc86d64231
Author: Robert Roth <robert roth off gmail com>
Date:   Fri Jan 26 03:33:57 2018 +0200

    Added shortcut to clear history (bgo#792814)

 src/gnome-calculator.vala |    1 +
 src/math-display.vala     |    7 ++++++-
 src/math-history.vala     |    8 +++++---
 src/math-shortcuts.ui     |    7 +++++++
 src/math-window.vala      |    6 ++++++
 5 files changed, 25 insertions(+), 4 deletions(-)
---
diff --git a/src/gnome-calculator.vala b/src/gnome-calculator.vala
index 079ec6e..d261d3a 100644
--- a/src/gnome-calculator.vala
+++ b/src/gnome-calculator.vala
@@ -75,6 +75,7 @@ public class Calculator : Gtk.Application
         Number.precision = precision;
 
         add_action_entries (app_entries, this);
+        add_accelerator ("<Primary>Escape",  "win.clear", null);
 
         var current_window = new MathWindow (this, equation);
         current_window.set_title (_("Calculator"));
diff --git a/src/math-display.vala b/src/math-display.vala
index e88a89d..fbbe113 100644
--- a/src/math-display.vala
+++ b/src/math-display.vala
@@ -103,11 +103,16 @@ public class MathDisplay : Gtk.Viewport
         _equation.display_selected (prev_eq);
     }
 
-    public  void update_history (string answer, Number number, int number_base, uint representation_base)
+    public void update_history (string answer, Number number, int number_base, uint representation_base)
     {
         history.insert_entry (answer, number, number_base, representation_base); /* Sends current equation 
and answer for updating History-View */
     }
 
+    public void clear_history ()
+    {
+        history.clear ();
+    }
+
     public void insert_text (string answer)
     {
         _equation.insert_selected (answer);
diff --git a/src/math-history.vala b/src/math-history.vala
index b35d3d6..53ab5ee 100644
--- a/src/math-history.vala
+++ b/src/math-history.vala
@@ -11,8 +11,6 @@
 [GtkTemplate (ui = "/org/gnome/calculator/history-view.ui")]
 public class HistoryView : Gtk.ScrolledWindow
 {
-    int no_ofitems = 0; /* No of entries in history-view listbox */
-
     string? last_answer = null;
     string? last_equation = null;
 
@@ -57,7 +55,6 @@ public class HistoryView : Gtk.ScrolledWindow
 
         listbox.insert (entry, -1);
         entry.show ();
-        no_ofitems++;
 
         entry.answer_clicked.connect ((ans) => { this.answer_clicked (ans); });
         entry.equation_clicked.connect ((eq) => { this.equation_clicked (eq); });
@@ -66,6 +63,11 @@ public class HistoryView : Gtk.ScrolledWindow
         last_equation = equation;
         row_added ();
     }
+
+    public void clear ()
+    {
+        listbox.foreach ((child) => { listbox.remove(child); });
+    }
 }
 
 [GtkTemplate (ui = "/org/gnome/calculator/history-entry.ui")]
diff --git a/src/math-shortcuts.ui b/src/math-shortcuts.ui
index 89a5d04..729d5d6 100644
--- a/src/math-shortcuts.ui
+++ b/src/math-shortcuts.ui
@@ -37,6 +37,13 @@
             <child>
               <object class="GtkShortcutsShortcut">
                 <property name="visible">1</property>
+                <property name="accelerator">&lt;primary&gt;Escape</property>
+                <property name="title" translatable="yes" context="shortcut window">Clear history</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="visible">1</property>
                 <property name="accelerator">&lt;ctrl&gt;q</property>
                 <property name="title" translatable="yes" context="shortcut window">Quit the 
application</property>
               </object>
diff --git a/src/math-window.vala b/src/math-window.vala
index e8b4ac1..dc244cc 100644
--- a/src/math-window.vala
+++ b/src/math-window.vala
@@ -38,6 +38,7 @@ public class MathWindow : Gtk.ApplicationWindow
         { "undo", undo_cb, null, null, null },
         { "redo", redo_cb, null, null, null },
         { "mode", mode_cb, "s", "\"basic\"", null },
+        { "clear", clear_cb, null, null, null },
         { "close",close, null, null, null },
     };
 
@@ -71,6 +72,11 @@ public class MathWindow : Gtk.ApplicationWindow
         Gtk.StyleContext.add_provider_for_screen (get_screen (), provider, 
Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION);
     }
 
+    private void clear_cb ()
+    {
+        _display.clear_history ();
+    }
+
     private void mode_changed_cb ()
     {
         var action = (SimpleAction) lookup_action ("mode");