keybindings for next and previous file

[ and ] are now keybindings for the next and the previous open file.

xdot.py

@@ -2015,6 +2015,8 @@ def __init__(self, command_line_files, widget=None):
         # to display a file menu
         self.widget.connect("button-press-event", self.on_file_menu)
 
+        self.connect('key-press-event', self.on_key_press_event)
+
         self.last_open_dir = "."
 
         self.set_focus(self.dotwidget)
@@ -2145,16 +2147,35 @@ def on_close_file(self, action):
         self.open_file_idx = min(len(self.open_files)-1, self.open_file_idx)
         self.open_file(self.open_files[self.open_file_idx])
 
-    def on_go_forward(self, action):
+    def on_go_forward(self, action = None):
         """Display the next file"""
         self.open_file_idx = min(self.open_file_idx + 1, len(self.open_files) - 1)
         self.open_file(self.open_files[self.open_file_idx])
 
-    def on_go_back(self, action):
+    def on_go_back(self, action = None):
         """Display the previous file"""
         self.open_file_idx = max(0, self.open_file_idx - 1)
         self.open_file(self.open_files[self.open_file_idx])
 
+    def on_file_menu(self, widget, event):
+        if event.type == gtk.gdk.BUTTON_PRESS and event.button == 3:
+            menu = gtk.Menu()
+            for filename in self.open_files:
+                label = os.path.basename(filename)
+                item  = gtk.MenuItem(label)
+                menu.append(item)
+                item.connect("activate", lambda _, f: self.open_file(f), filename)
+                item.show()
+            menu.popup(None, None, None, 3, event.time)
+
+    def on_key_press_event(self, widget, event):
+        if event.keyval == gtk.keysyms.bracketleft:
+            self.on_go_back()
+            return True
+        if event.keyval == gtk.keysyms.bracketright:
+            self.on_go_forward()
+            return True
+
 
 class OptionParser(optparse.OptionParser):
 
@@ -2173,6 +2194,8 @@ def main():
   Up, Down, Left, Right     scroll
   PageUp, +, =              zoom in
   PageDown, -               zoom out
+  [                         previous open file
+  ]                         next open file
   R                         reload dot file
   F                         find
   Q                         quit