Add compound selection usage example to examples.

examples/widgets/compound_selection.py

@@ -0,0 +1,57 @@
+from kivy.uix.gridlayout import GridLayout
+from kivy.uix.button import Button
+from kivy.uix.behaviors import CompoundSelectionBehavior
+from kivy.app import runTouchApp
+from kivy.core.window import Window
+
+
+class SelectableGrid(CompoundSelectionBehavior, GridLayout):
+
+    def __init__(self, **kwargs):
+        super(SelectableGrid, self).__init__(**kwargs)
+        keyboard = Window.request_keyboard(None, self)
+        keyboard.bind(on_key_down=self.select_with_key_down,
+                      on_key_up=self.select_with_key_up)
+
+        def print_selection(*l):
+            print [x.text for x in self.selected_nodes]
+        self.bind(selected_nodes=print_selection)
+
+    def goto_node(self, key, last_node, last_node_idx):
+        ''' This function is used to go to the node by typing the number
+        of the text of the button.
+        '''
+        node, idx = super(SelectableGrid, self).goto_node(key, last_node,
+                                                          last_node_idx)
+        if node == last_node:
+            children = self.children
+            for i in range(len(children)):
+                if children[i].text == key:
+                    return children[i], i
+        return node, idx
+
+    def select_node(self, node):
+        node.background_color = (1, 0, 0, 1)
+        return super(SelectableGrid, self).select_node(node)
+
+    def deselect_node(self, node):
+        node.background_color = (1, 1, 1, 1)
+        super(SelectableGrid, self).deselect_node(node)
+
+    def do_touch(self, instance, touch):
+        if ('button' in touch.profile and touch.button in
+            ('scrollup', 'scrolldown', 'scrollleft', 'scrollright')) or\
+            instance.collide_point(*touch.pos):
+            self.select_with_touch(instance, touch)
+        else:
+            return False
+        return True
+
+
+root = SelectableGrid(cols=5, up_count=5, multiselect=True, scroll_count=1)
+for i in range(40):
+    c = Button(text=str(i))
+    c.bind(on_touch_down=root.do_touch)
+    root.add_widget(c)
+
+runTouchApp(root)