Add EventIcon/CursorInvoker similar to CanvasIcon/CanvasInvoker

CanvasIcon and CanvasInvoker were removed in a previous GTK3-porting commit
as they were based on hippocanvas.

However, this leaves the toolkit with some missing functionality:
there is no longer a trivial way to show an icon which can receive mouse
events and pop up a palette. Such functionality is used in various
places throughout the shell and activities.

Reimplement this functionality as EventIcon and CursorInvoker.
Instead of reimplementing much of the Icon class (like CanvasIcon did),
EventIcon opts for a more simplistic encapsulation of an Icon object.
This means trivial API changes for CanvasIcon users who must now
use the 'icon' property with the Icon API.

Signed-off-by: Daniel Drake <dsd@laptop.org>
Acked-by: Simon Schampijer <simon@laptop.org>

src/sugar3/graphics/palettewindow.py

@@ -788,6 +788,68 @@ class WidgetInvoker(Invoker):
     widget = GObject.property(type=object, getter=_get_widget, setter=None)
 
 
+class CursorInvoker(Invoker):
+
+    def __init__(self, parent=None):
+        Invoker.__init__(self)
+
+        self._position_hint = self.AT_CURSOR
+        self._enter_hid = None
+        self._leave_hid = None
+        self._release_hid = None
+        self._item = None
+
+        if parent:
+            self.attach(parent)
+
+    def attach(self, parent):
+        Invoker.attach(self, parent)
+
+        self._item = parent
+        self._enter_hid = self._item.connect('enter-notify-event',
+                                             self.__enter_notify_event_cb)
+        self._leave_hid = self._item.connect('leave-notify-event',
+                                             self.__leave_notify_event_cb)
+        self._release_hid = self._item.connect('button-release-event',
+                                               self.__button_release_event_cb)
+
+    def detach(self):
+        Invoker.detach(self)
+        self._item.disconnect(self._enter_hid)
+        self._item.disconnect(self._leave_hid)
+        self._item.disconnect(self._release_hid)
+
+    def get_default_position(self):
+        return self.AT_CURSOR
+
+    def get_rect(self):
+        window = self._item.get_window()
+        allocation = self._item.get_allocation()
+        rect = Gdk.Rectangle()
+        rect.x, rect.y = window.get_root_coords(allocation.x, allocation.y)
+        rect.width = allocation.width
+        rect.height = allocation.height
+        return rect
+
+    def __enter_notify_event_cb(self, button, event):
+        self.notify_mouse_enter()
+        return False
+
+    def __leave_notify_event_cb(self, button, event):
+        self.notify_mouse_leave()
+        return False
+
+    def __button_release_event_cb(self, button, event):
+        if event.button == 3:
+            self.notify_right_click()
+            return True
+        else:
+            return False
+
+    def get_toplevel(self):
+        return self._item.get_toplevel()
+
+
 class ToolInvoker(WidgetInvoker):
 
     def __init__(self, parent=None):