Adds magnifier functionality to gnome-shell.

Adds the ability to create one or more zoom regions that show magnified or
enhanced views of the desktop.  The magnifier provides options for:
* magnification factor,
* four mouse tracking modes common to screen magnifiers,
* positioning the magnified view in one of four screen location, or full screen,
* crosshairs to accentuate the position of the mouse,
* user preferences persistence via GConf (schemas in
  .../data/gnome-shell.schemas).
* a DBus API to allow other processes to drive the magnifier as a service.

https://bugzilla.gnome.org/show_bug.cgi?id=595507

data/gnome-shell.schemas

@@ -244,6 +244,200 @@
         </locale>
       </schema>
 
+      <!-- Magnifier -->
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/show_magnifier</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/show_magnifier</applyto>
+        <owner>gnome-shell</owner>
+        <type>bool</type>
+        <default>false</default>
+        <locale name="C">
+            <short>Show or hide the magnifier</short>
+            <long>
+                Show or hide the magnifier and all of its zoom regions.
+            </long>
+        </locale>
+      </schema>
+
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/mouse_tracking</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/mouse_tracking</applyto>
+        <owner>gnome-shell</owner>
+        <type>int</type>
+        <default>1</default>
+        <locale name="C">
+            <short>Mouse Tracking Mode</short>
+            <long>
+                Determines the position of the magnified mouse image within
+                the magnified view and how it reacts to system mouse movement.
+                The values are 0 - none: no mouse tracking; 1 - centered: the
+                mouse  image is displayed at the center of the zoom region
+                (which also represents the point under the system mouse) and the
+                magnified contents are scrolled as the system mouse moves; 2 -
+                proportional: the position of the magnified mouse in the zoom
+                region is proportionally the same as the position of the system
+                mouse on screen; or 3 - push: when the magnified mouse
+                intersects a boundary of the zoom region, the contents are
+                scrolled into view.
+            </long>
+        </locale>
+      </schema>
+
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/screen_position</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/screen_position</applyto>
+        <owner>gnome-shell</owner>
+        <type>int</type>
+        <default>3</default>
+        <locale name="C">
+            <short>Screen position</short>
+            <long>
+                The magnified view either fills the entire screen (1), or
+                occupies the top-half (2), bottom-half (3), left-half (4), or
+                right-half (5) of the screen.
+            </long>
+        </locale>
+      </schema>
+
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/mag_factor</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/mag_factor</applyto>
+        <owner>gnome-shell</owner>
+        <type>float</type>
+        <default>2.0</default>
+        <locale name="C">
+            <short>Magnification factor</short>
+            <long>
+                The power of the magnification.  A value of 1.0 means no
+                magnification.  A value of 2.0 doubles the size.
+            </long>
+        </locale>
+      </schema>
+
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/lens_mode</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/lens_mode</applyto>
+        <owner>gnome-shell</owner>
+        <type>bool</type>
+        <default>false</default>
+        <locale name="C">
+            <short>Enable lens mode</short>
+            <long>
+                Whether the magnified view should be centered over the location
+                of the system mouse and move with it.
+            </long>
+        </locale>
+      </schema>
+
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/scroll_at_edges</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/scroll_at_edges</applyto>
+        <owner>gnome-shell</owner>
+        <type>bool</type>
+        <default>false</default>
+        <locale name="C">
+            <short>Scroll magnified contents beyond the edges of the desktop</short>
+            <long>
+                For centered mouse tracking, when the system pointer is at
+                or near the edge of the screen, the magnified contents continue
+                to scroll such that the screen edge moves into the magnified
+                view.
+            </long>
+        </locale>
+      </schema>
+
+      <!-- Magnifier: Crosshairs -->
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/show_cross_hairs</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/show_cross_hairs</applyto>
+        <owner>gnome-shell</owner>
+        <type>bool</type>
+        <default>false</default>
+        <locale name="C">
+            <short>Show or hide crosshairs</short>
+            <long>
+                Enables/disables display of crosshairs centered on the magnified mouse
+                sprite.
+            </long>
+        </locale>
+      </schema>
+
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/cross_hairs_thickness</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/cross_hairs_thickness</applyto>
+        <owner>gnome-shell</owner>
+        <type>int</type>
+        <default>8</default>
+        <locale name="C">
+            <short>Thickness of the crosshairs</short>
+            <long>
+                Width of the vertical and horizontal lines that make up the
+                crosshairs.
+            </long>
+        </locale>
+      </schema>
+
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/cross_hairs_color</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/cross_hairs_color</applyto>
+        <owner>gnome-shell</owner>
+        <type>string</type>
+        <default>#ff0000</default>
+        <locale name="C">
+            <short>Color of the crosshairs</short>
+            <long>
+                The color of the the vertical and horizontal lines that make up
+                the crosshairs.
+            </long>
+        </locale>
+      </schema>
+
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/cross_hairs_opacity</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/cross_hairs_opacity</applyto>
+        <owner>gnome-shell</owner>
+        <type>int</type>
+        <default>169</default>
+        <locale name="C">
+            <short>Opacity of the crosshairs</short>
+            <long>
+                Determines the transparency of the crosshairs, from fully opaque
+                to fully transparent.
+            </long>
+        </locale>
+      </schema>
+
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/cross_hairs_length</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/cross_hairs_length</applyto>
+        <owner>gnome-shell</owner>
+        <type>int</type>
+        <default>4096</default>
+        <locale name="C">
+            <short>Length of the crosshairs</short>
+            <long>
+                Determines the length of the vertical and horizontal lines that
+                make up the crosshairs.
+            </long>
+        </locale>
+      </schema>
+
+      <schema>
+        <key>/schemas/desktop/gnome/accessibility/magnifier/cross_hairs_clip</key>
+        <applyto>/desktop/gnome/accessibility/magnifier/cross_hairs_clip</applyto>
+        <owner>gnome-shell</owner>
+        <type>bool</type>
+        <default>false</default>
+        <locale name="C">
+            <short>Clip the crosshairs at the center</short>
+            <long>
+                Determines whether the crosshairs intersect the magnified mouse
+                sprite, or are clipped such that the ends of the horizontal
+                and vertical lines surround the mouse image.
+            </long>
+        </locale>
+      </schema>
+
   </schemalist>
 
 </gconfschemafile>

data/theme/gnome-shell.css

@@ -1006,3 +1006,13 @@ StTooltip {
 .lightbox {
     background-color: rgba(0, 0, 0, 0.27);
 }
+
+/* Magnifier */
+
+.magnifier-zoom-region {
+    border: 2px solid rgba(128, 0, 0, 255);
+}
+
+.magnifier-zoom-region.full-screen {
+    border-width: 0px;
+}

js/ui/Makefile.am

@@ -17,6 +17,8 @@ dist_jsui_DATA =		\
 	link.js			\
 	lookingGlass.js		\
 	main.js			\
+	magnifier.js		\
+	magnifierDBus.js	\
 	messageTray.js          \
 	notificationDaemon.js   \
 	overview.js		\

js/ui/main.js

@@ -26,6 +26,7 @@ const WindowAttentionHandler = imports.ui.windowAttentionHandler;
 const ShellDBus = imports.ui.shellDBus;
 const TelepathyClient = imports.ui.telepathyClient;
 const WindowManager = imports.ui.windowManager;
+const Magnifier = imports.ui.magnifier;
 
 const DEFAULT_BACKGROUND_COLOR = new Clutter.Color();
 DEFAULT_BACKGROUND_COLOR.from_pixel(0x2266bbff);
@@ -46,6 +47,7 @@ let shellDBusService = null;
 let modalCount = 0;
 let modalActorFocusStack = [];
 let uiGroup = null;
+let magnifier = null;
 let _errorLogStack = [];
 let _startDate;
 
@@ -162,6 +164,9 @@ function start() {
 
     global.stage.connect('captured-event', _globalKeyPressHandler);
 
+    // Install magnifier.
+    magnifier = new Magnifier.Magnifier();
+
     _log('info', 'loaded at ' + _startDate);
     log('GNOME Shell started at ' + _startDate);
 

src/Makefile.am

@@ -76,7 +76,8 @@ shell_public_headers_h =		\
 	shell-tray-manager.h		\
 	shell-uri-util.h		\
 	shell-window-tracker.h		\
-	shell-wm.h
+	shell-wm.h              \
+	shell-xfixes-cursor.h
 
 libgnome_shell_la_SOURCES =		\
 	$(shell_built_sources)		\
@@ -105,7 +106,9 @@ libgnome_shell_la_SOURCES =		\
 	shell-tray-manager.c		\
 	shell-uri-util.c		\
 	shell-window-tracker.c		\
-	shell-wm.c
+	shell-wm.c              \
+	shell-xfixes-cursor.c
+
 
 
 non_gir_sources =				\

src/shell-global.c

@@ -26,6 +26,7 @@
 #endif
 
 #define SHELL_DBUS_SERVICE "org.gnome.Shell"
+#define MAGNIFIER_DBUS_SERVICE "org.gnome.Magnifier"
 
 static void grab_notify (GtkWidget *widget, gboolean is_grab, gpointer user_data);
 static void update_root_window_pixmap (ShellGlobal *global);
@@ -853,6 +854,20 @@ shell_global_grab_dbus_service (ShellGlobal *global)
           exit (1);
         }
     }
+
+  /* ...and the org.gnome.Magnifier service.
+   */
+  if (!dbus_g_proxy_call (bus, "RequestName", &error,
+                          G_TYPE_STRING, MAGNIFIER_DBUS_SERVICE,
+                          G_TYPE_UINT, 0,
+                          G_TYPE_INVALID,
+                          G_TYPE_UINT, &request_name_result,
+                          G_TYPE_INVALID))
+    {
+      g_print ("failed to acquire %s: %s\n", MAGNIFIER_DBUS_SERVICE, error->message);
+      /* Failing to acquire the magnifer service is not fatal.  Log the error,
+       * but keep going. */
+    }
   g_object_unref (bus);
 }