[mousetrap/gnome3-wip: 92/240] Added a basic implementation of joystick-style movement

[Heidi Ellis <heidiellis src gnome org>]

commit fdcfa033316b340d7b260f6a2aa2b6617c5daa96
Author: Kevin Brown <kbrown rediker com>
Date:   Thu Jun 12 21:36:09 2014 -0400

    Added a basic implementation of joystick-style movement
    
    This uses the `NoseLocator` to allows users to turn their head in
    the direction where they want the cursor to go.  By using an
    initial tracking point that is determined, the cursor moves at
    varying speeds based on how far in any direction the head is turned.
    A threshold is used to determine when the cursor should be moved,
    so minute movements of the head do not cause the mouse to "jitter".
    
    This is not enabled by default.

 src/mousetrap/pointers/nose_joystick.py |   63 +++++++++++++++++++++++++++++++
 1 files changed, 63 insertions(+), 0 deletions(-)
---
diff --git a/src/mousetrap/pointers/nose_joystick.py b/src/mousetrap/pointers/nose_joystick.py
new file mode 100644
index 0000000..7a3b4d4
--- /dev/null
+++ b/src/mousetrap/pointers/nose_joystick.py
@@ -0,0 +1,63 @@
+import mousetrap.pointers.interface as interface
+from mousetrap.vision import FeatureDetector, FeatureNotFoundException
+from mousetrap.gui import Gui, ScreenPointer
+
+from mousetrap.pointers.nose import NoseLocator
+
+
+class Pointer(interface.Pointer):
+    THRESHOLD = 5
+
+    def __init__(self):
+        self._nose_locator = NoseLocator()
+        self._image = None
+
+        pointer = ScreenPointer()
+
+        self._last_pointer_location = pointer.get_position()
+        self._initial_image_location = (0, 0)
+
+        self._location = self._last_pointer_location
+
+    def update_image(self, image):
+        self._image = image
+
+        try:
+            point_image = self._nose_locator.locate(image)
+            point_screen = self._convert_image_to_screen_point(*point_image)
+            self._location = point_screen
+        except FeatureNotFoundException:
+            self._location = None
+
+    def _convert_image_to_screen_point(self, image_x, image_y):
+        initial_x, initial_y = self._initial_image_location
+
+        if initial_x == 0 and initial_y == 0:
+            self._initial_image_location = (image_x, image_y)
+
+            return self._initial_image_location
+
+        delta_x = initial_x - image_x
+        delta_y = image_y - initial_y
+
+        if abs(delta_x) < self.THRESHOLD:
+            delta_x = 0
+
+        if abs(delta_y) < self.THRESHOLD:
+            delta_y = 0
+
+        if delta_x == 0 and delta_y == 0:
+            return None
+
+        pointer_x, pointer_y = self._last_pointer_location
+
+        pointer_x += delta_x
+        pointer_y += delta_y
+
+        return (pointer_x, pointer_y)
+
+    def get_new_position(self):
+        if self._location:
+            self._last_pointer_location = self._location
+
+        return self._location