add position lock feature - center of view (mouse not tracked)

magnus

@@ -35,6 +35,13 @@ class Main(object):
         self.refresh_interval = 250
         self.started_by_keypress = False
         self.force_refresh = False
+        self.position_lock = False
+        self.position_x = 0
+        self.position_y = 0
+        self.drag_x = 0
+        self.drag_y = 0
+        self.drag_lock = False
+        self.drag_enable = False
 
     def handle_shutdown(self, app):
         if self.started_by_keypress:
@@ -60,13 +67,27 @@ class Main(object):
             print("  --force-refresh")
             print("    Refresh continually (according to refresh interval)")
             print("      even if the mouse has not moved")
+            print("  --position x y")
+            print("    Set center of view, disable mouse tracking")
+            print("  --drag")
+            print("    Enables drag ability of main view, when --position is used")
             return 0
 
         if "--force-refresh" in args:
             # If this argument is supplied, refresh the view even if the mouse
             # has not moved. Useful if the screen content is video.
             self.force_refresh = True
 
+
+        if '--position' in args:
+            i = args.index('--position')
+            self.position_lock = True
+            self.position_x = int(args[i+1])
+            self.position_y = int(args[i+2])
+
+        if '--drag' in args:
+            self.drag_enable = True
+
         # Override refresh rate on command line
         for arg in args:
             if arg.startswith("--refresh-interval="):
@@ -162,6 +183,10 @@ class Main(object):
             Keybinder.bind("<Alt><Super>equal", self.zoom_in, zoom)
             Keybinder.bind("<Alt><Super>minus", self.zoom_out, zoom)
 
+        # bind mouse drag
+        self.w.connect("button-press-event", self.drag_on)
+        self.w.connect("button-release-event", self.drag_off)
+
         # and, go
         self.w.show_all()
 
@@ -191,6 +216,18 @@ class Main(object):
         zoom.set_active(current_index + 1)
         self.set_zoom(zoom)
 
+    def drag_on(self, a,b):
+        if not self.drag_enable:
+            return
+        display = Gdk.Display.get_default()
+        (screen, x, y, modifier) = display.get_pointer()
+        self.drag_lock = True
+        self.drag_x = x
+        self.drag_y = y
+
+    def drag_off(self, a,b):
+        self.drag_lock = False
+
     def read_window_decorations_size(self, win, alloc):
         sz = self.w.get_size()
         self.decorations_width = alloc.width - sz.width
@@ -256,14 +293,40 @@ class Main(object):
             width, height, width * len(light))
 
     def poll(self, force_refresh=False):
-        display = Gdk.Display.get_default()
-        (screen, x, y, modifier) = display.get_pointer()
-        if x == self.last_x and y == self.last_y:
-            # bail if nothing would be different
-            if not force_refresh and not self.force_refresh:
-                return True
-        self.last_x = x
-        self.last_y = y
+        if self.position_lock:
+
+            if self.drag_lock:
+    			# if dragged, move position lock
+
+                display = Gdk.Display.get_default()
+                (screen, x, y, modifier) = display.get_pointer()
+
+                # get delta
+                dx = (self.drag_x - x) // self.zoomlevel
+                dy = (self.drag_y - y) // self.zoomlevel
+
+                # apply delta
+                self.position_x += dx
+                self.position_y += dy
+
+                # reset drag start to current position
+                self.drag_x = x
+                self.drag_y = y
+
+            # use coordinates from position lock
+            x,y = self.position_x,self.position_y
+
+        else:
+			# get new coordinates
+            display = Gdk.Display.get_default()
+            (screen, x, y, modifier) = display.get_pointer()
+            if x == self.last_x and y == self.last_y:
+                # bail if nothing would be different
+                if not force_refresh and not self.force_refresh:
+                    return True
+            self.last_x = x
+            self.last_y = y
+
         if (x > self.window_x and
                 x <= (self.window_x + self.width + self.decorations_width) and
                 y > self.window_y and