Add more details

Author: leolost2605

src/Gestures/Gesture.vala

@@ -45,12 +45,14 @@ namespace Gala {
         /**
          * The x coordinate of the initial contact point for the gesture.
          * Doesn't have to be set. In that case it is set to {@link INVALID_COORD}.
+         * Currently the only backend not setting this is {@link GestureTracker.enable_touchpad}.
          */
         public float origin_x = INVALID_COORD;
 
         /**
          * The y coordinate of the initial contact point for the gesture.
          * Doesn't have to be set. In that case it is set to {@link INVALID_COORD}.
+         * Currently the only backend not setting this is {@link GestureTracker.enable_touchpad}.
          */
         public float origin_y = INVALID_COORD;
     }