drag-action: Allow using settings for the drag threshold

ClutterDragAction should be able to use the newly added ClutterSettings
property exposing the system's drag threshold.

Currently, the x-drag-threshold and the y-drag-threshold properties (and
relative accessors) use an unsigned integer for their values; we should
be able to safely expand the range to include -1 as the minimum value,
and use this new value to tell the ClutterDragAction that it should query
the ClutterSettings object for the drag threshold.

The storage of the properties has been changed, albeit in a compatible
way, as GObject installs a uint ↔ int transformation function for GValue
automatically.

The setter for the drag thresholds has been changes to use a signed
integer, but the getter has been updated to always Do The Right Thing™:
it never returns -1 but, instead, will return the valid drag threshold,
either from the value set or from the Settings singleton.

This change is ABI compatible.

http://bugzilla.clutter-project.org/show_bug.cgi?id=2583

2 files changed, 108 insertions, 41 deletions

diff --git a/clutter/clutter-drag-action.c b/clutter/clutter-drag-action.c
index c2259d2da..39029644b 100644
--- a/clutter/clutter-drag-action.c
+++ b/clutter/clutter-drag-action.c
@@ -73,8 +73,8 @@ struct _ClutterDragActionPrivate
 {
   ClutterStage *stage;
 
-  gfloat x_drag_threshold;
-  gfloat y_drag_threshold;
+  gint x_drag_threshold;
+  gint y_drag_threshold;
   ClutterActor *drag_handle;
   ClutterDragAxis drag_axis;
 
@@ -129,6 +129,34 @@ static gboolean on_captured_event (ClutterActor      *stage,
 G_DEFINE_TYPE (ClutterDragAction, clutter_drag_action, CLUTTER_TYPE_ACTION);
 
 static void
+get_drag_threshold (ClutterDragAction *action,
+                    gint              *x_threshold,
+                    gint              *y_threshold)
+{
+  ClutterDragActionPrivate *priv = action->priv;
+  ClutterSettings *settings = clutter_settings_get_default ();
+  gint x_res, y_res, default_threshold;
+
+  g_object_get (settings, "dnd-drag-threshold", &default_threshold, NULL);
+
+  if (priv->x_drag_threshold < 0)
+    x_res = default_threshold;
+  else
+    x_res = priv->x_drag_threshold;
+
+  if (priv->y_drag_threshold < 0)
+    y_res = default_threshold;
+  else
+    y_res = priv->y_drag_threshold;
+
+  if (x_threshold != NULL)
+    *x_threshold = x_res;
+
+  if (y_threshold != NULL)
+    *y_threshold = y_res;
+}
+
+static void
 emit_drag_begin (ClutterDragAction *action,
                  ClutterActor      *actor,
                  ClutterEvent      *event)
@@ -191,8 +219,12 @@ emit_drag_motion (ClutterDragAction *action,
 
   if (priv->emit_delayed_press)
     {
-      if (ABS (delta_x) >= priv->x_drag_threshold ||
-          ABS (delta_y) >= priv->y_drag_threshold)
+      gint x_drag_threshold, y_drag_threshold;
+
+      get_drag_threshold (action, &x_drag_threshold, &y_drag_threshold);
+
+      if (ABS (delta_x) >= x_drag_threshold ||
+          ABS (delta_y) >= y_drag_threshold)
         {
           priv->emit_delayed_press = FALSE;
 
@@ -387,13 +419,15 @@ clutter_drag_action_set_property (GObject      *gobject,
   switch (prop_id)
     {
     case PROP_X_DRAG_THRESHOLD:
-      clutter_drag_action_set_drag_threshold (action, g_value_get_uint (value),
+      clutter_drag_action_set_drag_threshold (action,
+                                              g_value_get_int (value),
                                               priv->y_drag_threshold);
       break;
 
     case PROP_Y_DRAG_THRESHOLD:
-      clutter_drag_action_set_drag_threshold (action, priv->x_drag_threshold,
-                                              g_value_get_uint (value));
+      clutter_drag_action_set_drag_threshold (action,
+                                              priv->x_drag_threshold,
+                                              g_value_get_int (value));
       break;
 
     case PROP_DRAG_HANDLE:
@@ -420,11 +454,21 @@ clutter_drag_action_get_property (GObject    *gobject,
   switch (prop_id)
     {
     case PROP_X_DRAG_THRESHOLD:
-      g_value_set_uint (value, priv->x_drag_threshold);
+      {
+        gint threshold;
+
+        get_drag_threshold (CLUTTER_DRAG_ACTION (gobject), &threshold, NULL);
+        g_value_set_int (value, threshold);
+      }
       break;
 
     case PROP_Y_DRAG_THRESHOLD:
-      g_value_set_uint (value, priv->y_drag_threshold);
+      {
+        gint threshold;
+
+        get_drag_threshold (CLUTTER_DRAG_ACTION (gobject), NULL, &threshold);
+        g_value_set_int (value, threshold);
+      }
       break;
 
     case PROP_DRAG_HANDLE:
@@ -481,42 +525,58 @@ clutter_drag_action_class_init (ClutterDragActionClass *klass)
   /**
    * ClutterDragAction:x-drag-threshold:
    *
-   * The horizontal threshold, in pixels, that begins a drag action
+   * The horizontal threshold, in pixels, that the cursor must travel
+   * in order to begin a drag action.
    *
-   * When set to a non-zero value, #ClutterDragAction will only emit
+   * When set to a positive value, #ClutterDragAction will only emit
    * #ClutterDragAction::drag-begin if the pointer has moved
    * horizontally at least of the given amount of pixels since
-   * the button press event
+   * the button press event.
+   *
+   * When set to -1, #ClutterDragAction will use the default threshold
+   * stored in the #ClutterSettings:dnd-drag-threshold property of
+   * #ClutterSettings.
+   *
+   * When read, this property will always return a valid drag
+   * threshold, either as set or the default one.
    *
    * Since: 1.4
    */
   drag_props[PROP_X_DRAG_THRESHOLD] =
-    g_param_spec_uint ("x-drag-threshold",
-                       P_("Horizontal Drag Threshold"),
-                       P_("The horizontal amount of pixels required to start dragging"),
-                       0, G_MAXUINT,
-                       0,
-                       CLUTTER_PARAM_READWRITE);
+    g_param_spec_int ("x-drag-threshold",
+                      P_("Horizontal Drag Threshold"),
+                      P_("The horizontal amount of pixels required to start dragging"),
+                      -1, G_MAXINT,
+                      0,
+                      CLUTTER_PARAM_READWRITE);
 
   /**
    * ClutterDragAction:y-drag-threshold:
    *
-   * The vertical threshold, in pixels, that begins a drag action
+   * The vertical threshold, in pixels, that the cursor must travel
+   * in order to begin a drag action.
    *
-   * When set to a non-zero value, #ClutterDragAction will only emit
+   * When set to a positive value, #ClutterDragAction will only emit
    * #ClutterDragAction::drag-begin if the pointer has moved
    * vertically at least of the given amount of pixels since
-   * the button press event
+   * the button press event.
+   *
+   * When set to -1, #ClutterDragAction will use the value stored
+   * in the #ClutterSettings:dnd-drag-threshold property of
+   * #ClutterSettings.
+   *
+   * When read, this property will always return a valid drag
+   * threshold, either as set or the default one.
    *
    * Since: 1.4
    */
   drag_props[PROP_Y_DRAG_THRESHOLD] =
-    g_param_spec_uint ("y-drag-threshold",
-                       P_("Vertical Drag Threshold"),
-                       P_("The vertical amount of pixels required to start dragging"),
-                       0, G_MAXUINT,
-                       0,
-                       CLUTTER_PARAM_READWRITE);
+    g_param_spec_int ("y-drag-threshold",
+                      P_("Vertical Drag Threshold"),
+                      P_("The vertical amount of pixels required to start dragging"),
+                      -1, G_MAXINT,
+                      0,
+                      CLUTTER_PARAM_READWRITE);
 
   /**
    * ClutterDragAction:drag-handle:
@@ -687,18 +747,24 @@ clutter_drag_action_new (void)
 /**
  * clutter_drag_action_set_drag_threshold:
  * @action: a #ClutterDragAction
- * @x_threshold: a distance on the horizontal axis, in pixels
- * @y_threshold: a distance on the vertical axis, in pixels
+ * @x_threshold: a distance on the horizontal axis, in pixels, or
+ *   -1 to use the default drag threshold from #ClutterSettings
+ * @y_threshold: a distance on the vertical axis, in pixels, or
+ *   -1 to use the default drag threshold from #ClutterSettings
  *
  * Sets the horizontal and vertical drag thresholds that must be
- * cleared by the pointer before @action can begin the dragging
+ * cleared by the pointer before @action can begin the dragging.
+ *
+ * If @x_threshold or @y_threshold are set to -1 then the default
+ * drag threshold stored in the #ClutterSettings:dnd-drag-threshold
+ * property of #ClutterSettings will be used.
  *
  * Since: 1.4
  */
 void
 clutter_drag_action_set_drag_threshold (ClutterDragAction *action,
-                                        guint              x_threshold,
-					guint              y_threshold)
+                                        gint               x_threshold,
+                                        gint               y_threshold)
 {
   ClutterDragActionPrivate *priv;
   GObject *self;
@@ -735,22 +801,23 @@ clutter_drag_action_set_drag_threshold (ClutterDragAction *action,
  * @y_threshold: (out): return location for the vertical drag
  *   threshold value, in pixels
  *
- * Retrieves the values set by clutter_drag_action_set_drag_threshold()
+ * Retrieves the values set by clutter_drag_action_set_drag_threshold().
+ *
+ * If the #ClutterDragAction:x-drag-threshold property or the
+ * #ClutterDragAction:y-drag-threshold property have been set to -1 then
+ * this function will return the default drag threshold value as stored
+ * by the #ClutterSettings:dnd-drag-threshold property of #ClutterSettings.
  *
  * Since: 1.4
  */
 void
 clutter_drag_action_get_drag_threshold (ClutterDragAction *action,
                                         guint             *x_threshold,
-					guint             *y_threshold)
+                                        guint             *y_threshold)
 {
   g_return_if_fail (CLUTTER_IS_DRAG_ACTION (action));
 
-  if (x_threshold)
-    *x_threshold = action->priv->x_drag_threshold;
-
-  if (y_threshold)
-    *y_threshold = action->priv->y_drag_threshold;
+  get_drag_threshold (action, x_threshold, y_threshold);
 }
 
 /**
diff --git a/clutter/clutter-drag-action.h b/clutter/clutter-drag-action.h
index 90903a6ad..2cd066603 100644
--- a/clutter/clutter-drag-action.h
+++ b/clutter/clutter-drag-action.h
@@ -124,8 +124,8 @@ GType clutter_drag_action_get_type (void) G_GNUC_CONST;
 ClutterAction * clutter_drag_action_new                   (void);
 
 void            clutter_drag_action_set_drag_threshold (ClutterDragAction *action,
-                                                        guint              x_threshold,
-                                                        guint              y_threshold);
+                                                        gint               x_threshold,
+                                                        gint               y_threshold);
 void            clutter_drag_action_get_drag_threshold (ClutterDragAction *action,
                                                         guint             *x_threshold,
                                                         guint             *y_threshold);