[gnome-shell] dnd: Implement touch event support

[Carlos Garnacho <carlosg src gnome org>]

commit 508a13ae72201dbd5db0d32d3935c2a23d9946a6
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Oct 16 18:28:11 2015 +0200

    dnd: Implement touch event support
    
    We need to keep track of the pointer emulating touch sequence. In order
    to have events properly redirected on touch devices, the
    Clutter.grab_pointer and ungrab_pointer() have been replaced by the grab()
    and grab_sequence() ClutterInputDevice methods, one or the other is used
    depending on the device triggering DnD.
    
    An extra "sequence" argument has been added to startDrag, passing null here
    will resort to pointer grabs.
    
    This is enough to make thumbnails in the WorkspaceBox draggable through
    touch.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=756748

 js/ui/dnd.js |   71 +++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 files changed, 61 insertions(+), 10 deletions(-)
---
diff --git a/js/ui/dnd.js b/js/ui/dnd.js
index 2b87241..c7140a1 100644
--- a/js/ui/dnd.js
+++ b/js/ui/dnd.js
@@ -79,9 +79,12 @@ const _Draggable = new Lang.Class({
                                         dragActorOpacity: undefined });
 
         this.actor = actor;
-        if (!params.manualMode)
+        if (!params.manualMode) {
             this.actor.connect('button-press-event',
                                Lang.bind(this, this._onButtonPress));
+            this.actor.connect('touch-event',
+                               Lang.bind(this, this._onTouchEvent));
+        }
 
         this.actor.connect('destroy', Lang.bind(this, function() {
             this._actorDestroyed = true;
@@ -121,8 +124,50 @@ const _Draggable = new Lang.Class({
         return Clutter.EVENT_PROPAGATE;
     },
 
+    _onTouchEvent: function (actor, event) {
+        if (event.type() != Clutter.EventType.TOUCH_BEGIN ||
+            !global.display.is_pointer_emulating_sequence(event.get_event_sequence()))
+            return Clutter.EVENT_PROPAGATE;
+
+        if (Tweener.getTweenCount(actor))
+            return Clutter.EVENT_PROPAGATE;
+
+        this._touchSequence = event.get_event_sequence();
+
+        this._buttonDown = true;
+        this._grabActor();
+
+        let [stageX, stageY] = event.get_coords();
+        this._dragStartX = stageX;
+        this._dragStartY = stageY;
+
+        return Clutter.EVENT_PROPAGATE;
+    },
+
+    _grabDevice: function(actor) {
+        let manager = Clutter.DeviceManager.get_default();
+        let pointer = manager.get_core_device(Clutter.InputDeviceType.POINTER_DEVICE);
+
+        if (pointer && this._touchSequence)
+            pointer.sequence_grab(this._touchSequence, actor);
+        else if (pointer)
+            pointer.grab (actor);
+
+        this._grabbedDevice = pointer;
+    },
+
+    _ungrabDevice: function() {
+        if (this._touchSequence)
+            this._grabbedDevice.sequence_ungrab (this._touchSequence);
+        else
+            this._grabbedDevice.ungrab();
+
+        this._touchSequence = null;
+        this._grabbedDevice = null;
+    },
+
     _grabActor: function() {
-        Clutter.grab_pointer(this.actor);
+        this._grabDevice(this.actor);
         this._onEventId = this.actor.connect('event',
                                              Lang.bind(this, this._onEvent));
     },
@@ -131,7 +176,7 @@ const _Draggable = new Lang.Class({
         if (!this._onEventId)
             return;
 
-        Clutter.ungrab_pointer();
+        this._ungrabDevice();
         this.actor.disconnect(this._onEventId);
         this._onEventId = null;
     },
@@ -140,13 +185,13 @@ const _Draggable = new Lang.Class({
         if (!this._eventsGrabbed) {
             this._eventsGrabbed = Main.pushModal(_getEventHandlerActor());
             if (this._eventsGrabbed)
-                Clutter.grab_pointer(_getEventHandlerActor());
+                this._grabDevice(_getEventHandlerActor());
         }
     },
 
     _ungrabEvents: function() {
         if (this._eventsGrabbed) {
-            Clutter.ungrab_pointer();
+            this._ungrabDevice();
             Main.popModal(_getEventHandlerActor());
             this._eventsGrabbed = false;
         }
@@ -157,7 +202,9 @@ const _Draggable = new Lang.Class({
         // didn't start the drag, to drop the draggable in case the drag was in progress, and
         // to complete the drag and ensure that whatever happens to be under the pointer does
         // not get triggered if the drag was cancelled with Esc.
-        if (event.type() == Clutter.EventType.BUTTON_RELEASE) {
+        if (event.type() == Clutter.EventType.BUTTON_RELEASE ||
+            (event.type() == Clutter.EventType.TOUCH_END &&
+             global.display.is_pointer_emulating_sequence(event.get_event_sequence()))) {
             this._buttonDown = false;
             if (this._dragInProgress) {
                 return this._dragActorDropped(event);
@@ -172,7 +219,9 @@ const _Draggable = new Lang.Class({
             }
         // We intercept MOTION event to figure out if the drag has started and to draw
         // this._dragActor under the pointer when dragging is in progress
-        } else if (event.type() == Clutter.EventType.MOTION) {
+        } else if (event.type() == Clutter.EventType.MOTION ||
+                   (event.type() == Clutter.EventType.TOUCH_UPDATE &&
+                    global.display.is_pointer_emulating_sequence(event.get_event_sequence()))) {
             if (this._dragInProgress) {
                 return this._updateDragPosition(event);
             } else if (this._dragActor == null) {
@@ -214,7 +263,7 @@ const _Draggable = new Lang.Class({
      * This function is useful to call if you've specified manualMode
      * for the draggable.
      */
-    startDrag: function (stageX, stageY, time) {
+    startDrag: function (stageX, stageY, time, sequence) {
         currentDraggable = this;
         this._dragInProgress = true;
 
@@ -228,6 +277,8 @@ const _Draggable = new Lang.Class({
         this.emit('drag-begin', time);
         if (this._onEventId)
             this._ungrabActor();
+
+        this._touchSequence = sequence;
         this._grabEvents();
         global.screen.set_cursor(Meta.Cursor.DND_IN_DRAG);
 
@@ -338,8 +389,8 @@ const _Draggable = new Lang.Class({
         let threshold = Gtk.Settings.get_default().gtk_dnd_drag_threshold;
         if ((Math.abs(stageX - this._dragStartX) > threshold ||
              Math.abs(stageY - this._dragStartY) > threshold)) {
-                this.startDrag(stageX, stageY, event.get_time());
-                this._updateDragPosition(event);
+            this.startDrag(stageX, stageY, event.get_time(), this._touchSequence);
+            this._updateDragPosition(event);
         }
 
         return true;