1 files changed, 116 insertions, 0 deletions
diff --git a/js/ui/xdndHandler.js b/js/ui/xdndHandler.js
new file mode 100644
index 0000000..3a4880b
--- /dev/null
+++ b/js/ui/xdndHandler.js
@@ -0,0 +1,116 @@
+// -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
+/* exported XdndHandler */
+
+const { Clutter } = imports.gi;
+const Signals = imports.misc.signals;
+
+const DND = imports.ui.dnd;
+const Main = imports.ui.main;
+
+var XdndHandler = class extends Signals.EventEmitter {
+    constructor() {
+        super();
+
+        // Used to display a clone of the cursor window when the
+        // window group is hidden (like it happens in the overview)
+        this._cursorWindowClone = null;
+
+        // Used as a drag actor in case we don't have a cursor window clone
+        this._dummy = new Clutter.Actor({ width: 1, height: 1, opacity: 0 });
+        Main.uiGroup.add_actor(this._dummy);
+        this._dummy.hide();
+
+        var dnd = global.backend.get_dnd();
+        dnd.connect('dnd-enter', this._onEnter.bind(this));
+        dnd.connect('dnd-position-change', this._onPositionChanged.bind(this));
+        dnd.connect('dnd-leave', this._onLeave.bind(this));
+    }
+
+    // Called when the user cancels the drag (i.e release the button)
+    _onLeave() {
+        global.window_group.disconnectObject(this);
+        if (this._cursorWindowClone) {
+            this._cursorWindowClone.destroy();
+            this._cursorWindowClone = null;
+        }
+
+        this.emit('drag-end');
+    }
+
+    _onEnter() {
+        global.window_group.connectObject('notify::visible',
+            this._onWindowGroupVisibilityChanged.bind(this), this);
+
+        this.emit('drag-begin', global.get_current_time());
+    }
+
+    _onWindowGroupVisibilityChanged() {
+        if (!global.window_group.visible) {
+            if (this._cursorWindowClone)
+                return;
+
+            let windows = global.get_window_actors();
+            let cursorWindow = windows[windows.length - 1];
+
+            // FIXME: more reliable way?
+            if (!cursorWindow.get_meta_window().is_override_redirect())
+                return;
+
+            const constraintPosition = new Clutter.BindConstraint({
+                coordinate: Clutter.BindCoordinate.POSITION,
+                source: cursorWindow,
+            });
+
+            this._cursorWindowClone = new Clutter.Clone({ source: cursorWindow });
+            Main.uiGroup.add_actor(this._cursorWindowClone);
+
+            // Make sure that the clone has the same position as the source
+            this._cursorWindowClone.add_constraint(constraintPosition);
+        } else {
+            if (!this._cursorWindowClone)
+                return;
+
+            this._cursorWindowClone.destroy();
+            this._cursorWindowClone = null;
+        }
+    }
+
+    _onPositionChanged(obj, x, y) {
+        let pickedActor = global.stage.get_actor_at_pos(Clutter.PickMode.REACTIVE, x, y);
+
+        // Make sure that the cursor window is on top
+        if (this._cursorWindowClone)
+            Main.uiGroup.set_child_above_sibling(this._cursorWindowClone, null);
+
+        let dragEvent = {
+            x,
+            y,
+            dragActor: this._cursorWindowClone ?? this._dummy,
+            source: this,
+            targetActor: pickedActor,
+        };
+
+        for (let i = 0; i < DND.dragMonitors.length; i++) {
+            let motionFunc = DND.dragMonitors[i].dragMotion;
+            if (motionFunc) {
+                let result = motionFunc(dragEvent);
+                if (result != DND.DragMotionResult.CONTINUE)
+                    return;
+            }
+        }
+
+        while (pickedActor) {
+            if (pickedActor._delegate && pickedActor._delegate.handleDragOver) {
+                let [r_, targX, targY] = pickedActor.transform_stage_point(x, y);
+                let result = pickedActor._delegate.handleDragOver(this,
+                                                                  dragEvent.dragActor,
+                                                                  targX,
+                                                                  targY,
+                                                                  global.get_current_time());
+                if (result != DND.DragMotionResult.CONTINUE)
+                    return;
+            }
+            pickedActor = pickedActor.get_parent();
+        }
+    }
+};