appDisplay: Add a timeout when switching pages during DnD

Currently when dragging an icon to the space above or below the appGrid
to switch pages, we do so very quickly without checking when the last
page-switch happened. This makes it hard to move icons to pages which
are not the first or the last one, since the other pages are skipped
very quickly.

To fix this, add a timeout of 1 second that blocks switching pages after
a page-switch using drag overshoot occured.

Fixes https://gitlab.gnome.org/GNOME/gnome-shell/issues/1693

diff --git a/js/ui/appDisplay.js b/js/ui/appDisplay.js
index 155f33ed4798a913ecab6a706bc4178c77b4cbfe..00745ee7dbc799c437eef7b8fa967206f2d815ed 100644 (file)
--- a/js/ui/appDisplay.js
+++ b/js/ui/appDisplay.js
@@ -41,6 +41,7 @@ var APP_ICON_SCALE_IN_TIME = 500;
 var APP_ICON_SCALE_IN_DELAY = 700;
 
 const OVERSHOOT_THRESHOLD = 20;
+const OVERSHOOT_TIMEOUT = 1000;
 
 const SWITCHEROO_BUS_NAME = 'net.hadess.SwitcherooControl';
 const SWITCHEROO_OBJECT_PATH = '/net/hadess/SwitcherooControl';
@@ -379,6 +380,7 @@ var AllView = GObject.registerClass({
         this._availHeight = 0;
 
         this._lastOvershootY = -1;
+        this._lastOvershootTimeoutId = 0;
 
         Main.overview.connect('hidden', () => this.goToPage(0));
         this._grid.connect('space-opened', () => {
@@ -774,6 +776,13 @@ var AllView = GObject.registerClass({
             this.folderIcons[i].adaptToSize(availWidth, availHeight);
     }
 
+    _resetOvershoot() {
+        if (this._lastOvershootTimeoutId)
+            GLib.source_remove(this._lastOvershootTimeoutId);
+        this._lastOvershootTimeoutId = 0;
+        this._lastOvershootY = -1;
+    }
+
     _handleDragOvershoot(dragEvent) {
         let [, gridY] = this.get_transformed_position();
         let [, gridHeight] = this.get_transformed_size();
@@ -787,7 +796,8 @@ var AllView = GObject.registerClass({
         if (dragEvent.y > gridY && dragEvent.y < gridBottom) {
             // Check whether we moved out the area of the last switch
             if (Math.abs(this._lastOvershootY - dragEvent.y) > OVERSHOOT_THRESHOLD)
-                this._lastOvershootY = -1;
+                this._resetOvershoot();
+
             return;
         }
 
@@ -795,19 +805,29 @@ var AllView = GObject.registerClass({
         if (this._lastOvershootY >= 0)
             return;
 
-        this._lastOvershootY = dragEvent.y;
-
-        // Moving above the grid
         let currentY = this._adjustment.value;
-        if (dragEvent.y <= gridY && currentY > 0) {
-            this.goToPage(this._grid.currentPage - 1);
-            return;
-        }
-
-        // Moving below the grid
         let maxY = this._adjustment.upper - this._adjustment.page_size;
-        if (dragEvent.y >= gridBottom && currentY < maxY)
+
+        if (dragEvent.y <= gridY && currentY > 0)
+            this.goToPage(this._grid.currentPage - 1);
+        else if (dragEvent.y >= gridBottom && currentY < maxY)
             this.goToPage(this._grid.currentPage + 1);
+        else
+            return; // don't go beyond first/last page
+
+        this._lastOvershootY = dragEvent.y;
+
+        if (this._lastOvershootTimeoutId > 0)
+            GLib.source_remove(this._lastOvershootTimeoutId);
+
+        this._lastOvershootTimeoutId =
+            GLib.timeout_add(GLib.PRIORITY_DEFAULT, OVERSHOOT_TIMEOUT, () => {
+                this._resetOvershoot();
+                this._handleDragOvershoot(dragEvent);
+                return GLib.SOURCE_REMOVE;
+            });
+        GLib.Source.set_name_by_id(this._lastOvershootTimeoutId,
+            '[gnome-shell] this._lastOvershootTimeoutId');
     }
 
     _onDragBegin() {
@@ -841,7 +861,7 @@ var AllView = GObject.registerClass({
         }
 
         this._eventBlocker.visible = this._currentPopup !== null;
-        this._lastOvershootY = -1;
+        this._resetOvershoot();
     }
 
     _canAccept(source) {