1 files changed, 150 insertions, 0 deletions
diff --git a/browser/components/newtab/drop.js b/browser/components/newtab/drop.js
new file mode 100644
index 000000000..fe402a29b
--- /dev/null
+++ b/browser/components/newtab/drop.js
@@ -0,0 +1,150 @@
+#ifdef 0
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+#endif
+
+// A little delay that prevents the grid from being too sensitive when dragging
+// sites around.
+const DELAY_REARRANGE_MS = 100;
+
+/**
+ * This singleton implements site dropping functionality.
+ */
+var gDrop = {
+  /**
+   * The last drop target.
+   */
+  _lastDropTarget: null,
+
+  /**
+   * Handles the 'dragenter' event.
+   * @param aCell The drop target cell.
+   */
+  enter: function(aCell) {
+    this._delayedRearrange(aCell);
+  },
+
+  /**
+   * Handles the 'dragexit' event.
+   * @param aCell The drop target cell.
+   * @param aEvent The 'dragexit' event.
+   */
+  exit: function(aCell, aEvent) {
+    if (aEvent.dataTransfer && !aEvent.dataTransfer.mozUserCancelled) {
+      this._delayedRearrange();
+    } else {
+      // The drag operation has been cancelled.
+      this._cancelDelayedArrange();
+      this._rearrange();
+    }
+  },
+
+  /**
+   * Handles the 'drop' event.
+   * @param aCell The drop target cell.
+   * @param aEvent The 'dragexit' event.
+   */
+  drop: function(aCell, aEvent) {
+    // The cell that is the drop target could contain a pinned site. We need
+    // to find out where that site has gone and re-pin it there.
+    if (aCell.containsPinnedSite())
+      this._repinSitesAfterDrop(aCell);
+
+    // Pin the dragged or insert the new site.
+    this._pinDraggedSite(aCell, aEvent);
+
+    this._cancelDelayedArrange();
+
+    // Update the grid and move all sites to their new places.
+    gUpdater.updateGrid();
+  },
+
+  /**
+   * Re-pins all pinned sites in their (new) positions.
+   * @param aCell The drop target cell.
+   */
+  _repinSitesAfterDrop: function(aCell) {
+    let sites = gDropPreview.rearrange(aCell);
+
+    // Filter out pinned sites.
+    let pinnedSites = sites.filter(function(aSite) {
+      return aSite && aSite.isPinned();
+    });
+
+    // Re-pin all shifted pinned cells.
+    pinnedSites.forEach(aSite => aSite.pin(sites.indexOf(aSite)));
+  },
+
+  /**
+   * Pins the dragged site in its new place.
+   * @param aCell The drop target cell.
+   * @param aEvent The 'dragexit' event.
+   */
+  _pinDraggedSite: function(aCell, aEvent) {
+    let index = aCell.index;
+    let draggedSite = gDrag.draggedSite;
+
+    if (draggedSite) {
+      // Pin the dragged site at its new place.
+      if (aCell != draggedSite.cell)
+        draggedSite.pin(index);
+    } else {
+      let link = gDragDataHelper.getLinkFromDragEvent(aEvent);
+      if (link) {
+        // A new link was dragged onto the grid. Create it by pinning its URL.
+        gPinnedLinks.pin(link, index);
+
+        // Make sure the newly added link is not blocked.
+        gBlockedLinks.unblock(link);
+      }
+    }
+  },
+
+  /**
+   * Time a rearrange with a little delay.
+   * @param aCell The drop target cell.
+   */
+  _delayedRearrange: function(aCell) {
+    // The last drop target didn't change so there's no need to re-arrange.
+    if (this._lastDropTarget == aCell)
+      return;
+
+    let self = this;
+
+    function callback() {
+      self._rearrangeTimeout = null;
+      self._rearrange(aCell);
+    }
+
+    this._cancelDelayedArrange();
+    this._rearrangeTimeout = setTimeout(callback, DELAY_REARRANGE_MS);
+
+    // Store the last drop target.
+    this._lastDropTarget = aCell;
+  },
+
+  /**
+   * Cancels a timed rearrange, if any.
+   */
+  _cancelDelayedArrange: function() {
+    if (this._rearrangeTimeout) {
+      clearTimeout(this._rearrangeTimeout);
+      this._rearrangeTimeout = null;
+    }
+  },
+
+  /**
+   * Rearrange all sites in the grid depending on the current drop target.
+   * @param aCell The drop target cell.
+   */
+  _rearrange: function(aCell) {
+    let sites = gGrid.sites;
+
+    // We need to rearrange the grid only if there's a current drop target.
+    if (aCell)
+      sites = gDropPreview.rearrange(aCell);
+
+    gTransformation.rearrangeSites(sites, {unfreeze: !aCell});
+  }
+};