michael@0: #ifdef 0
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
michael@0:  * You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: #endif
michael@0: 
michael@0: /**
michael@0:  * This singleton provides a custom drop target detection. We need this because
michael@0:  * the default DnD target detection relies on the cursor's position. We want
michael@0:  * to pick a drop target based on the dragged site's position.
michael@0:  */
michael@0: let gDropTargetShim = {
michael@0:   /**
michael@0:    * Cache for the position of all cells, cleaned after drag finished.
michael@0:    */
michael@0:   _cellPositions: null,
michael@0: 
michael@0:   /**
michael@0:    * The last drop target that was hovered.
michael@0:    */
michael@0:   _lastDropTarget: null,
michael@0: 
michael@0:   /**
michael@0:    * Initializes the drop target shim.
michael@0:    */
michael@0:   init: function () {
michael@0:     gGrid.node.addEventListener("dragstart", this, true);
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Add all event listeners needed during a drag operation.
michael@0:    */
michael@0:   _addEventListeners: function () {
michael@0:     gGrid.node.addEventListener("dragend", this);
michael@0: 
michael@0:     let docElement = document.documentElement;
michael@0:     docElement.addEventListener("dragover", this);
michael@0:     docElement.addEventListener("dragenter", this);
michael@0:     docElement.addEventListener("drop", this);
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Remove all event listeners that were needed during a drag operation.
michael@0:    */
michael@0:   _removeEventListeners: function () {
michael@0:     gGrid.node.removeEventListener("dragend", this);
michael@0: 
michael@0:     let docElement = document.documentElement;
michael@0:     docElement.removeEventListener("dragover", this);
michael@0:     docElement.removeEventListener("dragenter", this);
michael@0:     docElement.removeEventListener("drop", this);
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Handles all shim events.
michael@0:    */
michael@0:   handleEvent: function (aEvent) {
michael@0:     switch (aEvent.type) {
michael@0:       case "dragstart":
michael@0:         this._dragstart(aEvent);
michael@0:         break;
michael@0:       case "dragenter":
michael@0:         aEvent.preventDefault();
michael@0:         break;
michael@0:       case "dragover":
michael@0:         this._dragover(aEvent);
michael@0:         break;
michael@0:       case "drop":
michael@0:         this._drop(aEvent);
michael@0:         break;
michael@0:       case "dragend":
michael@0:         this._dragend(aEvent);
michael@0:         break;
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Handles the 'dragstart' event.
michael@0:    * @param aEvent The 'dragstart' event.
michael@0:    */
michael@0:   _dragstart: function (aEvent) {
michael@0:     if (aEvent.target.classList.contains("newtab-link")) {
michael@0:       gGrid.lock();
michael@0:       this._addEventListeners();
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Handles the 'dragover' event.
michael@0:    * @param aEvent The 'dragover' event.
michael@0:    */
michael@0:   _dragover: function (aEvent) {
michael@0:     // XXX bug 505521 - Use the dragover event to retrieve the
michael@0:     //                  current mouse coordinates while dragging.
michael@0:     let sourceNode = aEvent.dataTransfer.mozSourceNode.parentNode;
michael@0:     gDrag.drag(sourceNode._newtabSite, aEvent);
michael@0: 
michael@0:     // Find the current drop target, if there's one.
michael@0:     this._updateDropTarget(aEvent);
michael@0: 
michael@0:     // If we have a valid drop target,
michael@0:     // let the drag-and-drop service know.
michael@0:     if (this._lastDropTarget) {
michael@0:       aEvent.preventDefault();
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Handles the 'drop' event.
michael@0:    * @param aEvent The 'drop' event.
michael@0:    */
michael@0:   _drop: function (aEvent) {
michael@0:     // We're accepting all drops.
michael@0:     aEvent.preventDefault();
michael@0: 
michael@0:     // Make sure to determine the current drop target
michael@0:     // in case the dragover event hasn't been fired.
michael@0:     this._updateDropTarget(aEvent);
michael@0: 
michael@0:     // A site was successfully dropped.
michael@0:     this._dispatchEvent(aEvent, "drop", this._lastDropTarget);
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Handles the 'dragend' event.
michael@0:    * @param aEvent The 'dragend' event.
michael@0:    */
michael@0:   _dragend: function (aEvent) {
michael@0:     if (this._lastDropTarget) {
michael@0:       if (aEvent.dataTransfer.mozUserCancelled) {
michael@0:         // The drag operation was cancelled.
michael@0:         this._dispatchEvent(aEvent, "dragexit", this._lastDropTarget);
michael@0:         this._dispatchEvent(aEvent, "dragleave", this._lastDropTarget);
michael@0:       }
michael@0: 
michael@0:       // Clean up.
michael@0:       this._lastDropTarget = null;
michael@0:       this._cellPositions = null;
michael@0:     }
michael@0: 
michael@0:     gGrid.unlock();
michael@0:     this._removeEventListeners();
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Tries to find the current drop target and will fire
michael@0:    * appropriate dragenter, dragexit, and dragleave events.
michael@0:    * @param aEvent The current drag event.
michael@0:    */
michael@0:   _updateDropTarget: function (aEvent) {
michael@0:     // Let's see if we find a drop target.
michael@0:     let target = this._findDropTarget(aEvent);
michael@0: 
michael@0:     if (target != this._lastDropTarget) {
michael@0:       if (this._lastDropTarget)
michael@0:         // We left the last drop target.
michael@0:         this._dispatchEvent(aEvent, "dragexit", this._lastDropTarget);
michael@0: 
michael@0:       if (target)
michael@0:         // We're now hovering a (new) drop target.
michael@0:         this._dispatchEvent(aEvent, "dragenter", target);
michael@0: 
michael@0:       if (this._lastDropTarget)
michael@0:         // We left the last drop target.
michael@0:         this._dispatchEvent(aEvent, "dragleave", this._lastDropTarget);
michael@0: 
michael@0:       this._lastDropTarget = target;
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Determines the current drop target by matching the dragged site's position
michael@0:    * against all cells in the grid.
michael@0:    * @return The currently hovered drop target or null.
michael@0:    */
michael@0:   _findDropTarget: function () {
michael@0:     // These are the minimum intersection values - we want to use the cell if
michael@0:     // the site is >= 50% hovering its position.
michael@0:     let minWidth = gDrag.cellWidth / 2;
michael@0:     let minHeight = gDrag.cellHeight / 2;
michael@0: 
michael@0:     let cellPositions = this._getCellPositions();
michael@0:     let rect = gTransformation.getNodePosition(gDrag.draggedSite.node);
michael@0: 
michael@0:     // Compare each cell's position to the dragged site's position.
michael@0:     for (let i = 0; i < cellPositions.length; i++) {
michael@0:       let inter = rect.intersect(cellPositions[i].rect);
michael@0: 
michael@0:       // If the intersection is big enough we found a drop target.
michael@0:       if (inter.width >= minWidth && inter.height >= minHeight)
michael@0:         return cellPositions[i].cell;
michael@0:     }
michael@0: 
michael@0:     // No drop target found.
michael@0:     return null;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Gets the positions of all cell nodes.
michael@0:    * @return The (cached) cell positions.
michael@0:    */
michael@0:   _getCellPositions: function DropTargetShim_getCellPositions() {
michael@0:     if (this._cellPositions)
michael@0:       return this._cellPositions;
michael@0: 
michael@0:     return this._cellPositions = gGrid.cells.map(function (cell) {
michael@0:       return {cell: cell, rect: gTransformation.getNodePosition(cell.node)};
michael@0:     });
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Dispatches a custom DragEvent on the given target node.
michael@0:    * @param aEvent The source event.
michael@0:    * @param aType The event type.
michael@0:    * @param aTarget The target node that receives the event.
michael@0:    */
michael@0:   _dispatchEvent: function (aEvent, aType, aTarget) {
michael@0:     let node = aTarget.node;
michael@0:     let event = document.createEvent("DragEvents");
michael@0: 
michael@0:     // The event should not bubble to prevent recursion.
michael@0:     event.initDragEvent(aType, false, true, window, 0, 0, 0, 0, 0, false, false,
michael@0:                         false, false, 0, node, aEvent.dataTransfer);
michael@0: 
michael@0:     node.dispatchEvent(event);
michael@0:   }
michael@0: };