Files.app: Added DragSelector class.

chrome/browser/resources/file_manager/js/drag_selector.js

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+'use strict';
+
+/**
+ * Drag selector used on the file list or the grid table.
+ * TODO(hirono): Support drag selection for grid view. crbug.com/224832
+ * @constructor
+ */
+function DragSelector() {
+  /**
+   * Target list of drag selection.
+   * @type {cr.ui.List}
+   * @private
+   */
+  this.target_ = null;
+
+  /**
+   * Border element of drag handle.
+   * @type {HtmlElement}
+   * @private
+   */
+  this.border_ = null;
+
+  /**
+   * Start point of dragging.
+   * @type {number?}
+   * @private
+   */
+  this.startX_ = null;
+
+  /**
+   * Start point of dragging.
+   * @type {number?}
+   * @private
+   */
+  this.startY_ = null;
+
+  /**
+   * Indexes of selected items by dragging at the last update.
+   * @type {Array.<number>}
+   * @private
+   */
+  this.lastSelection_ = null;

[yoshiki, 2013/06/04 01:16:01]

nit: I think it is better to assign '[]' instead of 'null'. (making this
non-nullable)

[hirono, 2013/06/04 02:16:10]

Done.

+
+  /**
+   * Indexes of selected items at the start of dragging.
+   * @type {Array.<number>}
+   * @private
+   */
+  this.originalSelection_ = null;

[yoshiki, 2013/06/04 01:16:01]

ditto

[hirono, 2013/06/04 02:16:10]

Done.

+
+  // Bind handlers to make them removable.
+  this.onMouseMoveBound_ = this.onMouseMove_.bind(this);
+  this.onMouseUpBound_ = this.onMouseUp_.bind(this);
+}
+
+/**
+ * Flag that shows whether the item is included in the selection or not.
+ * @enum {number}
+ * @private
+ */
+DragSelector.SelectionFlag_ = {
+  IN_LAST_SELECTION: 1 << 0,
+  IN_CURRENT_SELECTION: 1 << 1
+};
+
+/**
+ * Starts drag selection by reacting dragstart event.
+ * This function must be called from handlers of dragstart event.
+ *
+ * @this {DragSelector}
+ * @param {cr.ui.List} list List where the drag selection starts.
+ * @param {Event} event The dragstart event.
+ */
+DragSelector.prototype.startDragSelection = function(list, event) {
+  // Precondition check
+  if (!list.selectionModel_.multiple || this.target_)
+    return;
+
+  // Set the target of the drag selection
+  this.target_ = list;
+
+  // Create and add the border element
+  if (!this.border_) {
+    this.border_ = this.target_.ownerDocument.createElement('div');
+    this.border_.className = 'drag-selection-border';
+  }
+  list.appendChild(this.border_);
+
+  // Prevent default action.
+  event.preventDefault();
+
+  // If no modifier key is pressed, clear the original selection.
+  if (!event.shiftKey && !event.ctrlKey) {
+    this.target_.selectionModel_.unselectAll();
+  }
+
+  // Save the start state.
+  var rect = list.getBoundingClientRect();
+  this.startX_ = event.clientX - rect.left + list.scrollLeft;
+  this.startY_ = event.clientY - rect.top + list.scrollTop;
+  this.border_.style.left = this.startX_ + 'px';
+  this.border_.style.top = this.startY_ + 'px';
+  this.lastSelection_ = [];
+  this.originalSelection_ = this.target_.selectionModel_.selectedIndexes;
+
+  // Register event handlers.
+  // The handlers are bounded at the constructor.
+  this.target_.ownerDocument.addEventListener(
+      'mousemove', this.onMouseMoveBound_, true);
+  this.target_.ownerDocument.addEventListener(
+      'mouseup', this.onMouseUpBound_, true);
+};
+
+/**
+ * Handle the mousemove event.
+ * @private
+ * @param {MouseEvent} event The mousemove event.
+ */
+DragSelector.prototype.onMouseMove_ = function(event) {
+  // Get the selection bounds.
+  var inRect = this.target_.getBoundingClientRect();
+  var x = event.clientX - inRect.left + this.target_.scrollLeft;
+  var y = event.clientY - inRect.top + this.target_.scrollTop;
+  var borderBounds = {
+    left: Math.max(Math.min(this.startX_, x), 0),
+    top: Math.max(Math.min(this.startY_, y), 0),
+    right: Math.min(Math.max(this.startX_, x), this.target_.scrollWidth),
+    bottom: Math.min(Math.max(this.startY_, y), this.target_.scrollHeight)
+  };
+  borderBounds.width = borderBounds.right - borderBounds.left;
+  borderBounds.height = borderBounds.bottom - borderBounds.top;
+  this.border_.style.left = borderBounds.left + 'px';
+  this.border_.style.top = borderBounds.top + 'px';
+  this.border_.style.width = borderBounds.width + 'px';
+  this.border_.style.height = borderBounds.height + 'px';
+
+  // Collect items within the selection rect.
+  var currentSelection = [];
+  var leadIndex = -1;
+  for (var i = 0; i < this.target_.selectionModel_.length; i++) {
+    var itemMetrics = this.target_.getHeightsForIndex_(i);

[yoshiki, 2013/06/04 01:16:01]

getHeightsForIndex_() is private. Please make it public before use it. (and
cr.ui.List doesn't seem to have this method?)

[yoshiki, 2013/06/04 01:50:42]

Sorry, I was wrong. I did grep 'getHeightForIndex_'.  getHeightsForIndex_()
exists truly.

[hirono, 2013/06/04 02:16:10]

I added a TODO comment.

+    itemMetrics.bottom = itemMetrics.top + itemMetrics.height;
+    if (itemMetrics.top < borderBounds.bottom &&
+        itemMetrics.bottom >= borderBounds.top) {
+      currentSelection.push(i);
+    }
+    var pointed = itemMetrics.top <= y && y < itemMetrics.bottom;
+    if (pointed)
+      leadIndex = i;
+  }
+
+  // Diff the selection between currentSelection and this.lastSelection_.
+  var selectionFlag = [];
+  for (var i = 0; i < this.lastSelection_.length; i++) {
+    var index = this.lastSelection_[i];
+    // Bit operator can be used for undefined value.
+    selectionFlag[index] =
+        selectionFlag[index] | DragSelector.SelectionFlag_.IN_LAST_SELECTION;
+  }
+  for (var i = 0; i < currentSelection.length; i++) {
+    var index = currentSelection[i];
+    // Bit operator can be used for undefined value.
+    selectionFlag[index] =
+        selectionFlag[index] | DragSelector.SelectionFlag_.IN_CURRENT_SELECTION;
+  }
+
+  // Update the selection
+  this.target_.selectionModel_.beginChange();
+  for (var name in selectionFlag) {
+    var index = parseInt(name);
+    var flag = selectionFlag[name];
+    // flag may be one of followings:

[mtomasz, 2013/06/04 01:01:21]

nit: flag -> Flag / The flag

[hirono, 2013/06/04 01:08:08]

Done.

+    // - IN_LAST_SELECTION | IN_CURRENT_SELECTION
+    // - IN_LAST_SELECTION
+    // - IN_CURRENT_SELECTION
+    // - undefined
+
+    // If flag equals to (IN_LAST_SELECTION | IN_CURRENT_SELECTION),

[mtomasz, 2013/06/04 01:01:21]

nit: flag -> the flag

[hirono, 2013/06/04 01:08:08]

Done.

+    // this is included in both the last selection and the current selection.

[mtomasz, 2013/06/04 01:01:21]

nit: this -> then this item / then the item

[hirono, 2013/06/04 01:08:08]

Done.

+    // We have nothing to do for this item.
+
+    if (flag == DragSelector.SelectionFlag_.IN_LAST_SELECTION) {
+      // If flag equals to IN_LAST_SELECTION,

[mtomasz, 2013/06/04 01:01:21]

nit: flag -> the flag

[hirono, 2013/06/04 01:08:08]

Done.

+      // this is included in lastSelection but not in currentSelection.
+      // Revert the selection state to this.originalSelection_.
+      this.target_.selectionModel_.setIndexSelected(
+          index, this.originalSelection_.indexOf(index) != -1);
+    } else if (flag == DragSelector.SelectionFlag_.IN_CURRENT_SELECTION) {
+      // If flag equals to IN_CURRENT_SELECTION,
+      // this is included in currentSelection but no in lastSelection.

[mtomasz, 2013/06/04 01:01:21]

nit: no in -> not in

[hirono, 2013/06/04 01:08:08]

Done.

+      this.target_.selectionModel_.setIndexSelected(index, true);
+    }
+  }
+  if (leadIndex != -1) {
+    this.target_.selectionModel_.leadIndex = leadIndex;
+    this.target_.selectionModel_.anchorIndex = leadIndex;
+  }
+  this.target_.selectionModel_.endChange();
+  this.lastSelection_ = currentSelection;
+};
+
+/**
+ * Handle the mouseup event.
+ * @private
+ * @param {MouseEvent} event The mouseup event.
+ */
+DragSelector.prototype.onMouseUp_ = function(event) {
+  this.onMouseMove_(event);
+  this.target_.removeChild(this.border_);
+  this.target_.ownerDocument.removeEventListener(
+      'mousemove', this.onMouseMoveBound_, true);
+  this.target_.ownerDocument.removeEventListener(
+      'mouseup', this.onMouseUpBound_, true);
+  event.stopPropagation();
+  this.target_ = null;
+};