Files.app: Added DragSelector class.

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

Index: chrome/browser/resources/file_manager/js/drag_selector.js
diff --git a/chrome/browser/resources/file_manager/js/drag_selector.js b/chrome/browser/resources/file_manager/js/drag_selector.js
new file mode 100644
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+// 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.
+   * @private
+   * @type {cr.ui.list?}

[mtomasz, 2013/05/31 08:15:31]

Shouldn't be list? -> List

[hirono, 2013/06/03 04:40:33]

Done.

+   */
+  this.target_ = null;
+
+  /**
+   * Border element of drag handle.
+   * @private

[mtomasz, 2013/05/31 08:15:31]

@private after @type

[hirono, 2013/06/03 04:40:33]

Done.

+   * @type {HtmlElement?}

[mtomasz, 2013/05/31 08:15:31]

Isn't '?' redundant? Objects do not need ? for nullable afaik.

[hirono, 2013/06/03 04:40:33]

Done.

+   */
+  this.border_ = null;
+
+  /**
+   * Start point of dragging.
+   * @private
+   * @type {number?}
+   */
+  this.startX_ = null;
+
+  /**
+   * Start point of dragging.
+   * @private
+   * @type {number?}

[mtomasz, 2013/05/31 08:15:31]

For example, here ? is necessary, since it is not an object.

[hirono, 2013/06/03 04:40:33]

Done.

+   */
+  this.startY_ = null;
+
+  /**
+   * Indexes of selected items by dragging at the last update.
+   * @private
+   * @type {Array.<number>?}
+   */
+  this.lastSelection_ = null;
+
+  /**
+   * Indexes of selected items at the start of dragging.
+   * @private
+   * @type {Array.<number>?}
+   */
+  this.originalSelection_ = null;
+
+  // Bind handlers to make them removable.
+  this.onMouseMove_ = DragSelector.prototype.onMouseMove_.bind(this);

[mtomasz, 2013/05/31 08:15:31]

This looks tricky. For that we use:
this.onMouseMoveBound_ = DragSelector...

[hirono, 2013/06/03 04:40:33]

Done.

+  this.onMouseUp_ = DragSelector.prototype.onMouseUp_.bind(this);
+}
+
+/**
+ * Starts drag selection by reacting dragstart event.
+ * This function must be called from handlers of dragstart event.

[mtomasz, 2013/05/31 08:15:31]

When @jsdoc is long, you may want to add an empty line after the description for
better readability.

[hirono, 2013/06/03 04:40:33]

Done.

+ * @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 drag selection

[mtomasz, 2013/05/31 08:15:31]

of -> of the

[hirono, 2013/06/03 04:40:33]

Done.

+  this.target_ = list;

[mtomasz, 2013/05/31 08:15:31]

Please add empty lines in large blocks of code for better readability.

[hirono, 2013/06/03 04:40:33]

Done.

+  // 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

[mtomasz, 2013/05/31 08:15:31]

Add periods at the end of sentences.

[hirono, 2013/06/03 04:40:33]

Done.

+  event.preventDefault();
+  // Handle modifier keys.

[mtomasz, 2013/05/31 08:15:31]

Please change to more descriptive comment, eg. what the code actually does.

[hirono, 2013/06/03 04:40:33]

Done.

+  if (!event.modifiers & Event.SHIFT_MASK &&

[mtomasz, 2013/05/31 08:15:31]

Does it work as intended? I can start selection using dragging even without the
modifiers.

[hirono, 2013/06/03 04:40:33]

These modifier keys just specified that this selection is additional. (start
drag selection with keeping the original selection)
I'm planning on starting dragging selection without the modifiers.
Whether drag selection should start or not is decided where the dragging
started. (e.g. the drag selection starts in the case that the dragging started
on the background of the list)
This judgement will be implemented by the next CL.

+      !event.modifiers & Event.CONTROL_MASK) {
+    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 evnet handlers.
+  // The handlers are bounded at the constructor.
+  this.target_.ownerDocument.addEventListener(
+      'mousemove', this.onMouseMove_, true);
+  this.target_.ownerDocument.addEventListener(
+      'mouseup', this.onMouseUp_, true);
+};
+
+/**
+ * Handle the mousemove evnet.

[mtomasz, 2013/05/31 08:15:31]

evnet -> event

[hirono, 2013/06/03 04:40:33]

Done.

+ * @private
+ * @param {MouseEvent} event The mousemove event.
+ */
+DragSelector.prototype.onMouseMove_ = function(event) {
+  // Get current selection and leadIndex from geometry.
+  var inRect = this.target_.getBoundingClientRect();
+  var x = event.clientX - inRect.left + this.target_.scrollLeft;
+  var y = event.clientY - inRect.top + this.target_.scrollTop;
+  var borderMetrics = {

[mtomasz, 2013/05/31 08:15:31]

Metrics -> Bounds / Rect / Geometry?
(optional) border -> selection?

[hirono, 2013/06/03 04:40:33]

Done.

+    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)
+  };
+  borderMetrics.width = borderMetrics.right - borderMetrics.left;
+  borderMetrics.height = borderMetrics.bottom - borderMetrics.top;
+  this.border_.style.left = borderMetrics.left + 'px';
+  this.border_.style.top = borderMetrics.top + 'px';
+  this.border_.style.width = borderMetrics.width + 'px';
+  this.border_.style.height = borderMetrics.height + 'px';
+  var currentSelection = [];
+  var leadIndex = -1;

[mtomasz, 2013/05/31 08:15:31]

Can we add a comment, eg. Collect items within the selection rect.

[hirono, 2013/06/03 04:40:33]

Done.

+  for (var i = 0; i < this.target_.selectionModel_.length; i++) {
+    var itemMetrics = this.target_.getHeightsForIndex_(i);
+    itemMetrics.bottom = itemMetrics.top + itemMetrics.height;
+    if (itemMetrics.top < borderMetrics.bottom &&
+        itemMetrics.bottom >= borderMetrics.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] | 1;

[mtomasz, 2013/05/31 08:15:31]

1, 2 -> enum?

[hirono, 2013/06/03 04:40:33]

Done.

+  }
+  for (var i = 0; i < currentSelection.length; i++) {
+    var index = currentSelection[i];
+    // Bit operator can be used for undefined value.
+    selectionFlag[index] = selectionFlag[index] | 2;
+  }
+  // Update selection

[mtomasz, 2013/05/31 08:15:31]

selection -> the selection

[hirono, 2013/06/03 04:40:33]

Done.

+  this.target_.selectionModel_.beginChange();
+  for (var name in selectionFlag) {
+    var index = parseInt(name);

[mtomasz, 2013/05/31 08:15:31]

Is parseInt necessary here?

[hirono, 2013/06/03 04:40:33]

Yes, actually, I had used the name directly at first.
The name assigned by for..in loop is string and it cannot be found
by this.originalSelection_.indexOf(name).

+    var flag = selectionFlag[name];
+    if (flag == 1) {
+      // This is included in lastSelection but currentSelection.
+      // Revert the selection state to this.originalSelection_.
+      this.target_.selectionModel_.setIndexSelected(
+          index, this.originalSelection_.indexOf(index) != -1);
+    } else if (flag == 2) {
+      // This is included in currentSelection but lastSelection.
+      this.target_.selectionModel_.setIndexSelected(index, true);
+    }
+  }
+  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.onMouseMove_, true);
+  this.target_.ownerDocument.removeEventListener(
+    'mouseup', this.onMouseUp_, true);
+  event.stopPropagation();
+  this.target_ = null;
+};