Fix for Multipage selection by dragging mouse in OOP case in PDF.

chrome/browser/resources/pdf/viewport_scroller.js

+// Copyright 2015 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';
+
+/**
+ * @private
+ * The period of time in milliseconds to wait between updating the viewport
+ * position by the scroll velocity.
+ */
+ViewportScroller.DRAG_TIMER_INTERVAL_ = 100;
+
+/**
+ * @private
+ * The maximum drag scroll velocity in pixels.

[Bernhard Bauer, 2015/02/12 10:31:51]

Pixels isn't really a unit of velocity, pixels per <time unit> is. Or you
declare this as a the maximum drag distance per DRAG_TIMER_INTERVAL.

+ */
+ViewportScroller.MAX_DRAG_SCROLL_VELOCITY_ = 100;
+
+/**
+ * Creates a new ViewportScroller.
+ * A ViewportScroller scrolls the page in response to drag selection with the
+ * mouse.
+ * @param {Object} viewport The viewport info of the page.
+ * @param {Object} plugin The PDF plugin element.
+ * @param {Object} window The window containing the viewer.
+ */
+function ViewportScroller(viewport, plugin, window) {
+  this.viewport_ = viewport;
+  this.plugin_ = plugin;
+  this.window_ = window;
+  this.mousemoveCallback_ = null;
+  this.timerId_ = null;
+  this.scrollVelocity_ = null;
+}
+
+ViewportScroller.prototype = {
+  /**
+   * @private
+   * Start scrolling the page by |scrollVelocity_| every |DRAG_TIMER_INTERVAL|.
+   */
+  startDragScrollTimer_: function() {
+    if (this.timerId_ === null) {
+      this.timerId_ =
+          this.window_.setInterval(this.dragScrollPage_.bind(this),
+                                   ViewportScroller.DRAG_TIMER_INTERVAL_);
+    }
+  },
+
+  /**
+   * @private
+   * Stops the drag scroll timer if it is active.
+   */
+  stopDragScrollTimer_: function() {
+    if (this.timerId_ !== null) {
+      this.window_.clearInterval(this.timerId_);
+      this.timerId_ = null;
+    }
+  },
+
+  /**
+   * @private
+   * Scrolls the viewport by the current scroll velocity.
+   */
+  dragScrollPage_: function() {
+    var position = this.viewport_.position;
+    position.y += this.scrollVelocity_.y;
+    position.x += this.scrollVelocity_.x;
+    this.viewport_.position = position;
+  },
+
+  /**
+   * @private
+   * Calculate the velocity to scroll while dragging using the distance of the
+   * cursor outside the viewport.
+   * @param {Object} event The mousemove event.
+   * @return {Object} Object with x and y direction scroll velocity.
+   */
+  calculateVelocity_: function(event) {
+    var x = Math.min(Math.max(-event.offsetX,
+                              event.offsetX - this.plugin_.offsetWidth, 0),
+                     ViewportScroller.MAX_DRAG_SCROLL_VELOCITY_) *
+            Math.sign(event.offsetX);
+    var y = Math.min(Math.max(-event.offsetY,
+                              event.offsetY - this.plugin_.offsetHeight, 0),
+                     ViewportScroller.MAX_DRAG_SCROLL_VELOCITY_) *
+            Math.sign(event.offsetY);
+    return {
+      x: x,
+      y: y
+    };
+  },
+
+  /**
+   * @private
+   * Handles mousemove events. It updates the scroll velocity and starts and
+   * stops timer based on scroll velocity.
+   * @param {Object} event The mousemove event.
+   */
+  onMousemove_: function(event) {
+    this.scrollVelocity_ = this.calculateVelocity_(event);
+    if (!this.scrollVelocity_.x && !this.scrollVelocity_.y)
+      this.stopDragScrollTimer_();
+    else if (!this.timerId_)
+      this.startDragScrollTimer_();
+  },
+
+  /**
+   * Sets whether to scroll the viewport when the mouse is outside the
+   * viewport.
+   * @param {boolean} isSelecting Represents selection status.
+   */
+  setEnableScrolling: function(isSelecting) {
+    if (isSelecting) {
+      if (!this.mousemoveCallback_)
+        this.mousemoveCallback_ = this.onMousemove_.bind(this);
+      this.plugin_.addEventListener('mousemove', this.mousemoveCallback_,
+                                    false);
+    } else {
+      this.stopDragScrollTimer_();
+      if (this.mousemoveCallback_) {
+        this.plugin_.removeEventListener('mousemove', this.mousemoveCallback_,
+                                         false);
+      }
+    }
+  }
+};