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// 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';
/**
* Creates a new ViewportScroller.
* A ViewportScroller scrolls the page in response to drag selection with the
* mouse.
*
*/
class ViewportScroller {
/**
* @param {Object} viewport The viewport info of the page.
* @param {Object} plugin The PDF plugin element.
* @param {Object} window The window containing the viewer.
*/
constructor(viewport, plugin, window) {
this.viewport_ = viewport;
this.plugin_ = plugin;
this.window_ = window;
this.mousemoveCallback_ = null;
this.timerId_ = null;
this.scrollVelocity_ = null;
this.lastFrameTime_ = 0;
}
/**
* Start scrolling the page by |scrollVelocity_| every
* |DRAG_TIMER_INTERVAL_MS_|.
*
* @private
*/
startDragScrollTimer_() {
if (this.timerId_ === null) {
this.timerId_ = this.window_.setInterval(
this.dragScrollPage_.bind(this),
ViewportScroller.DRAG_TIMER_INTERVAL_MS_);
this.lastFrameTime_ = Date.now();
}
}
/**
* Stops the drag scroll timer if it is active.
*
* @private
*/
stopDragScrollTimer_() {
if (this.timerId_ !== null) {
this.window_.clearInterval(this.timerId_);
this.timerId_ = null;
this.lastFrameTime_ = 0;
}
}
/**
* Scrolls the viewport by the current scroll velocity.
*
* @private
*/
dragScrollPage_() {
const position = this.viewport_.position;
const currentFrameTime = Date.now();
const timeAdjustment = (currentFrameTime - this.lastFrameTime_) /
ViewportScroller.DRAG_TIMER_INTERVAL_MS_;
position.y += (this.scrollVelocity_.y * timeAdjustment);
position.x += (this.scrollVelocity_.x * timeAdjustment);
this.viewport_.position = position;
this.lastFrameTime_ = currentFrameTime;
}
/**
* 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.
* @private
*/
calculateVelocity_(event) {
const x =
Math.min(
Math.max(
-event.offsetX, event.offsetX - this.plugin_.offsetWidth, 0),
ViewportScroller.MAX_DRAG_SCROLL_DISTANCE_) *
Math.sign(event.offsetX);
const y =
Math.min(
Math.max(
-event.offsetY, event.offsetY - this.plugin_.offsetHeight, 0),
ViewportScroller.MAX_DRAG_SCROLL_DISTANCE_) *
Math.sign(event.offsetY);
return {x: x, y: y};
}
/**
* Handles mousemove events. It updates the scroll velocity and starts and
* stops timer based on scroll velocity.
*
* @param {Object} event The mousemove event.
* @private
*/
onMousemove_(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(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);
}
}
}
}
/**
* The period of time in milliseconds to wait between updating the viewport
* position by the scroll velocity.
*
* @private
*/
ViewportScroller.DRAG_TIMER_INTERVAL_MS_ = 100;
/**
* The maximum drag scroll distance per DRAG_TIMER_INTERVAL in pixels.
*
* @private
*/
ViewportScroller.MAX_DRAG_SCROLL_DISTANCE_ = 100;
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