135 lines
4.1 KiB
JavaScript
135 lines
4.1 KiB
JavaScript
// Copyright 2015 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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'use strict';
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/**
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* @private
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* The period of time in milliseconds to wait between updating the viewport
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* position by the scroll velocity.
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*/
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ViewportScroller.DRAG_TIMER_INTERVAL_MS_ = 100;
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/**
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* @private
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* The maximum drag scroll distance per DRAG_TIMER_INTERVAL in pixels.
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*/
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ViewportScroller.MAX_DRAG_SCROLL_DISTANCE_ = 100;
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/**
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* Creates a new ViewportScroller.
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* A ViewportScroller scrolls the page in response to drag selection with the
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* mouse.
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* @param {Object} viewport The viewport info of the page.
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* @param {Object} plugin The PDF plugin element.
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* @param {Object} window The window containing the viewer.
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*/
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function ViewportScroller(viewport, plugin, window) {
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this.viewport_ = viewport;
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this.plugin_ = plugin;
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this.window_ = window;
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this.mousemoveCallback_ = null;
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this.timerId_ = null;
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this.scrollVelocity_ = null;
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this.lastFrameTime_ = 0;
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}
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ViewportScroller.prototype = {
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/**
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* @private
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* Start scrolling the page by |scrollVelocity_| every
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* |DRAG_TIMER_INTERVAL_MS_|.
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*/
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startDragScrollTimer_: function() {
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if (this.timerId_ === null) {
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this.timerId_ =
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this.window_.setInterval(this.dragScrollPage_.bind(this),
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ViewportScroller.DRAG_TIMER_INTERVAL_MS_);
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this.lastFrameTime_ = Date.now();
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}
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},
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/**
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* @private
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* Stops the drag scroll timer if it is active.
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*/
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stopDragScrollTimer_: function() {
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if (this.timerId_ !== null) {
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this.window_.clearInterval(this.timerId_);
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this.timerId_ = null;
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this.lastFrameTime_ = 0;
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}
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},
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/**
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* @private
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* Scrolls the viewport by the current scroll velocity.
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*/
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dragScrollPage_: function() {
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var position = this.viewport_.position;
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var currentFrameTime = Date.now();
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var timeAdjustment = (currentFrameTime - this.lastFrameTime_) /
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ViewportScroller.DRAG_TIMER_INTERVAL_MS_;
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position.y += (this.scrollVelocity_.y * timeAdjustment);
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position.x += (this.scrollVelocity_.x * timeAdjustment);
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this.viewport_.position = position;
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this.lastFrameTime_ = currentFrameTime;
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},
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/**
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* @private
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* Calculate the velocity to scroll while dragging using the distance of the
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* cursor outside the viewport.
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* @param {Object} event The mousemove event.
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* @return {Object} Object with x and y direction scroll velocity.
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*/
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calculateVelocity_: function(event) {
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var x = Math.min(Math.max(-event.offsetX,
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event.offsetX - this.plugin_.offsetWidth, 0),
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ViewportScroller.MAX_DRAG_SCROLL_DISTANCE_) *
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Math.sign(event.offsetX);
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var y = Math.min(Math.max(-event.offsetY,
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event.offsetY - this.plugin_.offsetHeight, 0),
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ViewportScroller.MAX_DRAG_SCROLL_DISTANCE_) *
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Math.sign(event.offsetY);
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return {
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x: x,
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y: y
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};
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},
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/**
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* @private
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* Handles mousemove events. It updates the scroll velocity and starts and
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* stops timer based on scroll velocity.
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* @param {Object} event The mousemove event.
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*/
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onMousemove_: function(event) {
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this.scrollVelocity_ = this.calculateVelocity_(event);
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if (!this.scrollVelocity_.x && !this.scrollVelocity_.y)
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this.stopDragScrollTimer_();
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else if (!this.timerId_)
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this.startDragScrollTimer_();
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},
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/**
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* Sets whether to scroll the viewport when the mouse is outside the
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* viewport.
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* @param {boolean} isSelecting Represents selection status.
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*/
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setEnableScrolling: function(isSelecting) {
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if (isSelecting) {
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if (!this.mousemoveCallback_)
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this.mousemoveCallback_ = this.onMousemove_.bind(this);
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this.plugin_.addEventListener('mousemove', this.mousemoveCallback_,
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false);
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} else {
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this.stopDragScrollTimer_();
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if (this.mousemoveCallback_) {
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this.plugin_.removeEventListener('mousemove', this.mousemoveCallback_,
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false);
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}
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}
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}
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};
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