84 lines
2.8 KiB
JavaScript
84 lines
2.8 KiB
JavaScript
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// 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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* A class that manages updating the browser with zoom changes.
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*/
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class ZoomManager {
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/**
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* Constructs a ZoomManager
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* @param {!Viewport} viewport A Viewport for which to manage zoom.
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* @param {Function} setBrowserZoomFunction A function that sets the browser
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* zoom to the provided value.
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* @param {number} initialZoom The initial browser zoom level.
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*/
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constructor(viewport, setBrowserZoomFunction, initialZoom) {
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this.viewport_ = viewport;
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this.setBrowserZoomFunction_ = setBrowserZoomFunction;
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this.browserZoom_ = initialZoom;
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this.changingBrowserZoom_ = null;
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}
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/**
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* Invoked when a browser-initiated zoom-level change occurs.
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* @param {number} newZoom the zoom level to zoom to.
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*/
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onBrowserZoomChange(newZoom) {
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// If we are changing the browser zoom level, ignore any browser zoom level
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// change events. Either, the change occurred before our update and will be
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// overwritten, or the change being reported is the change we are making,
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// which we have already handled.
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if (this.changingBrowserZoom_)
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return;
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if (this.floatingPointEquals(this.browserZoom_, newZoom))
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return;
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this.browserZoom_ = newZoom;
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this.viewport_.setZoom(newZoom);
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}
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/**
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* Invoked when an extension-initiated zoom-level change occurs.
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*/
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onPdfZoomChange() {
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// If we are already changing the browser zoom level in response to a
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// previous extension-initiated zoom-level change, ignore this zoom change.
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// Once the browser zoom level is changed, we check whether the extension's
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// zoom level matches the most recently sent zoom level.
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if (this.changingBrowserZoom_)
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return;
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let zoom = this.viewport_.zoom;
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if (this.floatingPointEquals(this.browserZoom_, zoom))
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return;
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this.changingBrowserZoom_ = this.setBrowserZoomFunction_(zoom).then(
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function() {
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this.browserZoom_ = zoom;
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this.changingBrowserZoom_ = null;
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// The extension's zoom level may have changed while the browser zoom
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// change was in progress. We call back into onPdfZoomChange to ensure the
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// browser zoom is up to date.
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this.onPdfZoomChange();
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}.bind(this));
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}
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/**
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* Returns whether two numbers are approximately equal.
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* @param {number} a The first number.
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* @param {number} b The second number.
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*/
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floatingPointEquals(a, b) {
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let MIN_ZOOM_DELTA = 0.01;
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// If the zoom level is close enough to the current zoom level, don't
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// change it. This avoids us getting into an infinite loop of zoom changes
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// due to floating point error.
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return Math.abs(a - b) <= MIN_ZOOM_DELTA;
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}
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};
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