Propagate browser zoom changes to embedded PDFs.

chrome/browser/resources/pdf/zoom_manager.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';
 
 /**
- * A class that manages updating the browser with zoom changes.
+ * Abstract parent of classes that manage updating the browser
+ * with zoom changes and/or updating the viewer's zoom when
+ * the browser zoom changes.
  */
 class ZoomManager {
   /**
-   * Constructs a ZoomManager
+   * Constructs a ZoomManager.
+   * @param {!Viewport} viewport A Viewport for which to manage zoom.
+   * @param {number} initialZoom The initial browser zoom level.
+   */
+  constructor(viewport, initialZoom) {
+    if (this.constructor === ZoomManager) {
+      throw new TypeError('Instantiated abstract class: ZoomManager');
+    }
+    this.viewport_ = viewport;
+    this.browserZoom_ = initialZoom;
+  }
+
+  /**
+   * Creates the appropriate kind of zoom manager given the zoom behaviour.
+   * @param {BrowserApi.ZoomBehaviour} zoomBehaviour How to manage zoom.
+   * @param {!Viewport} viewport A Viewport for which to manage zoom.
+   * @param {Function} setBrowserZoomFunction A function that sets the browser
+   *     zoom to the provided value.
+   * @param {number} initialZoom The initial browser zoom level.
+   */
+  static create(zoomBehaviour, viewport, setBrowserZoomFunction, initialZoom) {
+    switch (zoomBehaviour) {
+      case BrowserApi.ZoomBehaviour.MANAGE:
+        return new ActiveZoomManager(
+            viewport, setBrowserZoomFunction, initialZoom);
+      case BrowserApi.ZoomBehaviour.PROPAGATE_PARENT:
+        return new EmbeddedZoomManager(viewport, initialZoom);
+      default:
+        return new InactiveZoomManager(viewport, initialZoom);
+    }
+  }
+
+  /**
+   * Invoked when a browser-initiated zoom-level change occurs.
+   * @param {number} newZoom the zoom level to zoom to.
+   */
+  onBrowserZoomChange(newZoom) {}
+
+  /**
+   * Invoked when an extension-initiated zoom-level change occurs.
+   */
+  onPdfZoomChange() {}
+
+  /**
+   * Combines the internal pdf zoom and the browser zoom to
+   * produce the total zoom level for the viewer.
+   * @param {number} internalZoom the zoom level internal to the viewer.
+   * @return {number} the total zoom level.
+   */
+  applyBrowserZoom(internalZoom) {
+    return this.browserZoom_ * internalZoom;
+  }
+
+  /**
+   * Given a zoom level, return the internal zoom level needed to
+   * produce that zoom level.
+   * @param {number} totalZoom the total zoom level.
+   * @return {number} the zoom level internal to the viewer.
+   */
+  internalZoomComponent(totalZoom) {
+    return totalZoom / this.browserZoom_;
+  }
+
+  /**
+   * Returns whether two numbers are approximately equal.
+   * @param {number} a The first number.
+   * @param {number} b The second number.
+   */
+  floatingPointEquals(a, b) {
+    let MIN_ZOOM_DELTA = 0.01;
+    // If the zoom level is close enough to the current zoom level, don't
+    // change it. This avoids us getting into an infinite loop of zoom changes
+    // due to floating point error.
+    return Math.abs(a - b) <= MIN_ZOOM_DELTA;
+  }
+};
+
+/**
+ * InactiveZoomManager has no control over the browser's zoom
+ * and does not respond to browser zoom changes.
+ */
+class InactiveZoomManager extends ZoomManager {};
+
+/**
+ * ActiveZoomManager controls the browser's zoom.
+ */
+class ActiveZoomManager extends ZoomManager {
+  /**
+   * Constructs a ActiveZoomManager.
    * @param {!Viewport} viewport A Viewport for which to manage zoom.
    * @param {Function} setBrowserZoomFunction A function that sets the browser
    *     zoom to the provided value.
    * @param {number} initialZoom The initial browser zoom level.
    */
   constructor(viewport, setBrowserZoomFunction, initialZoom) {
-    this.viewport_ = viewport;
+    super(viewport, initialZoom);
     this.setBrowserZoomFunction_ = setBrowserZoomFunction;
-    this.browserZoom_ = initialZoom;
     this.changingBrowserZoom_ = null;
   }
 
   /**
    * Invoked when a browser-initiated zoom-level change occurs.
    * @param {number} newZoom the zoom level to zoom to.
    */
   onBrowserZoomChange(newZoom) {
     // If we are changing the browser zoom level, ignore any browser zoom level
     // change events. Either, the change occurred before our update and will be
@@ skipping 26 matching lines @@
 
     this.changingBrowserZoom_ = this.setBrowserZoomFunction_(zoom).then(
         function() {
       this.browserZoom_ = zoom;
       this.changingBrowserZoom_ = null;
 
       // The extension's zoom level may have changed while the browser zoom
       // change was in progress. We call back into onPdfZoomChange to ensure the
       // browser zoom is up to date.
       this.onPdfZoomChange();
+    }.bind(this), function() {
+      this.changingBrowserZoom_ = null;

[Sam McNally, 2016/12/04 23:56:45]

Is this expected to occur?

[Kevin McNee, 2016/12/05 22:21:00]

Ah, this only affected a previous patch. Since the promise is currently resolved
when the browser zoom is not managed, |this.browserZoom_| was being set
incorrectly. While it's currently harmless, it led to a bug in my first
implementation, hence why I switched it to reject and added this onRejected
function for the embedded case. Now that the embedded case doesn't call the
|setBrowserZoomFunction_|, this won't occur. 

Removed.

     }.bind(this));
   }
 
   /**
-   * Returns whether two numbers are approximately equal.
-   * @param {number} a The first number.
-   * @param {number} b The second number.
+   * Combines the internal pdf zoom and the browser zoom to
+   * produce the total zoom level for the viewer.
+   * @param {number} internalZoom the zoom level internal to the viewer.
+   * @return {number} the total zoom level.
    */
-  floatingPointEquals(a, b) {
-    let MIN_ZOOM_DELTA = 0.01;
-    // If the zoom level is close enough to the current zoom level, don't
-    // change it. This avoids us getting into an infinite loop of zoom changes
-    // due to floating point error.
-    return Math.abs(a - b) <= MIN_ZOOM_DELTA;
+  applyBrowserZoom(internalZoom) {
+    // The internal zoom and browser zoom are changed together, so the
+    // browser zoom is already applied.
+    return internalZoom;
+  }
+
+  /**
+   * Given a zoom level, return the internal zoom level needed to
+   * produce that zoom level.
+   * @param {number} totalZoom the total zoom level.
+   * @return {number} the zoom level internal to the viewer.
+   */
+  internalZoomComponent(totalZoom) {
+    // The internal zoom and browser zoom are changed together, so the
+    // internal zoom is the total zoom.
+    return totalZoom;
   }
 };
+
+/**
+ * This EmbeddedZoomManager responds to changes in the browser zoom,
+ * but does not control the browser zoom.
+ */
+class EmbeddedZoomManager extends ZoomManager {
+  /**
+   * Invoked when a browser-initiated zoom-level change occurs.
+   * @param {number} newZoom the new browser zoom level.
+   */
+  onBrowserZoomChange(newZoom) {
+    let oldZoom = this.browserZoom_;
+    this.browserZoom_ = newZoom;
+    this.viewport_.updateZoomFromBrowserChange(oldZoom);
+  }
+};