Add a per-host desktopScale option, available via the JS console.

remoting/webapp/crd/js/client_session.js

 // Copyright (c) 2012 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.
 
 /**
  * @fileoverview
  * Class handling creation and teardown of a remoting client session.
  *
  * The ClientSession class controls lifetime of the client plugin
  * object and provides the plugin with the functionality it needs to
@@ skipping 111 matching lines @@
   /** @private */
   this.sessionId_ = '';
   /** @type {remoting.ClientPlugin}
     * @private */
   this.plugin_ = null;
   /** @private */
   this.shrinkToFit_ = true;
   /** @private */
   this.resizeToClient_ = true;
   /** @private */
+  this.desktopZoom_ = 1.0;
+  /** @private */
   this.remapKeys_ = '';
   /** @private */
   this.hasReceivedFrame_ = false;
   this.logToServer = new remoting.LogToServer(signalStrategy, mode);
 
   /** @private */
   this.signalStrategy_ = signalStrategy;
   base.debug.assert(this.signalStrategy_.getState() ==
                     remoting.SignalStrategy.State.CONNECTED);
   this.signalStrategy_.setIncomingStanzaCallback(
@@ skipping 228 matching lines @@
 remoting.ClientSession.STATS_KEY_CAPTURE_LATENCY = 'captureLatency';
 remoting.ClientSession.STATS_KEY_ENCODE_LATENCY = 'encodeLatency';
 remoting.ClientSession.STATS_KEY_DECODE_LATENCY = 'decodeLatency';
 remoting.ClientSession.STATS_KEY_RENDER_LATENCY = 'renderLatency';
 remoting.ClientSession.STATS_KEY_ROUNDTRIP_LATENCY = 'roundtripLatency';
 
 // Keys for per-host settings.
 remoting.ClientSession.KEY_REMAP_KEYS = 'remapKeys';
 remoting.ClientSession.KEY_RESIZE_TO_CLIENT = 'resizeToClient';
 remoting.ClientSession.KEY_SHRINK_TO_FIT = 'shrinkToFit';
+remoting.ClientSession.KEY_DESKTOP_ZOOM = 'desktopZoom';
 
 /**
  * Set of capabilities for which hasCapability_() can be used to test.
  *
  * @enum {string}
  */
 remoting.ClientSession.Capability = {
   // When enabled this capability causes the client to send its screen
   // resolution to the host once connection has been established. See
   // this.plugin_.notifyClientResolution().
@@ skipping 105 matching lines @@
           'boolean') {
     this.resizeToClient_ = /** @type {boolean} */
         options[remoting.ClientSession.KEY_RESIZE_TO_CLIENT];
   }
   if (remoting.ClientSession.KEY_SHRINK_TO_FIT in options &&
       typeof(options[remoting.ClientSession.KEY_SHRINK_TO_FIT]) ==
           'boolean') {
     this.shrinkToFit_ = /** @type {boolean} */
         options[remoting.ClientSession.KEY_SHRINK_TO_FIT];
   }
+  if (remoting.ClientSession.KEY_DESKTOP_ZOOM in options &&
+      typeof(options[remoting.ClientSession.KEY_DESKTOP_ZOOM]) ==
+          'number') {
+    this.desktopZoom_ = /** @type {number} */
+        options[remoting.ClientSession.KEY_DESKTOP_ZOOM];
+  }
 
   /** @param {boolean} result */
   this.plugin_.initialize(this.onPluginInitialized_.bind(this));
 };
 
 /**
  * Constrains the focus to the plugin element.
  * @private
  */
 remoting.ClientSession.prototype.setFocusHandlers_ = function() {
@@ skipping 250 matching lines @@
  * Sends a Print Screen keypress to the remoting client.
  *
  * @return {void} Nothing.
  */
 remoting.ClientSession.prototype.sendPrintScreen = function() {
   console.log('Sending Print Screen.');
   this.sendKeyCombination_([0x070046]);
 }
 
 /**
+ * Sets and stores the zoom factor to apply to host sizing requests.
+ *
+ * @param {number} desktopZoom Scale factor to apply.
+ */
+remoting.ClientSession.prototype.setDesktopZoom =
+    function(desktopZoom) {
+  // Apply the new desktop zoom, if resize to client is enabled.

[Jamie, 2014/12/15 18:39:06]

Nit: resize-to-client

[Wez, 2014/12/15 21:49:42]

Done.

+  this.desktopZoom_ = desktopZoom;
+  if (this.resizeToClient_) {
+    this.notifyClientResolution_();
+  }
+
+  // Save the new desktop zoom setting.
+  var options = {};
+  options[remoting.ClientSession.KEY_DESKTOP_ZOOM] = this.desktopZoom_;
+  remoting.HostSettings.save(this.hostId_, options);
+}
+
+/**
  * Sets and stores the key remapping setting for the current host.
  *
  * @param {string} remappings Comma separated list of key remappings.
  */
 remoting.ClientSession.prototype.setRemapKeys = function(remappings) {
   // Cancel any existing remappings and apply the new ones.
   this.applyRemapKeys_(false);
   this.remapKeys_ = remappings;
   this.applyRemapKeys_(true);
 
@@ skipping 50 matching lines @@
  *     should be added in this case.
  * @param {boolean} resizeToClient True if window resizes should cause the
  *     host to attempt to resize its desktop to match the client window size;
  *     false to disable this behaviour for subsequent window resizes--the
  *     current host desktop size is not restored in this case.
  * @return {void} Nothing.
  */
 remoting.ClientSession.prototype.setScreenMode =
     function(shrinkToFit, resizeToClient) {
   if (resizeToClient && !this.resizeToClient_) {
-    var clientArea = this.getClientArea_();
-    this.plugin_.notifyClientResolution(clientArea.width,
-                                        clientArea.height,
-                                        window.devicePixelRatio);
+    this.notifyClientResolution_();
   }
 
   // If enabling shrink, reset bump-scroll offsets.
   var needsScrollReset = shrinkToFit && !this.shrinkToFit_;
 
   this.shrinkToFit_ = shrinkToFit;
   this.resizeToClient_ = resizeToClient;
   this.updateScrollbarVisibility();
 
   if (this.hostId_ != '') {
@@ skipping 142 matching lines @@
  * @private
  * @param {number} status The plugin's status.
  * @param {number} error The plugin's error state, if any.
  */
 remoting.ClientSession.prototype.onConnectionStatusUpdate_ =
     function(status, error) {
   if (status == remoting.ClientSession.State.CONNECTED) {
     this.setFocusHandlers_();
     this.onDesktopSizeChanged_();
     if (this.resizeToClient_) {
-      var clientArea = this.getClientArea_();
-      this.plugin_.notifyClientResolution(clientArea.width,
-                                          clientArea.height,
-                                          window.devicePixelRatio);
+      this.notifyClientResolution_();
     }
     // Activate full-screen related UX.
     remoting.fullscreen.addListener(this.callOnFullScreenChanged_);
     this.updateClientSessionUi_(this);
     this.container_.addEventListener('mousemove',
                                      this.updateMouseCursorPosition_,
                                      true);
 
   } else if (status == remoting.ClientSession.State.FAILED) {
     switch (error) {
@@ skipping 72 matching lines @@
  */
 remoting.ClientSession.prototype.onSetCapabilities_ = function(capabilities) {
   if (this.capabilities_ != null) {
     console.error('onSetCapabilities_() is called more than once');
     return;
   }
 
   this.capabilities_ = capabilities;
   if (this.hasCapability_(
       remoting.ClientSession.Capability.SEND_INITIAL_RESOLUTION)) {
-    var clientArea = this.getClientArea_();
-    this.plugin_.notifyClientResolution(clientArea.width,
-                                        clientArea.height,
-                                        window.devicePixelRatio);
+    this.notifyClientResolution_();
   }
   if (this.hasCapability_(remoting.ClientSession.Capability.GOOGLE_DRIVE)) {
     this.sendGoogleDriveAccessToken_();
   }
   if (this.hasCapability_(
       remoting.ClientSession.Capability.VIDEO_RECORDER)) {
     this.videoFrameRecorder_ = new remoting.VideoFrameRecorder(this.plugin_);
   }
 };
 
@@ skipping 48 matching lines @@
   // Defer notifying the host of the change until the window stops resizing, to
   // avoid overloading the control channel with notifications.
   if (this.resizeToClient_) {
     var kResizeRateLimitMs = 1000;
     if (this.hasCapability_(
         remoting.ClientSession.Capability.RATE_LIMIT_RESIZE_REQUESTS)) {
       kResizeRateLimitMs = 250;
     }
     var clientArea = this.getClientArea_();
     this.notifyClientResolutionTimer_ = window.setTimeout(
-        this.plugin_.notifyClientResolution.bind(this.plugin_,
-                                                 clientArea.width,
-                                                 clientArea.height,
-                                                 window.devicePixelRatio),
+        this.notifyClientResolution_.bind(this),
         kResizeRateLimitMs);
   }
 
   // If bump-scrolling is enabled, adjust the plugin margins to fully utilize
   // the new window area.
   this.resetScroll_();
 
   this.updateScrollbarVisibility();
 };
 
@@ skipping 433 matching lines @@
  *     borders used by the latter.
  * @private
  */
 remoting.ClientSession.prototype.getClientArea_ = function() {
   return remoting.windowFrame ?
       remoting.windowFrame.getClientArea() :
       { 'width': window.innerWidth, 'height': window.innerHeight };
 };
 
 /**
+ * Notifies the host of the client's current dimensions and DPI.
+ * Also takes into account per-host scaling factor, if configured.
+ * @private
+ */
+remoting.ClientSession.prototype.notifyClientResolution_ = function() {
+  var clientArea = this.getClientArea_();
+  this.plugin_.notifyClientResolution(clientArea.width * this.desktopZoom_,
+                                      clientArea.height * this.desktopZoom_,
+                                      window.devicePixelRatio);

[Jamie, 2014/12/15 18:39:06]

Don't you also need to apply the inverse scale to the plugin element? This will
only work if scale-to-fit is enabled, I think.

[Wez, 2014/12/15 21:49:42]

That's a good question.

I've added code in updateDimensions() to include the desktopScale in the
hostPixelRatio, which will mean taking it into account, up to the limit of the
devicePixelRatio, i.e. we won't down-scale smaller than 1:1 host:device pixels.

+}
+
+/**
  * @param {string} url
  * @param {number} hotspotX
  * @param {number} hotspotY
  */
 remoting.ClientSession.prototype.updateMouseCursorImage_ =
     function(url, hotspotX, hotspotY) {
   this.mouseCursorOverlay_.hidden = !url;
   if (url) {
     this.mouseCursorOverlay_.style.marginLeft = '-' + hotspotX + 'px';
     this.mouseCursorOverlay_.style.marginTop = '-' + hotspotY + 'px';
@@ skipping 85 matching lines @@
  * @param {string} data Contents of the extension message.
  * @return {boolean} True if the message was recognized, false otherwise.
  */
 remoting.ClientSession.prototype.handleExtensionMessage =
     function(type, data) {
   if (this.videoFrameRecorder_) {
     return this.videoFrameRecorder_.handleMessage(type, data);
   }
   return false;
 }