CRD Viewport Management refactor

remoting/webapp/crd/js/desktop_viewport.js

Index: remoting/webapp/crd/js/desktop_viewport.js
diff --git a/remoting/webapp/crd/js/desktop_viewport.js b/remoting/webapp/crd/js/desktop_viewport.js
new file mode 100644
index 0000000000000000000000000000000000000000..00e4a8c999389cb3150f7d0433465c223b5505d7
--- /dev/null
+++ b/remoting/webapp/crd/js/desktop_viewport.js
@@ -0,0 +1,476 @@
+// 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.
+
+/**
+ * @fileoverview
+ * Provides view port management utilities below for a desktop remoting session.
+ * - Enabling bump scrolling
+ * - Resizing the viewport to fit the host desktop
+ * - Resizing the host desktop to fit the client viewport.
+ */
+
+/** @suppress {duplicate} */
+var remoting = remoting || {};
+
+(function() {
+
+'use strict';
+
+/**
+ * @param {HTMLElement} rootElement The outer element with id=scroller that we
+ *   are showing scrollbars on.
+ * @param {remoting.HostDesktop} hostDesktop
+ * @param {remoting.Host.Options} hostOptions
+ *
+ * @constructor
+ * @implements {base.Disposable}
+ */
+remoting.DesktopViewport = function(rootElement, hostDesktop, hostOptions) {
+  /** @private */
+  this.rootElement_ = rootElement;
+  /** @private */
+  // TODO(kelvinp): Query the container by class name instead of id.
+  this.pluginContainer_ = rootElement.querySelector('#client-container');
+  /** @private */
+  this.pluginElement_ = rootElement.querySelector('embed');
+  /** @private */
+  this.hostDesktop_ = hostDesktop;
+  /** @private */
+  this.hostOptions_ = hostOptions;
+  /** @private {number?} */
+  this.resizeTimer_ = null;
+  /** @private {remoting.BumpScroller} */
+  this.bumpScroller_ = null;
+  // Bump-scroll test variables. Override to use a fake value for the width
+  // and height of the client plugin so that bump-scrolling can be tested
+  // without relying on the actual size of the host desktop.
+  /** @private {number} */
+  this.pluginWidthForBumpScrollTesting = 0;
+  /** @private {number} */
+  this.pluginHeightForBumpScrollTesting = 0;
+
+  this.eventHooks_ = new base.Disposables(
+      new base.EventHook(
+        this.hostDesktop_, remoting.HostDesktop.Events.sizeChanged,
+        this.onDesktopSizeChanged_.bind(this)),
+      new base.EventHook(
+        this.hostDesktop_, remoting.HostDesktop.Events.shapeChanged,
+        remoting.windowShape.setDesktopRects));

[Jamie, 2015/02/18 00:33:10]

This is missing a bind(). Also, having a global dependency here is not ideal. I
think there are a couple of options:

* Treat the window shape as an intrinsic property of the viewport. in which case
get rid of remoting.windowShape and make it a member of this class.
* Treat the window shape as independent of the viewport, in which case it should
hook shape change notification itself, not relying on this class to do so.

[kelvinp, 2015/02/20 23:24:16]

I acknowledged that this is not ideal, but don't want to introduce more churn in
this change.  When the whole refactor is completed, there would be a class
AppConnectedView for looking glass, which will directly hooked into hostDesktop
and handle window shape changes.  I will add a TODO statement. 

+
+  if (this.hostOptions_.resizeToClient) {
+    this.resizeHostDesktop();
+  } else {
+    this.onDesktopSizeChanged_();
+  }
+};
+
+remoting.DesktopViewport.prototype.dispose = function() {
+  base.dispose(this.eventHooks_);
+  this.eventHooks_ = null;
+  base.dispose(this.bumpScroller_);
+  this.bumpScroller_ = null;
+};
+
+/**
+ * @return {boolean} True if shrink-to-fit is enabled; false otherwise.
+ */
+remoting.DesktopViewport.prototype.getShrinkToFit = function() {
+  return this.hostOptions_.shrinkToFit;
+};
+
+/**
+ * @return {boolean} True if resize-to-client is enabled; false otherwise.
+ */
+remoting.DesktopViewport.prototype.getResizeToClient = function() {
+  return this.hostOptions_.resizeToClient;
+};
+
+/**
+ * @return {{top:number, left:number}} The top-left corner of the plugin.
+ */
+remoting.DesktopViewport.prototype.getPluginPositionForTesting = function() {
+  var style = this.pluginContainer_.style;
+  return {
+    top: parseFloat(style.marginTop),
+    left: parseFloat(style.marginLeft)
+  };
+};
+
+/**
+ * @return {remoting.BumpScroller}
+ */
+remoting.DesktopViewport.prototype.getBumpScrollerForTesting = function() {
+  return this.bumpScroller_;
+};
+
+/**
+ * Set the shrink-to-fit and resize-to-client flags and save them if this is
+ * a Me2Me connection.
+ *
+ * @param {boolean} shrinkToFit True if the remote desktop should be scaled
+ *     down if it is larger than the client window; false if scroll-bars
+ *     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.DesktopViewport.prototype.setScreenMode =
+    function(shrinkToFit, resizeToClient) {
+  if (resizeToClient && !this.hostOptions_.resizeToClient) {
+    this.resizeHostDesktop();
+  }
+
+  // If enabling shrink, reset bump-scroll offsets.
+  var needsScrollReset = shrinkToFit && !this.hostOptions_.shrinkToFit;
+
+  this.hostOptions_.shrinkToFit = shrinkToFit;
+  this.hostOptions_.resizeToClient = resizeToClient;
+  this.hostOptions_.save();
+  this.updateScrollbarVisibility_();
+
+  this.updateDimensions_();
+  if (needsScrollReset) {
+    this.resetScroll_();
+  }
+};
+
+/**
+ * Scroll the client plugin by the specified amount, keeping it visible.
+ * Note that this is only used in content full-screen mode (not windowed or
+ * browser full-screen modes), where window.scrollBy and the scrollTop and
+ * scrollLeft properties don't work.

[Jamie, 2015/02/18 00:33:10]

Off-topic for this CL, but this may no longer be true for apps v2. If we could
use the appropriate scroll properties for our bump-scrolling, it would likely be
smoother.

[kelvinp, 2015/02/20 23:24:16]

Acknowledged.

+ *
+ * @param {number} dx The amount by which to scroll horizontally. Positive to
+ *     scroll right; negative to scroll left.
+ * @param {number} dy The amount by which to scroll vertically. Positive to
+ *     scroll down; negative to scroll up.
+ * @return {boolean} True if the requested scroll had no effect because both
+ *     vertical and horizontal edges of the screen have been reached.
+ */
+remoting.DesktopViewport.prototype.scroll = function(dx, dy) {
+  /**
+   * Helper function for x- and y-scrolling
+   * @param {number|string} curr The current margin, eg. "10px".
+   * @param {number} delta The requested scroll amount.
+   * @param {number} windowBound The size of the window, in pixels.
+   * @param {number} pluginBound The size of the plugin, in pixels.
+   * @param {{stop: boolean}} stop Reference parameter used to indicate when
+   *     the scroll has reached one of the edges and can be stopped in that
+   *     direction.
+   * @return {string} The new margin value.
+   */
+  var adjustMargin = function(curr, delta, windowBound, pluginBound, stop) {
+    var minMargin = Math.min(0, windowBound - pluginBound);
+    var result = (curr ? parseFloat(curr) : 0) - delta;
+    result = Math.min(0, Math.max(minMargin, result));
+    stop.stop = (result === 0 || result == minMargin);
+    return result + 'px';
+  };
+
+  var style = this.pluginContainer_.style;
+
+  var stopX = { stop: false };
+  var clientArea = this.getClientArea();
+  style.marginLeft = adjustMargin(
+      style.marginLeft, dx, clientArea.width,
+      this.pluginWidthForBumpScrollTesting || this.pluginElement_.clientWidth,
+      stopX);
+
+  var stopY = { stop: false };
+  style.marginTop = adjustMargin(
+      style.marginTop, dy, clientArea.height,
+      this.pluginHeightForBumpScrollTesting || this.pluginElement_.clientHeight,
+      stopY);
+  return stopX.stop && stopY.stop;
+};
+
+/**
+ * Enable or disable bump-scrolling. When disabling bump scrolling, also reset
+ * the scroll offsets to (0, 0).
+ * @param {boolean=} enable True to enable bump-scrolling, false to disable it.

[Jamie, 2015/02/18 00:33:10]

This parameter is not optional.

[kelvinp, 2015/02/20 23:24:16]

Done.

+ */
+remoting.DesktopViewport.prototype.enableBumpScroll = function(enable) {
+  if (enable) {
+    this.bumpScroller_ = new remoting.BumpScroller(this);
+  } else {
+    base.dispose(this.bumpScroller_);
+    this.bumpScroller_ = null;
+    this.resetScroll_();
+  }
+};
+
+/**
+ * This is a callback that gets called when the window is resized.
+ *
+ * @return {void} Nothing.
+ */
+remoting.DesktopViewport.prototype.onResize = function() {
+  this.updateDimensions_();
+
+  if (this.resizeTimer_) {
+    window.clearTimeout(this.resizeTimer_);
+    this.resizeTimer_ = null;
+  }
+
+  // Defer notifying the host of the change until the window stops resizing, to
+  // avoid overloading the control channel with notifications.
+  if (this.hostOptions_.resizeToClient) {
+    var kResizeRateLimitMs = 1000;
+    if (this.hostDesktop_.hasResizeRateLimit) {
+      kResizeRateLimitMs = 250;
+    }
+    var clientArea = this.getClientArea();
+    this.resizeTimer_ = window.setTimeout(this.resizeHostDesktop.bind(this),
+                                          kResizeRateLimitMs);
+  }
+
+  // If bump-scrolling is enabled, adjust the plugin margins to fully utilize
+  // the new window area.
+  this.resetScroll_();
+  this.updateScrollbarVisibility_();
+};
+
+/**
+ * @return {{width:number, height:number}} The height of the window's client
+ *     area. This differs between apps v1 and apps v2 due to the custom window
+ *     borders used by the latter.
+ */
+remoting.DesktopViewport.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.
+ */
+remoting.DesktopViewport.prototype.resizeHostDesktop = function() {

[Jamie, 2015/02/18 00:33:10]

This doesn't feel like it belongs on the DesktopViewport class. Can it be moved
to HostDestop? Maybe pass in an optional scale factor to HostDesktop.resize?

[kelvinp, 2015/02/20 23:24:16]

Removed.  The desktopViewport is only created when the session is connected.  By
that time, the capabilities are negotiated and it will auto resize the host if
resize to client is set to true.

[Jamie, 2015/02/21 02:01:32]

It doesn't look like you've removed this.

[kelvinp, 2015/02/23 17:56:00]

I made the function private in the latest iteration.  This function is called if
resizeToClient is set to true when the viewport gets resized.
HostDesktop cannot handle this completely by itself as it doesn't know the
client area.  

+  var clientArea = this.getClientArea();
+  this.hostDesktop_.resize(clientArea.width * this.hostOptions_.desktopScale,
+                           clientArea.height * this.hostOptions_.desktopScale,
+                           window.devicePixelRatio);
+};
+
+/**
+ * This is a callback that gets called when the plugin notifies us of a change
+ * in the size of the remote desktop.
+ *
+ * @return {void} Nothing.
+ * @private
+ */
+remoting.DesktopViewport.prototype.onDesktopSizeChanged_ = function() {
+  var dimensions = this.hostDesktop_.getDimensions();
+  console.log('desktop size changed: ' +
+              dimensions.width + 'x' +
+              dimensions.height +' @ ' +
+              dimensions.xDpi + 'x' +
+              dimensions.yDpi + ' DPI');
+  this.updateDimensions_();
+  this.updateScrollbarVisibility_();
+};
+
+/**
+ * Called when the window or desktop size or the scaling settings change,
+ * to set the scroll-bar visibility.
+ *
+ * TODO(jamiewalch): crbug.com/252796: Remove this once crbug.com/240772 is
+ * fixed.
+ */
+remoting.DesktopViewport.prototype.updateScrollbarVisibility_ = function() {
+  // TODO(kelvinp): Remove the check once looking glass no longer depends on
+  // this.
+  if (!this.rootElement_) {
+    return;
+  }
+
+  var needsScrollY = false;
+  var needsScrollX = false;
+  if (!this.hostOptions_.shrinkToFit) {
+    // Determine whether or not horizontal or vertical scrollbars are
+    // required, taking into account their width.
+    var clientArea = this.getClientArea();
+    var hostDesktop = this.hostDesktop_.getDimensions();
+    needsScrollY = clientArea.height < hostDesktop.height;
+    needsScrollX = clientArea.width < hostDesktop.width;
+    var kScrollBarWidth = 16;
+    if (needsScrollX && !needsScrollY) {
+      needsScrollY = clientArea.height - kScrollBarWidth < hostDesktop.height;
+    } else if (!needsScrollX && needsScrollY) {
+      needsScrollX = clientArea.width - kScrollBarWidth < hostDesktop.width;
+    }
+  }
+
+  this.rootElement_.classList.toggle('no-horizontal-scroll', !needsScrollX);
+  this.rootElement_.classList.toggle('no-vertical-scroll', !needsScrollY);
+};
+
+remoting.DesktopViewport.prototype.updateDimensions_ = function() {
+  var dimensions = this.hostDesktop_.getDimensions();
+  if (dimensions.width === 0 ||
+      dimensions.height === 0) {

[Jamie, 2015/02/18 00:33:10]

No need for a new line here.

[kelvinp, 2015/02/20 23:24:16]

Done.

+    return;
+  }
+
+  var desktopSize = { width: dimensions.width,
+                      height: dimensions.height };
+  var desktopDpi = { x: dimensions.xDpi,
+                     y: dimensions.yDpi };
+  var newSize = remoting.DesktopViewport.choosePluginSize(
+      this.getClientArea(), window.devicePixelRatio,
+      desktopSize, desktopDpi, this.hostOptions_.desktopScale,
+      remoting.fullscreen.isActive(), this.hostOptions_.shrinkToFit);
+
+  // Resize the plugin if necessary.
+  console.log('plugin dimensions:' + newSize.width + 'x' + newSize.height);
+  this.pluginElement_.style.width = newSize.width + 'px';
+  this.pluginElement_.style.height = newSize.height + 'px';
+
+  // When we receive the first plugin dimensions from the host, we know that
+  // remote host has started.
+  remoting.app.onVideoStreamingStarted();

[Jamie, 2015/02/18 00:33:10]

Can we eliminate this global dependency?

[kelvinp, 2015/02/20 23:24:16]

Yes, that would be the end goal.  We will expose events off the mediaChannel()
of the plugin and the app can listens to it. However, the plugin refactor would
need to be done we can do any further work on this.

+};
+
+/**
+ * Helper function accepting client and host dimensions, and returning a chosen
+ * size for the plugin element, in DIPs.
+ *
+ * @param {{width: number, height: number}} clientSizeDips Available client
+ *     dimensions, in DIPs.
+ * @param {number} clientPixelRatio Number of physical pixels per client DIP.
+ * @param {{width: number, height: number}} desktopSize Size of the host desktop
+ *     in physical pixels.
+ * @param {{x: number, y: number}} desktopDpi DPI of the host desktop in both
+ *     dimensions.
+ * @param {number} desktopScale The scale factor configured for the host.
+ * @param {boolean} isFullscreen True if full-screen mode is active.
+ * @param {boolean} shrinkToFit True if shrink-to-fit should be applied.
+ * @return {{width: number, height: number}} Chosen plugin dimensions, in DIPs.
+ */
+remoting.DesktopViewport.choosePluginSize = function(
+    clientSizeDips, clientPixelRatio, desktopSize, desktopDpi, desktopScale,
+    isFullscreen, shrinkToFit) {
+  base.debug.assert(clientSizeDips.width > 0);
+  base.debug.assert(clientSizeDips.height > 0);
+  base.debug.assert(clientPixelRatio >= 1.0);
+  base.debug.assert(desktopSize.width > 0);
+  base.debug.assert(desktopSize.height > 0);
+  base.debug.assert(desktopDpi.x > 0);
+  base.debug.assert(desktopDpi.y > 0);
+  base.debug.assert(desktopScale > 0);
+
+  // We have the following goals in sizing the desktop display at the client:
+  //  1. Avoid losing detail by down-scaling beyond 1:1 host:device pixels.
+  //  2. Avoid up-scaling if that will cause the client to need scrollbars.
+  //  3. Avoid introducing blurriness with non-integer up-scaling factors.
+  //  4. Avoid having huge "letterboxes" around the desktop, if it's really
+  //     small.
+  //  5. Compensate for mismatched DPIs, so that the behaviour of features like
+  //     shrink-to-fit matches their "natural" rather than their pixel size.
+  //     e.g. with shrink-to-fit active a 1024x768 low-DPI host on a 640x480
+  //     high-DPI client will be up-scaled to 1280x960, rather than displayed
+  //     at 1:1 host:physical client pixels.
+  //
+  // To determine the ideal size we follow a four-stage process:
+  //  1. Determine the "natural" size at which to display the desktop.
+  //    a. Initially assume 1:1 mapping of desktop to client device pixels.
+  //    b. If host DPI is less than the client's then up-scale accordingly.
+  //    c. If desktopScale is configured for the host then allow that to
+  //       reduce the amount of up-scaling from (b). e.g. if the client:host
+  //       DPIs are 2:1 then a desktopScale of 1.5 would reduce the up-scale
+  //       to 4:3, while a desktopScale of 3.0 would result in no up-scaling.
+  //  2. If the natural size of the desktop is smaller than the client device
+  //     then apply up-scaling by an integer scale factor to avoid excessive
+  //     letterboxing.
+  //  3. If shrink-to-fit is configured then:
+  //     a. If the natural size exceeds the client size then apply down-scaling
+  //        by an arbitrary scale factor.
+  //     b. If we're in full-screen mode and the client & host aspect-ratios
+  //        are radically different (e.g. the host is actually multi-monitor)
+  //        then shrink-to-fit to the shorter dimension, rather than leaving
+  //        huge letterboxes; the user can then bump-scroll around the desktop.
+  //  4. If the overall scale factor is fractionally over an integer factor
+  //     then reduce it to that integer factor, to avoid blurring.
+
+  // All calculations are performed in device pixels.
+  var clientWidth = clientSizeDips.width * clientPixelRatio;
+  var clientHeight = clientSizeDips.height * clientPixelRatio;
+
+  // 1. Determine a "natural" size at which to display the desktop.
+  var scale = 1.0;
+
+  // Determine the effective host device pixel ratio.
+  // Note that we round up or down to the closest integer pixel ratio.
+  var hostPixelRatioX = Math.round(desktopDpi.x / 96);
+  var hostPixelRatioY = Math.round(desktopDpi.y / 96);
+  var hostPixelRatio = Math.min(hostPixelRatioX, hostPixelRatioY);
+
+  // Allow up-scaling to account for DPI.
+  scale = Math.max(scale, clientPixelRatio / hostPixelRatio);
+
+  // Allow some or all of the up-scaling to be cancelled by the desktopScale.
+  if (desktopScale > 1.0) {
+    scale = Math.max(1.0, scale / desktopScale);
+  }
+
+  // 2. If the host is still much smaller than the client, then up-scale to
+  //    avoid wasting space, but only by an integer factor, to avoid blurring.
+  if (desktopSize.width * scale <= clientWidth &&
+      desktopSize.height * scale <= clientHeight) {
+    var scaleX = Math.floor(clientWidth / desktopSize.width);
+    var scaleY = Math.floor(clientHeight / desktopSize.height);
+    scale = Math.min(scaleX, scaleY);
+    base.debug.assert(scale >= 1.0);
+  }
+
+  // 3. Apply shrink-to-fit, if configured.
+  if (shrinkToFit) {
+    var scaleFitWidth = Math.min(scale, clientWidth / desktopSize.width);
+    var scaleFitHeight = Math.min(scale, clientHeight / desktopSize.height);
+    scale = Math.min(scaleFitHeight, scaleFitWidth);
+
+    // If we're running full-screen then try to handle common side-by-side
+    // multi-monitor combinations more intelligently.
+    if (isFullscreen) {
+      // If the host has two monitors each the same size as the client then
+      // scale-to-fit will have the desktop occupy only 50% of the client area,
+      // in which case it would be preferable to down-scale less and let the
+      // user bump-scroll around ("scale-and-pan").
+      // Triggering scale-and-pan if less than 65% of the client area would be
+      // used adds enough fuzz to cope with e.g. 1280x800 client connecting to
+      // a (2x1280)x1024 host nicely.
+      // Note that we don't need to account for scrollbars while fullscreen.
+      if (scale <= scaleFitHeight * 0.65) {
+        scale = scaleFitHeight;
+      }
+      if (scale <= scaleFitWidth * 0.65) {
+        scale = scaleFitWidth;
+      }
+    }
+  }
+
+  // 4. Avoid blurring for close-to-integer up-scaling factors.
+  if (scale > 1.0) {
+    var scaleBlurriness = scale / Math.floor(scale);
+    if (scaleBlurriness < 1.1) {
+      scale = Math.floor(scale);
+    }
+  }
+
+  // Return the necessary plugin dimensions in DIPs.
+  scale = scale / clientPixelRatio;
+  var pluginWidth = Math.round(desktopSize.width * scale);
+  var pluginHeight = Math.round(desktopSize.height * scale);
+  return { width: pluginWidth, height: pluginHeight };
+};
+
+/** @private */
+remoting.DesktopViewport.prototype.resetScroll_ = function() {
+  this.pluginContainer_.style.marginTop = '0px';
+  this.pluginContainer_.style.marginLeft = '0px';
+};
+
+}());