Bug 453650 - implement reflow observers for docShells; r=bz

docshell/base/moz.build

@@ -24,6 +24,7 @@ XPIDL_SOURCES += [
     'nsILoadContext.idl',
     'nsIMarkupDocumentViewer.idl',
     'nsIPrivacyTransitionObserver.idl',
+    'nsIReflowObserver.idl',
     'nsIRefreshURI.idl',
     'nsIScrollable.idl',
     'nsITextScroll.idl',

docshell/base/nsDocShell.cpp

@@ -83,6 +83,7 @@
 #include "nsIOfflineCacheUpdate.h"
 #include "nsITimedChannel.h"
 #include "nsIPrivacyTransitionObserver.h"
+#include "nsIReflowObserver.h"
 #include "nsCPrefetchService.h"
 #include "nsJSON.h"
 #include "nsIDocShellTreeItem.h"
@@ -2205,6 +2206,43 @@ nsDocShell::AddWeakPrivacyTransitionObserver(nsIPrivacyTransitionObserver* aObse
     return mPrivacyObservers.AppendElement(weakObs) ? NS_OK : NS_ERROR_FAILURE;
 }
 
+NS_IMETHODIMP
+nsDocShell::AddWeakReflowObserver(nsIReflowObserver* aObserver)
+{
+    nsWeakPtr weakObs = do_GetWeakReference(aObserver);
+    if (!weakObs) {
+        return NS_ERROR_FAILURE;
+    }
+    return mReflowObservers.AppendElement(weakObs) ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsDocShell::RemoveWeakReflowObserver(nsIReflowObserver* aObserver)
+{
+    nsWeakPtr obs = do_GetWeakReference(aObserver);
+    return mReflowObservers.RemoveElement(obs) ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsDocShell::NotifyReflowObservers(bool aInterruptible,
+                                  DOMHighResTimeStamp aStart,
+                                  DOMHighResTimeStamp aEnd)
+{
+    nsTObserverArray<nsWeakPtr>::ForwardIterator iter(mReflowObservers);
+    while (iter.HasMore()) {
+        nsWeakPtr ref = iter.GetNext();
+        nsCOMPtr<nsIReflowObserver> obs = do_QueryReferent(ref);
+        if (!obs) {
+            mReflowObservers.RemoveElement(ref);
+        } else if (aInterruptible) {
+            obs->ReflowInterruptible(aStart, aEnd);
+        } else {
+            obs->Reflow(aStart, aEnd);
+        }
+    }
+    return NS_OK;
+}
+
 NS_IMETHODIMP nsDocShell::GetAllowMetaRedirects(bool * aReturn)
 {
     NS_ENSURE_ARG_POINTER(aReturn);

docshell/base/nsDocShell.h

@@ -872,6 +872,7 @@ private:
     nsCString         mForcedCharset;
     nsCString         mParentCharset;
     nsTObserverArray<nsWeakPtr> mPrivacyObservers;
+    nsTObserverArray<nsWeakPtr> mReflowObservers;
     int32_t           mParentCharsetSource;
     nsCString         mOriginalUriString;
 

docshell/base/nsIDocShell.idl

@@ -4,6 +4,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+#include "domstubs.idl"
 #include "nsIDocShellTreeItem.idl"
 #include "nsIAtom.idl"
 
@@ -39,8 +40,9 @@ interface nsIPrincipal;
 interface nsIWebBrowserPrint;
 interface nsIVariant;
 interface nsIPrivacyTransitionObserver;
+interface nsIReflowObserver;
 
-[scriptable, builtinclass, uuid(2b192c9c-dea4-4696-a445-1bef7bc0db6d)]
+[scriptable, builtinclass, uuid(d15b07e0-c604-11e2-8bdc-651679957a39)]
 interface nsIDocShell : nsIDocShellTreeItem
 {
   /**
@@ -616,6 +618,30 @@ interface nsIDocShell : nsIDocShellTreeItem
    */
   void addWeakPrivacyTransitionObserver(in nsIPrivacyTransitionObserver obs);
 
+  /**
+   * Add an observer to the list of parties to be notified when reflows are
+   * occurring. |obs| must support weak references.
+   */
+  void addWeakReflowObserver(in nsIReflowObserver obs);
+
+  /**
+   * Remove an observer from the list of parties to be notified about reflows.
+   */
+  void removeWeakReflowObserver(in nsIReflowObserver obs);
+
+  /**
+   * Notify all attached observers that a reflow has just occurred.
+   *
+   * @param interruptible if true, the reflow was interruptible.
+   * @param start         timestamp when reflow started, in milliseconds since
+   *                      navigationStart (accurate to 1/1000 of a ms)
+   * @param end           timestamp when reflow ended, in milliseconds since
+   *                      navigationStart (accurate to 1/1000 of a ms)
+   */
+  [noscript] void notifyReflowObservers(in bool interruptible,
+                                        in DOMHighResTimeStamp start,
+                                        in DOMHighResTimeStamp end);
+
   /**
    * Returns true if this docshell corresponds to an <iframe mozbrowser>.
    * (<iframe mozapp mozbrowser> is not considered a browser.)

docshell/base/nsIReflowObserver.idl

@@ -0,0 +1,32 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "domstubs.idl"
+#include "nsISupports.idl"
+
+[scriptable, uuid(832e692c-c4a6-11e2-8fd1-dce678957a39)]
+interface nsIReflowObserver : nsISupports
+{
+  /**
+   * Called when an uninterruptible reflow has occurred.
+   *
+   * @param start timestamp when reflow ended, in milliseconds since
+   *              navigationStart (accurate to 1/1000 of a ms)
+   * @param end   timestamp when reflow ended, in milliseconds since
+   *              navigationStart (accurate to 1/1000 of a ms)
+   */
+  void reflow(in DOMHighResTimeStamp start,
+              in DOMHighResTimeStamp end);
+
+  /**
+   * Called when an interruptible reflow has occurred.
+   *
+   * @param start timestamp when reflow ended, in milliseconds since
+   *              navigationStart (accurate to 1/1000 of a ms)
+   * @param end   timestamp when reflow ended, in milliseconds since
+   *              navigationStart (accurate to 1/1000 of a ms)
+   */
+  void reflowInterruptible(in DOMHighResTimeStamp start,
+                           in DOMHighResTimeStamp end);
+};

docshell/test/chrome/Makefile.in

@@ -80,6 +80,7 @@ MOCHITEST_CHROME_FILES =	\
 		test_bug449780.xul \
 		bug449780_window.xul \
 		bug454235-subframe.xul \
+		test_bug453650.xul \
 		test_bug456980.xul \
 		test_bug662200.xul \
 		bug662200_window.xul \

docshell/test/chrome/test_bug453650.xul

@@ -0,0 +1,116 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet type="text/css" href="/tests/SimpleTest/test.css"?>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=453650
+-->
+<window title="Mozilla Bug 453650"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+
+  <title>Test for Bug 453650</title>
+  <script type="application/javascript"
+          src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+
+  <!-- test code goes here -->
+  <script type="application/javascript">
+  <![CDATA[
+
+  /** Test for Bug 453650 **/
+  SimpleTest.waitForExplicitFinish();
+
+  var Ci = Components.interfaces;
+  var Cr = Components.results;
+
+  var iter = runTests();
+  nextTest();
+
+  function runTests() {
+    var iframe = document.createElement("iframe");
+    iframe.style.width = "300px";
+    iframe.style.height = "300px";
+    iframe.setAttribute("src", "data:text/html,<h1 id='h'>hello</h1>");
+
+    document.documentElement.appendChild(iframe);
+    yield whenLoaded(iframe);
+    info("iframe loaded");
+
+    var h1 = iframe.contentDocument.getElementById("h");
+    h1.style.width = "400px";
+    yield waitForInterruptibleReflow(iframe.docShell);
+
+    h1.style.width = "300px";
+    waitForReflow(iframe.docShell);
+    yield is(300, h1.offsetWidth, "h1 has correct width");
+  }
+
+  function waitForInterruptibleReflow(docShell) {
+    waitForReflow(docShell, true);
+  }
+
+  function waitForReflow(docShell, interruptible = false) {
+    function done() {
+      docShell.removeWeakReflowObserver(observer);
+      SimpleTest.executeSoon(nextTest);
+    }
+
+    var observer = {
+      reflow: function (start, end) {
+        if (interruptible) {
+          ok(false, "expected interruptible reflow");
+        } else {
+          ok(true, "observed uninterruptible reflow");
+        }
+
+        info("times: " + start + ", " + end);
+        ok(start < end, "reflow start time lower than end time");
+        done();
+      },
+
+      reflowInterruptible: function (start, end) {
+        if (!interruptible) {
+          ok(false, "expected uninterruptible reflow");
+        } else {
+          ok(true, "observed interruptible reflow");
+        }
+
+        info("times: " + start + ", " + end);
+        ok(start < end, "reflow start time lower than end time");
+        done();
+      },
+
+      QueryInterface: function (iid) {
+        if (Ci.nsIReflowObserver.equals(iid) ||
+            Ci.nsISupportsWeakReference.equals(iid) ||
+            Ci.nsISupports.equals(iid))
+          return this;
+        throw Cr.NS_ERROR_NO_INTERFACE;
+      },
+    };
+
+    docShell.addWeakReflowObserver(observer);
+  }
+
+  function whenLoaded(iframe) {
+    iframe.addEventListener("load", function onLoad() {
+      iframe.removeEventListener("load", onLoad);
+      SimpleTest.executeSoon(nextTest);
+    });
+  }
+
+  function nextTest() {
+    try {
+      iter.next();
+    } catch (e if e instanceof StopIteration) {
+      SimpleTest.finish();
+    }
+  }
+
+  ]]>
+  </script>
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml">
+  <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=453650"
+     target="_blank">Mozilla Bug 453650</a>
+  </body>
+</window>

dom/interfaces/base/domstubs.idl

@@ -12,6 +12,7 @@ class nsWrapperCache;
 [ptr] native nsWrapperCachePtr(nsWrapperCache);
 
 typedef unsigned long long DOMTimeStamp;
+typedef double DOMHighResTimeStamp;
 
 // Core
 interface nsIDOMAttr;

layout/base/nsPresShell.cpp

@@ -123,7 +123,9 @@
 #include "nsSVGEffects.h"
 #include "SVGFragmentIdentifier.h"
 
+#include "nsPerformance.h"
 #include "nsRefreshDriver.h"
+#include "nsDOMNavigationTiming.h"
 
 // Drag & Drop, Clipboard
 #include "nsWidgetsCID.h"
@@ -7651,6 +7653,8 @@ PresShell::WillDoReflow()
   mPresContext->FlushUserFontSet();
 
   mFrameConstructor->BeginUpdate();
+
+  mLastReflowStart = GetPerformanceNow();
 }
 
 void
@@ -7659,6 +7663,16 @@ PresShell::DidDoReflow(bool aInterruptible, bool aWasInterrupted)
   mFrameConstructor->EndUpdate();
   
   HandlePostedReflowCallbacks(aInterruptible);
+
+  nsCOMPtr<nsISupports> container = mPresContext->GetContainer();
+  if (container) {
+    nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(container);
+    if (docShell) {
+      DOMHighResTimeStamp now = GetPerformanceNow();
+      docShell->NotifyReflowObservers(aInterruptible, mLastReflowStart, now);
+    }
+  }
+
   if (sSynthMouseMove) {
     SynthesizeMouseMove(false);
   }
@@ -7674,6 +7688,23 @@ PresShell::DidDoReflow(bool aInterruptible, bool aWasInterrupted)
   }
 }
 
+DOMHighResTimeStamp
+PresShell::GetPerformanceNow()
+{
+  DOMHighResTimeStamp now = 0;
+  nsPIDOMWindow* window = mDocument->GetWindow();
+
+  if (window) {
+    nsPerformance* perf = window->GetPerformance();
+
+    if (perf) {
+      now = perf->Now();
+    }
+  }
+
+  return now;
+}
+
 static PLDHashOperator
 MarkFramesDirtyToRoot(nsPtrHashKey<nsIFrame>* p, void* closure)
 {

layout/base/nsPresShell.h

@@ -701,6 +701,8 @@ protected:
 
   nscolor GetDefaultBackgroundColorToDraw();
 
+  DOMHighResTimeStamp GetPerformanceNow();
+
   // The callback for the mPaintSuppressionTimer timer.
   static void sPaintSuppressionCallback(nsITimer* aTimer, void* aPresShell);
 
@@ -783,6 +785,9 @@ protected:
   // moving/sizing loop is running, see bug 491700 for details.
   nsCOMPtr<nsITimer>        mReflowContinueTimer;
 
+  // The `performance.now()` value when we last started to process reflows.
+  DOMHighResTimeStamp       mLastReflowStart;
+
   // Information needed to properly handle scrolling content into view if the
   // pre-scroll reflow flush can be interrupted.  mContentToScrollTo is
   // non-null between the initial scroll attempt and the first time we finish