From b8dbdb1dbd38626a46604e94f7c8a0c70b54ca26 Mon Sep 17 00:00:00 2001
From: Jonathan Kew <jkew@mozilla.com>
Date: Wed, 12 Aug 2015 11:02:02 +0100
Subject: [PATCH] Bug 1191855 - Make the intrinsic size of <iframe> remain
 physical 300x150, regardless of writing mode. r=dholbert

---
 layout/generic/nsLeafFrame.h                  | 11 +++++++---
 layout/generic/nsSubDocumentFrame.cpp         | 21 ++++++++++++-------
 .../1183431-orthogonal-modes-7-ref.html       |  2 +-
 .../1183431-orthogonal-modes-8-ref.html       |  2 +-
 layout/style/nsStyleStruct.cpp                |  3 +++
 5 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/layout/generic/nsLeafFrame.h b/layout/generic/nsLeafFrame.h
index 97bb91a3b06c..5c8b69088b70 100644
--- a/layout/generic/nsLeafFrame.h
+++ b/layout/generic/nsLeafFrame.h
@@ -81,15 +81,20 @@ protected:
   virtual ~nsLeafFrame();
 
   /**
-   * Return the intrinsic width of the frame's content area. Note that this
+   * Return the intrinsic isize of the frame's content area. Note that this
    * should not include borders or padding and should not depend on the applied
    * styles.
+   * One exception to this is that the intrinsic (logical) size of an <iframe>
+   * depends on the writing-mode property (because the default intrinsic size
+   * is specified physically, for compat reasons). This should be OK because a
+   * change to writing-mode will trigger frame reconstruction anyhow, so the
+   * result will remain consistent for any given frame once constructed.
    */
   virtual nscoord GetIntrinsicISize() = 0;
 
   /**
-   * Return the intrinsic height of the frame's content area.  This should not
-   * include border or padding.  This will only matter if the specified height
+   * Return the intrinsic bsize of the frame's content area.  This should not
+   * include border or padding.  This will only matter if the specified bsize
    * is auto.  Note that subclasses must either implement this or override
    * Reflow and ComputeAutoSize; the default Reflow and ComputeAutoSize impls
    * call this method.
diff --git a/layout/generic/nsSubDocumentFrame.cpp b/layout/generic/nsSubDocumentFrame.cpp
index 78ef2c2daa53..c1e0ad271414 100644
--- a/layout/generic/nsSubDocumentFrame.cpp
+++ b/layout/generic/nsSubDocumentFrame.cpp
@@ -594,19 +594,23 @@ nscoord
 nsSubDocumentFrame::GetIntrinsicISize()
 {
   if (!IsInline()) {
-    return 0;  // HTML <frame> has no useful intrinsic width
+    return 0;  // HTML <frame> has no useful intrinsic isize
   }
 
   if (mContent->IsXULElement()) {
-    return 0;  // XUL <iframe> and <browser> have no useful intrinsic width
+    return 0;  // XUL <iframe> and <browser> have no useful intrinsic isize
   }
 
   NS_ASSERTION(ObtainIntrinsicSizeFrame() == nullptr,
-               "Intrinsic width should come from the embedded document.");
+               "Intrinsic isize should come from the embedded document.");
 
-  // We must be an HTML <iframe>.  Default to a width of 300, for IE
+  // We must be an HTML <iframe>.  Default to size of 300px x 150px, for IE
   // compat (and per CSS2.1 draft).
-  return nsPresContext::CSSPixelsToAppUnits(300);
+  // This depends on the applied styles, which the comments in nsLeafFrame.h
+  // say it should not, but we know it cannot change during the lifetime of
+  // the frame because changing writing-mode leads to frame reconstruction.
+  WritingMode wm = GetWritingMode();
+  return nsPresContext::CSSPixelsToAppUnits(wm.IsVertical() ? 150 : 300);
 }
 
 nscoord
@@ -620,10 +624,11 @@ nsSubDocumentFrame::GetIntrinsicBSize()
   }
 
   NS_ASSERTION(ObtainIntrinsicSizeFrame() == nullptr,
-               "Intrinsic height should come from the embedded document.");
+               "Intrinsic bsize should come from the embedded document.");
 
-  // Use 150px, for compatibility with IE, and per CSS2.1 draft.
-  return nsPresContext::CSSPixelsToAppUnits(150);
+  // Use size of 300px x 150px, for compatibility with IE, and per CSS2.1 draft.
+  WritingMode wm = GetWritingMode();
+  return nsPresContext::CSSPixelsToAppUnits(wm.IsVertical() ? 300 : 150);
 }
 
 #ifdef DEBUG_FRAME_DUMP
diff --git a/layout/reftests/writing-mode/abspos/1183431-orthogonal-modes-7-ref.html b/layout/reftests/writing-mode/abspos/1183431-orthogonal-modes-7-ref.html
index 5e8fa6b28704..77ad9c15bdd9 100644
--- a/layout/reftests/writing-mode/abspos/1183431-orthogonal-modes-7-ref.html
+++ b/layout/reftests/writing-mode/abspos/1183431-orthogonal-modes-7-ref.html
@@ -10,7 +10,7 @@ body>div { margin: 50px 20px; width: 400px; height: 500px; border: 5px solid blu
 iframe {
   position: absolute; left: 0; top: 34px;
   background: yellow; border: 5px solid green;
-  width: 150px; height: 300px; /* XXX this is probably wrong, pending CSSWG clarification */
+  width: 300px; height: 150px;
 }
 </style>
 <body>
diff --git a/layout/reftests/writing-mode/abspos/1183431-orthogonal-modes-8-ref.html b/layout/reftests/writing-mode/abspos/1183431-orthogonal-modes-8-ref.html
index e12339bb2b5e..33e90d3f80c4 100644
--- a/layout/reftests/writing-mode/abspos/1183431-orthogonal-modes-8-ref.html
+++ b/layout/reftests/writing-mode/abspos/1183431-orthogonal-modes-8-ref.html
@@ -10,7 +10,7 @@ body>div { margin: 50px 20px; width: 400px; height: 500px; border: 5px solid blu
 iframe {
   position: absolute; right: 0; top: 34px;
   background: yellow; border: 5px solid green;
-  width: 150px; height: 300px; /* XXX this is probably wrong, pending CSSWG clarification */
+  width: 300px; height: 150px;
 }
 </style>
 <body>
diff --git a/layout/style/nsStyleStruct.cpp b/layout/style/nsStyleStruct.cpp
index 2c37df954c08..fcc513248234 100644
--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -2956,6 +2956,9 @@ nsChangeHint nsStyleVisibility::CalcDifference(const nsStyleVisibility& aOther)
   nsChangeHint hint = nsChangeHint(0);
 
   if (mDirection != aOther.mDirection || mWritingMode != aOther.mWritingMode) {
+    // It's important that a change in mWritingMode results in frame
+    // reconstruction, because it may affect intrinsic size (see
+    // nsSubDocumentFrame::GetIntrinsicISize/BSize).
     NS_UpdateHint(hint, nsChangeHint_ReconstructFrame);
   } else {
     if ((mImageOrientation != aOther.mImageOrientation)) {