Bug 574621. Ensure that the prescontext DefaultBackgroundColor is painted on the background of root content documents. r=tnikkel

layout/base/nsPresShell.cpp

@@ -5776,22 +5776,41 @@ nsresult PresShell::AddCanvasBackgroundColorItem(nsDisplayListBuilder& aBuilder,
       new (&aBuilder) nsDisplaySolidColor(&aBuilder, aFrame, aBounds, bgcolor));
 }
 
+static PRBool IsTransparentContainerElement(nsPresContext* aPresContext)
+{
+  nsCOMPtr<nsISupports> container = aPresContext->GetContainerInternal();
+  nsCOMPtr<nsIDocShellTreeItem> docShellItem = do_QueryInterface(container);
+  nsCOMPtr<nsPIDOMWindow> pwin(do_GetInterface(docShellItem));
+  if (!pwin)
+    return PR_FALSE;
+  nsCOMPtr<nsIContent> containerElement =
+    do_QueryInterface(pwin->GetFrameElementInternal());
+  return containerElement &&
+         containerElement->HasAttr(kNameSpaceID_None, nsGkAtoms::transparent);
+}
+
 void PresShell::UpdateCanvasBackground()
 {
   // If we have a frame tree and it has style information that
   // specifies the background color of the canvas, update our local
   // cache of that color.
-  nsIFrame* rootFrame = FrameConstructor()->GetRootElementStyleFrame();
-  if (rootFrame) {
+  nsIFrame* rootStyleFrame = FrameConstructor()->GetRootElementStyleFrame();
+  if (rootStyleFrame) {
     nsStyleContext* bgStyle =
-      nsCSSRendering::FindRootFrameBackground(rootFrame);
+      nsCSSRendering::FindRootFrameBackground(rootStyleFrame);
     // XXX We should really be passing the canvasframe, not the root element
     // style frame but we don't have access to the canvasframe here. It isn't
     // a problem because only a few frames can return something other than true
     // and none of them would be a canvas frame or root element style frame.
     mCanvasBackgroundColor =
-      nsCSSRendering::DetermineBackgroundColor(GetPresContext(), bgStyle,
-                                               rootFrame);
+      nsCSSRendering::DetermineBackgroundColor(mPresContext, bgStyle,
+                                               rootStyleFrame);
+    if (nsLayoutUtils::GetCrossDocParentFrame(FrameManager()->GetRootFrame()) &&
+        !nsContentUtils::IsChildOfSameType(mDocument) &&
+        !IsTransparentContainerElement(mPresContext)) {
+      mCanvasBackgroundColor =
+        NS_ComposeColors(mPresContext->DefaultBackgroundColor(), mCanvasBackgroundColor);
+    }
   }
 
   // If the root element of the document (ie html) has style 'display: none'

layout/base/tests/chrome/Makefile.in

@@ -53,6 +53,8 @@ _CHROME_FILES = \
 	bug551434_childframe.html \
 	test_chrome_content_integration.xul \
 	     chrome_content_integration_window.xul \
+	test_default_background.xul \
+	     default_background_window.xul \
 	test_printpreview.xul \
 	     printpreview_helper.xul \
 	test_printpreview_bug396024.xul \

layout/base/tests/chrome/chrome_content_integration_window.xul

@@ -25,8 +25,6 @@
       window[import] = window.opener.wrappedJSObject[import];
     }
     
-    var HTMLNS = "http://www.w3.org/1999/xhtml";
-
     function runTests() {
       var testCanvas = snapshotWindow(window);
 
@@ -37,8 +35,6 @@
 
       var comparison = compareSnapshots(testCanvas, refCanvas, true);
       ok(comparison[0], "Rendering OK, got " + comparison[1] + ", expected " + comparison[2]);
-      dump(comparison[1] + "\n");
-      dump(comparison[2] + "\n");
 
       var tester = window.SimpleTest;
       window.close();

layout/base/tests/chrome/default_background_window.xul

@@ -0,0 +1,62 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet href="chrome://mochikit/content/tests/SimpleTest/test.css"
+                 type="text/css"?>
+<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
+        onload="runTests()">
+  <script type="application/javascript"
+          src="chrome://mochikit/content/MochiKit/packed.js"></script>
+  <script type="application/javascript"
+          src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript"
+          src="chrome://mochikit/content/tests/SimpleTest/WindowSnapshot.js"></script>
+
+  <iframe type="content" id="f" src="about:blank" style="border:1px solid black;"/>
+
+  <script type="application/javascript">
+  <![CDATA[
+    SimpleTest.waitForExplicitFinish();
+
+    var imports = [ "SimpleTest", "is", "isnot", "ok" ];
+    for each (var import in imports) {
+      window[import] = window.opener.wrappedJSObject[import];
+    }
+    
+    function snapshot(win) {
+      var el = document.createElementNS("http://www.w3.org/1999/xhtml", "canvas");
+      el.width = win.innerWidth;
+      el.height = win.innerHeight;
+
+      var ctx = el.getContext("2d");
+      ctx.drawWindow(win, 0, 0,
+                     win.innerWidth, win.innerHeight,
+                     "rgba(0,0,0,0)", 0);
+      return el;
+    }
+
+    var color = '#2468AC';
+    var prefs = Components.classes["@mozilla.org/preferences-service;1"]
+        .getService(Components.interfaces.nsIPrefBranch);
+    prefs.setCharPref('browser.display.background_color', color);
+
+    function runTests() {
+      var f = document.getElementById("f");
+
+      var testCanvas = snapshot(f.contentWindow);
+      prefs.clearUserPref('browser.display.background_color');
+
+      var refCanvas = snapshot(f.contentWindow);
+      var ctx = refCanvas.getContext('2d');
+      ctx.fillStyle = color;
+      ctx.fillRect(0, 0, refCanvas.width, refCanvas.height);
+
+      var comparison = compareSnapshots(testCanvas, refCanvas, true);
+      ok(comparison[0], "Rendering OK, got " + comparison[1] + ", expected " + comparison[2]);
+
+      var tester = window.SimpleTest;
+      window.close();
+      tester.finish();
+    }
+  ]]>
+  </script>
+</window>

layout/base/tests/chrome/test_chrome_content_integration.xul

@@ -16,6 +16,8 @@
   <script type="application/javascript">
   <![CDATA[
     SimpleTest.waitForExplicitFinish();
+    // Run the test in a separate window so that the test runs as a chrome
+    // window
     window.open("chrome_content_integration_window.xul", "chrome_content_integration",
                 "chrome,width=200,height=300");
   ]]>

layout/base/tests/chrome/test_default_background.xul

@@ -0,0 +1,25 @@
+<?xml version="1.0"?>
+<?xml-stylesheet type="text/css" href="chrome://global/skin"?>
+<?xml-stylesheet href="chrome://mochikit/content/tests/SimpleTest/test.css"
+                 type="text/css"?>
+<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <script type="application/javascript"
+          src="chrome://mochikit/content/MochiKit/packed.js"></script>
+  <script type="application/javascript"
+          src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+
+  <!-- test results are displayed in the html:body -->
+  <body xmlns="http://www.w3.org/1999/xhtml">
+  </body>
+
+  <!-- test code goes here -->
+  <script type="application/javascript">
+  <![CDATA[
+    SimpleTest.waitForExplicitFinish();
+    // Run the test in a separate window so that the test runs as a chrome
+    // window
+    window.open("default_background_window.xul", "default_background",
+                "chrome,width=200,height=300");
+  ]]>
+  </script>
+</window>