From 7850f5f46239a16a3e6722c6c68b88e618dd0056 Mon Sep 17 00:00:00 2001
From: Corey Ford <cford@mozilla.com>
Date: Thu, 15 Aug 2013 17:31:32 -0700
Subject: [PATCH] Bug 886646 - Part 3: Compute sticky positioning offsets for
 getComputedStyle(). r=heycam

---
 layout/style/nsComputedDOMStyle.cpp         | 76 ++++++++++++++++++
 layout/style/nsComputedDOMStyle.h           |  4 +
 layout/style/test/Makefile.in               |  2 +
 layout/style/test/file_position_sticky.html | 88 +++++++++++++++++++++
 layout/style/test/test_position_sticky.html | 42 ++++++++++
 5 files changed, 212 insertions(+)
 create mode 100644 layout/style/test/file_position_sticky.html
 create mode 100644 layout/style/test/test_position_sticky.html

diff --git a/layout/style/nsComputedDOMStyle.cpp b/layout/style/nsComputedDOMStyle.cpp
index 7f22a4cc671b..751e6abe9b67 100644
--- a/layout/style/nsComputedDOMStyle.cpp
+++ b/layout/style/nsComputedDOMStyle.cpp
@@ -3708,6 +3708,8 @@ nsComputedDOMStyle::GetOffsetWidthFor(mozilla::css::Side aSide)
       return GetStaticOffset(aSide);
     case NS_STYLE_POSITION_RELATIVE:
       return GetRelativeOffset(aSide);
+    case NS_STYLE_POSITION_STICKY:
+      return GetStickyOffset(aSide);
     case NS_STYLE_POSITION_ABSOLUTE:
     case NS_STYLE_POSITION_FIXED:
       return GetAbsoluteOffset(aSide);
@@ -3808,6 +3810,36 @@ nsComputedDOMStyle::GetRelativeOffset(mozilla::css::Side aSide)
   return val;
 }
 
+CSSValue*
+nsComputedDOMStyle::GetStickyOffset(mozilla::css::Side aSide)
+{
+  nsROCSSPrimitiveValue *val = new nsROCSSPrimitiveValue;
+
+  const nsStylePosition* positionData = StylePosition();
+  nsStyleCoord coord = positionData->mOffset.Get(aSide);
+
+  NS_ASSERTION(coord.GetUnit() == eStyleUnit_Coord ||
+               coord.GetUnit() == eStyleUnit_Percent ||
+               coord.GetUnit() == eStyleUnit_Auto ||
+               coord.IsCalcUnit(),
+               "Unexpected unit");
+
+  if (coord.GetUnit() == eStyleUnit_Auto) {
+    val->SetIdent(eCSSKeyword_auto);
+    return val;
+  }
+  PercentageBaseGetter baseGetter;
+  if (aSide == NS_SIDE_LEFT || aSide == NS_SIDE_RIGHT) {
+    baseGetter = &nsComputedDOMStyle::GetScrollFrameContentWidth;
+  } else {
+    baseGetter = &nsComputedDOMStyle::GetScrollFrameContentHeight;
+  }
+
+  val->SetAppUnits(StyleCoordToNSCoord(coord, baseGetter, 0, false));
+  return val;
+}
+
+
 CSSValue*
 nsComputedDOMStyle::GetStaticOffset(mozilla::css::Side aSide)
 
@@ -4126,6 +4158,50 @@ nsComputedDOMStyle::GetCBContentHeight(nscoord& aHeight)
   return true;
 }
 
+bool
+nsComputedDOMStyle::GetScrollFrameContentWidth(nscoord& aWidth)
+{
+  if (!mOuterFrame) {
+    return false;
+  }
+
+  AssertFlushedPendingReflows();
+
+  nsIScrollableFrame* scrollableFrame =
+    nsLayoutUtils::GetNearestScrollableFrame(mOuterFrame->GetParent(),
+      nsLayoutUtils::SCROLLABLE_SAME_DOC |
+      nsLayoutUtils::SCROLLABLE_INCLUDE_HIDDEN);
+
+  if (!scrollableFrame) {
+    return false;
+  }
+  aWidth =
+    scrollableFrame->GetScrolledFrame()->GetContentRectRelativeToSelf().width;
+  return true;
+}
+
+bool
+nsComputedDOMStyle::GetScrollFrameContentHeight(nscoord& aHeight)
+{
+  if (!mOuterFrame) {
+    return false;
+  }
+
+  AssertFlushedPendingReflows();
+
+  nsIScrollableFrame* scrollableFrame =
+    nsLayoutUtils::GetNearestScrollableFrame(mOuterFrame->GetParent(),
+      nsLayoutUtils::SCROLLABLE_SAME_DOC |
+      nsLayoutUtils::SCROLLABLE_INCLUDE_HIDDEN);
+
+  if (!scrollableFrame) {
+    return false;
+  }
+  aHeight =
+    scrollableFrame->GetScrolledFrame()->GetContentRectRelativeToSelf().height;
+  return true;
+}
+
 bool
 nsComputedDOMStyle::GetFrameBorderRectWidth(nscoord& aWidth)
 {
diff --git a/layout/style/nsComputedDOMStyle.h b/layout/style/nsComputedDOMStyle.h
index ae3040561eab..dfd6e41253db 100644
--- a/layout/style/nsComputedDOMStyle.h
+++ b/layout/style/nsComputedDOMStyle.h
@@ -125,6 +125,8 @@ private:
 
   mozilla::dom::CSSValue* GetRelativeOffset(mozilla::css::Side aSide);
 
+  mozilla::dom::CSSValue* GetStickyOffset(mozilla::css::Side aSide);
+
   mozilla::dom::CSSValue* GetStaticOffset(mozilla::css::Side aSide);
 
   mozilla::dom::CSSValue* GetPaddingWidthFor(mozilla::css::Side aSide);
@@ -491,6 +493,8 @@ private:
 
   bool GetCBContentWidth(nscoord& aWidth);
   bool GetCBContentHeight(nscoord& aWidth);
+  bool GetScrollFrameContentWidth(nscoord& aWidth);
+  bool GetScrollFrameContentHeight(nscoord& aHeight);
   bool GetFrameBoundsWidthForTransform(nscoord &aWidth);
   bool GetFrameBoundsHeightForTransform(nscoord &aHeight);
   bool GetFrameBorderRectWidth(nscoord& aWidth);
diff --git a/layout/style/test/Makefile.in b/layout/style/test/Makefile.in
index 2e898bcaeb06..ebc9aab2cd56 100644
--- a/layout/style/test/Makefile.in
+++ b/layout/style/test/Makefile.in
@@ -137,6 +137,8 @@ MOCHITEST_FILES =	test_acid3_test46.html \
 		test_parser_diagnostics_unprintables.html \
 		test_pixel_lengths.html \
 		test_pointer-events.html \
+		file_position_sticky.html \
+		test_position_sticky.html \
 		test_property_database.html \
 		test_priority_preservation.html \
 		test_property_syntax_errors.html \
diff --git a/layout/style/test/file_position_sticky.html b/layout/style/test/file_position_sticky.html
new file mode 100644
index 000000000000..20e1550cb71b
--- /dev/null
+++ b/layout/style/test/file_position_sticky.html
@@ -0,0 +1,88 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=886646
+-->
+<head>
+  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+  <style type="text/css">
+    #scroller {
+      width: 100px;
+      height: 100px;
+      padding: 10px;
+      border: 10px solid black;
+      margin: 10px;
+      overflow: hidden;
+    }
+    #container {
+      width: 50px;
+      height: 50px;
+    }
+    #sticky {
+      position: sticky;
+      width: 10px;
+      height: 10px;
+      overflow: hidden;
+    }
+  </style>
+</head>
+<body>
+<div id="display">
+  <div id="scroller">
+    <div id="container">
+      <div id="sticky"></div>
+    </div>
+  </div>
+</div>
+<pre id="test">
+<script type="application/javascript">
+
+/** Test for Bug 886646 - sticky positioning offsets **/
+
+// Use "is()", "ok()", and "todo()" from parent document.
+var is = parent.is;
+var ok = parent.ok;
+var todo = parent.todo;
+
+// Test that percentage sticky offsets are computed in terms of the
+// scroll container's content box
+var offsets = {
+  "top":    10,
+  "left":   20,
+  "bottom": 30,
+  "right":  40,
+};
+var scroller = document.getElementById("scroller");
+var container = document.getElementById("container");
+var sticky = document.getElementById("sticky");
+var cs = getComputedStyle(sticky, "");
+
+for (var prop in offsets) {
+  sticky.style[prop] = offsets[prop] + "%";
+  is(cs[prop], offsets[prop] + "px");
+}
+
+// ... even in the presence of scrollbars
+scroller.style.overflow = "scroll";
+container.style.width = "100%";
+container.style.height = "100%";
+
+var ccs = getComputedStyle(container, "");
+
+function isApproximatelyEqual(a, b) {
+  return Math.abs(a - b) < 0.001;
+}
+
+for (var prop in offsets) {
+  sticky.style[prop] = offsets[prop] + "%";
+  var basis = parseFloat(ccs[prop == "left" || prop == "right" ?
+                             "width" : "height"]) / 100;
+  ok(isApproximatelyEqual(parseFloat(cs[prop]), offsets[prop] * basis));
+}
+
+parent.finish();
+</script>
+</pre>
+</body>
+</html>
diff --git a/layout/style/test/test_position_sticky.html b/layout/style/test/test_position_sticky.html
new file mode 100644
index 000000000000..0164f2219a0b
--- /dev/null
+++ b/layout/style/test/test_position_sticky.html
@@ -0,0 +1,42 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=886646
+-->
+<head>
+  <meta charset="utf-8">
+  <title>Test for Bug 886646</title>
+  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=886646">Mozilla Bug 886646</a>
+<div id="display">
+  <iframe id="iframe" style="height: 200px; width: 200px"></iframe>
+</div>
+<pre id="test">
+<script type="application/javascript">
+
+/** Test for Bug 886646 - sticky positioning offsets **/
+
+/*
+ * This mochitest runs in an iframe so that we can selectively turn on the
+ * sticky about:config pref before its document is instantiated.
+ *
+ * See the iframe's source ("file_position_sticky.html") for the actual
+ * test code and for more documentation.
+ */
+
+SimpleTest.waitForExplicitFinish();
+
+SpecialPowers.setBoolPref("layout.css.sticky.enabled", true);
+document.getElementById("iframe").src = "file_position_sticky.html";
+
+function finish() {
+  SpecialPowers.clearUserPref("layout.css.sticky.enabled");
+  SimpleTest.finish();
+}
+</script>
+</pre>
+</body>
+</html>