Make line-height specified in ch units work. Bug 391909, r+sr+a+dbaron

layout/base/nsLayoutUtils.cpp

@@ -39,7 +39,6 @@
  * ***** END LICENSE BLOCK ***** */
 
 #include "nsLayoutUtils.h"
-#include "nsIFrame.h"
 #include "nsIFontMetrics.h"
 #include "nsIFormControlFrame.h"
 #include "nsPresContext.h"
@@ -1254,7 +1253,7 @@ static nscoord AddPercents(nsLayoutUtils::IntrinsicWidthType aType,
 /* static */ PRBool
 nsLayoutUtils::GetAbsoluteCoord(const nsStyleCoord& aStyle,
                                 nsIRenderingContext* aRenderingContext,
-                                nsIFrame* aFrame,
+                                nsStyleContext* aStyleContext,
                                 nscoord& aResult)
 {
   nsStyleUnit unit = aStyle.GetUnit();
@@ -1264,7 +1263,7 @@ nsLayoutUtils::GetAbsoluteCoord(const nsStyleCoord& aStyle,
   }
   if (eStyleUnit_Chars == unit) {
     aResult = nsLayoutUtils::CharsToCoord(aStyle, aRenderingContext,
-                                          aFrame->GetStyleContext());
+                                          aStyleContext);
     return PR_TRUE;
   }
   return PR_FALSE;

layout/base/nsLayoutUtils.h

@@ -41,7 +41,6 @@
 #ifndef nsLayoutUtils_h__
 #define nsLayoutUtils_h__
 
-class nsIFrame;
 class nsIFormControlFrame;
 class nsPresContext;
 class nsIContent;
@@ -58,6 +57,7 @@ class nsIFontMetrics;
 #include "nsAutoPtr.h"
 #include "nsStyleSet.h"
 #include "nsIView.h"
+#include "nsIFrame.h"
 
 class nsBlockFrame;
 
@@ -547,6 +547,18 @@ public:
   static PRBool GetAbsoluteCoord(const nsStyleCoord& aStyle,
                                  nsIRenderingContext* aRenderingContext,
                                  nsIFrame* aFrame,
+                                 nscoord& aResult)
+  {
+    return GetAbsoluteCoord(aStyle, aRenderingContext,
+                            aFrame->GetStyleContext(), aResult);
+  }
+
+  /**
+   * Same as above but doesn't need a frame
+   */
+  static PRBool GetAbsoluteCoord(const nsStyleCoord& aStyle,
+                                 nsIRenderingContext* aRenderingContext,
+                                 nsStyleContext* aStyleContext,
                                  nscoord& aResult);
   /**
    * Get the contribution of aFrame to its containing block's intrinsic

layout/generic/nsHTMLReflowState.cpp

@@ -2040,62 +2040,40 @@ GetNormalLineHeight(nsIFontMetrics* aFontMetrics)
 // Need only one of aRenderingContext and aDeviceContext
 static nscoord
 ComputeLineHeight(nsIRenderingContext* aRenderingContext,
-                  nsIDeviceContext* aDeviceContext,
                   nsStyleContext* aStyleContext)
 {
-  NS_PRECONDITION(aRenderingContext || aDeviceContext,
-                  "Need to have a way of getting a device context");
-
   nscoord lineHeight;
 
-  const nsStyleFont* font = aStyleContext->GetStyleFont();
   const nsStyleCoord& lhCoord = aStyleContext->GetStyleText()->mLineHeight;
   
-  nsStyleUnit unit = lhCoord.GetUnit();
-
-  if (unit == eStyleUnit_Coord) {
-    // For length values just use the pre-computed value
-    lineHeight = lhCoord.GetCoordValue();
-  } else if (unit == eStyleUnit_Factor) {
-    // For factor units the computed value of the line-height property 
-    // is found by multiplying the factor by the font's computed size
-    // (adjusted for min-size prefs and text zoom).
-    float factor = lhCoord.GetFactorValue();
-    lineHeight = NSToCoordRound(factor * font->mFont.size);
-  } else {
-    NS_ASSERTION(eStyleUnit_Normal == unit, "bad unit");
-    nsCOMPtr<nsIFontMetrics> fm;
-    nsLayoutUtils::GetFontMetricsForStyleContext(aStyleContext,
-                                                 getter_AddRefs(fm));
-    lineHeight = GetNormalLineHeight(fm);
+  if (!nsLayoutUtils::GetAbsoluteCoord(lhCoord, aRenderingContext,
+                                       aStyleContext, lineHeight)) {
+    const nsStyleFont* font = aStyleContext->GetStyleFont();
+    if (lhCoord.GetUnit() == eStyleUnit_Factor) {
+      // For factor units the computed value of the line-height property 
+      // is found by multiplying the factor by the font's computed size
+      // (adjusted for min-size prefs and text zoom).
+      float factor = lhCoord.GetFactorValue();
+      lineHeight = NSToCoordRound(factor * font->mFont.size);
+    } else {
+      NS_ASSERTION(eStyleUnit_Normal == lhCoord.GetUnit(), "bad unit");
+      nsCOMPtr<nsIFontMetrics> fm;
+      nsLayoutUtils::GetFontMetricsForStyleContext(aStyleContext,
+                                                   getter_AddRefs(fm));
+      lineHeight = GetNormalLineHeight(fm);
+    }
   }
   return lineHeight;
 }
 
 nscoord
 nsHTMLReflowState::CalcLineHeight(nsIRenderingContext* aRenderingContext,
-                                  nsIFrame* aFrame)
-{
-  NS_ASSERTION(aFrame && aFrame->GetStyleContext(),
-               "Bogus data passed in to CalcLineHeight");
-
-  nscoord lineHeight = ComputeLineHeight(aRenderingContext, nsnull,
-                                         aFrame->GetStyleContext());
-
-  NS_ASSERTION(lineHeight >= 0, "ComputeLineHeight screwed up");
-
-  return lineHeight;
-}
-
-nscoord
-nsHTMLReflowState::CalcLineHeight(nsStyleContext* aStyleContext,
-                                  nsIDeviceContext* aDeviceContext)
+                                  nsStyleContext* aStyleContext)
 {
+  NS_PRECONDITION(aRenderingContext, "Must have a rendering context");
   NS_PRECONDITION(aStyleContext, "Must have a style context");
-  NS_PRECONDITION(aDeviceContext, "Must have a device context");
   
-  nscoord lineHeight = ComputeLineHeight(nsnull, aDeviceContext,
-                                         aStyleContext);
+  nscoord lineHeight = ComputeLineHeight(aRenderingContext, aStyleContext);
 
   NS_ASSERTION(lineHeight >= 0, "ComputeLineHeight screwed up");
 

layout/generic/nsHTMLReflowState.h

@@ -419,12 +419,16 @@ public:
    * value will be >= 0.
    */
   static nscoord CalcLineHeight(nsIRenderingContext* aRenderingContext,
-                                nsIFrame* aFrame);
+                                nsIFrame* aFrame)
+  {
+    return CalcLineHeight(aRenderingContext, aFrame->GetStyleContext());
+  }
+  
   /**
-   * Same as above, but doesn't need quite as much info.
+   * Same as above, but doesn't need a frame.
    */
-  static nscoord CalcLineHeight(nsStyleContext* aStyleContext,
-                                nsIDeviceContext* aDeviceContext);
+  static nscoord CalcLineHeight(nsIRenderingContext* aRenderingContext,
+                                nsStyleContext* aStyleContext);
 
 
   void ComputeContainingBlockRectangle(nsPresContext*          aPresContext,

layout/reftests/bugs/391909-1-ref.html

@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<html>
+ <body>
+   <div id="source" style="width: 3ch"></div>
+   <div id="target" style="width: 0">
+    This is a test
+   </div>
+   <script>
+    document.getElementById("target").style.lineHeight =
+      document.defaultView
+              .getComputedStyle(document.getElementById("source"), "").width;
+   </script>
+ </body>
+</html>

layout/reftests/bugs/391909-1.html

@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<html>
+<body>
+<div style="line-height: 3ch; width: 0">
+This is a test
+</div>
+</body>
+</html>

layout/reftests/bugs/reftest.list

@@ -365,4 +365,5 @@ random-if(MOZ_WIDGET_TOOLKIT=="cocoa") == 379316-2.html 379316-2-ref.html # bug
 == 390318-1a.html 390318-1-ref.html
 == 390318-1b.html 390318-1-ref.html
 == 391140-1.html 391140-1-ref.html
+== 391909-1.html 391909-1-ref.html
 == 391994-1.html 391994-1-ref.html

layout/style/nsComputedDOMStyle.cpp

@@ -2765,9 +2765,20 @@ nsComputedDOMStyle::GetPaddingWidthFor(PRUint8 aSide, nsIDOMCSSValue** aValue)
 PRBool
 nsComputedDOMStyle::GetLineHeightCoord(nscoord& aCoord)
 {
-  aCoord = nsHTMLReflowState::CalcLineHeight(mStyleContextHolder,
-                                             mPresShell->GetPresContext()->
-                                               DeviceContext());
+  // Get a rendering context
+  nsCOMPtr<nsIRenderingContext> cx;
+  nsIFrame* frame = mPresShell->FrameManager()->GetRootFrame();
+  if (frame) {
+    mPresShell->CreateRenderingContext(frame, getter_AddRefs(cx));
+  }
+  if (!cx) {
+    // Give up
+    aCoord = 0;
+    return PR_FALSE;
+  }
+  
+  aCoord = nsHTMLReflowState::CalcLineHeight(cx, mStyleContextHolder);
+  
   // CalcLineHeight uses font->mFont.size, but we want to use
   // font->mSize as the font size.  Adjust for that.  Also adjust for
   // the text zoom, if any.