Bug 486778 Spell checker's wavy line is sometimes drawn through misspelled words r+sr=roc

layout/base/nsCSSRendering.cpp

@@ -2758,10 +2758,9 @@ nsCSSRendering::GetTextDecorationRectInternal(const gfxPoint& aPt,
   lineHeight = PR_MAX(lineHeight, 1.0);
 
   gfxFloat ascent = NS_round(aAscent);
-  gfxFloat descentLimit = NS_round(aDescentLimit);
+  gfxFloat descentLimit = NS_floor(aDescentLimit);
 
   gfxFloat suggestedMaxRectHeight = PR_MAX(PR_MIN(ascent, descentLimit), 1.0);
-  gfxFloat underlineOffsetAdjust = 0.0;
   r.size.height = lineHeight;
   if (aStyle == DECORATION_STYLE_DOUBLE) {
     /**
@@ -2805,12 +2804,6 @@ nsCSSRendering::GetTextDecorationRectInternal(const gfxPoint& aPt,
      */
     r.size.height = lineHeight > 2.0 ? lineHeight * 4.0 : lineHeight * 3.0;
     if (canLiftUnderline) {
-      // Wavy line's top edge can overlap to the baseline, because even if the
-      // wavy line overlaps the baseline of the text, that shouldn't cause
-      // unreadability.
-      descentLimit += lineHeight;
-      // Recompute suggestedMaxRectHeight with new descentLimit value.
-      suggestedMaxRectHeight = PR_MAX(PR_MIN(ascent, descentLimit), 1.0);
       if (r.Height() > suggestedMaxRectHeight) {
         // Don't shrink the line height even if there is not enough space,
         // because the thickness has some meaning.  E.g., the 1px wavy line and
@@ -2819,18 +2812,13 @@ nsCSSRendering::GetTextDecorationRectInternal(const gfxPoint& aPt,
         r.size.height = PR_MAX(suggestedMaxRectHeight, lineHeight * 2.0);
       }
     }
-    // If this is underline, the middle of the rect should be aligned to the
-    // specified underline offset.  So, wavy line's top edge can overlap to
-    // baseline.  Because even if the wavy line overlaps the baseline of the
-    // text, that shouldn't cause unreadability.
-    underlineOffsetAdjust = r.Height() / 2.0;
   }
 
   gfxFloat baseline = NS_floor(aPt.y + aAscent + 0.5);
   gfxFloat offset = 0.0;
   switch (aDecoration) {
     case NS_STYLE_TEXT_DECORATION_UNDERLINE:
-      offset = aOffset + underlineOffsetAdjust;
+      offset = aOffset;
       if (canLiftUnderline) {
         if (descentLimit < -offset + r.Height()) {
           // If we can ignore the offset and the decoration line is overflowing,
@@ -2838,7 +2826,7 @@ nsCSSRendering::GetTextDecorationRectInternal(const gfxPoint& aPt,
           // possible.  Otherwise, we should lift up the top edge of the rect as
           // far as possible.
           gfxFloat offsetBottomAligned = -descentLimit + r.Height();
-          gfxFloat offsetTopAligned = underlineOffsetAdjust;
+          gfxFloat offsetTopAligned = 0.0;
           offset = PR_MIN(offsetBottomAligned, offsetTopAligned);
         }
       }

layout/base/tests/decoration_line_rendering.js

@@ -164,10 +164,9 @@ function getTextDecorationRect(aPt, aLineSize, aAscent, aOffset, aStyle,
   lineHeight = Math.max(lineHeight, 1.0);
 
   var ascent = round(aAscent);
-  var descentLimit = round(aDescentLimit);
+  var descentLimit = Math.floor(aDescentLimit);
 
   var suggestedMaxRectHeight = Math.max(Math.min(ascent, descentLimit), 1.0);
-  var underlineOffsetAdjust = 0.0;
   r.height = lineHeight;
   if (aStyle == kDecorationStyleDouble) {
     var gap = round(lineHeight / 2.0);
@@ -181,23 +180,20 @@ function getTextDecorationRect(aPt, aLineSize, aAscent, aOffset, aStyle,
   } else if (aStyle == kDecorationStyleWavy) {
     r.height = lineHeight > 2.0 ? lineHeight * 4.0 : lineHeight * 3.0;
     if (liftupUnderline) {
-      descentLimit += lineHeight;
-      suggestedMaxRectHeight = Math.max(Math.min(ascent, descentLimit), 1.0);
       if (r.height > suggestedMaxRectHeight) {
         r.height = Math.max(suggestedMaxRectHeight, lineHeight * 2.0);
       }
     }
-    underlineOffsetAdjust = r.height / 2.0;
   }
 
   var baseline = Math.floor(aPt.y + aAscent + 0.5);
   var offset = 0.0;
 
-  offset = aOffset + underlineOffsetAdjust;
+  offset = aOffset;
   if (liftupUnderline) {
     if (descentLimit < -offset + r.height) {
       var offsetBottomAligned = -descentLimit + r.height;
-      var offsetTopAligned = underlineOffsetAdjust;
+      var offsetTopAligned = 0.0;
       offset = Math.min(offsetBottomAligned, offsetTopAligned);
     }
   }

layout/generic/nsTextFrameThebes.cpp

@@ -4091,6 +4091,22 @@ nsTextFrame::PaintTextDecorations(gfxContext* aCtx, const gfxRect& aDirtyRect,
   }
 }
 
+static gfxFloat
+ComputeDescentLimitForSelectionUnderline(nsPresContext* aPresContext,
+                                         nsTextFrame* aFrame,
+                                         const gfxFont::Metrics& aFontMetrics)
+{
+  gfxFloat app = aPresContext->AppUnitsPerDevPixel();
+  nscoord lineHeightApp =
+    nsHTMLReflowState::CalcLineHeight(aFrame->GetStyleContext(), NS_AUTOHEIGHT);
+  gfxFloat lineHeight = gfxFloat(lineHeightApp) / app;
+  if (lineHeight <= aFontMetrics.maxHeight) {
+    return aFontMetrics.maxDescent;
+  }
+  return aFontMetrics.maxDescent + (lineHeight - aFontMetrics.maxHeight) / 2;
+}
+
+
 // Make sure this stays in sync with DrawSelectionDecorations below
 static const SelectionType SelectionTypesWithDecorations =
   nsISelectionController::SELECTION_SPELLCHECK |
@@ -4128,6 +4144,7 @@ GetTextDecorationStyle(const nsTextRangeStyle &aRangeStyle)
  * drawing text decoration for selections.
  */
 static void DrawSelectionDecorations(gfxContext* aContext, SelectionType aType,
+    nsTextFrame* aFrame,
     nsTextPaintStyle& aTextPaintStyle,
     const nsTextRangeStyle &aRangeStyle,
     const gfxPoint& aPt, gfxFloat aWidth,
@@ -4135,7 +4152,9 @@ static void DrawSelectionDecorations(gfxContext* aContext, SelectionType aType,
 {
   gfxPoint pt(aPt);
   gfxSize size(aWidth, aFontMetrics.underlineSize);
-  gfxFloat descentLimit = aFontMetrics.maxDescent;
+  gfxFloat descentLimit =
+    ComputeDescentLimitForSelectionUnderline(aTextPaintStyle.PresContext(),
+                                             aFrame, aFontMetrics);
 
   float relativeSize;
   PRUint8 style;
@@ -4595,7 +4614,7 @@ nsTextFrame::PaintTextSelectionDecorations(gfxContext* aCtx,
       pt.x = (aFramePt.x + xOffset -
              (mTextRun->IsRightToLeft() ? advance : 0)) / app;
       gfxFloat width = PR_ABS(advance) / app;
-      DrawSelectionDecorations(aCtx, aSelectionType, aTextPaintStyle,
+      DrawSelectionDecorations(aCtx, aSelectionType, this, aTextPaintStyle,
                                selectedStyle,
                                pt, width, mAscent / app, decorationMetrics);
     }
@@ -4900,7 +4919,8 @@ nsTextFrame::CombineSelectionUnderlineRect(nsPresContext* aPresContext,
   const gfxFont::Metrics& metrics = firstFont->GetMetrics();
   gfxFloat underlineOffset = fontGroup->GetUnderlineOffset();
   gfxFloat ascent = aPresContext->AppUnitsToGfxUnits(mAscent);
-  gfxFloat descentLimit = metrics.maxDescent;
+  gfxFloat descentLimit =
+    ComputeDescentLimitForSelectionUnderline(aPresContext, this, metrics);
 
   SelectionDetails *details = GetSelectionDetails();
   for (SelectionDetails *sd = details; sd; sd = sd->mNext) {