Issue #1673 - Part 1: Allow tab-size to accept <length>.

Currently -moz-tab-size only accepts <number> values, and both Chrome and Firefox currently support <length> values and have for some time now. So with this you would be able to support sizes in px or em, for instance. This was implemented in Firefox 53 and was trivial to backport.

1 files changed, 45 insertions, 29 deletions

diff --git a/layout/generic/nsTextFrame.cpp b/layout/generic/nsTextFrame.cpp
index c7b55961c..749b8b944 100644
--- a/layout/generic/nsTextFrame.cpp
+++ b/layout/generic/nsTextFrame.cpp
@@ -3178,7 +3178,7 @@ public:
     return mFontMetrics;
   }
 
-  void CalcTabWidths(Range aTransformedRange);
+  void CalcTabWidths(Range aTransformedRange, gfxFloat aTabWidth);
 
   const gfxSkipCharsIterator& GetEndHint() { return mTempIterator; }
 
@@ -3364,6 +3364,28 @@ CanAddSpacingAfter(const gfxTextRun* aTextRun, uint32_t aOffset)
     aTextRun->IsLigatureGroupStart(aOffset + 1);
 }
 
+static gfxFloat
+ComputeTabWidthAppUnits(nsIFrame* aFrame, gfxTextRun* aTextRun)
+{
+  const nsStyleText* textStyle = aFrame->StyleText();
+  if (textStyle->mTabSize.GetUnit() != eStyleUnit_Factor) {
+    nscoord w = textStyle->mTabSize.GetCoordValue();
+    MOZ_ASSERT(w >= 0);
+    return w;
+  }
+
+  gfxFloat spaces = textStyle->mTabSize.GetFactorValue();
+  MOZ_ASSERT(spaces >= 0);
+
+  // Round the space width when converting to appunits the same way
+  // textruns do.
+  gfxFloat spaceWidthAppUnits =
+    NS_round(GetFirstFontMetrics(aTextRun->GetFontGroup(),
+                                 aTextRun->IsVertical()).spaceWidth *
+             aTextRun->GetAppUnitsPerDevUnit());
+  return spaces * spaceWidthAppUnits;
+}
+
 void
 PropertyProvider::GetSpacingInternal(Range aRange, Spacing* aSpacing,
                                      bool aIgnoreTabs)
@@ -3411,17 +3433,16 @@ PropertyProvider::GetSpacingInternal(Range aRange, Spacing* aSpacing,
     }
   }
 
-  // Ignore tab spacing rather than computing it, if the tab size is 0
-  if (!aIgnoreTabs)
-    aIgnoreTabs = mFrame->StyleText()->mTabSize == 0;
-
   // Now add tab spacing, if there is any
   if (!aIgnoreTabs) {
-    CalcTabWidths(aRange);
-    if (mTabWidths) {
-      mTabWidths->ApplySpacing(aSpacing,
-                               aRange.start - mStart.GetSkippedOffset(),
-                               aRange.Length());
+    gfxFloat tabWidth = ComputeTabWidthAppUnits(mFrame, mTextRun);
+    if (tabWidth > 0) {
+      CalcTabWidths(aRange);
+      if (mTabWidths) {
+        mTabWidths->ApplySpacing(aSpacing,
+                                 aRange.start - mStart.GetSkippedOffset(),
+                                 aRange.Length());
+      }
     }
   }
 
@@ -3444,33 +3465,23 @@ PropertyProvider::GetSpacingInternal(Range aRange, Spacing* aSpacing,
   }
 }
 
-static gfxFloat
-ComputeTabWidthAppUnits(nsIFrame* aFrame, const gfxTextRun* aTextRun)
-{
-  // Get the number of spaces from CSS -moz-tab-size
-  const nsStyleText* textStyle = aFrame->StyleText();
-
-  return textStyle->mTabSize * GetSpaceWidthAppUnits(aTextRun);
-}
-
 // aX and the result are in whole appunits.
 static gfxFloat
 AdvanceToNextTab(gfxFloat aX, nsIFrame* aFrame,
-                 const gfxTextRun* aTextRun, gfxFloat* aCachedTabWidth)
+                 gfxTextRun* aTextRun, gfxFloat* aTabWidth)
 {
-  if (*aCachedTabWidth < 0) {
-    *aCachedTabWidth = ComputeTabWidthAppUnits(aFrame, aTextRun);
-  }
 
   // Advance aX to the next multiple of *aCachedTabWidth. We must advance
   // by at least 1 appunit.
   // XXX should we make this 1 CSS pixel?
-  return ceil((aX + 1)/(*aCachedTabWidth))*(*aCachedTabWidth);
+  return ceil((aX + 1)/ aTabWidth) * aTabWidth;
 }
 
 void
-PropertyProvider::CalcTabWidths(Range aRange)
+PropertyProvider::CalcTabWidths(Range aRange, gfxFloat aTabWidth)
 {
+  MOZ_ASSERT(aTabWidth > 0);
+
   if (!mTabWidths) {
     if (mReflowing && !mLineContainer) {
       // Intrinsic width computation does its own tab processing. We
@@ -3505,7 +3516,6 @@ PropertyProvider::CalcTabWidths(Range aRange)
     NS_ASSERTION(mReflowing,
                  "We need precomputed tab widths, but don't have enough.");
 
-    gfxFloat tabWidth = -1;
     for (uint32_t i = tabsEnd; i < aRange.end; ++i) {
       Spacing spacing;
       GetSpacingInternal(Range(i, i + 1), &spacing, true);
@@ -3527,7 +3537,7 @@ PropertyProvider::CalcTabWidths(Range aRange)
           mFrame->SetProperty(TabWidthProperty(), mTabWidths);
         }
         double nextTab = AdvanceToNextTab(mOffsetFromBlockOriginForTabs,
-                mFrame, mTextRun, &tabWidth);
+                mFrame, mTextRun, aTabWidth);
         mTabWidths->mWidths.AppendElement(TabWidth(i - startOffset, 
                 NSToIntRound(nextTab - mOffsetFromBlockOriginForTabs)));
         mOffsetFromBlockOriginForTabs = nextTab;
@@ -8321,9 +8331,12 @@ nsTextFrame::AddInlineMinISizeForFlow(nsRenderingContext *aRenderingContext,
       PropertyProvider::Spacing spacing;
       provider.GetSpacing(Range(i, i + 1), &spacing);
       aData->mCurrentLine += nscoord(spacing.mBefore);
+      if (tabWidth < 0) {
+	tabWidth = ComputeTabWidthAppUnits(this, textRun);
+      }
       gfxFloat afterTab =
         AdvanceToNextTab(aData->mCurrentLine, this,
-                         textRun, &tabWidth);
+                         textRun, tabWidth);
       aData->mCurrentLine = nscoord(afterTab + spacing.mAfter);
       wordStart = i + 1;
     } else if (i < flowEndInTextRun ||
@@ -8480,9 +8493,12 @@ nsTextFrame::AddInlinePrefISizeForFlow(nsRenderingContext *aRenderingContext,
       PropertyProvider::Spacing spacing;
       provider.GetSpacing(Range(i, i + 1), &spacing);
       aData->mCurrentLine += nscoord(spacing.mBefore);
+      if (tabWidth < 0) {
+	tabWidth = ComputeTabWidthAppUnits(this, textRun);
+      }
       gfxFloat afterTab =
         AdvanceToNextTab(aData->mCurrentLine, this,
-                         textRun, &tabWidth);
+                         textRun, tabWidth);
       aData->mCurrentLine = nscoord(afterTab + spacing.mAfter);
       lineStart = i + 1;
     } else if (preformattedNewline) {