Issue #1230 - Part 1: Fix Back-computing percentages for intrinsic sizing in Layout CSS-Grid

List of relevant patches applied:

1398537 part 2 - [css-multicol] Implement percentages for 'column-gap' (Gecko part).

1434478 part 1 - [css-grid] Stop back-computing percentage grid gaps when the percentage basis is indefinite. Treat them as zero sized instead.

1434478 part 2 - Stop back-computing percentage padding/margin when the percentage basis is indefinite. Treat them as zero sized instead.

1434478 part 3 - Remove IntrinsicISizeOffsetData::hPctPadding/hPctMargin members since they are now unused.

1434478 part 4 - Factor out constants like NS_UNCONSTRAINEDSIZE so they can be used in headers without needing nsIFrame.h (idempotent patch).

1434478 part 5 - Create nsLayoutUtils::ResolveToLength for resolving CSS <length-percentage> (idempotent patch).

1434478 part 6 - Propagate a percentage basis to nsIFrame::IntrinsicISizeOffsets for resolving padding/margin.

This is needed only for CSS Grid since in other cases we're only using IntrinsicISizeOffsets in the inline-axis and the percentage basis is always indefinite for *intrinsic sizing*. When calculating the intrinsic size of grid items in the grid container's block axis however, we do have a definite size for the grid area in the inline-axis and it should be used per: https://drafts.csswg.org/css-grid/#algo-overview "2. Next, the track sizing algorithm resolves the sizes of the grid rows, using the grid column sizes calculated in the previous step." (Percentage padding/margin for grid items is always resolved against the grid area's inline-size nowadays.)

1 files changed, 34 insertions, 59 deletions

diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index bd96f213b0..a531dea07f 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -4515,68 +4515,44 @@ nsIFrame::InlinePrefISizeData::ForceBreak()
   mSkipWhitespace = true;
 }
 
-static void
-AddCoord(const nsStyleCoord& aStyle,
-         nsIFrame* aFrame,
-         nscoord* aCoord, float* aPercent,
-         bool aClampNegativeToZero)
-{
-  switch (aStyle.GetUnit()) {
-    case eStyleUnit_Coord: {
-      NS_ASSERTION(!aClampNegativeToZero || aStyle.GetCoordValue() >= 0,
-                   "unexpected negative value");
-      *aCoord += aStyle.GetCoordValue();
-      return;
-    }
-    case eStyleUnit_Percent: {
-      NS_ASSERTION(!aClampNegativeToZero || aStyle.GetPercentValue() >= 0.0f,
-                   "unexpected negative value");
-      *aPercent += aStyle.GetPercentValue();
-      return;
-    }
-    case eStyleUnit_Calc: {
-      const nsStyleCoord::Calc *calc = aStyle.GetCalcValue();
-      if (aClampNegativeToZero) {
-        // This is far from ideal when one is negative and one is positive.
-        *aCoord += std::max(calc->mLength, 0);
-        *aPercent += std::max(calc->mPercent, 0.0f);
-      } else {
-        *aCoord += calc->mLength;
-        *aPercent += calc->mPercent;
-      }
-      return;
-    }
-    default: {
-      return;
-    }
+static nscoord
+ResolveMargin(const nsStyleCoord& aStyle, nscoord aPercentageBasis)
+{
+  if (aStyle.GetUnit() == eStyleUnit_Auto) {
+    return nscoord(0);
   }
+  return nsLayoutUtils::ResolveToLength<false>(aStyle, aPercentageBasis);
+}
+
+static nscoord
+ResolvePadding(const nsStyleCoord& aStyle, nscoord aPercentageBasis)
+{
+  return nsLayoutUtils::ResolveToLength<true>(aStyle, aPercentageBasis);
 }
 
 static nsIFrame::IntrinsicISizeOffsetData
-IntrinsicSizeOffsets(nsIFrame* aFrame, bool aForISize)
+IntrinsicSizeOffsets(nsIFrame* aFrame, nscoord aPercentageBasis, bool aForISize)
 {
   nsIFrame::IntrinsicISizeOffsetData result;
   WritingMode wm = aFrame->GetWritingMode();
-  const nsStyleMargin* styleMargin = aFrame->StyleMargin();
+  const auto& margin = aFrame->StyleMargin()->mMargin;
   bool verticalAxis = aForISize == wm.IsVertical();
-  AddCoord(verticalAxis ? styleMargin->mMargin.GetTop()
-                        : styleMargin->mMargin.GetLeft(),
-           aFrame, &result.hMargin, &result.hPctMargin,
-           false);
-  AddCoord(verticalAxis ? styleMargin->mMargin.GetBottom()
-                        : styleMargin->mMargin.GetRight(),
-           aFrame, &result.hMargin, &result.hPctMargin,
-           false);
-
-  const nsStylePadding* stylePadding = aFrame->StylePadding();
-  AddCoord(verticalAxis ? stylePadding->mPadding.GetTop()
-                        : stylePadding->mPadding.GetLeft(),
-           aFrame, &result.hPadding, &result.hPctPadding,
-           true);
-  AddCoord(verticalAxis ? stylePadding->mPadding.GetBottom()
-                        : stylePadding->mPadding.GetRight(),
-           aFrame, &result.hPadding, &result.hPctPadding,
-           true);
+  if (verticalAxis) {
+    result.hMargin += ResolveMargin(margin.GetTop(), aPercentageBasis);
+    result.hMargin += ResolveMargin(margin.GetBottom(), aPercentageBasis);
+  } else {
+    result.hMargin += ResolveMargin(margin.GetLeft(), aPercentageBasis);
+    result.hMargin += ResolveMargin(margin.GetRight(), aPercentageBasis);
+  }
+
+  const auto& padding = aFrame->StylePadding()->mPadding;
+  if (verticalAxis) {
+    result.hPadding += ResolvePadding(padding.GetTop(), aPercentageBasis);
+    result.hPadding += ResolvePadding(padding.GetBottom(), aPercentageBasis);
+  } else {
+    result.hPadding += ResolvePadding(padding.GetLeft(), aPercentageBasis);
+    result.hPadding += ResolvePadding(padding.GetRight(), aPercentageBasis);
+  }
 
   const nsStyleBorder* styleBorder = aFrame->StyleBorder();
   if (verticalAxis) {
@@ -4606,22 +4582,21 @@ IntrinsicSizeOffsets(nsIFrame* aFrame, bool aForISize)
       result.hPadding =
         presContext->DevPixelsToAppUnits(verticalAxis ? padding.TopBottom()
                                                       : padding.LeftRight());
-      result.hPctPadding = 0;
     }
   }
   return result;
 }
 
 /* virtual */ nsIFrame::IntrinsicISizeOffsetData
-nsFrame::IntrinsicISizeOffsets()
+nsFrame::IntrinsicISizeOffsets(nscoord aPercentageBasis)
 {
-  return IntrinsicSizeOffsets(this, true);
+  return IntrinsicSizeOffsets(this, aPercentageBasis, true);
 }
 
 nsIFrame::IntrinsicISizeOffsetData
-nsIFrame::IntrinsicBSizeOffsets()
+nsIFrame::IntrinsicBSizeOffsets(nscoord aPercentageBasis)
 {
-  return IntrinsicSizeOffsets(this, false);
+  return IntrinsicSizeOffsets(this, aPercentageBasis, false);
 }
 
 /* virtual */ IntrinsicSize