Bug 1300369 part 2 - Make nsLayoutUtils::IntrinsicForAxis handle margin-box min-size clamping. r=dholbert

layout/base/nsLayoutUtils.cpp

@@ -4911,7 +4911,8 @@ nsLayoutUtils::IntrinsicForAxis(PhysicalAxis        aAxis,
                                 nsRenderingContext* aRenderingContext,
                                 nsIFrame*           aFrame,
                                 IntrinsicISizeType  aType,
-                                uint32_t            aFlags)
+                                uint32_t            aFlags,
+                                nscoord             aMarginBoxMinSizeClamp)
 {
   NS_PRECONDITION(aFrame, "null frame");
   NS_PRECONDITION(aFrame->GetParent(),
@@ -4993,11 +4994,22 @@ nsLayoutUtils::IntrinsicForAxis(PhysicalAxis        aAxis,
     // For -moz-max-content and -moz-min-content, we handle them like
     // specified widths, but ignore box-sizing.
     boxSizing = StyleBoxSizing::Content;
+    if (aMarginBoxMinSizeClamp != NS_MAXSIZE &&
+        styleISize.GetIntValue() == NS_STYLE_WIDTH_MIN_CONTENT) {
+      // We need |result| to be the 'min-content size' for the clamping below.
+      result = aFrame->GetMinISize(aRenderingContext);
+    }
   } else if (!styleISize.ConvertsToLength() &&
              !(haveFixedMinISize && haveFixedMaxISize && maxISize <= minISize)) {
 #ifdef DEBUG_INTRINSIC_WIDTH
     ++gNoiseIndent;
 #endif
+    if (aType != MIN_ISIZE) {
+      // At this point, |styleISize| is auto/-moz-fit-content/-moz-available or
+      // has a percentage.  The intrinisic size for those under a max-content
+      // constraint is the max-content contribution which we shouldn't clamp.
+      aMarginBoxMinSizeClamp = NS_MAXSIZE;
+    }
     if (MOZ_UNLIKELY(aAxis != ourInlineAxis)) {
       IntrinsicSize intrinsicSize = aFrame->GetIntrinsicSize();
       const nsStyleCoord intrinsicBCoord =
@@ -5115,6 +5127,7 @@ nsLayoutUtils::IntrinsicForAxis(PhysicalAxis        aAxis,
   nsIFrame::IntrinsicISizeOffsetData offsets =
     MOZ_LIKELY(aAxis == ourInlineAxis) ? aFrame->IntrinsicISizeOffsets()
                                        : aFrame->IntrinsicBSizeOffsets();
+  nscoord contentBoxSize = result;
   result = AddIntrinsicSizeOffset(aRenderingContext, aFrame, offsets, aType,
                                   boxSizing, result, min, styleISize,
                                   haveFixedMinISize ? &minISize : nullptr,
@@ -5122,6 +5135,11 @@ nsLayoutUtils::IntrinsicForAxis(PhysicalAxis        aAxis,
                                   haveFixedMaxISize ? &maxISize : nullptr,
                                   styleMaxISize,
                                   aFlags, aAxis);
+  nscoord overflow = result - aMarginBoxMinSizeClamp;
+  if (MOZ_UNLIKELY(overflow > 0)) {
+    nscoord newContentBoxSize = std::max(nscoord(0), contentBoxSize - overflow);
+    result -= contentBoxSize - newContentBoxSize;
+  }
 
 #ifdef DEBUG_INTRINSIC_WIDTH
   nsFrame::IndentBy(stderr, gNoiseIndent);

layout/base/nsLayoutUtils.h

@@ -1373,6 +1373,9 @@ public:
    * width, its 'width', 'min-width', and 'max-width' properties (or 'height'
    * variations if that's what matches aAxis) and its padding, border and margin
    * in the corresponding dimension.
+   * @param aMarginBoxMinSizeClamp make the result fit within this margin-box
+   * size by reducing the *content size* (flooring at zero).  This is used for:
+   * https://drafts.csswg.org/css-grid/#min-size-auto
    */
   enum class IntrinsicISizeType { MIN_ISIZE, PREF_ISIZE };
   static const auto MIN_ISIZE = IntrinsicISizeType::MIN_ISIZE;
@@ -1383,11 +1386,13 @@ public:
     MIN_INTRINSIC_ISIZE = 0x04, // use min-width/height instead of width/height
     ADD_PERCENTS = 0x08, // apply AddPercents also for MIN_ISIZE
   };
-  static nscoord IntrinsicForAxis(mozilla::PhysicalAxis aAxis,
-                                  nsRenderingContext*   aRenderingContext,
-                                  nsIFrame*             aFrame,
-                                  IntrinsicISizeType    aType,
-                                  uint32_t              aFlags = 0);
+  static nscoord
+  IntrinsicForAxis(mozilla::PhysicalAxis aAxis,
+                   nsRenderingContext*   aRenderingContext,
+                   nsIFrame*             aFrame,
+                   IntrinsicISizeType    aType,
+                   uint32_t              aFlags = 0,
+                   nscoord               aMarginBoxMinSizeClamp = NS_MAXSIZE);
   /**
    * Calls IntrinsicForAxis with aFrame's parent's inline physical axis.
    */