1 files changed, 29 insertions, 12 deletions

diff --git a/layout/generic/nsGridContainerFrame.cpp b/layout/generic/nsGridContainerFrame.cpp
index 71d5bba212..f3e28acc49 100644
--- a/layout/generic/nsGridContainerFrame.cpp
+++ b/layout/generic/nsGridContainerFrame.cpp
@@ -818,8 +818,11 @@ struct nsGridContainerFrame::GridItemInfo
     // Ditto *-content:[last ]baseline. Mutually exclusive w. eSelfBaseline.
     eContentBaseline =       0x10,
     eAllBaselineBits = eIsBaselineAligned | eSelfBaseline | eContentBaseline,
+    // Should apply Automatic Minimum Size per:
+    // https://drafts.csswg.org/css-grid/#min-size-auto
+    eApplyAutoMinSize =      0x20,
     // Clamp per https://drafts.csswg.org/css-grid/#min-size-auto
-    eClampMarginBoxMinSize = 0x20,
+    eClampMarginBoxMinSize = 0x40,
   };
 
   explicit GridItemInfo(nsIFrame* aFrame,
@@ -851,11 +854,11 @@ struct nsGridContainerFrame::GridItemInfo
     return aAlign;
   }
 
-  // Return true if we should we clamp this item's Automatic Minimum Size.
+  // Return true if we should apply Automatic Minimum Size to this item.
   // https://drafts.csswg.org/css-grid/#min-size-auto
-  bool ShouldClampMinSize(WritingMode aContainerWM,
-                          LogicalAxis aContainerAxis,
-                          nscoord aPercentageBasis) const
+  bool ShouldApplyAutoMinSize(WritingMode aContainerWM,
+                              LogicalAxis aContainerAxis,
+                              nscoord aPercentageBasis) const
   {
     const auto pos = mFrame->StylePosition();
     const auto& size = aContainerAxis == eLogicalAxisInline ?
@@ -3977,9 +3980,9 @@ nsGridContainerFrame::Tracks::ResolveIntrinsicSizeStep1(
   WritingMode wm = aState.mWM;
   // Calculate data for "Automatic Minimum Size" clamping, if needed.
   bool needed = ((sz.mState & TrackSize::eIntrinsicMinSizing) ||
-                 aConstraint == SizingConstraint::eNoConstraint);
-  if (needed && TrackSize::IsDefiniteMaxSizing(sz.mState) &&
-      aGridItem.ShouldClampMinSize(wm, mAxis, aPercentageBasis)) {
+                 aConstraint == SizingConstraint::eNoConstraint) &&
+                (aGridItem.mState[mAxis] & ItemState::eApplyAutoMinSize);
+  if (needed && TrackSize::IsDefiniteMaxSizing(sz.mState)) {
     if (sz.mState & TrackSize::eIntrinsicMinSizing) {
       auto maxCoord = aFunctions.MaxSizingFor(aRange.mStart);
       cache.mMinSizeClamp =
@@ -4382,6 +4385,14 @@ nsGridContainerFrame::Tracks::ResolveIntrinsicSize(
   iter.Reset();
   for (; !iter.AtEnd(); iter.Next()) {
     auto& gridItem = aGridItems[iter.GridItemIndex()];
+
+    // Check if we need to apply "Automatic Minimum Size" and cache it.
+    MOZ_ASSERT(!(gridItem.mState[mAxis] & ItemState::eApplyAutoMinSize),
+               "Why is eApplyAutoMinSize set already?");
+    if (gridItem.ShouldApplyAutoMinSize(wm, mAxis, aPercentageBasis)) {
+      gridItem.mState[mAxis] |= ItemState::eApplyAutoMinSize;
+    }
+
     const GridArea& area = gridItem.mArea;
     const LineRange& lineRange = area.*aRange;
     uint32_t span = lineRange.Extent();
@@ -4407,9 +4418,9 @@ nsGridContainerFrame::Tracks::ResolveIntrinsicSize(
         CachedIntrinsicSizes cache;
         // Calculate data for "Automatic Minimum Size" clamping, if needed.
         bool needed = ((state & TrackSize::eIntrinsicMinSizing) ||
-                       aConstraint == SizingConstraint::eNoConstraint);
-        if (needed && TrackSize::IsDefiniteMaxSizing(state) &&
-            gridItem.ShouldClampMinSize(wm, mAxis, aPercentageBasis)) {
+                       aConstraint == SizingConstraint::eNoConstraint) &&
+                      (gridItem.mState[mAxis] & ItemState::eApplyAutoMinSize);
+        if (needed && TrackSize::IsDefiniteMaxSizing(state)) {
           nscoord minSizeClamp = 0;
           for (auto i = lineRange.mStart, end = lineRange.mEnd; i < end; ++i) {
             auto maxCoord = aFunctions.MaxSizingFor(i);
@@ -4445,11 +4456,14 @@ nsGridContainerFrame::Tracks::ResolveIntrinsicSize(
           gridItem.mState[mAxis] |= ItemState::eIsFlexing;
         } else if (aConstraint == SizingConstraint::eNoConstraint &&
                    TrackSize::IsDefiniteMaxSizing(state) &&
-                   gridItem.ShouldClampMinSize(wm, mAxis, aPercentageBasis)) {
+                   (gridItem.mState[mAxis] & ItemState::eApplyAutoMinSize)) {
           gridItem.mState[mAxis] |= ItemState::eClampMarginBoxMinSize;
         }
       }
     }
+    MOZ_ASSERT(!(gridItem.mState[mAxis] & ItemState::eClampMarginBoxMinSize) ||
+               (gridItem.mState[mAxis] & ItemState::eApplyAutoMinSize),
+               "clamping only applies to Automatic Minimum Size");
   }
 
   // Step 2.
@@ -5231,6 +5245,9 @@ nsGridContainerFrame::ReflowInFlowChild(nsIFrame*              aChild,
     } else {
       aChild->Properties().Delete(BClampMarginBoxMinSizeProperty());
     }
+    if ((aGridItemInfo->mState[childIAxis] & ItemState::eApplyAutoMinSize)) {
+      flags |= ReflowInput::I_APPLY_AUTO_MIN_SIZE;
+    }
   }
 
   if (!isConstrainedBSize) {