Issue #2284 - Add exception for flex/grid items resolving percentages against parent.

This folds in BZ bugs 1578586 and 1092007 part 2.

3 files changed, 68 insertions, 4 deletions

diff --git a/layout/generic/ReflowInput.cpp b/layout/generic/ReflowInput.cpp
index 1af7e798ef..4f5424dc44 100644
--- a/layout/generic/ReflowInput.cpp
+++ b/layout/generic/ReflowInput.cpp
@@ -226,6 +226,7 @@ ReflowInput::ReflowInput(
   mFlags.mAssumingHScrollbar = mFlags.mAssumingVScrollbar = false;
   mFlags.mIsColumnBalancing = false;
   mFlags.mIsFlexContainerMeasuringHeight = false;
+  mFlags.mTreatBSizeAsIndefinite = false;
   mFlags.mDummyParentReflowInput = false;
   mFlags.mShrinkWrap = !!(aFlags & COMPUTE_SIZE_SHRINK_WRAP);
   mFlags.mUseAutoBSize = !!(aFlags & COMPUTE_SIZE_USE_AUTO_BSIZE);
@@ -2041,6 +2042,10 @@ ReflowInput::ComputeContainingBlockRectangle(
 
   WritingMode wm = aContainingBlockRI->GetWritingMode();
 
+  if (aContainingBlockRI->mFlags.mTreatBSizeAsIndefinite) {
+    cbSize.BSize(wm) = NS_UNCONSTRAINEDSIZE;
+  }
+
   // mFrameType for abs-pos tables is NS_CSS_FRAME_TYPE_BLOCK, so we need to
   // special case them here.
   if (NS_FRAME_GET_TYPE(mFrameType) == NS_CSS_FRAME_TYPE_ABSOLUTE ||
@@ -2077,12 +2082,13 @@ ReflowInput::ComputeContainingBlockRectangle(
     }
   } else {
     // an element in quirks mode gets a containing block based on looking for a
-    // parent with a non-auto height if the element has a percent height
-    // Note: We don't emulate this quirk for percents in calc() or in
-    // vertical writing modes.
+    // parent with a non-auto height if the element has a percent height.
+    // Note: We don't emulate this quirk for percents in calc(), or in vertical
+    // writing modes, or if the containing block is a flex or grid item.
     if (!wm.IsVertical() &&
         NS_AUTOHEIGHT == cbSize.BSize(wm)) {
       if (eCompatibility_NavQuirks == aPresContext->CompatibilityMode() &&
+          !aContainingBlockRI->mFrame->IsFlexOrGridItem() &&
           mStylePosition->mHeight.GetUnit() == eStyleUnit_Percent) {
         cbSize.BSize(wm) = CalcQuirkContainingBlockHeight(aContainingBlockRI);
       }
@@ -2218,7 +2224,8 @@ ReflowInput::InitConstraints(nsPresContext*     aPresContext,
           // in quirks mode, get the cb height using the special quirk method
           if (!wm.IsVertical() &&
               eCompatibility_NavQuirks == aPresContext->CompatibilityMode()) {
-            if (!IS_TABLE_CELL(fType)) {
+            if (!IS_TABLE_CELL(fType) &&
+                !cbrs->mFrame->IsFlexOrGridItem()) {
               cbSize.BSize(wm) = CalcQuirkContainingBlockHeight(cbrs);
               if (cbSize.BSize(wm) == NS_AUTOHEIGHT) {
                 blockSizeUnit = eStyleUnit_Auto;
diff --git a/layout/generic/ReflowInput.h b/layout/generic/ReflowInput.h
index a70549d8eb..52c90e6eeb 100644
--- a/layout/generic/ReflowInput.h
+++ b/layout/generic/ReflowInput.h
@@ -206,6 +206,13 @@ public:
     uint32_t mIsFlexContainerMeasuringHeight:1; // nsFlexContainerFrame is
                                                 // reflowing this child to
                                                 // measure its intrinsic height.
+    uint32_t mTreatBSizeAsIndefinite:1; // If this flag is set, the BSize of this frame should be considered
+                                        // indefinite for the purposes of percent resolution on child frames (we
+                                        // should behave as if ComputedBSize() were NS_INTRINSIC_ISIZE when doing
+                                        // percent resolution against this.ComputedBSize()).  For example: flex
+                                        // items may have their ComputedBSize() resolved ahead-of-time by their
+                                        // flex container, and yet their BSize might have to be considered
+                                        // indefinite per https://drafts.csswg.org/css-flexbox/#definite-sizes
     uint32_t mDummyParentReflowInput:1; // a "fake" reflow state made
                                         // in order to be the parent
                                         // of a real one
diff --git a/layout/generic/nsFlexContainerFrame.cpp b/layout/generic/nsFlexContainerFrame.cpp
index 18a0643f14..d60308f424 100644
--- a/layout/generic/nsFlexContainerFrame.cpp
+++ b/layout/generic/nsFlexContainerFrame.cpp
@@ -557,6 +557,8 @@ public:
     return mFlexShrink * mFlexBaseSize;
   }
 
+  bool TreatBSizeAsIndefinite() const { return mTreatBSizeAsIndefinite; }
+
   const AspectRatio IntrinsicRatio() const { return mIntrinsicRatio; }
   bool HasIntrinsicRatio() const { return !!mIntrinsicRatio; }
 
@@ -799,6 +801,9 @@ protected:
   // Does this item need to resolve a min-[width|height]:auto (in main-axis).
   bool mNeedsMinSizeAutoResolution;
 
+  // Should we take care to treat this item's resolved BSize as indefinite?
+  bool mTreatBSizeAsIndefinite;
+
   const WritingMode mWM; // The flex item's writing mode.
   uint8_t mAlignSelf; // My "align-self" computed value (with "auto"
                       // swapped out for parent"s "align-items" value,
@@ -1990,6 +1995,40 @@ FlexItem::FlexItem(ReflowInput& aFlexItemReflowInput,
     mAlignSelf &= ~NS_STYLE_ALIGN_FLAG_BITS;
   }
 
+  // Our main-size is considered definite if any of these are true:
+  // (a) flex container has definite main size.
+  // (b) flex item has a definite flex basis and is fully inflexible
+  //     (NOTE: We don't actually check "fully inflexible" because webcompat
+  //     may not agree with that restriction...)
+  //
+  // Hence, we need to take care to treat the final main-size as *indefinite*
+  // if none of these conditions are satisfied.
+
+  // The flex item's main size is its BSize, and is considered definite under
+  // certain conditions laid out for definite flex-item main-sizes in the spec.
+  if (aAxisTracker.IsMainAxisHorizontal() ||
+      (containerRS->ComputedBSize() != NS_UNCONSTRAINEDSIZE &&
+       !containerRS->mFlags.mTreatBSizeAsIndefinite)) {
+    // The flex *container* has a definite main-size (either by being
+    // row-oriented [and using its own inline size which is by definition
+    // definite, or by being column-oriented and having a definite
+    // block-size).  The spec says this means all of the flex items'
+    // post-flexing main sizes should *also* be treated as definite.
+    mTreatBSizeAsIndefinite = false;
+  } else if (aFlexBaseSize != NS_UNCONSTRAINEDSIZE) {
+    // The flex item has a definite flex basis, which we'll treat as making
+    // its main-size definite.
+    // XXXdholbert Technically the spec requires the flex item to *also* be
+    // fully inflexible in order to have its size treated as definite in this
+    // scenario, but no browser implements that additional restriction, so
+    // it's not clear that this additional requirement would be
+    // web-compatible...
+    mTreatBSizeAsIndefinite = false;
+  } else {
+    // Otherwise, we have to treat the item's BSize as indefinite.
+    mTreatBSizeAsIndefinite = true;
+  }
+
   SetFlexBaseSizeAndMainSize(aFlexBaseSize);
   CheckForMinSizeAuto(aFlexItemReflowInput, aAxisTracker);
 
@@ -2054,6 +2093,7 @@ FlexItem::FlexItem(nsIFrame* aChildFrame, nscoord aCrossSize,
     mIsStretched(false),
     mIsStrut(true), // (this is the constructor for making struts, after all)
     mNeedsMinSizeAutoResolution(false),
+    mTreatBSizeAsIndefinite(false),
     mWM(aContainerWM),
     mAlignSelf(NS_STYLE_ALIGN_FLEX_START)
 {
@@ -4463,6 +4503,9 @@ nsFlexContainerFrame::DoFlexLayout(nsPresContext*           aPresContext,
             childReflowInput.SetComputedWidth(item->GetMainSize());
           } else {
             childReflowInput.SetComputedHeight(item->GetMainSize());
+            if (item->TreatBSizeAsIndefinite()) {
+              childReflowInput.mFlags.mTreatBSizeAsIndefinite = true;
+            }
           }
         }
 
@@ -4802,6 +4845,9 @@ nsFlexContainerFrame::ReflowFlexItem(nsPresContext* aPresContext,
   } else {
     childReflowInput.SetComputedHeight(aItem.GetMainSize());
     didOverrideComputedHeight = true;
+    if (aItem.TreatBSizeAsIndefinite()) {
+      childReflowInput.mFlags.mTreatBSizeAsIndefinite = true;
+    }
   }
 
   // Override reflow state's computed cross-size if either:
@@ -4819,6 +4865,10 @@ nsFlexContainerFrame::ReflowFlexItem(nsPresContext* aPresContext,
       childReflowInput.SetComputedWidth(aItem.GetCrossSize());
       didOverrideComputedWidth = true;
     } else {
+      // Note that in the above cases we don't need to worry about the BSize
+      // needing to be treated as indefinite, because this is for cases where
+      // the block size would always be considered definite (or where its
+      // definiteness would be irrelevant).
       childReflowInput.SetComputedHeight(aItem.GetCrossSize());
       didOverrideComputedHeight = true;
     }