Bug 1932800 - Use ShouldHaveLineIfEmpty() to guarantee buttons have at least one line of height. r=dshin

This is similar to how we treat <div contenteditable>, and allows us to
remove the specialness about anon boxes.

Differential Revision: https://phabricator.services.mozilla.com/D229939

layout/generic/nsBlockFrame.cpp

@@ -4969,26 +4969,9 @@ void nsBlockFrame::DoReflowInlineFrames(
   // because it might get disabled there
   aLine->EnableResizeReflowOptimization();
 
-  // We want to be able to collapse the height of empty inline elements in empty
-  // lines in general - See [1]. Two exceptions:
-  // 1. There is an outside ::marker frame, which is physical on this line, but
-  //    is not part of the line layout.
-  // 2. The line is inside an anonymous box, like `<input type=button>`. A
-  //    scrolled block frame internally has an anonymous box of the scrolled
-  //    content, which we still want to carry out the collapsing for.
-  //
-  // [1]: https://drafts.csswg.org/css-inline-3/#invisible-line-boxes
-  auto collapseEmptyInlineFramesInLine =
-      HasOutsideMarker() ||
-              (Style()->IsAnonBox() &&
-               Style()->GetPseudoType() != PseudoStyleType::scrolledContent)
-          ? CollapseEmptyInlineFramesInLine::Preserve
-          : CollapseEmptyInlineFramesInLine::Collapse;
-
   aLineLayout.BeginLineReflow(iStart, aState.mBCoord, availISize, availBSize,
                               aFloatAvailableSpace.HasFloats(),
-                              false /*XXX isTopOfPage*/,
-                              collapseEmptyInlineFramesInLine, lineWM,
+                              false /*XXX isTopOfPage*/, lineWM,
                               aState.mContainerSize, aState.mInsetForBalance);
 
   aState.mFlags.mIsLineLayoutEmpty = false;

layout/generic/nsFirstLetterFrame.cpp

@@ -226,7 +226,7 @@ void nsFirstLetterFrame::Reflow(nsPresContext* aPresContext,
     // `CollapseEmptyInlineFramesInLine` should not matter.
     ll.BeginLineReflow(
         bp.IStart(wm), bp.BStart(wm), availSize.ISize(wm), NS_UNCONSTRAINEDSIZE,
-        false, true, CollapseEmptyInlineFramesInLine::Collapse, kidWritingMode,
+        false, true, kidWritingMode,
         nsSize(aReflowInput.AvailableWidth(), aReflowInput.AvailableHeight()));
     rs.mLineLayout = ≪
     ll.SetInFirstLetter(true);

layout/generic/nsIFrame.cpp

@@ -4673,9 +4673,18 @@ bool nsIFrame::IsSelectable(StyleUserSelect* aSelectStyle) const {
 }
 
 bool nsIFrame::ShouldHaveLineIfEmpty() const {
-  if (Style()->IsPseudoOrAnonBox() &&
-      Style()->GetPseudoType() != PseudoStyleType::scrolledContent) {
-    return false;
+  switch (Style()->GetPseudoType()) {
+    case PseudoStyleType::NotPseudo:
+      break;
+    case PseudoStyleType::scrolledContent:
+      return GetParent()->ShouldHaveLineIfEmpty();
+    case PseudoStyleType::mozTextControlEditingRoot:
+      return true;
+    case PseudoStyleType::buttonContent:
+      // HTML quirk.
+      return GetContent()->IsHTMLElement(nsGkAtoms::input);
+    default:
+      return false;
   }
   return IsEditingHost(this);
 }

layout/generic/nsLineLayout.cpp

@@ -91,11 +91,12 @@ nsLineLayout::nsLineLayout(nsPresContext* aPresContext,
   }
 }
 
-void nsLineLayout::BeginLineReflow(
-    nscoord aICoord, nscoord aBCoord, nscoord aISize, nscoord aBSize,
-    bool aImpactedByFloats, bool aIsTopOfPage,
-    CollapseEmptyInlineFramesInLine aCollapseEmptyInlineFramesInLine,
-    WritingMode aWritingMode, const nsSize& aContainerSize, nscoord aInset) {
+void nsLineLayout::BeginLineReflow(nscoord aICoord, nscoord aBCoord,
+                                   nscoord aISize, nscoord aBSize,
+                                   bool aImpactedByFloats, bool aIsTopOfPage,
+                                   WritingMode aWritingMode,
+                                   const nsSize& aContainerSize,
+                                   nscoord aInset) {
   MOZ_ASSERT(nullptr == mRootSpan, "bad linelayout user");
   LAYOUT_WARN_IF_FALSE(aISize != NS_UNCONSTRAINEDSIZE,
                        "have unconstrained width; this should only result from "
@@ -148,9 +149,6 @@ void nsLineLayout::BeginLineReflow(
   psd->mIStart = aICoord;
   psd->mICoord = aICoord;
   psd->mIEnd = aICoord + aISize;
-  psd->mDoCollapseEmptyInlineFramesInLine =
-      aCollapseEmptyInlineFramesInLine ==
-      CollapseEmptyInlineFramesInLine::Collapse;
   // Set up inset to be used for text-wrap:balance implementation, but only if
   // the available size is greater than inset.
   psd->mInset = aISize > aInset ? aInset : 0;
@@ -356,7 +354,6 @@ nsLineLayout::PerSpanData* nsLineLayout::NewPerSpanData() {
   psd->mContainsFloat = false;
   psd->mHasNonemptyContent = false;
   psd->mBaseline = nullptr;
-  psd->mDoCollapseEmptyInlineFramesInLine = false;
 
 #ifdef DEBUG
   outerLineLayout->mSpansAllocated++;
@@ -1381,6 +1378,7 @@ void nsLineLayout::AddMarkerFrame(nsIFrame* aFrame,
   nsBlockFrame* blockFrame = do_QueryFrame(LineContainerFrame());
   MOZ_ASSERT(blockFrame, "must be for block");
   if (!blockFrame->MarkerIsEmpty(aFrame)) {
+    mLineIsEmpty = false;
     mHasMarker = true;
     mLineBox->SetHasMarker();
   }
@@ -1493,7 +1491,7 @@ void nsLineLayout::VerticalAlignLine() {
   // this operation is set to zero so that the y coordinates for all
   // of the placed children will be relative to there.
   PerSpanData* psd = mRootSpan;
-  if (mLineIsEmpty && psd->mDoCollapseEmptyInlineFramesInLine) {
+  if (mLineIsEmpty) {
     // This line is empty, and should be consisting of only inline elements.
     // (inline-block elements would make the line non-empty).
     WritingMode lineWM = psd->mWritingMode;

layout/generic/nsLineLayout.h

@@ -20,18 +20,6 @@
 class nsFloatManager;
 struct nsStyleText;
 
-/**
- * Flag indicating if inline frames within a line should be collapsed
- * to zero block-size if all frames within it are empty.
- * Declared as typed enum for clearer semantics in function calls, though
- * it is reflected as a boolean in
- * PerSpanData::mDoCollapseEmptyInlineFramesInLine.
- */
-enum class CollapseEmptyInlineFramesInLine {
-  Preserve,
-  Collapse,
-};
-
 class nsLineLayout {
   using BlockReflowState = mozilla::BlockReflowState;
   using ReflowInput = mozilla::ReflowInput;
@@ -61,14 +49,13 @@ class nsLineLayout {
 
   int32_t GetLineNumber() const { return mLineNumber; }
 
-  void BeginLineReflow(
-      nscoord aICoord, nscoord aBCoord, nscoord aISize, nscoord aBSize,
-      bool aImpactedByFloats, bool aIsTopOfPage,
-      CollapseEmptyInlineFramesInLine aCollapseEmptyInlineFramesInLine,
-      mozilla::WritingMode aWritingMode, const nsSize& aContainerSize,
-      // aInset is used during text-wrap:balance to reduce
-      // the effective available space on the line.
-      nscoord aInset = 0);
+  void BeginLineReflow(nscoord aICoord, nscoord aBCoord, nscoord aISize,
+                       nscoord aBSize, bool aImpactedByFloats,
+                       bool aIsTopOfPage, mozilla::WritingMode aWritingMode,
+                       const nsSize& aContainerSize,
+                       // aInset is used during text-wrap:balance to reduce
+                       // the effective available space on the line.
+                       nscoord aInset = 0);
 
   /**
    * Returns true if the line had to use an overflow-wrap break position.
@@ -510,7 +497,6 @@ class nsLineLayout {
     mozilla::WritingMode mWritingMode;
     bool mContainsFloat;
     bool mHasNonemptyContent;
-    bool mDoCollapseEmptyInlineFramesInLine;
 
     nscoord mIStart;
     nscoord mICoord;

layout/generic/nsRubyBaseContainerFrame.cpp

@@ -341,9 +341,9 @@ void nsRubyBaseContainerFrame::Reflow(nsPresContext* aPresContext,
     // If the writing mode is vertical-rl, the horizontal position of
     // rt frames will be updated when reflowing this text container,
     // hence leave container size 0 here for now.
-    lineLayout->BeginLineReflow(
-        0, 0, reflowInput->ComputedISize(), NS_UNCONSTRAINEDSIZE, false, false,
-        CollapseEmptyInlineFramesInLine::Collapse, reflowWM, nsSize(0, 0));
+    lineLayout->BeginLineReflow(0, 0, reflowInput->ComputedISize(),
+                                NS_UNCONSTRAINEDSIZE, false, false, reflowWM,
+                                nsSize(0, 0));
     lineLayout->AttachRootFrameToBaseLineLayout();
   }