Bug 1665657 - Whitespace that will hang should not contribute to the min inline-size of a textframe. r=emilio

This affects a few of the examples in the text/white-space-2 reftest, but the changes look sensible;
more significantly from an interop point of view, there are specific web-platform reftests that are
currently failing, but will pass after the patch.

Differential Revision: https://phabricator.services.mozilla.com/D95811

layout/generic/nsTextFrame.cpp

@@ -801,12 +801,13 @@ static bool IsTrimmableSpace(char aCh) {
 }
 
 static bool IsTrimmableSpace(const nsTextFragment* aFrag, uint32_t aPos,
-                             const nsStyleText* aStyleText) {
+                             const nsStyleText* aStyleText,
+                             bool aAllowHangingWS = false) {
   NS_ASSERTION(aPos < aFrag->GetLength(), "No text for IsSpace!");
 
   switch (aFrag->CharAt(aPos)) {
     case ' ':
-      return !aStyleText->WhiteSpaceIsSignificant() &&
+      return (!aStyleText->WhiteSpaceIsSignificant() || aAllowHangingWS) &&
              !IsSpaceCombiningSequenceTail(aFrag, aPos + 1);
     case '\n':
       return !aStyleText->NewlineIsSignificantStyle() &&
@@ -814,7 +815,7 @@ static bool IsTrimmableSpace(const nsTextFragment* aFrag, uint32_t aPos,
     case '\t':
     case '\r':
     case '\f':
-      return !aStyleText->WhiteSpaceIsSignificant();
+      return !aStyleText->WhiteSpaceIsSignificant() || aAllowHangingWS;
     default:
       return false;
   }
@@ -3049,11 +3050,13 @@ gfxSkipCharsIterator nsTextFrame::EnsureTextRun(
 static uint32_t GetEndOfTrimmedText(const nsTextFragment* aFrag,
                                     const nsStyleText* aStyleText,
                                     uint32_t aStart, uint32_t aEnd,
-                                    gfxSkipCharsIterator* aIterator) {
+                                    gfxSkipCharsIterator* aIterator,
+                                    bool aAllowHangingWS = false) {
   aIterator->SetSkippedOffset(aEnd);
   while (aIterator->GetSkippedOffset() > aStart) {
     aIterator->AdvanceSkipped(-1);
-    if (!IsTrimmableSpace(aFrag, aIterator->GetOriginalOffset(), aStyleText))
+    if (!IsTrimmableSpace(aFrag, aIterator->GetOriginalOffset(), aStyleText,
+                          aAllowHangingWS))
       return aIterator->GetSkippedOffset() + 1;
   }
   return aStart;
@@ -8348,6 +8351,7 @@ void nsTextFrame::AddInlineMinISizeForFlow(gfxContext* aRenderingContext,
   bool collapseWhitespace = !textStyle->WhiteSpaceIsSignificant();
   bool preformatNewlines = textStyle->NewlineIsSignificant(this);
   bool preformatTabs = textStyle->WhiteSpaceIsSignificant();
+  bool whitespaceCanHang = textStyle->WhiteSpaceCanHangOrVisuallyCollapse();
   gfxFloat tabWidth = -1;
   uint32_t start = FindStartAfterSkippingWhitespace(&provider, aData, textStyle,
                                                     &iter, flowEndInTextRun);
@@ -8408,9 +8412,9 @@ void nsTextFrame::AddInlineMinISizeForFlow(gfxContext* aRenderingContext,
       aData->mCurrentLine = NSCoordSaturatingAdd(aData->mCurrentLine, width);
       aData->mAtStartOfLine = false;
 
-      if (collapseWhitespace) {
+      if (collapseWhitespace || whitespaceCanHang) {
         uint32_t trimStart =
-            GetEndOfTrimmedText(frag, textStyle, wordStart, i, &iter);
+            GetEndOfTrimmedText(frag, textStyle, wordStart, i, &iter, whitespaceCanHang);
         if (trimStart == start) {
           // This is *all* trimmable whitespace, so whatever trailingWhitespace
           // we saw previously is still trailing...
@@ -9275,9 +9279,7 @@ void nsTextFrame::ReflowText(nsLineLayout& aLineLayout, nscoord aAvailableWidth,
 
   bool isBreakSpaces = textStyle->mWhiteSpace == StyleWhiteSpace::BreakSpaces;
   // allow whitespace to overflow the container
-  bool whitespaceCanHang = !isBreakSpaces &&
-                           textStyle->WhiteSpaceCanWrapStyle() &&
-                           textStyle->WhiteSpaceIsSignificant();
+  bool whitespaceCanHang = textStyle->WhiteSpaceCanHangOrVisuallyCollapse();
   gfxBreakPriority breakPriority = aLineLayout.LastOptionalBreakPriority();
   gfxTextRun::SuppressBreak suppressBreak = gfxTextRun::eNoSuppressBreak;
   bool shouldSuppressLineBreak = ShouldSuppressLineBreak();

layout/reftests/text/white-space-2-ref.html

@@ -3,11 +3,14 @@
 <head>
 <!-- Reference -->
 <style>
-div { border:1px solid black; }
+div { font:16px sans-serif; border:1px solid black; }
 .container { float:left; width:20%; border-color:cyan; }
 p { width:0; }
 b { font-weight:normal; background-color:yellow; white-space:pre; }
 .cell { display:table-cell; border:1px solid green; }
+.hang { display:inline-block; width:0; overflow:visible; }
+.hang span { display:inline; background-color:yellow; }
+.clip { overflow: hidden; }
 </style>
 </head>
 <body>
@@ -37,7 +40,7 @@ Kitty</b></span>
  Kitty</b></span>
 <p><span class="cell"><b>Hello  Kitty</b></span>
 <p><span class="cell"><b>Hello  Kitty</b></span>
-<p><span class="cell"><b>Hello 
+<p><span class="cell clip"><b>Hello<span class="hang"><span> </span></span>
  Kitty</b></span>
 </div>
 
@@ -51,11 +54,11 @@ Kitty</b></span>
 </div>
 
 <div class="container">
-<p><span class="cell"><b>Hello  
+<p><span class="cell"><b>Hello<span class="hang"><span> </span></span>
 Kitty</b></span>
 <p><span class="cell"><b>Hello 
 Kitty</b></span>
-<p><span class="cell"><b>Hello  
+<p><span class="cell"><b>Hello<span class="hang"><span> </span></span>
 Kitty</b></span>
 <p><span class="cell"><b>Hello
 Kitty</b></span>

layout/reftests/text/white-space-2.html

@@ -3,7 +3,7 @@
 <head>
 <!-- Wrapping tests in table-cell to test min-width computation -->
 <style>
-div { border:1px solid black; }
+div { font:16px sans-serif; border:1px solid black; }
 .container { float:left; width:20%; border-color:cyan; }
 p { width:0; }
 b { font-weight:normal; background-color:yellow; }

layout/style/nsStyleStruct.h

@@ -963,6 +963,15 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleText {
            mWhiteSpace == mozilla::StyleWhiteSpace::PreSpace;
   }
 
+  bool WhiteSpaceCanHangOrVisuallyCollapse() const {
+    // This was originally expressed in nsTextFrame in terms of:
+    //   mWhiteSpace != StyleWhiteSpace::BreakSpaces &&
+    //       WhiteSpaceCanWrapStyle() &&
+    //       WhiteSpaceIsSignificant()
+    // which simplifies to:
+    return mWhiteSpace == mozilla::StyleWhiteSpace::PreWrap;
+  }
+
   bool NewlineIsSignificantStyle() const {
     return mWhiteSpace == mozilla::StyleWhiteSpace::Pre ||
            mWhiteSpace == mozilla::StyleWhiteSpace::PreWrap ||

testing/web-platform/meta/css/css-text/white-space/white-space-intrinsic-size-003.html.ini

@@ -1,2 +0,0 @@
-[white-space-intrinsic-size-003.html]
-  expected: FAIL

testing/web-platform/meta/css/css-text/white-space/white-space-intrinsic-size-013.html.ini

@@ -1,2 +0,0 @@
-[white-space-intrinsic-size-013.html]
-  expected: FAIL

testing/web-platform/meta/css/css-text/white-space/white-space-intrinsic-size-014.html.ini

@@ -1,2 +0,0 @@
-[white-space-intrinsic-size-014.html]
-  expected: FAIL

testing/web-platform/meta/css/css-text/white-space/white-space-pre-wrap-trailing-spaces-003.html.ini

@@ -1,2 +0,0 @@
-[white-space-pre-wrap-trailing-spaces-003.html]
-  expected: FAIL