Issue #1914 - Implement white-space: break-spaces

This also simplifies GetCSSWhitespaceToCompressionMode (FFS with the function
names, Mozilla!) to be less fragile.

9 files changed, 57 insertions, 37 deletions

diff --git a/devtools/shared/css/generated/properties-db.js b/devtools/shared/css/generated/properties-db.js
index 5a7e6d815d..9ccebc8481 100644
--- a/devtools/shared/css/generated/properties-db.js
+++ b/devtools/shared/css/generated/properties-db.js
@@ -9519,6 +9519,7 @@ exports.CSS_PROPERTIES = {
     "supports": [],
     "values": [
       "-moz-pre-space",
+      "break-spaces",
       "inherit",
       "initial",
       "normal",
diff --git a/gfx/thebes/gfxTextRun.cpp b/gfx/thebes/gfxTextRun.cpp
index fd97615366..438f6f61ae 100644
--- a/gfx/thebes/gfxTextRun.cpp
+++ b/gfx/thebes/gfxTextRun.cpp
@@ -851,6 +851,7 @@ gfxTextRun::BreakAndMeasureText(uint32_t aStart, uint32_t aMaxLength,
                                 bool *aUsedHyphenation,
                                 uint32_t *aLastBreak,
                                 bool aCanWordWrap,
+                                bool aCanWhitespaceWrap,
                                 gfxBreakPriority *aBreakPriority)
 {
     aMaxLength = std::min(aMaxLength, GetLength() - aStart);
@@ -918,7 +919,15 @@ gfxTextRun::BreakAndMeasureText(uint32_t aStart, uint32_t aMaxLength,
                 aCanWordWrap && mCharacterGlyphs[i].IsClusterStart() &&
                 *aBreakPriority <= gfxBreakPriority::eWordWrapBreak;
 
-            if (atBreak || wordWrapping) {
+            bool whitespaceWrapping = false;
+            if (i > aStart) {
+                // The spec says the breaking opportunity is *after* whitespace.
+                auto const& g = mCharacterGlyphs[i - 1];
+                whitespaceWrapping = aCanWhitespaceWrap &&
+                                     (g.CharIsSpace() || g.CharIsTab() || g.CharIsNewline());
+            }
+
+            if (atBreak || wordWrapping || whitespaceWrapping) {
                 gfxFloat hyphenatedAdvance = advance;
                 if (atHyphenationBreak) {
                     hyphenatedAdvance += aProvider->GetHyphenWidth();
@@ -930,8 +939,9 @@ gfxTextRun::BreakAndMeasureText(uint32_t aStart, uint32_t aMaxLength,
                     lastBreakTrimmableChars = trimmableChars;
                     lastBreakTrimmableAdvance = trimmableAdvance;
                     lastBreakUsedHyphenation = atHyphenationBreak;
-                    *aBreakPriority = atBreak ? gfxBreakPriority::eNormalBreak
-                                              : gfxBreakPriority::eWordWrapBreak;
+                    *aBreakPriority = (atBreak || whitespaceWrapping)
+                                          ? gfxBreakPriority::eNormalBreak
+                                          : gfxBreakPriority::eWordWrapBreak;
                 }
 
                 width += advance;
diff --git a/gfx/thebes/gfxTextRun.h b/gfx/thebes/gfxTextRun.h
index d61992527b..2ef835f189 100644
--- a/gfx/thebes/gfxTextRun.h
+++ b/gfx/thebes/gfxTextRun.h
@@ -409,6 +409,7 @@ public:
                                  bool *aUsedHyphenation,
                                  uint32_t *aLastBreak,
                                  bool aCanWordWrap,
+                                 bool aCanWhitespaceWrap,
                                  gfxBreakPriority *aBreakPriority);
 
     // Utility getters
diff --git a/layout/generic/nsTextFrame.cpp b/layout/generic/nsTextFrame.cpp
index 07e7a36557..1fccf48a18 100644
--- a/layout/generic/nsTextFrame.cpp
+++ b/layout/generic/nsTextFrame.cpp
@@ -1988,35 +1988,31 @@ GetHyphenTextRun(const gfxTextRun* aTextRun, DrawTarget* aDrawTarget,
     MakeHyphenTextRun(dt, aTextRun->GetAppUnitsPerDevUnit());
 }
 
-static_assert(NS_STYLE_WHITESPACE_NORMAL == 0, "Convention: NS_STYLE_WHITESPACE_NORMAL should be 0");
-static_assert(NS_STYLE_WHITESPACE_PRE == 1, "Convention: NS_STYLE_WHITESPACE_PRE should be 1");
-static_assert(NS_STYLE_WHITESPACE_NOWRAP == 2, "Convention: NS_STYLE_WHITESPACE_NOWRAP should be 2");
-static_assert(NS_STYLE_WHITESPACE_PRE_WRAP == 3, "Convention: NS_STYLE_WHITESPACE_PRE_WRAP should be 3");
-static_assert(NS_STYLE_WHITESPACE_PRE_LINE == 4, "Convention: NS_STYLE_WHITESPACE_PRE_LINE should be 4");
-static_assert(NS_STYLE_WHITESPACE_PRE_SPACE == 5, "Convention: NS_STYLE_WHITESPACE_PRE_SPACE should be 5");
-
 static nsTextFrameUtils::CompressionMode
 GetCSSWhitespaceToCompressionMode(nsTextFrame* aFrame,
                                   const nsStyleText* aStyleText)
 {
-  static const nsTextFrameUtils::CompressionMode sModes[] =
-  {
-    nsTextFrameUtils::COMPRESS_WHITESPACE_NEWLINE,     // normal
-    nsTextFrameUtils::COMPRESS_NONE,                   // pre
-    nsTextFrameUtils::COMPRESS_WHITESPACE_NEWLINE,     // nowrap
-    nsTextFrameUtils::COMPRESS_NONE,                   // pre-wrap
-    nsTextFrameUtils::COMPRESS_WHITESPACE,             // pre-line
-    nsTextFrameUtils::COMPRESS_NONE_TRANSFORM_TO_SPACE // -moz-pre-space
-  };
-
-  auto compression = sModes[aStyleText->mWhiteSpace];
-  if (compression == nsTextFrameUtils::COMPRESS_NONE &&
-      !aStyleText->NewlineIsSignificant(aFrame)) {
-    // If newline is set to be preserved, but then suppressed,
-    // transform newline to space.
-    compression = nsTextFrameUtils::COMPRESS_NONE_TRANSFORM_TO_SPACE;
+  switch (aStyleText->mWhiteSpace) {
+    case NS_STYLE_WHITESPACE_NORMAL:
+    case NS_STYLE_WHITESPACE_NOWRAP:
+      return nsTextFrameUtils::COMPRESS_WHITESPACE_NEWLINE;
+    case NS_STYLE_WHITESPACE_PRE:
+    case NS_STYLE_WHITESPACE_PRE_WRAP:
+    case NS_STYLE_WHITESPACE_BREAK_SPACES:
+      if (!aStyleText->NewlineIsSignificant(aFrame)) {
+        // If newline is set to be preserved, but then suppressed,
+        // transform newline to space.
+        return nsTextFrameUtils::COMPRESS_NONE_TRANSFORM_TO_SPACE;
+      }
+      return nsTextFrameUtils::COMPRESS_NONE;
+    case NS_STYLE_WHITESPACE_PRE_SPACE:
+      return nsTextFrameUtils::COMPRESS_NONE_TRANSFORM_TO_SPACE;
+    case NS_STYLE_WHITESPACE_PRE_LINE:
+      return nsTextFrameUtils::COMPRESS_WHITESPACE;
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unknown white-space value");
+      return nsTextFrameUtils::COMPRESS_WHITESPACE_NEWLINE;
   }
-  return compression;
 }
 
 already_AddRefed<gfxTextRun>
@@ -9206,8 +9202,10 @@ nsTextFrame::ReflowText(nsLineLayout& aLineLayout, nscoord aAvailableWidth,
   }
   bool canTrimTrailingWhitespace = !textStyle->WhiteSpaceIsSignificant() ||
                                    (GetStateBits() & TEXT_IS_IN_TOKEN_MATHML);
+  bool isBreakSpaces = textStyle->mWhiteSpace == NS_STYLE_WHITESPACE_BREAK_SPACES;
   // allow whitespace to overflow the container
-  bool whitespaceCanHang = textStyle->WhiteSpaceCanWrapStyle() &&
+  bool whitespaceCanHang = !isBreakSpaces &&
+                           textStyle->WhiteSpaceCanWrapStyle() &&
                            textStyle->WhiteSpaceIsSignificant();
   gfxBreakPriority breakPriority = aLineLayout.LastOptionalBreakPriority();
   gfxTextRun::SuppressBreak suppressBreak = gfxTextRun::eNoSuppressBreak;
@@ -9227,7 +9225,9 @@ nsTextFrame::ReflowText(nsLineLayout& aLineLayout, nscoord aAvailableWidth,
                                   &textMetrics, boundingBoxType,
                                   aDrawTarget,
                                   &usedHyphenation, &transformedLastBreak,
-                                  textStyle->WordCanWrap(this), &breakPriority);
+                                  textStyle->WordCanWrap(this),
+                                  isBreakSpaces,
+                                  &breakPriority);
   if (!length && !textMetrics.mAscent && !textMetrics.mDescent) {
     // If we're measuring a zero-length piece of text, update
     // the height manually.
diff --git a/layout/style/nsCSSKeywordList.h b/layout/style/nsCSSKeywordList.h
index 7e661bc483..d6486b18cf 100644
--- a/layout/style/nsCSSKeywordList.h
+++ b/layout/style/nsCSSKeywordList.h
@@ -171,6 +171,7 @@ CSS_KEY(both, both)
 CSS_KEY(bottom, bottom)
 CSS_KEY(bottom-outside, bottom_outside)
 CSS_KEY(break-all, break_all)
+CSS_KEY(break-spaces, break_spaces)
 CSS_KEY(break-word, break_word)
 CSS_KEY(brightness, brightness)
 CSS_KEY(browser, browser)
diff --git a/layout/style/nsCSSProps.cpp b/layout/style/nsCSSProps.cpp
index 4aff3dc5bf..f084e45992 100644
--- a/layout/style/nsCSSProps.cpp
+++ b/layout/style/nsCSSProps.cpp
@@ -2251,6 +2251,7 @@ const KTableEntry nsCSSProps::kWhitespaceKTable[] = {
   { eCSSKeyword_pre_wrap, NS_STYLE_WHITESPACE_PRE_WRAP },
   { eCSSKeyword_pre_line, NS_STYLE_WHITESPACE_PRE_LINE },
   { eCSSKeyword__moz_pre_space, NS_STYLE_WHITESPACE_PRE_SPACE },
+  { eCSSKeyword_break_spaces, NS_STYLE_WHITESPACE_BREAK_SPACES },
   { eCSSKeyword_UNKNOWN, -1 }
 };
 
diff --git a/layout/style/nsStyleConsts.h b/layout/style/nsStyleConsts.h
index 4d2043cc47..9cb3c9edea 100644
--- a/layout/style/nsStyleConsts.h
+++ b/layout/style/nsStyleConsts.h
@@ -993,12 +993,13 @@ enum class StyleDisplay : uint8_t {
 #define NS_STYLE_TABSIZE_INITIAL                8
 
 // See nsStyleText
-#define NS_STYLE_WHITESPACE_NORMAL               0
-#define NS_STYLE_WHITESPACE_PRE                  1
-#define NS_STYLE_WHITESPACE_NOWRAP               2
-#define NS_STYLE_WHITESPACE_PRE_WRAP             3
-#define NS_STYLE_WHITESPACE_PRE_LINE             4
-#define NS_STYLE_WHITESPACE_PRE_SPACE            5
+#define NS_STYLE_WHITESPACE_NORMAL              0
+#define NS_STYLE_WHITESPACE_PRE                 1
+#define NS_STYLE_WHITESPACE_NOWRAP              2
+#define NS_STYLE_WHITESPACE_PRE_WRAP            3
+#define NS_STYLE_WHITESPACE_PRE_LINE            4
+#define NS_STYLE_WHITESPACE_PRE_SPACE           5
+#define NS_STYLE_WHITESPACE_BREAK_SPACES        6
 
 // See nsStyleText
 #define NS_STYLE_WORDBREAK_NORMAL               0
diff --git a/layout/style/nsStyleStruct.h b/layout/style/nsStyleStruct.h
index a01685cc44..da9643594e 100644
--- a/layout/style/nsStyleStruct.h
+++ b/layout/style/nsStyleStruct.h
@@ -2105,30 +2105,35 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleText
   bool WhiteSpaceIsSignificant() const {
     return mWhiteSpace == NS_STYLE_WHITESPACE_PRE ||
            mWhiteSpace == NS_STYLE_WHITESPACE_PRE_WRAP ||
+           mWhiteSpace == NS_STYLE_WHITESPACE_BREAK_SPACES ||
            mWhiteSpace == NS_STYLE_WHITESPACE_PRE_SPACE;
   }
 
   bool NewlineIsSignificantStyle() const {
     return mWhiteSpace == NS_STYLE_WHITESPACE_PRE ||
            mWhiteSpace == NS_STYLE_WHITESPACE_PRE_WRAP ||
+           mWhiteSpace == NS_STYLE_WHITESPACE_BREAK_SPACES ||
            mWhiteSpace == NS_STYLE_WHITESPACE_PRE_LINE;
   }
 
   bool WhiteSpaceOrNewlineIsSignificant() const {
     return mWhiteSpace == NS_STYLE_WHITESPACE_PRE ||
            mWhiteSpace == NS_STYLE_WHITESPACE_PRE_WRAP ||
+           mWhiteSpace == NS_STYLE_WHITESPACE_BREAK_SPACES ||
            mWhiteSpace == NS_STYLE_WHITESPACE_PRE_LINE ||
            mWhiteSpace == NS_STYLE_WHITESPACE_PRE_SPACE;
   }
 
   bool TabIsSignificant() const {
     return mWhiteSpace == NS_STYLE_WHITESPACE_PRE ||
-           mWhiteSpace == NS_STYLE_WHITESPACE_PRE_WRAP;
+           mWhiteSpace == NS_STYLE_WHITESPACE_PRE_WRAP ||
+           mWhiteSpace == NS_STYLE_WHITESPACE_BREAK_SPACES;
   }
 
   bool WhiteSpaceCanWrapStyle() const {
     return mWhiteSpace == NS_STYLE_WHITESPACE_NORMAL ||
            mWhiteSpace == NS_STYLE_WHITESPACE_PRE_WRAP ||
+           mWhiteSpace == NS_STYLE_WHITESPACE_BREAK_SPACES ||
            mWhiteSpace == NS_STYLE_WHITESPACE_PRE_LINE;
   }
 
diff --git a/layout/style/test/property_database.js b/layout/style/test/property_database.js
index 5c6e2f6d86..0abe930832 100644
--- a/layout/style/test/property_database.js
+++ b/layout/style/test/property_database.js
@@ -4052,7 +4052,7 @@ var gCSSProperties = {
     inherited: true,
     type: CSS_TYPE_LONGHAND,
     initial_values: [ "normal" ],
-    other_values: [ "pre", "nowrap", "pre-wrap", "pre-line", "-moz-pre-space" ],
+    other_values: [ "pre", "nowrap", "pre-wrap", "pre-line", "-moz-pre-space", "break-spaces" ],
     invalid_values: []
   },
   "width": {