Bug 1157064 - font-display descriptor parsing. r=dbaron

gfx/thebes/gfxFontConstants.h

@@ -41,6 +41,12 @@
 #define NS_FONT_SYNTHESIS_WEIGHT                    0x1
 #define NS_FONT_SYNTHESIS_STYLE                     0x2
 
+#define NS_FONT_DISPLAY_AUTO            0
+#define NS_FONT_DISPLAY_BLOCK           1
+#define NS_FONT_DISPLAY_SWAP            2
+#define NS_FONT_DISPLAY_FALLBACK        3
+#define NS_FONT_DISPLAY_OPTIONAL        4
+
 enum {
     eFeatureAlternates_historical,
     eFeatureAlternates_stylistic,

layout/style/nsCSSFontDescList.h

@@ -11,3 +11,4 @@ CSS_FONT_DESC(src, Src)
 CSS_FONT_DESC(unicode-range, UnicodeRange)
 CSS_FONT_DESC(font-feature-settings, FontFeatureSettings)
 CSS_FONT_DESC(font-language-override, FontLanguageOverride)
+CSS_FONT_DESC(font-display, Display)

layout/style/nsCSSKeywordList.h

@@ -261,6 +261,7 @@ CSS_KEY(extends, extends)
 CSS_KEY(extra-condensed, extra_condensed)
 CSS_KEY(extra-expanded, extra_expanded)
 CSS_KEY(ew-resize, ew_resize)
+CSS_KEY(fallback, fallback)
 CSS_KEY(fantasy, fantasy)
 CSS_KEY(farthest-side, farthest_side)
 CSS_KEY(farthest-corner, farthest_corner)
@@ -409,6 +410,7 @@ CSS_KEY(oldstyle-nums, oldstyle_nums)
 CSS_KEY(opacity, opacity)
 CSS_KEY(open, open)
 CSS_KEY(open-quote, open_quote)
+CSS_KEY(optional, optional)
 CSS_KEY(ordinal, ordinal)
 CSS_KEY(ornaments, ornaments)
 CSS_KEY(outset, outset)
@@ -548,6 +550,7 @@ CSS_KEY(subgrid, subgrid)
 CSS_KEY(super, super)
 CSS_KEY(sw-resize, sw_resize)
 CSS_KEY(swash, swash)
+CSS_KEY(swap, swap)
 CSS_KEY(table, table)
 CSS_KEY(table-caption, table_caption)
 CSS_KEY(table-cell, table_cell)

layout/style/nsCSSParser.cpp

@@ -3948,7 +3948,9 @@ CSSParserImpl::ParseFontDescriptor(nsCSSFontFaceRule* aRule)
   nsCSSFontDesc descID = nsCSSProps::LookupFontDesc(descName);
   nsCSSValue value;
 
-  if (descID == eCSSFontDesc_UNKNOWN) {
+  if (descID == eCSSFontDesc_UNKNOWN ||
+      (descID == eCSSFontDesc_Display &&
+       !Preferences::GetBool("layout.css.font-display.enabled"))) {
     if (NonMozillaVendorIdentifier(descName)) {
       // silently skip other vendors' extensions
       SkipDeclaration(true);
@@ -11603,6 +11605,10 @@ CSSParserImpl::ParseFontDescriptorValue(nsCSSFontDesc aDescID,
     return ParseSingleTokenVariant(aValue, VARIANT_KEYWORD | VARIANT_NORMAL,
                                    nsCSSProps::kFontStyleKTable);
 
+  case eCSSFontDesc_Display:
+    return ParseSingleTokenVariant(aValue, VARIANT_KEYWORD,
+                                   nsCSSProps::kFontDisplayKTable);
+
   case eCSSFontDesc_Weight:
     return (ParseFontWeight(aValue) &&
             aValue.GetUnit() != eCSSUnit_Inherit &&

layout/style/nsCSSProps.cpp

@@ -613,7 +613,19 @@ nsCSSFontDesc
 nsCSSProps::LookupFontDesc(const nsACString& aFontDesc)
 {
   MOZ_ASSERT(gFontDescTable, "no lookup table, needs addref");
-  return nsCSSFontDesc(gFontDescTable->Lookup(aFontDesc));
+  nsCSSFontDesc which = nsCSSFontDesc(gFontDescTable->Lookup(aFontDesc));
+
+  if (which == eCSSFontDesc_Display &&
+      !Preferences::GetBool("layout.css.font-display.enabled")) {
+    which = eCSSFontDesc_UNKNOWN;
+  } else if (which == eCSSFontDesc_UNKNOWN) {
+    // check for unprefixed font-feature-settings/font-language-override
+    nsAutoCString prefixedProp;
+    prefixedProp.AppendLiteral("-moz-");
+    prefixedProp.Append(aFontDesc);
+    which = nsCSSFontDesc(gFontDescTable->Lookup(prefixedProp));
+  }
+  return which;
 }
 
 nsCSSFontDesc
@@ -622,8 +634,11 @@ nsCSSProps::LookupFontDesc(const nsAString& aFontDesc)
   MOZ_ASSERT(gFontDescTable, "no lookup table, needs addref");
   nsCSSFontDesc which = nsCSSFontDesc(gFontDescTable->Lookup(aFontDesc));
 
-  // check for unprefixed font-feature-settings/font-language-override
-  if (which == eCSSFontDesc_UNKNOWN) {
+  if (which == eCSSFontDesc_Display &&
+      !Preferences::GetBool("layout.css.font-display.enabled")) {
+    which = eCSSFontDesc_UNKNOWN;
+  } else if (which == eCSSFontDesc_UNKNOWN) {
+    // check for unprefixed font-feature-settings/font-language-override
     nsAutoString prefixedProp;
     prefixedProp.AppendLiteral("-moz-");
     prefixedProp.Append(aFontDesc);
@@ -1381,6 +1396,15 @@ const KTableEntry nsCSSProps::kFloatEdgeKTable[] = {
   { eCSSKeyword_UNKNOWN, -1 }
 };
 
+const KTableEntry nsCSSProps::kFontDisplayKTable[] = {
+  { eCSSKeyword_auto, NS_FONT_DISPLAY_AUTO },
+  { eCSSKeyword_block, NS_FONT_DISPLAY_BLOCK },
+  { eCSSKeyword_swap, NS_FONT_DISPLAY_SWAP },
+  { eCSSKeyword_fallback, NS_FONT_DISPLAY_FALLBACK },
+  { eCSSKeyword_optional, NS_FONT_DISPLAY_OPTIONAL },
+  { eCSSKeyword_UNKNOWN, -1 }
+};
+
 const KTableEntry nsCSSProps::kFontKTable[] = {
   // CSS2.
   { eCSSKeyword_caption, NS_STYLE_FONT_CAPTION },

layout/style/nsCSSProps.h

@@ -741,6 +741,7 @@ public:
   // "layout.css.float-logical-values.enabled" changes:
   static KTableEntry kFloatKTable[];
   static const KTableEntry kFloatEdgeKTable[];
+  static const KTableEntry kFontDisplayKTable[];
   static const KTableEntry kFontKTable[];
   static const KTableEntry kFontKerningKTable[];
   static const KTableEntry kFontSizeKTable[];

layout/style/nsCSSRules.cpp

@@ -1302,6 +1302,13 @@ nsCSSFontFaceStyleDecl::GetPropertyValue(nsCSSFontDesc aFontDescID,
                        nsCSSValue::eNormalized);
     return NS_OK;
 
+  case eCSSFontDesc_Display:
+    NS_ASSERTION(val.GetUnit() == eCSSUnit_Enumerated,
+                 "unknown unit for font-display descriptor");
+    AppendASCIItoUTF16(nsCSSProps::ValueToKeyword(val.GetIntValue(),
+                                       nsCSSProps::kFontDisplayKTable), aResult);
+    return NS_OK;
+
   case eCSSFontDesc_Src:
     nsStyleUtil::AppendSerializedFontSrc(val, aResult);
     return NS_OK;

layout/style/test/test_font_face_parser.html

@@ -14,6 +14,7 @@
 <pre id="display"></pre>
 <style type="text/css" id="testbox"></style>
 <script class="testbody" type="text/javascript">
+function runTest() {
   function _(b) { return "@font-face { " + b + " }"; };
   var testset = [
     // Complete nonsense - shouldn't make a font-face rule at all.
@@ -287,6 +288,24 @@
     { rule: _("font-language-override: #999;"), d: {} },
     { rule: _("font-language-override: 'TRK' 'SRB'"), d: {} },
     { rule: _("font-language-override: 'TRK', 'SRB'"), d: {} },
+
+    // font-display:
+    { rule: _("font-display: auto;"),
+      d: { "font-display" : "auto" } },
+    { rule: _("font-display: block;"),
+      d: { "font-display" : "block" } },
+    { rule: _("font-display: swap;"),
+      d: { "font-display" : "swap" } },
+    { rule: _("font-display: fallback;"),
+      d: { "font-display" : "fallback" } },
+    { rule: _("font-display: optional;"),
+      d: { "font-display" : "optional" } },
+
+    // incorrect font-display
+    { rule: _("font-display: hidden"), d: {} },
+    { rule: _("font-display: swap 3"), d: {} },
+    { rule: _("font-display: block 2 swap 0"), d: {} },
+    { rule: _("font-display: all"), d: {} },
   ];
 
   var display = document.getElementById("display");
@@ -352,6 +371,12 @@
       ok(false, testset[curTest].rule, "During test: " + e);
     }
   }
+  SimpleTest.finish();
+}
+
+SimpleTest.waitForExplicitFinish();
+SpecialPowers.pushPrefEnv({ set: [["layout.css.font-display.enabled", true]] },
+                          runTest);
 </script>
 </body>
 </html>

modules/libpref/init/all.js

@@ -2297,6 +2297,9 @@ pref("layout.css.float-logical-values.enabled", false);
 // Is support for the CSS4 image-orientation property enabled?
 pref("layout.css.image-orientation.enabled", true);
 
+// Is support for the font-display @font-face descriptor enabled?
+pref("layout.css.font-display.enabled", false);
+
 // Are sets of prefixed properties supported?
 pref("layout.css.prefixes.border-image", true);
 pref("layout.css.prefixes.transforms", true);