Bug 1706080 - [css-fonts] Implement 'font-synthesis: small-caps'. r=jfkthame

Differential Revision: https://phabricator.services.mozilla.com/D114313

devtools/shared/css/generated/properties-db.js

@@ -6393,7 +6393,9 @@ exports.CSS_PROPERTIES = {
     "values": [
       "inherit",
       "initial",
+      "none",
       "revert",
+      "small-caps",
       "style",
       "unset",
       "weight"

gfx/src/nsFont.h

@@ -82,8 +82,9 @@ struct nsFont final {
   // that include an 'opsz' axis
   uint8_t opticalSizing = NS_FONT_OPTICAL_SIZING_AUTO;
 
-  // Synthesis setting, controls use of fake bolding/italics
+  // Synthesis setting, controls use of fake bolding/italics/small-caps
-  uint8_t synthesis = NS_FONT_SYNTHESIS_WEIGHT | NS_FONT_SYNTHESIS_STYLE;
+  uint8_t synthesis = NS_FONT_SYNTHESIS_WEIGHT | NS_FONT_SYNTHESIS_STYLE |
+                      NS_FONT_SYNTHESIS_SMALL_CAPS;
 
   // initialize the font with a fontlist
   nsFont(const mozilla::StyleFontFamily&, mozilla::Length aSize);

gfx/src/nsFontMetrics.cpp

@@ -123,7 +123,8 @@ nsFontMetrics::nsFontMetrics(const nsFont& aFont, const Params& aParams,
       gfxFloat(aFont.size.ToAppUnits()) / mP2A, aFont.sizeAdjust,
       aFont.family.is_system_font, mDeviceContext->IsPrinterContext(),
       aFont.synthesis & NS_FONT_SYNTHESIS_WEIGHT,
-      aFont.synthesis & NS_FONT_SYNTHESIS_STYLE, aFont.languageOverride);
+      aFont.synthesis & NS_FONT_SYNTHESIS_STYLE,
+      aFont.synthesis & NS_FONT_SYNTHESIS_SMALL_CAPS, aFont.languageOverride);
 
   aFont.AddFontFeaturesToStyle(&style, mOrientation == eVertical);
   style.featureValueLookup = aParams.featureValueLookup;

gfx/thebes/gfxFont.cpp

@@ -4032,6 +4032,7 @@ gfxFontStyle::gfxFontStyle()
       useGrayscaleAntialiasing(false),
       allowSyntheticWeight(true),
       allowSyntheticStyle(true),
+      allowSyntheticSmallCaps(true),
       noFallbackVariantFeatures(true) {}
 
 gfxFontStyle::gfxFontStyle(FontSlantStyle aStyle, FontWeight aWeight,
@@ -4039,6 +4040,7 @@ gfxFontStyle::gfxFontStyle(FontSlantStyle aStyle, FontWeight aWeight,
                            const FontSizeAdjust& aSizeAdjust, bool aSystemFont,
                            bool aPrinterFont, bool aAllowWeightSynthesis,
                            bool aAllowStyleSynthesis,
+                           bool aAllowSmallCapsSynthesis,
                            uint32_t aLanguageOverride)
     : size(aSize),
       baselineOffset(0.0f),
@@ -4054,6 +4056,7 @@ gfxFontStyle::gfxFontStyle(FontSlantStyle aStyle, FontWeight aWeight,
       useGrayscaleAntialiasing(false),
       allowSyntheticWeight(aAllowWeightSynthesis),
       allowSyntheticStyle(aAllowStyleSynthesis),
+      allowSyntheticSmallCaps(aAllowSmallCapsSynthesis),
       noFallbackVariantFeatures(true) {
   MOZ_ASSERT(!mozilla::IsNaN(size));
 

gfx/thebes/gfxFont.h

@@ -103,7 +103,8 @@ struct gfxFontStyle {
   gfxFontStyle(FontSlantStyle aStyle, FontWeight aWeight, FontStretch aStretch,
                gfxFloat aSize, const FontSizeAdjust& aSizeAdjust,
                bool aSystemFont, bool aPrinterFont, bool aWeightSynthesis,
-               bool aStyleSynthesis, uint32_t aLanguageOverride);
+               bool aStyleSynthesis, bool aSmallCapsSynthesis,
+               uint32_t aLanguageOverride);
   // Features are composed of (1) features from style rules (2) features
   // from feature settings rules and (3) family-specific features.  (1) and
   // (3) are guaranteed to be mutually exclusive
@@ -198,6 +199,7 @@ struct gfxFontStyle {
   // Whether synthetic styles are allowed
   bool allowSyntheticWeight : 1;
   bool allowSyntheticStyle : 1;
+  bool allowSyntheticSmallCaps : 1;
 
   // some variant features require fallback which complicates the shaping
   // code, so set up a bool to indicate when shaping with fallback is needed

gfx/thebes/gfxFontConstants.h

@@ -40,6 +40,7 @@
 
 #define NS_FONT_SYNTHESIS_WEIGHT 0x1
 #define NS_FONT_SYNTHESIS_STYLE 0x2
+#define NS_FONT_SYNTHESIS_SMALL_CAPS 0x4
 
 #define NS_FONT_OPTICAL_SIZING_AUTO 0
 #define NS_FONT_OPTICAL_SIZING_NONE 1

gfx/thebes/gfxTextRun.cpp

@@ -2758,6 +2758,7 @@ void gfxFontGroup::InitScriptRun(DrawTarget* aDrawTarget, gfxTextRun* aTextRun,
           matchedFont = nullptr;
         }
       } else if (mStyle.variantCaps != NS_FONT_VARIANT_CAPS_NORMAL &&
+                 mStyle.allowSyntheticSmallCaps &&
                  !matchedFont->SupportsVariantCaps(
                      aRunScript, mStyle.variantCaps, petiteToSmallCaps,
                      syntheticLower, syntheticUpper)) {

layout/style/test/property_database.js

@@ -5761,8 +5761,8 @@ var gCSSProperties = {
     applies_to_marker: true,
     applies_to_placeholder: true,
     applies_to_cue: true,
-    initial_values: ["weight style"],
+    initial_values: ["weight style small-caps"],
-    other_values: ["none", "weight", "style"],
+    other_values: ["none", "weight", "style", "small-caps"],
     invalid_values: [
       "weight none",
       "style none",
@@ -5770,6 +5770,8 @@ var gCSSProperties = {
       "weight 10px",
       "weight weight",
       "style style",
+      "small-caps none",
+      "small-caps small-caps",
     ],
   },
   "font-variant": {

modules/libpref/init/StaticPrefList.yaml

@@ -7618,6 +7618,13 @@
   mirror: always
   rust: true
 
+# Is 'font-synthesis: small-caps' supported?
+- name: layout.css.font-synthesis-small-caps.enabled
+  type: RelaxedAtomicBool
+  value: true
+  mirror: always
+  rust: true
+
 # Whether frame visibility tracking is enabled globally.
 - name: layout.framevisibility.enabled
   type: bool

servo/components/style/values/specified/font.rs

@@ -1950,23 +1950,24 @@ impl Parse for FontFeatureSettings {
     Debug,
     MallocSizeOf,
     PartialEq,
-    SpecifiedValueInfo,
     ToComputedValue,
     ToResolvedValue,
     ToShmem,
 )]
 /// Whether user agents are allowed to synthesize bold or oblique font faces
-/// when a font family lacks bold or italic faces
+/// when a font family lacks those faces, or a small-caps variant when this is
+/// not supported by the face.
 pub struct FontSynthesis {
     /// If a `font-weight` is requested that the font family does not contain,
     /// the user agent may synthesize the requested weight from the weights
     /// that do exist in the font family.
-    #[css(represents_keyword)]
     pub weight: bool,
     /// If a font-style is requested that the font family does not contain,
     /// the user agent may synthesize the requested style from the normal face in the font family.
-    #[css(represents_keyword)]
     pub style: bool,
+    /// This bit controls whether the user agent is allowed to synthesize small caps variant
+    /// when a font face lacks it.
+    pub small_caps: bool,
 }
 
 impl FontSynthesis {
@@ -1976,6 +1977,7 @@ impl FontSynthesis {
         FontSynthesis {
             weight: true,
             style: true,
+            small_caps: true,
         }
     }
     #[inline]
@@ -1984,8 +1986,14 @@ impl FontSynthesis {
         FontSynthesis {
             weight: false,
             style: false,
+            small_caps: false,
         }
     }
+    #[inline]
+    /// Return true if this is the 'none' value
+    pub fn is_none(&self) -> bool {
+        *self == Self::none()
+    }
 }
 
 impl Parse for FontSynthesis {
@@ -1993,26 +2001,23 @@ impl Parse for FontSynthesis {
         _: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<FontSynthesis, ParseError<'i>> {
-        let mut result = FontSynthesis {
+        use crate::values::SelectorParseErrorKind;
-            weight: false,
+        let mut result = Self::none();
-            style: false,
+        while let Ok(ident) = input.try_parse(|i| i.expect_ident_cloned()) {
-        };
+            match_ignore_ascii_case! { &ident,
-        try_match_ident_ignore_ascii_case! { input,
+                "none" if result.is_none() => return Ok(result),
-            "none" => Ok(result),
+                "weight" if !result.weight => result.weight = true,
-            "weight" => {
+                "style" if !result.style => result.style = true,
-                result.weight = true;
+                "small-caps" if !result.small_caps &&
-                if input.try_parse(|input| input.expect_ident_matching("style")).is_ok() {
+                                static_prefs::pref!("layout.css.font-synthesis-small-caps.enabled")
-                    result.style = true;
+                                    => result.small_caps = true,
-                }
+                _ => return Err(input.new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident))),
-                Ok(result)
+            }
-            },
+        }
-            "style" => {
+        if !result.is_none() {
-                result.style = true;
+            Ok(result)
-                if input.try_parse(|input| input.expect_ident_matching("weight")).is_ok() {
+        } else {
-                    result.weight = true;
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
-                }
-                Ok(result)
-            },
         }
     }
 }
@@ -2022,14 +2027,41 @@ impl ToCss for FontSynthesis {
     where
         W: Write,
     {
-        if self.weight && self.style {
+        if self.is_none() {
-            dest.write_str("weight style")
+            return dest.write_str("none");
-        } else if self.style {
+        }
-            dest.write_str("style")
+
-        } else if self.weight {
+        let mut need_space = false;
-            dest.write_str("weight")
+        if self.weight {
-        } else {
+            dest.write_str("weight")?;
-            dest.write_str("none")
+            need_space = true;
+        }
+        if self.style {
+            if need_space {
+                dest.write_str(" ")?;
+            }
+            dest.write_str("style")?;
+            need_space = true;
+        }
+        if self.small_caps {
+            if need_space {
+                dest.write_str(" ")?;
+            }
+            dest.write_str("small-caps")?;
+        }
+        Ok(())
+    }
+}
+
+impl SpecifiedValueInfo for FontSynthesis {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        f(&[
+            "none",
+            "weight",
+            "style",
+        ]);
+        if static_prefs::pref!("layout.css.font-synthesis-small-caps.enabled") {
+            f(&["small-caps"]);
         }
     }
 }
@@ -2042,6 +2074,7 @@ impl From<u8> for FontSynthesis {
         FontSynthesis {
             weight: bits & structs::NS_FONT_SYNTHESIS_WEIGHT as u8 != 0,
             style: bits & structs::NS_FONT_SYNTHESIS_STYLE as u8 != 0,
+            small_caps: bits & structs::NS_FONT_SYNTHESIS_SMALL_CAPS as u8 != 0,
         }
     }
 }
@@ -2058,6 +2091,9 @@ impl From<FontSynthesis> for u8 {
         if v.style {
             bits |= structs::NS_FONT_SYNTHESIS_STYLE as u8;
         }
+        if v.small_caps {
+            bits |= structs::NS_FONT_SYNTHESIS_SMALL_CAPS as u8;
+        }
         bits
     }
 }

testing/web-platform/tests/css/css-fonts/font-synthesis-06-ref.html

@@ -0,0 +1,16 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>Reference: 'font-synthesis:none' with a font that support small-caps</title>
+<link rel="author" title="Mats Palmgren" href="mailto:mats@mozilla.com">
+<style>
+  @font-face {
+    font-family: fwf;
+    src: url(support/fonts/FontWithFancyFeatures.otf);
+  }
+  .test {
+     font: 2em/1 fwf;
+  }
+</style>
+
+<p>Test passes if there are four check marks (✓), and zero crosses (✗). </p>
+<p class="test">CCC C</p>

testing/web-platform/tests/css/css-fonts/font-synthesis-06.html

@@ -0,0 +1,21 @@
+<!doctype html>
+<meta charset=utf-8>
+<title>CSS Test: 'font-synthesis:none' with a font that support small-caps</title>
+<link rel="author" title="Mats Palmgren" href="mailto:mats@mozilla.com">
+<link rel="help" href="https://drafts.csswg.org/css-fonts/#font-synthesis">
+<link rel="match" href="font-synthesis-06-ref.html">
+<meta name="assert" content="font-synthesis:none should not affect a font that supports small-caps">
+<style>
+  @font-face {
+    font-family: fwf;
+    src: url(support/fonts/FontWithFancyFeatures.otf);
+  }
+  .test {
+     font: 2em/1 fwf;
+     font-variant: small-caps;
+     font-synthesis: none;
+  }
+</style>
+
+<p>Test passes if there are four check marks (✓), and zero crosses (✗). </p>
+<p class="test">JJJ J</p>

testing/web-platform/tests/css/css-fonts/font-synthesis-07-ref.html

@@ -0,0 +1,16 @@
+<!doctype html>
+<meta charset=utf-8>
+<title>Reference: 'font-synthesis:none' with a font that doesn't support small-caps</title>
+<link rel="author" title="Mats Palmgren" href="mailto:mats@mozilla.com">
+<style>
+  @font-face {
+    font-family: Lato;
+    src: url(support/fonts/Lato-Medium.ttf);
+  }
+  .test {
+     font: 2em/1 Lato;
+  }
+</style>
+
+<p>Test passes if "A" is upper-case and "bcd e" is lower-case.</p>
+<p class="test">Abcd e</p>

testing/web-platform/tests/css/css-fonts/font-synthesis-07.html

@@ -0,0 +1,21 @@
+<!doctype html>
+<meta charset=utf-8>
+<title>CSS Test: 'font-synthesis:none' with a font that doesn't support small-caps</title>
+<link rel="author" title="Mats Palmgren" href="mailto:mats@mozilla.com">
+<link rel="help" href="https://drafts.csswg.org/css-fonts/#font-synthesis">
+<link rel="match" href="font-synthesis-07-ref.html">
+<meta name="assert" content="font-synthesis:none inhibits synthesising small-caps">
+<style>
+  @font-face {
+    font-family: Lato;
+    src: url(support/fonts/Lato-Medium.ttf);
+  }
+  .test {
+     font: 2em/1 Lato;
+     font-variant: small-caps;
+     font-synthesis: none;
+  }
+</style>
+
+<p>Test passes if "A" is upper-case and "bcd e" is lower-case.</p>
+<p class="test">Abcd e</p>

testing/web-platform/tests/css/css-fonts/inheritance.html

@@ -35,7 +35,7 @@ assert_inherited('font-size', mediumFontSize /* medium */, '123px');
 assert_inherited('font-size-adjust', 'none', '1.5');
 assert_inherited('font-stretch', '100%' /* normal */, '75%');
 assert_inherited('font-style', 'normal', 'italic');
-assert_inherited('font-synthesis', 'weight style', 'none');
+assert_inherited('font-synthesis', 'weight style small-caps', 'none');
 assert_inherited('font-variant', 'normal', 'none');
 assert_inherited('font-variant-alternates', 'normal', 'historical-forms');
 assert_inherited('font-variant-caps', 'normal', 'small-caps');

testing/web-platform/tests/css/css-fonts/parsing/font-synthesis-computed.html

@@ -2,8 +2,8 @@
 <html>
 <head>
 <meta charset="utf-8">
-<title>CSS Fonts Module Level 3: getComputedStyle().fontSynthesis</title>
+<title>CSS Fonts Module: getComputedStyle().fontSynthesis</title>
-<link rel="help" href="https://www.w3.org/TR/css-fonts-3/#font-synthesis-prop">
+<link rel="help" href="https://drafts.csswg.org/css-fonts/#font-synthesis">
 <meta name="assert" content="font-synthesis computed value is as specified.">
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
@@ -15,7 +15,11 @@
 test_computed_value('font-synthesis', 'none');
 test_computed_value('font-synthesis', 'weight');
 test_computed_value('font-synthesis', 'style');
+test_computed_value('font-synthesis', 'small-caps');
+test_computed_value('font-synthesis', 'style small-caps');
+test_computed_value('font-synthesis', 'weight small-caps');
 test_computed_value('font-synthesis', 'weight style');
+test_computed_value('font-synthesis', 'weight style small-caps');
 </script>
 </body>
 </html>

testing/web-platform/tests/css/css-fonts/parsing/font-synthesis-invalid.html

@@ -2,9 +2,9 @@
 <html>
 <head>
 <meta charset="utf-8">
-<title>CSS Fonts Module Level 3: parsing font-synthesis with invalid values</title>
+<title>CSS Fonts Module: parsing font-synthesis with invalid values</title>
-<link rel="help" href="https://www.w3.org/TR/css-fonts-3/#font-synthesis-prop">
+<link rel="help" href="https://drafts.csswg.org/css-fonts/#font-synthesis">
-<meta name="assert" content="font-synthesis supports only the grammar 'none | [ weight || style ]'.">
+<meta name="assert" content="font-synthesis supports only the grammar 'none | [ weight || style || small-caps ]'.">
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 <script src="/css/support/parsing-testcommon.js"></script>
@@ -13,6 +13,10 @@
 <script>
 test_invalid_value('font-synthesis', 'auto');
 test_invalid_value('font-synthesis', 'none weight');
+test_invalid_value('font-synthesis', 'none style');
+test_invalid_value('font-synthesis', 'style none');
+test_invalid_value('font-synthesis', 'none small-caps');
+test_invalid_value('font-synthesis', 'small-caps none');
 </script>
 </body>
 </html>

testing/web-platform/tests/css/css-fonts/parsing/font-synthesis-valid.html

@@ -2,9 +2,9 @@
 <html>
 <head>
 <meta charset="utf-8">
-<title>CSS Fonts Module Level 3: parsing font-synthesis with valid values</title>
+<title>CSS Fonts Module: parsing font-synthesis with valid values</title>
-<link rel="help" href="https://www.w3.org/TR/css-fonts-3/#font-synthesis-prop">
+<link rel="help" href="https://drafts.csswg.org/css-fonts/#font-synthesis">
-<meta name="assert" content="font-synthesis supports the full grammar 'none | [ weight || style ]'.">
+<meta name="assert" content="font-synthesis supports the full grammar 'none | [ weight || style || small-caps ]'.">
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 <script src="/css/support/parsing-testcommon.js"></script>
@@ -14,7 +14,13 @@
 test_valid_value('font-synthesis', 'none');
 test_valid_value('font-synthesis', 'weight');
 test_valid_value('font-synthesis', 'style');
+test_valid_value('font-synthesis', 'small-caps');
 test_valid_value('font-synthesis', 'style weight', 'weight style');
+test_valid_value('font-synthesis', 'small-caps weight', 'weight small-caps');
+test_valid_value('font-synthesis', 'small-caps style', 'style small-caps');
+test_valid_value('font-synthesis', 'style weight small-caps', 'weight style small-caps');
+test_valid_value('font-synthesis', 'style small-caps weight ', 'weight style small-caps');
+test_valid_value('font-synthesis', 'small-caps style weight ', 'weight style small-caps');
 </script>
 </body>
 </html>