Decoupling from-font resolution from FontCascadeFonts::primaryFont

https://bugs.webkit.org/show_bug.cgi?id=273339
rdar://127132471

Reviewed by Brent Fulgham.

font-size-adjust from-font resolution was fixed by [1]. It now works correctly and
it uses the primary font for resolution. However, this patch changed FontCascadeFonts::primaryFont
to receive a mutable (non-const) FontCascadeDescription object, such that it could resolve the
from-font reference after the primary font is resolved.

This means that now FontCascadeFonts::primaryFont does two different things:
a) resolving and caching a font as the primary font
b) resolving from-font according to the primary font if necessary

The (a) part of primaryFont doesn't require a mutable FontCascadeDescription.
We can update FontCascadeDescription to have a method for resolving font-size-adjust
from-font at the point where we own a mutable FontCascadeDescription instead.

This allows us to compute the primaryFont itself from places where we only have access
to a const FontCascadeDescription. This is for example, required for solving
https://bugs.webkit.org/show_bug.cgi?id=273233, where we need to access to primaryFont
from FontCascadeFonts::glyphDataForVariant

This patch should have no side effects, as it is a preparation
for solving 273233.

[1] https://commits.webkit.org/269041@main

* Source/WebCore/css/ComputedStyleExtractor.cpp:
(WebCore::fontSizeAdjustFromStyle):
* Source/WebCore/platform/graphics/FontCascade.h:
(WebCore::FontCascade::primaryFont const):
* Source/WebCore/platform/graphics/FontCascadeDescription.cpp:
(WebCore::FontCascadeDescription::resolveFontSizeAdjustFromFontIfNeeded):
* Source/WebCore/platform/graphics/FontCascadeDescription.h:
* Source/WebCore/platform/graphics/FontCascadeFonts.h:
(WebCore::FontCascadeFonts::primaryFont):
* Source/WebCore/platform/graphics/FontSizeAdjust.h:
(WebCore::FontSizeAdjust::shouldResolveFromFont const):

Canonical link: https://commits.webkit.org/278219@main

Source/WebCore/css/ComputedStyleExtractor.cpp

@@ -370,7 +370,7 @@ static Ref<CSSValue> fontSizeAdjustFromStyle(const RenderStyle& style)
         return CSSPrimitiveValue::create(CSSValueNone);
 
     auto metric = fontSizeAdjust.metric;
-    auto value = fontSizeAdjust.isFromFont() ? fontSizeAdjust.resolve(style.computedFontSize(), style.metricsOfPrimaryFont()) : fontSizeAdjust.value.asOptional();
+    auto value = fontSizeAdjust.shouldResolveFromFont() ? fontSizeAdjust.resolve(style.computedFontSize(), style.metricsOfPrimaryFont()) : fontSizeAdjust.value.asOptional();
     if (metric == FontSizeAdjust::Metric::ExHeight)
         return CSSPrimitiveValue::create(*value);
 

Source/WebCore/platform/graphics/FontCascade.h

@@ -373,7 +373,9 @@ class FontCascade final : public CanMakeWeakPtr<FontCascade>, public CanMakeChec
 inline const Font& FontCascade::primaryFont() const
 {
     ASSERT(m_fonts);
-    return protectedFonts()->primaryFont(m_fontDescription);
+    auto& font = protectedFonts()->primaryFont(m_fontDescription);
+    m_fontDescription.resolveFontSizeAdjustFromFontIfNeeded(font);
+    return font;
 }
 
 inline const FontRanges& FontCascade::fallbackRangesAt(unsigned index) const

Source/WebCore/platform/graphics/FontCascadeDescription.cpp

@@ -147,4 +147,14 @@ FontSmoothingMode FontCascadeDescription::usedFontSmoothing() const
     return fontSmoothingMode;
 }
 
+void FontCascadeDescription::resolveFontSizeAdjustFromFontIfNeeded(const Font& font)
+{
+    const auto& fontSizeAdjust = this->fontSizeAdjust();
+    if (!fontSizeAdjust.shouldResolveFromFont())
+        return;
+
+    auto aspectValue = fontSizeAdjust.resolve(computedSize(), font.fontMetrics());
+    setFontSizeAdjust({ fontSizeAdjust.metric, FontSizeAdjust::ValueType::FromFont, aspectValue });
+}
+
 } // namespace WebCore

Source/WebCore/platform/graphics/FontCascadeDescription.h

@@ -45,6 +45,8 @@ typedef FontFamilySpecificationNull FontFamilyPlatformSpecification;
 
 typedef std::variant<AtomString, FontFamilyPlatformSpecification> FontFamilySpecification;
 
+class Font;
+
 class FontCascadeDescription : public FontDescription {
 public:
     WEBCORE_EXPORT FontCascadeDescription();
@@ -118,6 +120,8 @@ class FontCascadeDescription : public FontDescription {
     }
 #endif
 
+    WEBCORE_EXPORT void resolveFontSizeAdjustFromFontIfNeeded(const Font&);
+
     // Initial values for font properties.
     static std::optional<FontSelectionValue> initialItalic() { return std::nullopt; }
     static FontStyleAxis initialFontStyleAxis() { return FontStyleAxis::slnt; }

Source/WebCore/platform/graphics/FontCascadeFonts.h

@@ -74,7 +74,7 @@ class FontCascadeFonts : public RefCounted<FontCascadeFonts> {
     WidthCache& widthCache() { return m_widthCache; }
     const WidthCache& widthCache() const { return m_widthCache; }
 
-    const Font& primaryFont(FontCascadeDescription&);
+    const Font& primaryFont(const FontCascadeDescription&);
     WEBCORE_EXPORT const FontRanges& realizeFallbackRangesAt(const FontCascadeDescription&, unsigned fallbackIndex);
 
     void pruneSystemFallbacks();
@@ -144,7 +144,7 @@ inline bool FontCascadeFonts::canTakeFixedPitchFastContentMeasuring(const FontCa
     return m_canTakeFixedPitchFastContentMeasuring == TriState::True;
 }
 
-inline const Font& FontCascadeFonts::primaryFont(FontCascadeDescription& description)
+inline const Font& FontCascadeFonts::primaryFont(const FontCascadeDescription& description)
 {
     ASSERT(m_thread ? m_thread->ptr() == &Thread::current() : isMainThread());
     if (!m_cachedPrimaryFont) {
@@ -164,14 +164,8 @@ inline const Font& FontCascadeFonts::primaryFont(FontCascadeDescription& descrip
                 }
             }
         }
-
-        ASSERT(m_cachedPrimaryFont);
-        auto fontSizeAdjust = description.fontSizeAdjust();
-        if (fontSizeAdjust.isFromFont()) {
-            auto aspectValue = fontSizeAdjust.resolve(description.computedSize(), m_cachedPrimaryFont->fontMetrics());
-            description.setFontSizeAdjust({ fontSizeAdjust.metric, FontSizeAdjust::ValueType::FromFont, aspectValue });
-        }
     }
+    ASSERT(m_cachedPrimaryFont);
     return *m_cachedPrimaryFont;
 }
 

Source/WebCore/platform/graphics/FontSizeAdjust.h

@@ -71,6 +71,7 @@ struct FontSizeAdjust {
 
     bool isNone() const { return !value && type != ValueType::FromFont; }
     bool isFromFont() const { return type == ValueType::FromFont; }
+    bool shouldResolveFromFont() const { return isFromFont() && !value; }
 
     Metric metric { Metric::ExHeight };
     ValueType type { ValueType::Number };