LibWeb: Use CSS::ValueID for 'text-align' values

Let's start moving away from using raw strings for CSS identifiers.
The idea here is to use IdentifierStyleValue with a CSS::ValueID inside
for all CSS identifier values.

Libraries/LibWeb/CSS/Parser/CSSParser.cpp

@@ -350,10 +350,16 @@ static Optional<CSS::ValueID> value_id_from_string(const String& string)
         return CSS::ValueID::Bold;
     if (string.equals_ignoring_case("bolder"))
         return CSS::ValueID::Bolder;
+    if (string.equals_ignoring_case("center"))
+        return CSS::ValueID::Center;
+    if (string.equals_ignoring_case("justify"))
+        return CSS::ValueID::Justify;
     if (string.equals_ignoring_case("large"))
         return CSS::ValueID::Large;
     if (string.equals_ignoring_case("larger"))
         return CSS::ValueID::Larger;
+    if (string.equals_ignoring_case("left"))
+        return CSS::ValueID::Left;
     if (string.equals_ignoring_case("lighter"))
         return CSS::ValueID::Lighter;
     if (string.equals_ignoring_case("medium"))
@@ -362,6 +368,8 @@ static Optional<CSS::ValueID> value_id_from_string(const String& string)
         return CSS::ValueID::Normal;
     if (string.equals_ignoring_case("small"))
         return CSS::ValueID::Small;
+    if (string.equals_ignoring_case("right"))
+        return CSS::ValueID::Right;
     if (string.equals_ignoring_case("smaller"))
         return CSS::ValueID::Smaller;
     if (string.equals_ignoring_case("x-large"))
@@ -374,6 +382,8 @@ static Optional<CSS::ValueID> value_id_from_string(const String& string)
         return CSS::ValueID::XxSmall;
     if (string.equals_ignoring_case("xxx-large"))
         return CSS::ValueID::XxxLarge;
+    if (string.equals_ignoring_case("-libweb-center"))
+        return CSS::ValueID::VendorSpecificCenter;
     if (string.equals_ignoring_case("-libweb-link"))
         return CSS::ValueID::VendorSpecificLink;
     if (string.starts_with("-libweb-palette-", CaseSensitivity::CaseInsensitive))

Libraries/LibWeb/CSS/StyleProperties.cpp

@@ -261,19 +261,26 @@ bool StyleProperties::operator==(const StyleProperties& other) const
     return true;
 }
 
-CSS::TextAlign StyleProperties::text_align() const
+Optional<CSS::TextAlign> StyleProperties::text_align() const
 {
-    auto string = string_or_fallback(CSS::PropertyID::TextAlign, "left");
+    auto value = property(CSS::PropertyID::TextAlign);
-    if (string == "center")
+    if (!value.has_value() || !value.value()->is_identifier())
+        return {};
+
+    switch (static_cast<const IdentifierStyleValue&>(*value.value()).id()) {
+    case CSS::ValueID::Left:
+        return CSS::TextAlign::Left;
+    case CSS::ValueID::Center:
         return CSS::TextAlign::Center;
-    if (string == "right")
+    case CSS::ValueID::Right:
         return CSS::TextAlign::Right;
-    if (string == "justify")
+    case CSS::ValueID::Justify:
         return CSS::TextAlign::Justify;
-    if (string == "-libweb-center")
+    case CSS::ValueID::VendorSpecificCenter:
         return CSS::TextAlign::VendorSpecificCenter;
-    // Otherwise, just assume "left"..
+    default:
-    return CSS::TextAlign::Left;
+        return {};
+    }
 }
 
 Optional<CSS::WhiteSpace> StyleProperties::white_space() const

Libraries/LibWeb/CSS/StyleProperties.h

@@ -60,7 +60,7 @@ public:
     LengthBox length_box(CSS::PropertyID left_id, CSS::PropertyID top_id, CSS::PropertyID right_id, CSS::PropertyID bottom_id) const;
     String string_or_fallback(CSS::PropertyID, const StringView& fallback) const;
     Color color_or_fallback(CSS::PropertyID, const DOM::Document&, Color fallback) const;
-    CSS::TextAlign text_align() const;
+    Optional<CSS::TextAlign> text_align() const;
     CSS::Display display() const;
     Optional<CSS::Float> float_() const;
     Optional<CSS::Clear> clear() const;

Libraries/LibWeb/Layout/LayoutStyle.h

@@ -37,6 +37,7 @@ public:
     static CSS::Float float_() { return CSS::Float::None; }
     static CSS::Clear clear() { return CSS::Clear::None; }
     static CSS::WhiteSpace white_space() { return CSS::WhiteSpace::Normal; }
+    static CSS::TextAlign text_align() { return CSS::TextAlign::Left; }
 };
 
 struct BorderData {
@@ -74,7 +75,7 @@ protected:
     CSS::Float m_float { InitialValues::float_() };
     CSS::Clear m_clear { InitialValues::clear() };
     Optional<int> m_z_index;
-    CSS::TextAlign m_text_align;
+    CSS::TextAlign m_text_align { InitialValues::text_align() };
     CSS::Position m_position;
     CSS::WhiteSpace m_white_space { InitialValues::white_space() };
     CSS::Length m_width;

Libraries/LibWeb/Layout/Node.cpp

@@ -220,7 +220,10 @@ void NodeWithStyle::apply_style(const CSS::StyleProperties& specified_style)
     auto& style = static_cast<MutableLayoutStyle&>(m_style);
 
     style.set_position(specified_style.position());
-    style.set_text_align(specified_style.text_align());
+
+    auto text_align = specified_style.text_align();
+    if (text_align.has_value())
+        style.set_text_align(text_align.value());
 
     auto white_space = specified_style.white_space();
     if (white_space.has_value())