LibWeb: Add an initial implementation of SVG text-anchor

This only handles very simple <text> elements, but this is enough (with
the font-size changes) to improve the badges on the GitHub README a fair
bit.

Userland/Libraries/LibWeb/SVG/AttributeParser.h

@@ -125,6 +125,12 @@ enum class FillRule {
     Evenodd
 };
 
+enum class TextAnchor {
+    Start,
+    Middle,
+    End
+};
+
 class AttributeParser final {
 public:
     ~AttributeParser() = default;

Userland/Libraries/LibWeb/SVG/SVGTextContentElement.cpp

@@ -8,6 +8,7 @@
 #include <AK/Utf16View.h>
 #include <LibJS/Runtime/Completion.h>
 #include <LibJS/Runtime/Utf16String.h>
+#include <LibWeb/CSS/Parser/Parser.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/Layout/SVGTextBox.h>
 #include <LibWeb/SVG/AttributeNames.h>
@@ -30,6 +31,22 @@ JS::ThrowCompletionOr<void> SVGTextContentElement::initialize(JS::Realm& realm)
     return {};
 }
 
+Optional<TextAnchor> SVGTextContentElement::text_anchor() const
+{
+    if (!layout_node())
+        return {};
+    switch (layout_node()->computed_values().text_anchor()) {
+    case CSS::TextAnchor::Start:
+        return TextAnchor::Start;
+    case CSS::TextAnchor::Middle:
+        return TextAnchor::Middle;
+    case CSS::TextAnchor::End:
+        return TextAnchor::End;
+    default:
+        VERIFY_NOT_REACHED();
+    }
+}
+
 void SVGTextContentElement::attribute_changed(DeprecatedFlyString const& name, DeprecatedString const& value)
 {
     SVGGraphicsElement::attribute_changed(name, value);

Userland/Libraries/LibWeb/SVG/SVGTextContentElement.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <LibWeb/SVG/AttributeParser.h>
 #include <LibWeb/SVG/SVGGraphicsElement.h>
 #include <LibWeb/WebIDL/ExceptionOr.h>
 
@@ -24,6 +25,8 @@ public:
 
     Gfx::FloatPoint get_offset() const;
 
+    Optional<TextAnchor> text_anchor() const;
+
 protected:
     SVGTextContentElement(DOM::Document&, DOM::QualifiedName);