LibWeb: Implement SVG `preserveAspectRatio` attribute

This attribute is used to define how the viewBox should be scaled.
Previously the behaviour implemented was that of "xMidYMid meet", now
all of them work (expect none :P).

With this the Discord login backend is now correctly scaled/positioned.

This also brings our SVG code a little closer to the spec! With spec
comments and all :^)

(Minor non-visible update to layout tests)

4 files changed, 94 insertions, 6 deletions

diff --git a/Userland/Libraries/LibWeb/SVG/AttributeParser.cpp b/Userland/Libraries/LibWeb/SVG/AttributeParser.cpp
index 05ca7537f4..644f2843a5 100644
--- a/Userland/Libraries/LibWeb/SVG/AttributeParser.cpp
+++ b/Userland/Libraries/LibWeb/SVG/AttributeParser.cpp
@@ -397,16 +397,77 @@ int AttributeParser::parse_sign()
     return 1;
 }
 
-// https://drafts.csswg.org/css-transforms/#svg-syntax
-Optional<Vector<Transform>> AttributeParser::parse_transform()
+static bool whitespace(char c)
 {
     // wsp:
     // Either a U+000A LINE FEED, U+000D CARRIAGE RETURN, U+0009 CHARACTER TABULATION, or U+0020 SPACE.
-    auto wsp = [](char c) {
-        return AK::first_is_one_of(c, '\n', '\r', '\t', '\f', ' ');
-    };
+    return AK::first_is_one_of(c, '\n', '\r', '\t', '\f', ' ');
+}
+
+// https://svgwg.org/svg2-draft/coords.html#PreserveAspectRatioAttribute
+Optional<PreserveAspectRatio> AttributeParser::parse_preserve_aspect_ratio(StringView input)
+{
+    // <align> <meetOrSlice>?
+    GenericLexer lexer { input };
+    lexer.ignore_while(whitespace);
+    auto align_string = lexer.consume_until(whitespace);
+    if (align_string.is_empty())
+        return {};
+    lexer.ignore_while(whitespace);
+    auto meet_or_slice_string = lexer.consume_until(whitespace);
+
+    // <align> =
+    //     none
+    //     | xMinYMin | xMidYMin | xMaxYMin
+    //     | xMinYMid | xMidYMid | xMaxYMid
+    //     | xMinYMax | xMidYMax | xMaxYMax
+    auto align = [&]() -> Optional<PreserveAspectRatio::Align> {
+        if (align_string == "none"sv)
+            return PreserveAspectRatio::Align::None;
+        if (align_string == "xMinYMin"sv)
+            return PreserveAspectRatio::Align::xMinYMin;
+        if (align_string == "xMidYMin"sv)
+            return PreserveAspectRatio::Align::xMidYMin;
+        if (align_string == "xMaxYMin"sv)
+            return PreserveAspectRatio::Align::xMaxYMin;
+        if (align_string == "xMinYMid"sv)
+            return PreserveAspectRatio::Align::xMinYMid;
+        if (align_string == "xMidYMid"sv)
+            return PreserveAspectRatio::Align::xMidYMid;
+        if (align_string == "xMaxYMid"sv)
+            return PreserveAspectRatio::Align::xMaxYMid;
+        if (align_string == "xMinYMax"sv)
+            return PreserveAspectRatio::Align::xMinYMax;
+        if (align_string == "xMidYMax"sv)
+            return PreserveAspectRatio::Align::xMidYMax;
+        if (align_string == "xMaxYMax"sv)
+            return PreserveAspectRatio::Align::xMaxYMax;
+        return {};
+    }();
+
+    if (!align.has_value())
+        return {};
+
+    // <meetOrSlice> = meet | slice
+    auto meet_or_slice = [&]() -> Optional<PreserveAspectRatio::MeetOrSlice> {
+        if (meet_or_slice_string.is_empty() || meet_or_slice_string == "meet"sv)
+            return PreserveAspectRatio::MeetOrSlice::Meet;
+        if (meet_or_slice_string == "slice"sv)
+            return PreserveAspectRatio::MeetOrSlice::Slice;
+        return {};
+    }();
+
+    if (!meet_or_slice.has_value())
+        return {};
+
+    return PreserveAspectRatio { *align, *meet_or_slice };
+}
+
+// https://drafts.csswg.org/css-transforms/#svg-syntax
+Optional<Vector<Transform>> AttributeParser::parse_transform()
+{
     auto consume_whitespace = [&] {
-        m_lexer.consume_while(wsp);
+        m_lexer.ignore_while(whitespace);
     };
 
     auto consume_comma_whitespace = [&] {
diff --git a/Userland/Libraries/LibWeb/SVG/AttributeParser.h b/Userland/Libraries/LibWeb/SVG/AttributeParser.h
index e7b5e075c5..164b184a9a 100644
--- a/Userland/Libraries/LibWeb/SVG/AttributeParser.h
+++ b/Userland/Libraries/LibWeb/SVG/AttributeParser.h
@@ -67,6 +67,27 @@ struct Transform {
     Operation operation;
 };
 
+struct PreserveAspectRatio {
+    enum class Align {
+        None,
+        xMinYMin,
+        xMidYMin,
+        xMaxYMin,
+        xMinYMid,
+        xMidYMid,
+        xMaxYMid,
+        xMinYMax,
+        xMidYMax,
+        xMaxYMax
+    };
+    enum class MeetOrSlice {
+        Meet,
+        Slice
+    };
+    Align align { Align::xMidYMid };
+    MeetOrSlice meet_or_slice { MeetOrSlice::Meet };
+};
+
 class AttributeParser final {
 public:
     ~AttributeParser() = default;
@@ -77,6 +98,7 @@ public:
     static Vector<Gfx::FloatPoint> parse_points(StringView input);
     static Vector<PathInstruction> parse_path_data(StringView input);
     static Optional<Vector<Transform>> parse_transform(StringView input);
+    static Optional<PreserveAspectRatio> parse_preserve_aspect_ratio(StringView input);
 
 private:
     AttributeParser(StringView source);
diff --git a/Userland/Libraries/LibWeb/SVG/SVGSVGElement.cpp b/Userland/Libraries/LibWeb/SVG/SVGSVGElement.cpp
index abfab45dbf..69b89bdfbc 100644
--- a/Userland/Libraries/LibWeb/SVG/SVGSVGElement.cpp
+++ b/Userland/Libraries/LibWeb/SVG/SVGSVGElement.cpp
@@ -73,6 +73,8 @@ void SVGSVGElement::parse_attribute(DeprecatedFlyString const& name, DeprecatedS
 
     if (name.equals_ignoring_ascii_case(SVG::AttributeNames::viewBox))
         m_view_box = try_parse_view_box(value);
+    if (name.equals_ignoring_ascii_case(SVG::AttributeNames::preserveAspectRatio))
+        m_preserve_aspect_ratio = AttributeParser::parse_preserve_aspect_ratio(value);
 }
 
 }
diff --git a/Userland/Libraries/LibWeb/SVG/SVGSVGElement.h b/Userland/Libraries/LibWeb/SVG/SVGSVGElement.h
index 7f03fda104..a214843f8f 100644
--- a/Userland/Libraries/LibWeb/SVG/SVGSVGElement.h
+++ b/Userland/Libraries/LibWeb/SVG/SVGSVGElement.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <LibGfx/Bitmap.h>
+#include <LibWeb/SVG/AttributeParser.h>
 #include <LibWeb/SVG/SVGGraphicsElement.h>
 #include <LibWeb/SVG/ViewBox.h>
 
@@ -24,6 +25,7 @@ public:
     virtual bool is_svg_container() const override { return true; }
 
     Optional<ViewBox> const& view_box() const { return m_view_box; }
+    Optional<PreserveAspectRatio> const& preserve_aspect_ratio() const { return m_preserve_aspect_ratio; }
 
 private:
     SVGSVGElement(DOM::Document&, DOM::QualifiedName);
@@ -35,6 +37,7 @@ private:
     virtual void parse_attribute(DeprecatedFlyString const& name, DeprecatedString const& value) override;
 
     Optional<ViewBox> m_view_box;
+    Optional<PreserveAspectRatio> m_preserve_aspect_ratio;
 };
 
 }