LibWeb: Respect `font-stretch` in `StyleComputer::compute_font`

Userland/Libraries/LibWeb/CSS/StyleComputer.cpp

@@ -997,8 +997,63 @@ void StyleComputer::compute_font(StyleProperties& style, DOM::Element const* ele
     auto font_size = style.property(CSS::PropertyID::FontSize);
     auto font_style = style.property(CSS::PropertyID::FontStyle);
     auto font_weight = style.property(CSS::PropertyID::FontWeight);
+    auto font_stretch = style.property(CSS::PropertyID::FontStretch);
 
     int width = Gfx::FontWidth::Normal;
+    if (font_stretch->is_identifier()) {
+        switch (static_cast<IdentifierStyleValue const&>(*font_stretch).id()) {
+        case CSS::ValueID::UltraCondensed:
+            width = Gfx::FontWidth::UltraCondensed;
+            break;
+        case CSS::ValueID::ExtraCondensed:
+            width = Gfx::FontWidth::ExtraCondensed;
+            break;
+        case CSS::ValueID::Condensed:
+            width = Gfx::FontWidth::Condensed;
+            break;
+        case CSS::ValueID::SemiCondensed:
+            width = Gfx::FontWidth::SemiCondensed;
+            break;
+        case CSS::ValueID::Normal:
+            width = Gfx::FontWidth::Normal;
+            break;
+        case CSS::ValueID::SemiExpanded:
+            width = Gfx::FontWidth::SemiExpanded;
+            break;
+        case CSS::ValueID::Expanded:
+            width = Gfx::FontWidth::Expanded;
+            break;
+        case CSS::ValueID::ExtraExpanded:
+            width = Gfx::FontWidth::ExtraExpanded;
+            break;
+        case CSS::ValueID::UltraExpanded:
+            width = Gfx::FontWidth::UltraExpanded;
+            break;
+        default:
+            break;
+        }
+    } else if (font_stretch->is_percentage()) {
+        float percentage = font_stretch->as_percentage().percentage().value();
+        if (percentage <= 50) {
+            width = Gfx::FontWidth::UltraCondensed;
+        } else if (percentage <= 62.5f) {
+            width = Gfx::FontWidth::ExtraCondensed;
+        } else if (percentage <= 75.0f) {
+            width = Gfx::FontWidth::Condensed;
+        } else if (percentage <= 87.5f) {
+            width = Gfx::FontWidth::SemiCondensed;
+        } else if (percentage <= 100.0f) {
+            width = Gfx::FontWidth::Normal;
+        } else if (percentage <= 112.5f) {
+            width = Gfx::FontWidth::SemiExpanded;
+        } else if (percentage <= 125.0f) {
+            width = Gfx::FontWidth::Expanded;
+        } else if (percentage <= 150.0f) {
+            width = Gfx::FontWidth::ExtraExpanded;
+        } else {
+            width = Gfx::FontWidth::UltraExpanded;
+        }
+    }
 
     int weight = Gfx::FontWeight::Regular;
     if (font_weight->is_identifier()) {