LibWeb: Implement gradient offset clamping for color stops

Author: https://github.com/gmta
Commit: 4d7da9878d
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2026
Reviewed-by: https://github.com/kalenikaliaksandr ✅

Userland/Libraries/LibWeb/SVG/SVGGradientElement.cpp

@@ -96,15 +96,20 @@ Gfx::AffineTransform SVGGradientElement::gradient_paint_transform(SVGPaintContex
 
 void SVGGradientElement::add_color_stops(Painting::SVGGradientPaintStyle& paint_style) const
 {
+    auto largest_offset = 0.0f;
     for_each_color_stop([&](auto& stop) {
         // https://svgwg.org/svg2-draft/pservers.html#StopNotes
         // Gradient offset values less than 0 (or less than 0%) are rounded up to 0%.
         // Gradient offset values greater than 1 (or greater than 100%) are rounded down to 100%.
         float stop_offset = AK::clamp(stop.stop_offset().value(), 0.0f, 1.0f);
-        // FIXME: Each gradient offset value is required to be equal to or greater than the previous gradient
+
+        // Each gradient offset value is required to be equal to or greater than the previous gradient
         // stop's offset value. If a given gradient stop's offset value is not equal to or greater than all
         // previous offset values, then the offset value is adjusted to be equal to the largest of all previous
         // offset values.
+        stop_offset = AK::max(stop_offset, largest_offset);
+        largest_offset = stop_offset;
+
         paint_style.add_color_stop(stop_offset, stop.stop_color().with_opacity(stop.stop_opacity()));
     });
 }