LibWeb: Support transforms, stroking, gradients, etc for SVG <text>

This makes use of the new Gfx::Path::text() to handle SVG text elements,
with this text is just a regular path, and can be manipulated like any
other graphics element.

This removes the SVGTextPaintable and makes both <text> and geometry
elements use a new (shared) SVGPathPaintable. This is identical to the
old SVGGeometryPaintable. This simplifies painting as once something is
resolved to a Gfx::Path, the painting logic is the same.

Userland/Libraries/LibWeb/Painting/SVGPathPaintable.cpp

@@ -0,0 +1,143 @@
+/*
+ * Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2023, MacDue <macdue@dueutil.tech>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibGfx/AntiAliasingPainter.h>
+#include <LibWeb/Painting/SVGPathPaintable.h>
+#include <LibWeb/SVG/SVGSVGElement.h>
+
+namespace Web::Painting {
+
+JS::NonnullGCPtr<SVGPathPaintable> SVGPathPaintable::create(Layout::SVGGraphicsBox const& layout_box)
+{
+    return layout_box.heap().allocate_without_realm<SVGPathPaintable>(layout_box);
+}
+
+SVGPathPaintable::SVGPathPaintable(Layout::SVGGraphicsBox const& layout_box)
+    : SVGGraphicsPaintable(layout_box)
+{
+}
+
+Layout::SVGGraphicsBox const& SVGPathPaintable::layout_box() const
+{
+    return static_cast<Layout::SVGGraphicsBox const&>(layout_node());
+}
+
+Optional<HitTestResult> SVGPathPaintable::hit_test(CSSPixelPoint position, HitTestType type) const
+{
+    auto result = SVGGraphicsPaintable::hit_test(position, type);
+    if (!result.has_value() || !computed_path().has_value())
+        return {};
+    auto transformed_bounding_box = computed_transforms().svg_to_css_pixels_transform().map_to_quad(computed_path()->bounding_box());
+    if (!transformed_bounding_box.contains(position.to_type<float>()))
+        return {};
+    return result;
+}
+
+static Gfx::Painter::WindingRule to_gfx_winding_rule(SVG::FillRule fill_rule)
+{
+    switch (fill_rule) {
+    case SVG::FillRule::Nonzero:
+        return Gfx::Painter::WindingRule::Nonzero;
+    case SVG::FillRule::Evenodd:
+        return Gfx::Painter::WindingRule::EvenOdd;
+    default:
+        VERIFY_NOT_REACHED();
+    }
+}
+
+void SVGPathPaintable::paint(PaintContext& context, PaintPhase phase) const
+{
+    if (!is_visible() || !computed_path().has_value())
+        return;
+
+    SVGGraphicsPaintable::paint(context, phase);
+
+    if (phase != PaintPhase::Foreground)
+        return;
+
+    auto& geometry_element = layout_box().dom_node();
+
+    auto const* svg_element = geometry_element.shadow_including_first_ancestor_of_type<SVG::SVGSVGElement>();
+    auto svg_element_rect = svg_element->paintable_box()->absolute_rect();
+
+    // FIXME: This should not be trucated to an int.
+    RecordingPainterStateSaver save_painter { context.painter() };
+
+    auto offset = context.floored_device_point(svg_element_rect.location()).to_type<int>().to_type<float>();
+    auto maybe_view_box = geometry_element.view_box();
+
+    auto paint_transform = computed_transforms().svg_to_device_pixels_transform(context);
+    Gfx::Path path = computed_path()->copy_transformed(paint_transform);
+
+    // Fills are computed as though all subpaths are closed (https://svgwg.org/svg2-draft/painting.html#FillProperties)
+    auto closed_path = [&] {
+        // We need to fill the path before applying the stroke, however the filled
+        // path must be closed, whereas the stroke path may not necessary be closed.
+        // Copy the path and close it for filling, but use the previous path for stroke
+        auto copy = path;
+        copy.close_all_subpaths();
+        return copy;
+    };
+
+    // Note: This is assuming .x_scale() == .y_scale() (which it does currently).
+    auto viewbox_scale = paint_transform.x_scale();
+
+    auto svg_viewport = [&] {
+        if (maybe_view_box.has_value())
+            return Gfx::FloatRect { maybe_view_box->min_x, maybe_view_box->min_y, maybe_view_box->width, maybe_view_box->height };
+        return Gfx::FloatRect { { 0, 0 }, svg_element_rect.size().to_type<float>() };
+    }();
+
+    SVG::SVGPaintContext paint_context {
+        .viewport = svg_viewport,
+        .path_bounding_box = computed_path()->bounding_box(),
+        .transform = paint_transform
+    };
+
+    auto fill_opacity = geometry_element.fill_opacity().value_or(1);
+    auto winding_rule = to_gfx_winding_rule(geometry_element.fill_rule().value_or(SVG::FillRule::Nonzero));
+    if (auto paint_style = geometry_element.fill_paint_style(paint_context); paint_style.has_value()) {
+        context.painter().fill_path({
+            .path = closed_path(),
+            .paint_style = *paint_style,
+            .winding_rule = winding_rule,
+            .opacity = fill_opacity,
+            .translation = offset,
+        });
+    } else if (auto fill_color = geometry_element.fill_color(); fill_color.has_value()) {
+        context.painter().fill_path({
+            .path = closed_path(),
+            .color = fill_color->with_opacity(fill_opacity),
+            .winding_rule = winding_rule,
+            .translation = offset,
+        });
+    }
+
+    auto stroke_opacity = geometry_element.stroke_opacity().value_or(1);
+
+    // Note: This is assuming .x_scale() == .y_scale() (which it does currently).
+    float stroke_thickness = geometry_element.stroke_width().value_or(1) * viewbox_scale;
+
+    if (auto paint_style = geometry_element.stroke_paint_style(paint_context); paint_style.has_value()) {
+        context.painter().stroke_path({
+            .path = path,
+            .paint_style = *paint_style,
+            .thickness = stroke_thickness,
+            .opacity = stroke_opacity,
+            .translation = offset,
+        });
+    } else if (auto stroke_color = geometry_element.stroke_color(); stroke_color.has_value()) {
+        context.painter().stroke_path({
+            .path = path,
+            .color = stroke_color->with_opacity(stroke_opacity),
+            .thickness = stroke_thickness,
+            .translation = offset,
+        });
+    }
+}
+
+}