LibWeb: Render multiple box-shadows

Because why not? :^)

8 files changed, 104 insertions, 62 deletions

diff --git a/Userland/Libraries/LibWeb/CSS/ComputedValues.h b/Userland/Libraries/LibWeb/CSS/ComputedValues.h
index d07c38ee6d..df0f42bb5a 100644
--- a/Userland/Libraries/LibWeb/CSS/ComputedValues.h
+++ b/Userland/Libraries/LibWeb/CSS/ComputedValues.h
@@ -104,7 +104,7 @@ public:
     CSS::AlignItems align_items() const { return m_noninherited.align_items; }
     float opacity() const { return m_noninherited.opacity; }
     CSS::JustifyContent justify_content() const { return m_noninherited.justify_content; }
-    Optional<BoxShadowData> const& box_shadow() const { return m_noninherited.box_shadow; }
+    Vector<BoxShadowData> const& box_shadow() const { return m_noninherited.box_shadow; }
     CSS::BoxSizing box_sizing() const { return m_noninherited.box_sizing; }
     CSS::LengthPercentage const& width() const { return m_noninherited.width; }
     CSS::LengthPercentage const& min_width() const { return m_noninherited.min_width; }
@@ -201,7 +201,7 @@ protected:
         CSS::Overflow overflow_x { InitialValues::overflow() };
         CSS::Overflow overflow_y { InitialValues::overflow() };
         float opacity { InitialValues::opacity() };
-        Optional<BoxShadowData> box_shadow {};
+        Vector<BoxShadowData> box_shadow {};
         Vector<CSS::Transformation> transformations {};
         CSS::BoxSizing box_sizing { InitialValues::box_sizing() };
     } m_noninherited;
@@ -255,7 +255,7 @@ public:
     void set_align_items(CSS::AlignItems value) { m_noninherited.align_items = value; }
     void set_opacity(float value) { m_noninherited.opacity = value; }
     void set_justify_content(CSS::JustifyContent value) { m_noninherited.justify_content = value; }
-    void set_box_shadow(Optional<BoxShadowData> value) { m_noninherited.box_shadow = move(value); }
+    void set_box_shadow(Vector<BoxShadowData>&& value) { m_noninherited.box_shadow = move(value); }
     void set_transformations(Vector<CSS::Transformation> value) { m_noninherited.transformations = move(value); }
     void set_box_sizing(CSS::BoxSizing value) { m_noninherited.box_sizing = value; }
 
diff --git a/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp b/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp
index adeafb00ce..72b463d07b 100644
--- a/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp
+++ b/Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp
@@ -518,12 +518,23 @@ RefPtr<StyleValue> ResolvedCSSStyleDeclaration::style_value_for_property(Layout:
     case CSS::PropertyID::JustifyContent:
         return IdentifierStyleValue::create(to_css_value_id(layout_node.computed_values().justify_content()));
     case CSS::PropertyID::BoxShadow: {
-        auto maybe_box_shadow = layout_node.computed_values().box_shadow();
-        if (!maybe_box_shadow.has_value())
+        auto box_shadow_layers = layout_node.computed_values().box_shadow();
+        if (box_shadow_layers.is_empty())
             return {};
-        auto box_shadow_data = maybe_box_shadow.release_value();
-        // FIXME: Add extra properties to BoxShadowData so we can include them here!
-        return BoxShadowStyleValue::create(box_shadow_data.color, box_shadow_data.offset_x, box_shadow_data.offset_y, box_shadow_data.blur_radius, Length::make_px(0), BoxShadowPlacement::Outer);
+
+        auto make_box_shadow_style_value = [](BoxShadowData const& data) {
+            // FIXME: Add extra properties to BoxShadowData so we can include them here!
+            return BoxShadowStyleValue::create(data.color, data.offset_x, data.offset_y, data.blur_radius, Length::make_px(0), BoxShadowPlacement::Outer);
+        };
+
+        if (box_shadow_layers.size() == 1)
+            return make_box_shadow_style_value(box_shadow_layers.first());
+
+        NonnullRefPtrVector<StyleValue> box_shadow;
+        box_shadow.ensure_capacity(box_shadow_layers.size());
+        for (auto const& layer : box_shadow_layers)
+            box_shadow.append(make_box_shadow_style_value(layer));
+        return StyleValueList::create(move(box_shadow), StyleValueList::Separator::Comma);
     }
     case CSS::PropertyID::Width:
         return style_value_for_length_percentage(layout_node.computed_values().width());
diff --git a/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp b/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
index 9575ddf138..65d2b054e7 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
+++ b/Userland/Libraries/LibWeb/CSS/StyleProperties.cpp
@@ -769,18 +769,35 @@ Optional<CSS::Overflow> StyleProperties::overflow(CSS::PropertyID property_id) c
     }
 }
 
-Optional<CSS::BoxShadowData> StyleProperties::box_shadow() const
+Vector<BoxShadowData> StyleProperties::box_shadow() const
 {
-    auto value_or_error = property(CSS::PropertyID::BoxShadow);
+    auto value_or_error = property(PropertyID::BoxShadow);
     if (!value_or_error.has_value())
         return {};
 
     auto value = value_or_error.value();
-    if (!value->is_box_shadow())
-        return {};
 
-    auto& box = value->as_box_shadow();
-    return { { box.offset_x(), box.offset_y(), box.blur_radius(), box.color() } };
+    auto make_box_shadow_data = [](BoxShadowStyleValue const& box) {
+        return BoxShadowData { box.offset_x(), box.offset_y(), box.blur_radius(), box.color() };
+    };
+
+    if (value->is_value_list()) {
+        auto& value_list = value->as_value_list();
+
+        Vector<BoxShadowData> box_shadow_data;
+        box_shadow_data.ensure_capacity(value_list.size());
+        for (auto const& layer_value : value_list.values())
+            box_shadow_data.append(make_box_shadow_data(layer_value.as_box_shadow()));
+
+        return box_shadow_data;
+    }
+
+    if (value->is_box_shadow()) {
+        auto& box = value->as_box_shadow();
+        return { make_box_shadow_data(box) };
+    }
+
+    return {};
 }
 
 CSS::BoxSizing StyleProperties::box_sizing() const
diff --git a/Userland/Libraries/LibWeb/CSS/StyleProperties.h b/Userland/Libraries/LibWeb/CSS/StyleProperties.h
index 777a7a65c5..4c86749b7a 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleProperties.h
+++ b/Userland/Libraries/LibWeb/CSS/StyleProperties.h
@@ -64,7 +64,7 @@ public:
     Optional<CSS::JustifyContent> justify_content() const;
     Optional<CSS::Overflow> overflow_x() const;
     Optional<CSS::Overflow> overflow_y() const;
-    Optional<CSS::BoxShadowData> box_shadow() const;
+    Vector<CSS::BoxShadowData> box_shadow() const;
     CSS::BoxSizing box_sizing() const;
     Optional<CSS::PointerEvents> pointer_events() const;
 
diff --git a/Userland/Libraries/LibWeb/Layout/Box.cpp b/Userland/Libraries/LibWeb/Layout/Box.cpp
index a8d68d6693..897e1ae375 100644
--- a/Userland/Libraries/LibWeb/Layout/Box.cpp
+++ b/Userland/Libraries/LibWeb/Layout/Box.cpp
@@ -99,15 +99,18 @@ void Box::paint_background(PaintContext& context)
 void Box::paint_box_shadow(PaintContext& context)
 {
     auto box_shadow_data = computed_values().box_shadow();
-    if (!box_shadow_data.has_value())
+    if (box_shadow_data.is_empty())
         return;
 
-    auto resolved_box_shadow_data = Painting::BoxShadowData {
-        .offset_x = (int)box_shadow_data->offset_x.resolved_or_zero(*this).to_px(*this),
-        .offset_y = (int)box_shadow_data->offset_y.resolved_or_zero(*this).to_px(*this),
-        .blur_radius = (int)box_shadow_data->blur_radius.resolved_or_zero(*this).to_px(*this),
-        .color = box_shadow_data->color
-    };
+    Vector<Painting::BoxShadowData> resolved_box_shadow_data;
+    resolved_box_shadow_data.ensure_capacity(box_shadow_data.size());
+    for (auto const& layer : box_shadow_data) {
+        resolved_box_shadow_data.empend(
+            static_cast<int>(layer.offset_x.resolved_or_zero(*this).to_px(*this)),
+            static_cast<int>(layer.offset_y.resolved_or_zero(*this).to_px(*this)),
+            static_cast<int>(layer.blur_radius.resolved_or_zero(*this).to_px(*this)),
+            layer.color);
+    }
     Painting::paint_box_shadow(context, enclosing_int_rect(bordered_rect()), resolved_box_shadow_data);
 }
 
diff --git a/Userland/Libraries/LibWeb/Layout/InlineNode.cpp b/Userland/Libraries/LibWeb/Layout/InlineNode.cpp
index afd320d17c..c4ba68df0f 100644
--- a/Userland/Libraries/LibWeb/Layout/InlineNode.cpp
+++ b/Userland/Libraries/LibWeb/Layout/InlineNode.cpp
@@ -43,14 +43,17 @@ void InlineNode::paint(PaintContext& context, PaintPhase phase)
             auto border_radius_data = Painting::normalized_border_radius_data(*this, absolute_fragment_rect, top_left_border_radius, top_right_border_radius, bottom_right_border_radius, bottom_left_border_radius);
             Painting::paint_background(context, *this, enclosing_int_rect(absolute_fragment_rect), computed_values().background_color(), &computed_values().background_layers(), border_radius_data);
 
-            if (auto computed_box_shadow = computed_values().box_shadow(); computed_box_shadow.has_value()) {
-                auto box_shadow_data = Painting::BoxShadowData {
-                    .offset_x = (int)computed_box_shadow->offset_x.resolved_or_zero(*this).to_px(*this),
-                    .offset_y = (int)computed_box_shadow->offset_y.resolved_or_zero(*this).to_px(*this),
-                    .blur_radius = (int)computed_box_shadow->blur_radius.resolved_or_zero(*this).to_px(*this),
-                    .color = computed_box_shadow->color
-                };
-                Painting::paint_box_shadow(context, enclosing_int_rect(absolute_fragment_rect), box_shadow_data);
+            if (auto computed_box_shadow = computed_values().box_shadow(); !computed_box_shadow.is_empty()) {
+                Vector<Painting::BoxShadowData> resolved_box_shadow_data;
+                resolved_box_shadow_data.ensure_capacity(computed_box_shadow.size());
+                for (auto const& layer : computed_box_shadow) {
+                    resolved_box_shadow_data.empend(
+                        static_cast<int>(layer.offset_x.resolved_or_zero(*this).to_px(*this)),
+                        static_cast<int>(layer.offset_y.resolved_or_zero(*this).to_px(*this)),
+                        static_cast<int>(layer.blur_radius.resolved_or_zero(*this).to_px(*this)),
+                        layer.color);
+                }
+                Painting::paint_box_shadow(context, enclosing_int_rect(absolute_fragment_rect), resolved_box_shadow_data);
             }
 
             return IterationDecision::Continue;
diff --git a/Userland/Libraries/LibWeb/Painting/ShadowPainting.cpp b/Userland/Libraries/LibWeb/Painting/ShadowPainting.cpp
index 91c09737d5..5fa8eafdf5 100644
--- a/Userland/Libraries/LibWeb/Painting/ShadowPainting.cpp
+++ b/Userland/Libraries/LibWeb/Painting/ShadowPainting.cpp
@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
- * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2021-2022, Sam Atkins <atkinssj@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -13,42 +13,50 @@
 
 namespace Web::Painting {
 
-void paint_box_shadow(PaintContext& context, Gfx::IntRect const& content_rect, BoxShadowData const& box_shadow_data)
+void paint_box_shadow(PaintContext& context, Gfx::IntRect const& content_rect, Vector<BoxShadowData> const& box_shadow_layers)
 {
-    Gfx::IntRect bitmap_rect = {
-        0,
-        0,
-        content_rect.width() + 4 * box_shadow_data.blur_radius,
-        content_rect.height() + 4 * box_shadow_data.blur_radius
-    };
-
-    Gfx::IntPoint blur_rect_position = {
-        content_rect.x() - 2 * box_shadow_data.blur_radius + box_shadow_data.offset_x,
-        content_rect.y() - 2 * box_shadow_data.blur_radius + box_shadow_data.offset_y
-    };
-
-    if (bitmap_rect.is_empty())
+    if (box_shadow_layers.is_empty())
         return;
 
-    auto bitmap_or_error = Gfx::Bitmap::try_create(Gfx::BitmapFormat::BGRA8888, bitmap_rect.size());
-    if (bitmap_or_error.is_error()) {
-        dbgln("Unable to allocate temporary bitmap for box-shadow rendering: {}", bitmap_or_error.error());
-        return;
-    }
-    auto new_bitmap = bitmap_or_error.release_value_but_fixme_should_propagate_errors();
+    // Note: Box-shadow layers are ordered front-to-back, so we paint them in reverse
+    for (int layer_index = box_shadow_layers.size() - 1; layer_index >= 0; layer_index--) {
+        auto& box_shadow_data = box_shadow_layers[layer_index];
+
+        Gfx::IntRect bitmap_rect = {
+            0,
+            0,
+            content_rect.width() + 4 * box_shadow_data.blur_radius,
+            content_rect.height() + 4 * box_shadow_data.blur_radius
+        };
+
+        Gfx::IntPoint blur_rect_position = {
+            content_rect.x() - 2 * box_shadow_data.blur_radius + box_shadow_data.offset_x,
+            content_rect.y() - 2 * box_shadow_data.blur_radius + box_shadow_data.offset_y
+        };
 
-    Gfx::Painter painter(*new_bitmap);
-    painter.fill_rect({ { 2 * box_shadow_data.blur_radius, 2 * box_shadow_data.blur_radius }, content_rect.size() }, box_shadow_data.color);
+        if (bitmap_rect.is_empty())
+            return;
 
-    Gfx::FastBoxBlurFilter filter(*new_bitmap);
-    filter.apply_three_passes(box_shadow_data.blur_radius);
+        auto bitmap_or_error = Gfx::Bitmap::try_create(Gfx::BitmapFormat::BGRA8888, bitmap_rect.size());
+        if (bitmap_or_error.is_error()) {
+            dbgln("Unable to allocate temporary bitmap for box-shadow rendering: {}", bitmap_or_error.error());
+            return;
+        }
+        auto new_bitmap = bitmap_or_error.release_value_but_fixme_should_propagate_errors();
 
-    Gfx::DisjointRectSet rect_set;
-    rect_set.add(bitmap_rect);
-    auto shattered = rect_set.shatter({ content_rect.location() - blur_rect_position, content_rect.size() });
+        Gfx::Painter painter(*new_bitmap);
+        painter.fill_rect({ { 2 * box_shadow_data.blur_radius, 2 * box_shadow_data.blur_radius }, content_rect.size() }, box_shadow_data.color);
 
-    for (auto& rect : shattered.rects())
-        context.painter().blit(rect.location() + blur_rect_position, *new_bitmap, rect);
+        Gfx::FastBoxBlurFilter filter(*new_bitmap);
+        filter.apply_three_passes(box_shadow_data.blur_radius);
+
+        Gfx::DisjointRectSet rect_set;
+        rect_set.add(bitmap_rect);
+        auto shattered = rect_set.shatter({ content_rect.location() - blur_rect_position, content_rect.size() });
+
+        for (auto& rect : shattered.rects())
+            context.painter().blit(rect.location() + blur_rect_position, *new_bitmap, rect);
+    }
 }
 
 }
diff --git a/Userland/Libraries/LibWeb/Painting/ShadowPainting.h b/Userland/Libraries/LibWeb/Painting/ShadowPainting.h
index 5926b539fd..4484a76f8c 100644
--- a/Userland/Libraries/LibWeb/Painting/ShadowPainting.h
+++ b/Userland/Libraries/LibWeb/Painting/ShadowPainting.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
+ * Copyright (c) 2021-2022, Sam Atkins <atkinssj@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -18,6 +18,6 @@ struct BoxShadowData {
     Gfx::Color color;
 };
 
-void paint_box_shadow(PaintContext&, Gfx::IntRect const&, BoxShadowData const&);
+void paint_box_shadow(PaintContext&, Gfx::IntRect const&, Vector<BoxShadowData> const&);
 
 }