LibHTML: Implement rendering

Author: https://github.com/bugaevc
Commit: https://github.com/SerenityOS/serenity/commit/235dee8c421
Pull-request: https://github.com/SerenityOS/serenity/pull/609
Reviewed-by: https://github.com/awesomekling ✅

Libraries/LibHTML/Layout/LayoutBlock.cpp

@@ -1,3 +1,4 @@
+#include <LibGUI/GPainter.h>
 #include <LibHTML/DOM/Element.h>
 #include <LibHTML/Layout/LayoutBlock.h>
 
@@ -143,3 +144,19 @@ void LayoutBlock::compute_height()
     if (height_length.is_absolute())
         rect().set_height(height_length.to_px());
 }
+
+void LayoutBlock::render(RenderingContext& context)
+{
+    LayoutNode::render(context);
+
+    // FIXME: position this properly
+    if (style_properties().string_or_fallback("display", "block") == "list-item") {
+        Rect bullet_rect {
+            rect().x() - 8,
+            rect().y() + 4,
+            3,
+            3
+        };
+        context.painter().fill_rect(bullet_rect, Color::Black);
+    }
+}

Libraries/LibHTML/Layout/LayoutBlock.h

@@ -12,6 +12,7 @@ public:
     virtual const char* class_name() const override { return "LayoutBlock"; }
 
     virtual void layout() override;
+    virtual void render(RenderingContext&) override;
 
     virtual LayoutNode& inline_wrapper() override;
 

Libraries/LibHTML/Layout/LayoutNode.cpp

@@ -26,3 +26,11 @@ const LayoutBlock* LayoutNode::containing_block() const
     }
     return nullptr;
 }
+
+void LayoutNode::render(RenderingContext& context)
+{
+    // TODO: render our background and border
+    for_each_child([&](auto& child) {
+        child.render(context);
+    });
+}

Libraries/LibHTML/Layout/LayoutNode.h

@@ -5,6 +5,7 @@
 #include <LibDraw/Rect.h>
 #include <LibHTML/CSS/StyleProperties.h>
 #include <LibHTML/Layout/ComputedStyle.h>
+#include <LibHTML/RenderingContext.h>
 #include <LibHTML/TreeNode.h>
 
 class Node;
@@ -44,6 +45,7 @@ public:
     virtual bool is_inline() const { return false; }
 
     virtual void layout();
+    virtual void render(RenderingContext&);
 
     const LayoutBlock* containing_block() const;
 

Libraries/LibHTML/Layout/LayoutText.cpp

@@ -1,6 +1,7 @@
 #include <AK/StringBuilder.h>
 #include <LibCore/CDirIterator.h>
 #include <LibDraw/Font.h>
+#include <LibGUI/GPainter.h>
 #include <LibHTML/Layout/LayoutBlock.h>
 #include <LibHTML/Layout/LayoutText.h>
 #include <ctype.h>
@@ -216,3 +217,19 @@ void LayoutText::layout()
     rect().set_right(last_run.pos.x() + m_font->width(last_run.text));
     rect().set_bottom(last_run.pos.y() + m_font->glyph_height());
 }
+
+void LayoutText::render(RenderingContext& context)
+{
+    auto& painter = context.painter();
+    painter.set_font(*m_font);
+
+    for (auto& run : m_runs) {
+        Rect rect {
+            run.pos.x(),
+            run.pos.y(),
+            m_font->width(run.text),
+            m_font->glyph_height()
+        };
+        painter.draw_text(rect, run.text);
+    }
+}

Libraries/LibHTML/Layout/LayoutText.h

@@ -17,6 +17,7 @@ public:
     virtual const char* class_name() const override { return "LayoutText"; }
     virtual bool is_text() const final { return true; }
     virtual void layout() override;
+    virtual void render(RenderingContext&) override;
 
     struct Run {
         Point pos;

Libraries/LibHTML/RenderingContext.h

@@ -0,0 +1,16 @@
+#pragma once
+
+class GPainter;
+
+class RenderingContext {
+public:
+    explicit RenderingContext(GPainter& painter)
+        : m_painter(painter)
+    {
+    }
+
+    GPainter& painter() const { return m_painter; }
+
+private:
+    GPainter& m_painter;
+};