LibHTML: Make hit testing work for LayoutText

LayoutText can't simply rely on its LayoutNode::rect() for hit testing.
Instead, we have to iterate over the individual runs and see if we're
hitting any of them.

Also, LayoutNode::hit_test() now always recurses into children, since
we can't trust the rect() to tell the truth (inline rects are wrong.)

Libraries/LibHTML/Layout/LayoutNode.cpp

@@ -1,7 +1,10 @@
+#include <LibGUI/GPainter.h>
 #include <LibHTML/DOM/Element.h>
 #include <LibHTML/Layout/LayoutBlock.h>
 #include <LibHTML/Layout/LayoutNode.h>
 
+//#define DRAW_BOXES_AROUND_LAYOUT_NODES
+
 LayoutNode::LayoutNode(const Node* node, StyleProperties&& style_properties)
     : m_node(node)
     , m_style_properties(style_properties)
@@ -30,6 +33,9 @@ const LayoutBlock* LayoutNode::containing_block() const
 
 void LayoutNode::render(RenderingContext& context)
 {
+#ifdef DRAW_BOXES_AROUND_LAYOUT_NODES
+    context.painter().draw_rect(m_rect, Color::Blue);
+#endif
     // TODO: render our background and border
     for_each_child([&](auto& child) {
         child.render(context);
@@ -38,9 +44,10 @@ void LayoutNode::render(RenderingContext& context)
 
 HitTestResult LayoutNode::hit_test(const Point& position) const
 {
-    if (!m_rect.contains(position))
-        return {};
-    HitTestResult result { this };
+    // FIXME: It would be nice if we could confidently skip over hit testing
+    //        parts of the layout tree, but currently we can't just check
+    //        m_rect.contains() since inline text rects can't be trusted..
+    HitTestResult result { m_rect.contains(position) ? this : nullptr };
     for_each_child([&](auto& child) {
         auto child_result = child.hit_test(position);
         if (child_result.layout_node)

Libraries/LibHTML/Layout/LayoutText.cpp

@@ -222,6 +222,21 @@ void LayoutText::layout()
     rect().set_bottom(last_run.pos.y() + m_font->glyph_height());
 }
 
+template<typename Callback>
+void LayoutText::for_each_run(Callback callback) const
+{
+    for (auto& run : m_runs) {
+        Rect rect {
+            run.pos.x(),
+            run.pos.y(),
+            m_font->width(run.text),
+            m_font->glyph_height()
+        };
+        if (callback(run, rect) == IterationDecision::Break)
+            break;
+    }
+}
+
 void LayoutText::render(RenderingContext& context)
 {
     auto& painter = context.painter();
@@ -232,16 +247,23 @@ void LayoutText::render(RenderingContext& context)
 
     bool is_underline = text_decoration == "underline";
 
-    for (auto& run : m_runs) {
-        Rect rect {
-            run.pos.x(),
-            run.pos.y(),
-            m_font->width(run.text),
-            m_font->glyph_height()
-        };
+    for_each_run([&](auto& run, auto& rect) {
         painter.draw_text(rect, run.text, TextAlignment::TopLeft, color);
-
         if (is_underline)
             painter.draw_line(rect.bottom_left().translated(0, 1), rect.bottom_right().translated(0, 1), color);
-    }
+        return IterationDecision::Continue;
+    });
+}
+
+HitTestResult LayoutText::hit_test(const Point& position) const
+{
+    HitTestResult result;
+    for_each_run([&](auto&, auto& rect) {
+        if (rect.contains(position)) {
+            result.layout_node = this;
+            return IterationDecision::Break;
+        }
+        return IterationDecision::Continue;
+    });
+    return result;
 }

Libraries/LibHTML/Layout/LayoutText.h

@@ -26,7 +26,12 @@ public:
 
     const Vector<Run>& runs() const { return m_runs; }
 
+    virtual HitTestResult hit_test(const Point&) const override;
+
 private:
+    template<typename Callback>
+    void for_each_run(Callback) const;
+
     void load_font();
     void compute_runs();