LibWeb: Specialize hit testing for text cursor purposes

The text cursor follows slightly different "intuitive" rules than the
regular hit testing. Clicking past the right edge of a text box should
still "hit" the text box, and place the cursor at its end, for example.

We solve this by adding a HitTestType enum that is passed to hit_test()
and determines whether past-the-edge candidates are considered.

Libraries/LibWeb/Layout/LayoutBlock.cpp

@@ -717,10 +717,10 @@ void LayoutBlock::paint(PaintContext& context, PaintPhase phase)
     }
 }
 
-HitTestResult LayoutBlock::hit_test(const Gfx::IntPoint& position) const
+HitTestResult LayoutBlock::hit_test(const Gfx::IntPoint& position, HitTestType type) const
 {
     if (!children_are_inline())
-        return LayoutBox::hit_test(position);
+        return LayoutBox::hit_test(position, type);
 
     HitTestResult last_good_candidate;
     for (auto& line_box : m_line_boxes) {
@@ -729,7 +729,7 @@ HitTestResult LayoutBlock::hit_test(const Gfx::IntPoint& position) const
                 continue;
             if (enclosing_int_rect(fragment.absolute_rect()).contains(position)) {
                 if (fragment.layout_node().is_block())
-                    return downcast<LayoutBlock>(fragment.layout_node()).hit_test(position);
+                    return downcast<LayoutBlock>(fragment.layout_node()).hit_test(position, type);
                 return { fragment.layout_node(), fragment.text_index_at(position.x()) };
             }
             if (fragment.absolute_rect().top() <= position.y())
@@ -737,7 +737,7 @@ HitTestResult LayoutBlock::hit_test(const Gfx::IntPoint& position) const
         }
     }
 
-    if (last_good_candidate.layout_node)
+    if (type == HitTestType::TextCursor && last_good_candidate.layout_node)
         return last_good_candidate;
     return { absolute_rect().contains(position.x(), position.y()) ? this : nullptr };
 }

Libraries/LibWeb/Layout/LayoutBlock.h

@@ -49,7 +49,7 @@ public:
     LineBox& ensure_last_line_box();
     LineBox& add_line_box();
 
-    virtual HitTestResult hit_test(const Gfx::IntPoint&) const override;
+    virtual HitTestResult hit_test(const Gfx::IntPoint&, HitTestType) const override;
 
     LayoutBlock* previous_sibling() { return downcast<LayoutBlock>(LayoutNode::previous_sibling()); }
     const LayoutBlock* previous_sibling() const { return downcast<LayoutBlock>(LayoutNode::previous_sibling()); }

Libraries/LibWeb/Layout/LayoutBox.cpp

@@ -224,7 +224,7 @@ void LayoutBox::paint(PaintContext& context, PaintPhase phase)
     }
 }
 
-HitTestResult LayoutBox::hit_test(const Gfx::IntPoint& position) const
+HitTestResult LayoutBox::hit_test(const Gfx::IntPoint& position, HitTestType type) const
 {
     // 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
@@ -233,7 +233,7 @@ HitTestResult LayoutBox::hit_test(const Gfx::IntPoint& position) const
     for_each_child([&](auto& child) {
         if (is<LayoutBox>(child) && downcast<LayoutBox>(child).stacking_context())
             return;
-        auto child_result = child.hit_test(position);
+        auto child_result = child.hit_test(position, type);
         if (child_result.layout_node)
             result = child_result;
     });

Libraries/LibWeb/Layout/LayoutBox.h

@@ -55,7 +55,7 @@ public:
     float absolute_y() const { return absolute_rect().y(); }
     Gfx::FloatPoint absolute_position() const { return absolute_rect().location(); }
 
-    virtual HitTestResult hit_test(const Gfx::IntPoint& absolute_position) const override;
+    virtual HitTestResult hit_test(const Gfx::IntPoint&, HitTestType) const override;
     virtual void set_needs_display() override;
 
     bool is_body() const;

Libraries/LibWeb/Layout/LayoutDocument.cpp

@@ -113,9 +113,9 @@ void LayoutDocument::paint(PaintContext& context, PaintPhase phase)
     stacking_context()->paint(context, phase);
 }
 
-HitTestResult LayoutDocument::hit_test(const Gfx::IntPoint& position) const
+HitTestResult LayoutDocument::hit_test(const Gfx::IntPoint& position, HitTestType type) const
 {
-    return stacking_context()->hit_test(position);
+    return stacking_context()->hit_test(position, type);
 }
 
 }

Libraries/LibWeb/Layout/LayoutDocument.h

@@ -43,7 +43,7 @@ public:
     void paint_all_phases(PaintContext&);
     virtual void paint(PaintContext&, PaintPhase) override;
 
-    virtual HitTestResult hit_test(const Gfx::IntPoint&) const override;
+    virtual HitTestResult hit_test(const Gfx::IntPoint&, HitTestType) const override;
 
     const LayoutRange& selection() const { return m_selection; }
     LayoutRange& selection() { return m_selection; }

Libraries/LibWeb/Layout/LayoutNode.cpp

@@ -102,7 +102,7 @@ void LayoutNode::paint(PaintContext& context, PaintPhase phase)
     });
 }
 
-HitTestResult LayoutNode::hit_test(const Gfx::IntPoint& position) const
+HitTestResult LayoutNode::hit_test(const Gfx::IntPoint& position, HitTestType type) const
 {
     HitTestResult result;
     for_each_child([&](auto& child) {
@@ -110,7 +110,7 @@ HitTestResult LayoutNode::hit_test(const Gfx::IntPoint& position) const
         // The outer loop who called us will take care of those.
         if (is<LayoutBox>(child) && downcast<LayoutBox>(child).stacking_context())
             return;
-        auto child_result = child.hit_test(position);
+        auto child_result = child.hit_test(position, type);
         if (child_result.layout_node)
             result = child_result;
     });

Libraries/LibWeb/Layout/LayoutNode.h

@@ -45,11 +45,16 @@ struct HitTestResult {
     int index_in_node { 0 };
 };
 
+enum class HitTestType {
+    Exact,      // Exact matches only
+    TextCursor, // Clicking past the right/bottom edge of text will still hit the text
+};
+
 class LayoutNode : public TreeNode<LayoutNode> {
 public:
     virtual ~LayoutNode();
 
-    virtual HitTestResult hit_test(const Gfx::IntPoint&) const;
+    virtual HitTestResult hit_test(const Gfx::IntPoint&, HitTestType) const;
 
     bool is_anonymous() const { return !m_node; }
     const DOM::Node* node() const { return m_node; }

Libraries/LibWeb/Page/EventHandler.cpp

@@ -77,7 +77,7 @@ bool EventHandler::handle_mouseup(const Gfx::IntPoint& position, unsigned button
         return false;
     bool handled_event = false;
 
-    auto result = layout_root()->hit_test(position);
+    auto result = layout_root()->hit_test(position, HitTestType::Exact);
     if (result.layout_node && result.layout_node->node()) {
         RefPtr<DOM::Node> node = result.layout_node->node();
         if (is<HTML::HTMLIFrameElement>(*node)) {
@@ -104,7 +104,7 @@ bool EventHandler::handle_mousedown(const Gfx::IntPoint& position, unsigned butt
     NonnullRefPtr document = *m_frame.document();
     auto& page_client = m_frame.page().client();
 
-    auto result = layout_root()->hit_test(position);
+    auto result = layout_root()->hit_test(position, HitTestType::Exact);
     if (!result.layout_node)
         return false;
 
@@ -151,10 +151,13 @@ bool EventHandler::handle_mousedown(const Gfx::IntPoint& position, unsigned butt
         }
     } else {
         if (button == GUI::MouseButton::Left) {
-            m_frame.set_cursor_position(DOM::Position(*node, result.index_in_node));
+            auto result = layout_root()->hit_test(position, HitTestType::TextCursor);
-            layout_root()->selection().set({ result.layout_node, result.index_in_node }, {});
+            if (result.layout_node && result.layout_node->node()) {
-            dump_selection("MouseDown");
+                m_frame.set_cursor_position(DOM::Position(*node, result.index_in_node));
-            m_in_mouse_selection = true;
+                layout_root()->selection().set({ result.layout_node, result.index_in_node }, {});
+                dump_selection("MouseDown");
+                m_in_mouse_selection = true;
+            }
         } else if (button == GUI::MouseButton::Right) {
             page_client.page_did_request_context_menu(m_frame.to_main_frame_position(position));
         }
@@ -171,7 +174,7 @@ bool EventHandler::handle_mousemove(const Gfx::IntPoint& position, unsigned butt
 
     bool hovered_node_changed = false;
     bool is_hovering_link = false;
-    auto result = layout_root()->hit_test(position);
+    auto result = layout_root()->hit_test(position, HitTestType::Exact);
     const HTML::HTMLAnchorElement* hovered_link_element = nullptr;
     if (result.layout_node) {
         RefPtr<DOM::Node> node = result.layout_node->node();
@@ -198,7 +201,10 @@ bool EventHandler::handle_mousemove(const Gfx::IntPoint& position, unsigned butt
                 return true;
         }
         if (m_in_mouse_selection) {
-            layout_root()->selection().set_end({ result.layout_node, result.index_in_node });
+            auto hit = layout_root()->hit_test(position, HitTestType::TextCursor);
+            if (hit.layout_node && hit.layout_node->node()) {
+                layout_root()->selection().set_end({ hit.layout_node, hit.index_in_node });
+            }
             dump_selection("MouseMove");
             page_client.page_did_change_selection();
         }

Libraries/LibWeb/Painting/StackingContext.cpp

@@ -61,19 +61,19 @@ void StackingContext::paint(PaintContext& context, LayoutNode::PaintPhase phase)
     }
 }
 
-HitTestResult StackingContext::hit_test(const Gfx::IntPoint& position) const
+HitTestResult StackingContext::hit_test(const Gfx::IntPoint& position, HitTestType type) const
 {
     HitTestResult result;
     if (!m_box.is_root()) {
-        result = m_box.hit_test(position);
+        result = m_box.hit_test(position, type);
     } else {
         // NOTE: LayoutDocument::hit_test() merely calls StackingContext::hit_test()
         //       so we call its base class instead.
-        result = downcast<LayoutDocument>(m_box).LayoutBlock::hit_test(position);
+        result = downcast<LayoutDocument>(m_box).LayoutBlock::hit_test(position, type);
     }
 
     for (auto* child : m_children) {
-        auto result_here = child->hit_test(position);
+        auto result_here = child->hit_test(position, type);
         if (result_here.layout_node)
             result = result_here;
     }

Libraries/LibWeb/Painting/StackingContext.h

@@ -41,7 +41,7 @@ public:
     const StackingContext* parent() const { return m_parent; }
 
     void paint(PaintContext&, LayoutNode::PaintPhase);
-    HitTestResult hit_test(const Gfx::IntPoint&) const;
+    HitTestResult hit_test(const Gfx::IntPoint&, HitTestType) const;
 
     void dump(int indent = 0) const;