LibWeb: Add a blinking text cursor :^)

Each Web::Frame now has a cursor that sits at a DOM::Position. It will
blink and look like a nice regular text cursor.

It doesn't really do anything yet, but it will eventually.

Libraries/LibWeb/Layout/LayoutText.cpp

@@ -32,6 +32,7 @@
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/Layout/LayoutBlock.h>
 #include <LibWeb/Layout/LayoutText.h>
+#include <LibWeb/Page/Frame.h>
 #include <ctype.h>
 
 namespace Web {
@@ -101,6 +102,28 @@ void LayoutText::paint_fragment(PaintContext& context, const LineBoxFragment& fr
         painter.add_clip_rect(enclosing_int_rect(selection_rect));
         painter.draw_text(enclosing_int_rect(fragment.absolute_rect()), text.substring_view(fragment.start(), fragment.length()), Gfx::TextAlignment::TopLeft, context.palette().selection_text());
     }
+
+    paint_cursor_if_needed(context, fragment);
+}
+
+void LayoutText::paint_cursor_if_needed(PaintContext& context, const LineBoxFragment& fragment) const
+{
+    if (!frame().cursor_blink_state())
+        return;
+
+    if (frame().cursor_position().node() != &node())
+        return;
+
+    if (!(frame().cursor_position().offset() >= (unsigned)fragment.start() && frame().cursor_position().offset() < (unsigned)(fragment.start() + fragment.length())))
+        return;
+
+    auto fragment_rect = fragment.absolute_rect();
+
+    float cursor_x = fragment_rect.x() + specified_style().font().width(fragment.text().substring_view(0, frame().cursor_position().offset() - fragment.start()));
+    float cursor_top = fragment_rect.top();
+    float cursor_height = fragment_rect.height();
+    Gfx::IntRect cursor_rect(cursor_x, cursor_top, 1, cursor_height);
+    context.painter().draw_rect(cursor_rect, context.palette().text_cursor());
 }
 
 template<typename Callback>

Libraries/LibWeb/Layout/LayoutText.h

@@ -54,6 +54,7 @@ public:
 
 private:
     void split_into_lines_by_rules(LayoutBlock& container, LayoutMode, bool do_collapse, bool do_wrap_lines, bool do_wrap_breaks);
+    void paint_cursor_if_needed(PaintContext&, const LineBoxFragment&) const;
 
     template<typename Callback>
     void for_each_chunk(Callback, LayoutMode, bool do_wrap_lines, bool do_wrap_breaks) const;

Libraries/LibWeb/Page/EventHandler.cpp

@@ -150,6 +150,7 @@ 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));
             layout_root()->selection().set({ result.layout_node, result.index_in_node }, {});
             dump_selection("MouseDown");
             m_in_mouse_selection = true;

Libraries/LibWeb/Page/Frame.cpp

@@ -40,6 +40,7 @@ Frame::Frame(DOM::Element& host_element, Frame& main_frame)
     , m_event_handler({}, *this)
     , m_host_element(host_element.make_weak_ptr())
 {
+    setup();
 }
 
 Frame::Frame(Page& page)
@@ -48,12 +49,23 @@ Frame::Frame(Page& page)
     , m_loader(*this)
     , m_event_handler({}, *this)
 {
+    setup();
 }
 
 Frame::~Frame()
 {
 }
 
+void Frame::setup()
+{
+    m_cursor_blink_timer = Core::Timer::construct(500, [this] {
+        if (m_cursor_position.node() && m_cursor_position.node()->layout_node()) {
+            m_cursor_blink_state = !m_cursor_blink_state;
+            m_cursor_position.node()->layout_node()->set_needs_display();
+        }
+    });
+}
+
 void Frame::set_document(DOM::Document* document)
 {
     if (m_document == document)
@@ -168,4 +180,20 @@ Gfx::IntPoint Frame::to_main_frame_position(const Gfx::IntPoint& a_position)
     return position;
 }
 
+void Frame::set_cursor_position(const DOM::Position & position)
+{
+    if (m_cursor_position == position)
+        return;
+
+    if (m_cursor_position.node() && m_cursor_position.node()->layout_node())
+        m_cursor_position.node()->layout_node()->set_needs_display();
+
+    m_cursor_position = position;
+
+    if (m_cursor_position.node() && m_cursor_position.node()->layout_node())
+        m_cursor_position.node()->layout_node()->set_needs_display();
+
+    dbg() << "Cursor position: " << m_cursor_position;
+}
+
 }

Libraries/LibWeb/Page/Frame.h

@@ -30,9 +30,11 @@
 #include <AK/Noncopyable.h>
 #include <AK/RefPtr.h>
 #include <AK/WeakPtr.h>
+#include <LibCore/Timer.h>
 #include <LibGfx/Bitmap.h>
 #include <LibGfx/Rect.h>
 #include <LibGfx/Size.h>
+#include <LibWeb/DOM/Position.h>
 #include <LibWeb/Loader/FrameLoader.h>
 #include <LibWeb/Page/EventHandler.h>
 #include <LibWeb/TreeNode.h>
@@ -83,10 +85,17 @@ public:
     Gfx::IntPoint to_main_frame_position(const Gfx::IntPoint&);
     Gfx::IntRect to_main_frame_rect(const Gfx::IntRect&);
 
+    const DOM::Position& cursor_position() const { return m_cursor_position; }
+    void set_cursor_position(const DOM::Position&);
+
+    bool cursor_blink_state() const { return m_cursor_blink_state; }
+
 private:
     explicit Frame(DOM::Element& host_element, Frame& main_frame);
     explicit Frame(Page&);
 
+    void setup();
+
     Page& m_page;
     Frame& m_main_frame;
 
@@ -97,6 +106,10 @@ private:
     RefPtr<DOM::Document> m_document;
     Gfx::IntSize m_size;
     Gfx::IntRect m_viewport_rect;
+
+    DOM::Position m_cursor_position;
+    RefPtr<Core::Timer> m_cursor_blink_timer;
+    bool m_cursor_blink_state { false };
 };
 
 }