LibGUI+WindowServer: Introduce new mouse tracking mechanism

Userland/Libraries/LibGUI/CMakeLists.txt

@@ -66,6 +66,7 @@ set(SOURCES
     Model.cpp
     ModelIndex.cpp
     ModelSelection.cpp
+    MouseTracker.cpp
     MultiView.cpp
     Notification.cpp
     OpacitySlider.cpp

Userland/Libraries/LibGUI/MouseTracker.cpp

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2021, Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibGUI/MouseTracker.h>
+#include <LibGUI/WindowServerConnection.h>
+
+namespace GUI {
+
+MouseTracker::List MouseTracker::s_trackers;
+
+MouseTracker::MouseTracker()
+{
+    if (s_trackers.is_empty()) {
+        WindowServerConnection::the().async_set_global_mouse_tracking(true);
+    }
+    s_trackers.append(*this);
+}
+MouseTracker::~MouseTracker()
+{
+    m_list_node.remove();
+    if (s_trackers.is_empty()) {
+        WindowServerConnection::the().async_set_global_mouse_tracking(false);
+    }
+}
+
+void MouseTracker::track_mouse_move(Badge<WindowServerConnection>, Gfx::IntPoint const& point)
+{
+    for (auto& tracker : s_trackers) {
+        tracker.track_mouse_move(point);
+    }
+}
+
+}

Userland/Libraries/LibGUI/MouseTracker.h

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2021, Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Badge.h>
+#include <AK/Function.h>
+#include <AK/IntrusiveList.h>
+#include <LibGUI/Forward.h>
+#include <LibGfx/Point.h>
+
+namespace GUI {
+
+class MouseTracker {
+public:
+    MouseTracker();
+    virtual ~MouseTracker();
+
+    static void track_mouse_move(Badge<WindowServerConnection>, Gfx::IntPoint const&);
+
+protected:
+    virtual void track_mouse_move(Gfx::IntPoint const&) = 0;
+
+private:
+    IntrusiveListNode<MouseTracker> m_list_node;
+    using List = IntrusiveList<MouseTracker, RawPtr<MouseTracker>, &MouseTracker::m_list_node>;
+    static List s_trackers;
+};
+
+}

Userland/Libraries/LibGUI/WindowServerConnection.cpp

@@ -16,6 +16,7 @@
 #include <LibGUI/EmojiInputDialog.h>
 #include <LibGUI/Event.h>
 #include <LibGUI/Menu.h>
+#include <LibGUI/MouseTracker.h>
 #include <LibGUI/Window.h>
 #include <LibGUI/WindowServerConnection.h>
 #include <LibGfx/Bitmap.h>
@@ -370,6 +371,11 @@ void WindowServerConnection::display_link_notification()
     });
 }
 
+void WindowServerConnection::track_mouse_move(Gfx::IntPoint const& mouse_position)
+{
+    MouseTracker::track_mouse_move({}, mouse_position);
+}
+
 void WindowServerConnection::ping()
 {
     async_pong();

Userland/Libraries/LibGUI/WindowServerConnection.h

@@ -55,6 +55,7 @@ private:
     virtual void update_system_fonts(String const&, String const&) override;
     virtual void window_state_changed(i32, bool, bool) override;
     virtual void display_link_notification() override;
+    virtual void track_mouse_move(Gfx::IntPoint const&) override;
     virtual void ping() override;
 
     bool m_display_link_notification_pending { false };