LibGUI+WindowServer: Introduce new mouse tracking mechanism

Author: https://github.com/BenWiederhake
Commit: https://github.com/SerenityOS/serenity/commit/45126655cdd
Pull-request: https://github.com/SerenityOS/serenity/pull/9881

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 };

Userland/Services/WindowServer/ClientConnection.cpp

@@ -663,6 +663,11 @@ void ClientConnection::set_global_cursor_tracking(i32 window_id, bool enabled)
     it->value->set_global_cursor_tracking_enabled(enabled);
 }
 
+void ClientConnection::set_global_mouse_tracking(bool enabled)
+{
+    m_does_global_mouse_tracking = enabled;
+}
+
 void ClientConnection::set_window_cursor(i32 window_id, i32 cursor_type)
 {
     auto it = m_windows.find(window_id);

Userland/Services/WindowServer/ClientConnection.h

@@ -38,6 +38,7 @@ public:
     ~ClientConnection() override;
 
     bool is_unresponsive() const { return m_unresponsive; }
+    bool does_global_mouse_tracking() const { return m_does_global_mouse_tracking; }
 
     static ClientConnection* from_client_id(int client_id);
     static void for_each_client(Function<void(ClientConnection&)>);
@@ -113,6 +114,7 @@ private:
     virtual void invalidate_rect(i32, Vector<Gfx::IntRect> const&, bool) override;
     virtual void did_finish_painting(i32, Vector<Gfx::IntRect> const&) override;
     virtual void set_global_cursor_tracking(i32, bool) override;
+    virtual void set_global_mouse_tracking(bool) override;
     virtual void set_window_opacity(i32, float) override;
     virtual void set_window_backing_store(i32, i32, i32, IPC::File const&, i32, bool, Gfx::IntSize const&, bool) override;
     virtual void set_window_has_alpha_channel(i32, bool) override;
@@ -179,6 +181,7 @@ private:
     bool m_has_display_link { false };
     bool m_show_screen_number { false };
     bool m_unresponsive { false };
+    bool m_does_global_mouse_tracking { false };
 
     // Need this to get private client connection stuff
     friend WMClientConnection;

Userland/Services/WindowServer/WindowClient.ipc

@@ -44,5 +44,7 @@ endpoint WindowClient
 
     display_link_notification() =|
 
+    track_mouse_move(Gfx::IntPoint mouse_position) =|
+
     ping() =|
 }

Userland/Services/WindowServer/WindowManager.cpp

@@ -1200,15 +1200,18 @@ void WindowManager::process_mouse_event(MouseEvent& event)
     if (process_ongoing_drag(event))
         return;
 
-    // 2. Send the mouse event to all windows with global cursor tracking enabled.
-    // The active input tracking window is excluded here because we're sending the event to it
-    // in the next step.
+    // 2. Send the mouse event to all clients with global cursor tracking enabled.
     auto& window_stack = current_window_stack();
     for_each_visible_window_from_front_to_back([&](Window& window) {
         if (window.global_cursor_tracking() && &window != window_stack.active_input_tracking_window())
             deliver_mouse_event(window, event, false);
         return IterationDecision::Continue;
     });
+    ClientConnection::for_each_client([&](ClientConnection& conn) {
+        if (conn.does_global_mouse_tracking()) {
+            conn.async_track_mouse_move(event.position());
+        }
+    });
 
     // 3. If there's an active input tracking window, all mouse events go there.
     //    Tracking ends after all mouse buttons have been released.

Userland/Services/WindowServer/WindowServer.ipc

@@ -75,6 +75,7 @@ endpoint WindowServer
     did_finish_painting(i32 window_id, Vector<Gfx::IntRect> rects) =|
 
     set_global_cursor_tracking(i32 window_id, bool enabled) =|
+    set_global_mouse_tracking(bool enabled) =|
     set_window_opacity(i32 window_id, float opacity) =|
 
     set_window_alpha_hit_threshold(i32 window_id, float threshold) =|