WindowServer+LibGUI: Implement automatic cursor tracking.

When a mouse button is pressed inside a window, put that window into an
automatic mouse tracking state where all mouse events are sent to that
window until all mouse buttons are released.

This might feel even better if it only cared about the mouse buttons you
actually pressed while *inside* the windows to get released, I don't know.
I'll have to use it for a while and see how it's like.

LibGUI/GButton.cpp

@@ -46,7 +46,7 @@ void GButton::paint_event(GPaintEvent& event)
 
 void GButton::mousemove_event(GMouseEvent& event)
 {
-    if (m_tracking_cursor) {
+    if (event.buttons() == GMouseButton::Left) {
         bool being_pressed = rect().contains(event.position());
         if (being_pressed != m_being_pressed) {
             m_being_pressed = being_pressed;
@@ -63,8 +63,6 @@ void GButton::mousedown_event(GMouseEvent& event)
 #endif
     if (event.button() == GMouseButton::Left) {
         m_being_pressed = true;
-        m_tracking_cursor = true;
-        set_global_cursor_tracking(true);
         update();
     }
     GWidget::mousedown_event(event);
@@ -84,8 +82,6 @@ void GButton::mouseup_event(GMouseEvent& event)
     if (event.button() == GMouseButton::Left) {
         bool was_being_pressed = m_being_pressed;
         m_being_pressed = false;
-        m_tracking_cursor = false;
-        set_global_cursor_tracking(false);
         update();
         if (was_being_pressed)
             click();

LibGUI/GButton.h

@@ -39,7 +39,6 @@ private:
     RetainPtr<GraphicsBitmap> m_icon;
     GButtonStyle m_button_style { GButtonStyle::Normal };
     bool m_being_pressed { false };
-    bool m_tracking_cursor { false };
     bool m_hovered { false };
 };
 

LibGUI/GCheckBox.cpp

@@ -90,10 +90,10 @@ void GCheckBox::paint_event(GPaintEvent& event)
 
 void GCheckBox::mousemove_event(GMouseEvent& event)
 {
-    if (m_tracking_cursor) {
-        bool being_pressed = rect().contains(event.position());
-        if (being_pressed != m_being_modified) {
-            m_being_modified = being_pressed;
+    if (event.buttons() == GMouseButton::Left) {
+        bool being_modified = rect().contains(event.position());
+        if (being_modified != m_being_modified) {
+            m_being_modified = being_modified;
             update();
         }
     }
@@ -107,8 +107,6 @@ void GCheckBox::mousedown_event(GMouseEvent& event)
 #endif
     if (event.button() == GMouseButton::Left) {
         m_being_modified = true;
-        m_tracking_cursor = true;
-        set_global_cursor_tracking(true);
         update();
     }
     GWidget::mousedown_event(event);
@@ -122,11 +120,8 @@ void GCheckBox::mouseup_event(GMouseEvent& event)
     if (event.button() == GMouseButton::Left) {
         bool was_being_pressed = m_being_modified;
         m_being_modified = false;
-        m_tracking_cursor = false;
-        set_global_cursor_tracking(false);
-        if (was_being_pressed) {
+        if (was_being_pressed)
             set_checked(!is_checked());
-        }
         update();
     }
     GWidget::mouseup_event(event);
@@ -134,7 +129,7 @@ void GCheckBox::mouseup_event(GMouseEvent& event)
 
 void GCheckBox::keydown_event(GKeyEvent& event)
 {
-    if (!m_tracking_cursor && event.key() == KeyCode::Key_Space) {
+    if (event.key() == KeyCode::Key_Space) {
         set_checked(!is_checked());
         update();
     }

LibGUI/GCheckBox.h

@@ -30,6 +30,5 @@ private:
     String m_caption;
     bool m_checked { false };
     bool m_being_modified { false };
-    bool m_tracking_cursor { false };
 };
 

LibGUI/GScrollBar.cpp

@@ -222,7 +222,6 @@ void GScrollBar::mousedown_event(GMouseEvent& event)
         m_scrubbing = true;
         m_scrub_start_value = value();
         m_scrub_origin = event.position();
-        set_global_cursor_tracking(true);
         update();
         return;
     }
@@ -235,7 +234,6 @@ void GScrollBar::mouseup_event(GMouseEvent& event)
     if (!m_scrubbing)
         return;
     m_scrubbing = false;
-    set_global_cursor_tracking(false);
     update();
 }
 

LibGUI/GTextEditor.cpp

@@ -88,7 +88,6 @@ void GTextEditor::mousedown_event(GMouseEvent& event)
         }
 
         m_in_drag_select = true;
-        set_global_cursor_tracking(true);
 
         set_cursor(text_position_at(event.position()));
 
@@ -111,7 +110,6 @@ void GTextEditor::mouseup_event(GMouseEvent& event)
     if (event.button() == GMouseButton::Left) {
         if (m_in_drag_select) {
             m_in_drag_select = false;
-            set_global_cursor_tracking(false);
         }
         return;
     }

LibGUI/GWindow.cpp

@@ -143,21 +143,34 @@ void GWindow::set_rect(const Rect& a_rect)
 void GWindow::event(GEvent& event)
 {
     if (event.is_mouse_event()) {
+        auto& mouse_event = static_cast<GMouseEvent&>(event);
         if (m_global_cursor_tracking_widget) {
-            auto& mouse_event = static_cast<GMouseEvent&>(event);
             auto window_relative_rect = m_global_cursor_tracking_widget->window_relative_rect();
             Point local_point { mouse_event.x() - window_relative_rect.x(), mouse_event.y() - window_relative_rect.y() };
             auto local_event = make<GMouseEvent>(event.type(), local_point, mouse_event.buttons(), mouse_event.button(), mouse_event.modifiers());
             m_global_cursor_tracking_widget->event(*local_event);
+            return;
+        }
+        if (m_automatic_cursor_tracking_widget) {
+            auto window_relative_rect = m_automatic_cursor_tracking_widget->window_relative_rect();
+            Point local_point { mouse_event.x() - window_relative_rect.x(), mouse_event.y() - window_relative_rect.y() };
+            auto local_event = make<GMouseEvent>(event.type(), local_point, mouse_event.buttons(), mouse_event.button(), mouse_event.modifiers());
+            m_automatic_cursor_tracking_widget->event(*local_event);
+            if (mouse_event.buttons() == 0) {
+                m_automatic_cursor_tracking_widget = nullptr;
+                return;
+            }
+            return;
         }
         if (!m_main_widget)
             return;
-        auto& mouse_event = static_cast<GMouseEvent&>(event);
         if (m_main_widget) {
             auto result = m_main_widget->hit_test(mouse_event.x(), mouse_event.y());
             auto local_event = make<GMouseEvent>(event.type(), Point { result.localX, result.localY }, mouse_event.buttons(), mouse_event.button(), mouse_event.modifiers());
             ASSERT(result.widget);
             set_hovered_widget(result.widget);
+            if (mouse_event.buttons() != 0 && !m_automatic_cursor_tracking_widget)
+                m_automatic_cursor_tracking_widget = result.widget->make_weak_ptr();
             if (result.widget != m_global_cursor_tracking_widget.ptr())
                 return result.widget->event(*local_event);
         }
@@ -298,18 +311,16 @@ void GWindow::set_focused_widget(GWidget* widget)
 
 void GWindow::set_global_cursor_tracking_widget(GWidget* widget)
 {
-    ASSERT(m_window_id);
     if (widget == m_global_cursor_tracking_widget.ptr())
         return;
     m_global_cursor_tracking_widget = widget ? widget->make_weak_ptr() : nullptr;
+}
 
-    WSAPI_ClientMessage request;
-    request.type = WSAPI_ClientMessage::Type::SetGlobalCursorTracking;
-    request.window_id = m_window_id;
-    request.value = widget != nullptr;
-    // FIXME: What if the cursor moves out of our interest range before the server can handle this?
-    //        Maybe there could be a response that includes the current cursor location as of enabling.
-    GEventLoop::current().post_message_to_server(request);
+void GWindow::set_automatic_cursor_tracking_widget(GWidget* widget)
+{
+    if (widget == m_automatic_cursor_tracking_widget.ptr())
+        return;
+    m_automatic_cursor_tracking_widget = widget ? widget->make_weak_ptr() : nullptr;
 }
 
 void GWindow::set_has_alpha_channel(bool value)

LibGUI/GWindow.h

@@ -65,6 +65,10 @@ public:
     GWidget* global_cursor_tracking_widget() { return m_global_cursor_tracking_widget.ptr(); }
     const GWidget* global_cursor_tracking_widget() const { return m_global_cursor_tracking_widget.ptr(); }
 
+    void set_automatic_cursor_tracking_widget(GWidget*);
+    GWidget* automatic_cursor_tracking_widget() { return m_automatic_cursor_tracking_widget.ptr(); }
+    const GWidget* automatic_cursor_tracking_widget() const { return m_automatic_cursor_tracking_widget.ptr(); }
+
     bool should_exit_event_loop_on_close() const { return m_should_exit_app_on_close; }
     void set_should_exit_event_loop_on_close(bool b) { m_should_exit_app_on_close = b; }
 
@@ -96,6 +100,7 @@ private:
     GWidget* m_main_widget { nullptr };
     GWidget* m_focused_widget { nullptr };
     WeakPtr<GWidget> m_global_cursor_tracking_widget;
+    WeakPtr<GWidget> m_automatic_cursor_tracking_widget;
     WeakPtr<GWidget> m_hovered_widget;
     Rect m_rect_when_windowless;
     String m_title_when_windowless;

Servers/WindowServer/WSWindow.cpp

@@ -69,6 +69,28 @@ static WSAPI_MouseButton to_api(MouseButton button)
     ASSERT_NOT_REACHED();
 }
 
+void WSWindow::handle_mouse_event(const WSMouseEvent& event)
+{
+    set_automatic_cursor_tracking_enabled(event.buttons() != 0);
+
+    WSAPI_ServerMessage server_message;
+    server_message.window_id = window_id();
+
+    switch (event.type()) {
+    case WSMessage::MouseMove: server_message.type = WSAPI_ServerMessage::Type::MouseMove; break;
+    case WSMessage::MouseDown: server_message.type = WSAPI_ServerMessage::Type::MouseDown; break;
+    case WSMessage::MouseUp: server_message.type = WSAPI_ServerMessage::Type::MouseUp; break;
+    default: ASSERT_NOT_REACHED();
+    }
+
+    server_message.mouse.position = event.position();
+    server_message.mouse.button = to_api(event.button());
+    server_message.mouse.buttons = event.buttons();
+    server_message.mouse.modifiers = event.modifiers();
+
+    m_client->post_message(server_message);
+}
+
 void WSWindow::on_message(WSMessage& message)
 {
     if (m_internal_owner)
@@ -80,28 +102,10 @@ void WSWindow::on_message(WSMessage& message)
     WSAPI_ServerMessage server_message;
     server_message.window_id = window_id();
 
+    if (message.is_mouse_event())
+        return handle_mouse_event(static_cast<const WSMouseEvent&>(message));
+
     switch (message.type()) {
-    case WSMessage::MouseMove:
-        server_message.type = WSAPI_ServerMessage::Type::MouseMove;
-        server_message.mouse.position = static_cast<WSMouseEvent&>(message).position();
-        server_message.mouse.button = WSAPI_MouseButton::NoButton;
-        server_message.mouse.buttons = static_cast<WSMouseEvent&>(message).buttons();
-        server_message.mouse.modifiers = static_cast<WSMouseEvent&>(message).modifiers();
-        break;
-    case WSMessage::MouseDown:
-        server_message.type = WSAPI_ServerMessage::Type::MouseDown;
-        server_message.mouse.position = static_cast<WSMouseEvent&>(message).position();
-        server_message.mouse.button = to_api(static_cast<WSMouseEvent&>(message).button());
-        server_message.mouse.buttons = static_cast<WSMouseEvent&>(message).buttons();
-        server_message.mouse.modifiers = static_cast<WSMouseEvent&>(message).modifiers();
-        break;
-    case WSMessage::MouseUp:
-        server_message.type = WSAPI_ServerMessage::Type::MouseUp;
-        server_message.mouse.position = static_cast<WSMouseEvent&>(message).position();
-        server_message.mouse.button = to_api(static_cast<WSMouseEvent&>(message).button());
-        server_message.mouse.buttons = static_cast<WSMouseEvent&>(message).buttons();
-        server_message.mouse.modifiers = static_cast<WSMouseEvent&>(message).modifiers();
-        break;
     case WSMessage::WindowEntered:
         server_message.type = WSAPI_ServerMessage::Type::WindowEntered;
         break;

Servers/WindowServer/WSWindow.h

@@ -9,6 +9,7 @@
 
 class WSClientConnection;
 class WSMenu;
+class WSMouseEvent;
 
 class WSWindow final : public WSMessageReceiver, public InlineLinkedListNode<WSWindow> {
 public:
@@ -78,7 +79,8 @@ public:
     GraphicsBitmap* last_backing_store() { return m_last_backing_store.ptr(); }
 
     void set_global_cursor_tracking_enabled(bool);
-    bool global_cursor_tracking() const { return m_global_cursor_tracking_enabled; }
+    void set_automatic_cursor_tracking_enabled(bool enabled) { m_automatic_cursor_tracking_enabled = enabled; }
+    bool global_cursor_tracking() const { return m_global_cursor_tracking_enabled || m_automatic_cursor_tracking_enabled; }
 
     bool has_alpha_channel() const { return m_has_alpha_channel; }
     void set_has_alpha_channel(bool value) { m_has_alpha_channel = value; }
@@ -104,12 +106,15 @@ public:
     WSWindow* m_prev { nullptr };
 
 private:
+    void handle_mouse_event(const WSMouseEvent&);
+
     WSClientConnection* m_client { nullptr };
     WSMessageReceiver* m_internal_owner { nullptr };
     String m_title;
     Rect m_rect;
     WSWindowType m_type { WSWindowType::Normal };
     bool m_global_cursor_tracking_enabled { false };
+    bool m_automatic_cursor_tracking_enabled { false };
     bool m_visible { true };
     bool m_has_alpha_channel { false };
     bool m_has_painted_since_last_resize { false };

Servers/WindowServer/WSWindowManager.cpp

@@ -660,7 +660,7 @@ void WSWindowManager::start_window_resize(WSWindow& window, WSMouseEvent& event)
     invalidate(window);
 }
 
-bool WSWindowManager::process_ongoing_window_drag(WSMouseEvent& event, WSWindow*& event_window)
+bool WSWindowManager::process_ongoing_window_drag(WSMouseEvent& event, WSWindow*&)
 {
     if (!m_drag_window)
         return false;
@@ -687,7 +687,7 @@ bool WSWindowManager::process_ongoing_window_drag(WSMouseEvent& event, WSWindow*
     return false;
 }
 
-bool WSWindowManager::process_ongoing_window_resize(WSMouseEvent& event, WSWindow*& event_window)
+bool WSWindowManager::process_ongoing_window_resize(WSMouseEvent& event, WSWindow*&)
 {
     if (!m_resize_window)
         return false;