LibGUI: Add Widget override cursor concept

We got ourselves into a mess by making widgets override the window
cursor whenever they wanted a custom cursor. This patch introduces a
better solution to that issue: per-widget override cursors.

Each widget now has an override cursor that overrides the window
cursor when that widget is hovered.

Libraries/LibGUI/Widget.cpp

@@ -318,12 +318,14 @@ void Widget::handle_mousedoubleclick_event(MouseEvent& event)
 
 void Widget::handle_enter_event(Core::Event& event)
 {
+    window()->update_cursor({});
     show_tooltip();
     enter_event(event);
 }
 
 void Widget::handle_leave_event(Core::Event& event)
 {
+    window()->update_cursor({});
     Application::the()->hide_tooltip();
     leave_event(event);
 }
@@ -878,4 +880,14 @@ Gfx::IntRect Widget::children_clip_rect() const
     return rect();
 }
 
+void Widget::set_override_cursor(Gfx::StandardCursor cursor)
+{
+    if (m_override_cursor == cursor)
+        return;
+
+    m_override_cursor = cursor;
+    if (auto* window = this->window())
+        window->update_cursor({});
+}
+
 }

Libraries/LibGUI/Widget.h

@@ -36,6 +36,7 @@
 #include <LibGfx/Forward.h>
 #include <LibGfx/Orientation.h>
 #include <LibGfx/Rect.h>
+#include <LibGfx/StandardCursor.h>
 
 #define REGISTER_WIDGET(class_name)                           \
     extern WidgetClassRegistration registration_##class_name; \
@@ -277,6 +278,9 @@ public:
 
     virtual Gfx::IntRect children_clip_rect() const;
 
+    Gfx::StandardCursor override_cursor() const { return m_override_cursor; }
+    void set_override_cursor(Gfx::StandardCursor);
+
 protected:
     Widget();
 
@@ -349,6 +353,8 @@ private:
     NonnullRefPtr<Gfx::PaletteImpl> m_palette;
 
     WeakPtr<Widget> m_focus_proxy;
+
+    Gfx::StandardCursor m_override_cursor { Gfx::StandardCursor::None };
 };
 
 inline Widget* Widget::parent_widget()

Libraries/LibGUI/Window.cpp

@@ -228,23 +228,20 @@ void Window::set_window_type(WindowType window_type)
 
 void Window::set_cursor(Gfx::StandardCursor cursor)
 {
-    if (!is_visible())
+    if (m_cursor == cursor)
         return;
-    if (!m_custom_cursor && m_cursor == cursor)
-        return;
-    WindowServerConnection::the().send_sync<Messages::WindowServer::SetWindowCursor>(m_window_id, (u32)cursor);
     m_cursor = cursor;
     m_custom_cursor = nullptr;
+    update_cursor();
 }
 
 void Window::set_cursor(const Gfx::Bitmap& cursor)
 {
-    if (!is_visible())
+    if (m_custom_cursor == &cursor)
-        return;
-    if (&cursor == m_custom_cursor.ptr())
         return;
+    m_cursor = Gfx::StandardCursor::None;
     m_custom_cursor = &cursor;
-    WindowServerConnection::the().send_sync<Messages::WindowServer::SetWindowCustomCursor>(m_window_id, m_custom_cursor->to_shareable_bitmap(WindowServerConnection::the().server_pid()));
+    update_cursor();
 }
 
 void Window::handle_drop_event(DropEvent& event)
@@ -871,4 +868,24 @@ void Window::set_progress(int progress)
     ASSERT(m_window_id);
     WindowServerConnection::the().post_message(Messages::WindowServer::SetWindowProgress(m_window_id, progress));
 }
+
+void Window::update_cursor()
+{
+    Gfx::StandardCursor new_cursor;
+
+    if (m_hovered_widget && m_hovered_widget->override_cursor() != Gfx::StandardCursor::None)
+        new_cursor = m_hovered_widget->override_cursor();
+    else
+        new_cursor = m_cursor;
+
+    if (m_effective_cursor == new_cursor)
+        return;
+    m_effective_cursor = new_cursor;
+
+    if (m_custom_cursor)
+        WindowServerConnection::the().send_sync<Messages::WindowServer::SetWindowCustomCursor>(m_window_id, m_custom_cursor->to_shareable_bitmap(WindowServerConnection::the().server_pid()));
+    else
+        WindowServerConnection::the().send_sync<Messages::WindowServer::SetWindowCursor>(m_window_id, (u32)m_effective_cursor);
+}
+
 }

Libraries/LibGUI/Window.h

@@ -196,6 +196,8 @@ public:
 
     void set_progress(int);
 
+    void update_cursor(Badge<Widget>) { update_cursor(); }
+
 protected:
     Window(Core::Object* parent = nullptr);
     virtual void wm_event(WMEvent&);
@@ -203,6 +205,8 @@ protected:
 private:
     virtual bool is_window() const override final { return true; }
 
+    void update_cursor();
+
     void handle_drop_event(DropEvent&);
     void handle_mouse_event(MouseEvent&);
     void handle_multi_paint_event(MultiPaintEvent&);
@@ -242,6 +246,7 @@ private:
     Color m_background_color { Color::WarmGray };
     WindowType m_window_type { WindowType::Normal };
     Gfx::StandardCursor m_cursor { Gfx::StandardCursor::None };
+    Gfx::StandardCursor m_effective_cursor { Gfx::StandardCursor::None };
     bool m_is_active { false };
     bool m_is_active_input { false };
     bool m_has_alpha_channel { false };