Make buttons unpress when the cursor leaves the button rect.

Implement this functionality by adding global cursor tracking.
It's currently only possible for one GWidget per GWindow to track the cursor.

LibGUI/GButton.cpp

@@ -65,12 +65,24 @@ void GButton::paint_event(GPaintEvent&)
     }
 }
 
+void GButton::mousemove_event(GMouseEvent& event)
+{
+    if (m_tracking_cursor) {
+        bool being_pressed = rect().contains(event.position());
+        if (being_pressed != m_being_pressed) {
+            m_being_pressed = being_pressed;
+            update();
+        }
+    }
+    GWidget::mousemove_event(event);
+}
+
 void GButton::mousedown_event(GMouseEvent& event)
 {
     dbgprintf("Button::mouseDownEvent: x=%d, y=%d, button=%u\n", event.x(), event.y(), (unsigned)event.button());
-
     m_being_pressed = true;
-
+    m_tracking_cursor = true;
+    set_global_cursor_tracking(true);
     update();
     GWidget::mousedown_event(event);
 }
@@ -78,13 +90,15 @@ void GButton::mousedown_event(GMouseEvent& event)
 void GButton::mouseup_event(GMouseEvent& event)
 {
     dbgprintf("Button::mouseUpEvent: x=%d, y=%d, button=%u\n", event.x(), event.y(), (unsigned)event.button());
-
+    bool was_being_pressed = m_being_pressed;
     m_being_pressed = false;
-
+    m_tracking_cursor = false;
+    set_global_cursor_tracking(false);
     update();
     GWidget::mouseup_event(event);
-
-    if (on_click)
-        on_click(*this);
+    if (was_being_pressed) {
+        if (on_click)
+            on_click(*this);
+    }
 }
 

LibGUI/GButton.h

@@ -18,10 +18,12 @@ private:
     virtual void paint_event(GPaintEvent&) override;
     virtual void mousedown_event(GMouseEvent&) override;
     virtual void mouseup_event(GMouseEvent&) override;
+    virtual void mousemove_event(GMouseEvent&) override;
 
     virtual const char* class_name() const override { return "GButton"; }
 
     String m_caption;
     bool m_being_pressed { false };
+    bool m_tracking_cursor { false };
 };
 

LibGUI/GWidget.cpp

@@ -170,3 +170,19 @@ void GWidget::set_font(RetainPtr<Font>&& font)
     else
         m_font = move(font);
 }
+
+void GWidget::set_global_cursor_tracking(bool enabled)
+{
+    auto* win = window();
+    if (!win)
+        return;
+    win->set_global_cursor_tracking_widget(enabled ? this : nullptr);
+}
+
+bool GWidget::global_cursor_tracking() const
+{
+    auto* win = window();
+    if (!win)
+        return false;
+    return win->global_cursor_tracking_widget() == this;
+}

LibGUI/GWidget.h

@@ -88,6 +88,9 @@ public:
     const Font& font() const { return *m_font; }
     void set_font(RetainPtr<Font>&&);
 
+    void set_global_cursor_tracking(bool);
+    bool global_cursor_tracking() const;
+
 private:
     GWindow* m_window { nullptr };
 

LibGUI/GWindow.cpp

@@ -72,6 +72,13 @@ void GWindow::set_rect(const Rect& a_rect)
 void GWindow::event(GEvent& event)
 {
     if (event.is_mouse_event()) {
+        if (m_global_cursor_tracking_widget) {
+            // FIXME: This won't work for widgets-within-widgets.
+            auto& mouse_event = static_cast<GMouseEvent&>(event);
+            Point local_point { mouse_event.x() - m_global_cursor_tracking_widget->relative_rect().x(), mouse_event.y() - m_global_cursor_tracking_widget->relative_rect().y() };
+            auto local_event = make<GMouseEvent>(event.type(), local_point, mouse_event.buttons(), mouse_event.button());
+            m_global_cursor_tracking_widget->event(*local_event);
+        }
         if (!m_main_widget)
             return;
         auto& mouse_event = static_cast<GMouseEvent&>(event);
@@ -158,3 +165,11 @@ void GWindow::set_focused_widget(GWidget* widget)
         m_focused_widget->update();
     }
 }
+
+void GWindow::set_global_cursor_tracking_widget(GWidget* widget)
+{
+    if (widget == m_global_cursor_tracking_widget.ptr())
+        return;
+    m_global_cursor_tracking_widget = widget ? widget->makeWeakPtr() : nullptr;
+    gui_set_global_cursor_tracking_enabled(m_window_id, widget != nullptr);
+}

LibGUI/GWindow.h

@@ -4,6 +4,7 @@
 #include <SharedGraphics/Rect.h>
 #include <SharedGraphics/GraphicsBitmap.h>
 #include <AK/AKString.h>
+#include <AK/WeakPtr.h>
 
 class GWidget;
 
@@ -48,11 +49,16 @@ public:
 
     void update(const Rect& = Rect());
 
+    void set_global_cursor_tracking_widget(GWidget*);
+    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(); }
+
 private:
     RetainPtr<GraphicsBitmap> m_backing;
     int m_window_id { -1 };
     bool m_is_active { false };
     GWidget* m_main_widget { nullptr };
     GWidget* m_focused_widget { nullptr };
+    WeakPtr<GWidget> m_global_cursor_tracking_widget;
 };