LibGUI: Notify widgets when their enabled state changes.

This is done by dispatching a (synchronous) "EnabledChange" event that can
be picked up in change_event(). Use this event to kick widgets out of their
"being pressed"-type modes if the user is interacting with them while the
state is programmatically changed.

LibGUI/GAbstractButton.cpp

@@ -124,3 +124,16 @@ void GAbstractButton::paint_text(GPainter& painter, const Rect& rect, const Font
     if (is_focused())
         painter.draw_rect(clipped_rect.inflated(6, 4), Color(140, 140, 140));
 }
+
+void GAbstractButton::change_event(GEvent& event)
+{
+    if (event.type() == GEvent::Type::EnabledChange) {
+        if (!is_enabled()) {
+            bool was_being_pressed = m_being_pressed;
+            m_being_pressed = false;
+            if (was_being_pressed)
+                update();
+        }
+    }
+    GWidget::change_event(event);
+}

LibGUI/GAbstractButton.h

@@ -37,6 +37,7 @@ protected:
     virtual void keydown_event(GKeyEvent&) override;
     virtual void enter_event(CEvent&) override;
     virtual void leave_event(CEvent&) override;
+    virtual void change_event(GEvent&) override;
 
     void paint_text(GPainter&, const Rect&, const Font&, TextAlignment);
 

LibGUI/GEvent.h

@@ -33,6 +33,7 @@ public:
         FocusOut,
         WindowCloseRequest,
         ContextMenu,
+        EnabledChange,
 
         __Begin_WM_Events,
         WM_WindowRemoved,

LibGUI/GScrollBar.cpp

@@ -300,3 +300,12 @@ void GScrollBar::leave_event(CEvent&)
         update();
     }
 }
+
+void GScrollBar::change_event(GEvent& event)
+{
+    if (event.type() == GEvent::Type::EnabledChange) {
+        if (!is_enabled())
+            m_scrubbing = false;
+    }
+    return GWidget::change_event(event);
+}

LibGUI/GScrollBar.h

@@ -42,6 +42,7 @@ private:
     virtual void mouseup_event(GMouseEvent&) override;
     virtual void mousemove_event(GMouseEvent&) override;
     virtual void leave_event(CEvent&) override;
+    virtual void change_event(GEvent&) override;
 
     int button_size() const { return 16; }
     int button_width() const { return orientation() == Orientation::Vertical ? width() : button_size(); }

LibGUI/GSlider.cpp

@@ -120,6 +120,15 @@ void GSlider::leave_event(CEvent& event)
     GWidget::leave_event(event);
 }
 
+void GSlider::change_event(GEvent& event)
+{
+    if (event.type() == GEvent::Type::EnabledChange) {
+        if (!is_enabled()))
+            m_dragging = false;
+    }
+    GWidget::change_event(event);
+}
+
 void GSlider::set_knob_hovered(bool hovered)
 {
     if (m_knob_hovered == hovered)

LibGUI/GSlider.h

@@ -32,6 +32,7 @@ protected:
     virtual void mousemove_event(GMouseEvent&) override;
     virtual void mouseup_event(GMouseEvent&) override;
     virtual void leave_event(CEvent&) override;
+    virtual void change_event(GEvent&) override;
 
 private:
     void set_knob_hovered(bool);

LibGUI/GWidget.cpp

@@ -94,6 +94,8 @@ void GWidget::event(CEvent& event)
         return handle_enter_event(event);
     case GEvent::Leave:
         return handle_leave_event(event);
+    case GEvent::EnabledChange:
+        return change_event(static_cast<GEvent&>(event));
     default:
         return CObject::event(event);
     }
@@ -271,6 +273,10 @@ void GWidget::leave_event(CEvent&)
 {
 }
 
+void GWidget::change_event(GEvent&)
+{
+}
+
 void GWidget::update()
 {
     if (rect().is_empty())
@@ -454,6 +460,8 @@ void GWidget::set_enabled(bool enabled)
     if (m_enabled == enabled)
         return;
     m_enabled = enabled;
+    GEvent e(GEvent::EnabledChange);
+    event(e);
     update();
 }
 

LibGUI/GWidget.h

@@ -67,6 +67,7 @@ public:
     virtual void enter_event(CEvent&);
     virtual void leave_event(CEvent&);
     virtual void child_event(CChildEvent&) override;
+    virtual void change_event(GEvent&);
 
     // This is called after children have been painted.
     virtual void second_paint_event(GPaintEvent&);