LibGUI: Use a sunken GUI::Frame for the ColorPicker color spectrum

This looks a lot nicer than just a plain widget. :^)

Libraries/LibGUI/ColorPicker.cpp

@@ -61,7 +61,7 @@ class ColorButton : public AbstractButton {
  bool m_selected { false };
 };
 
-class CustomColorWidget final : public GUI::Widget {
+class CustomColorWidget final : public GUI::Frame {
  C_OBJECT(CustomColorWidget);
 
 public:
@@ -414,8 +414,8 @@ void CustomColorWidget::pick_color_at_position(GUI::MouseEvent& event)
  if (!m_being_pressed)
  return;
 
- auto position = event.position();
- if (!rect().contains(position))
+ auto position = event.position().translated(-frame_thickness(), -frame_thickness());
+ if (!frame_inner_rect().contains(position))
  return;
 
  auto color = m_custom_colors->get_pixel(position);
@@ -451,15 +451,17 @@ void CustomColorWidget::mousemove_event(GUI::MouseEvent& event)
 
 void CustomColorWidget::paint_event(GUI::PaintEvent& event)
 {
- GUI::Painter painter(*this);
- Gfx::Rect rect = event.rect();
+ Frame::paint_event(event);
 
- painter.add_clip_rect(rect);
+ Painter painter(*this);
+ painter.add_clip_rect(event.rect());
+ painter.add_clip_rect(frame_inner_rect());
 
- painter.draw_scaled_bitmap(rect, *m_custom_colors, m_custom_colors->rect());
+ painter.draw_scaled_bitmap(frame_inner_rect(), *m_custom_colors, m_custom_colors->rect());
 
- painter.draw_line({ m_last_position.x(), 0 }, { m_last_position.x(), rect.height() }, Color::Black);
- painter.draw_line({ 0, m_last_position.y() }, { rect.width(), m_last_position.y() }, Color::Black);
+ painter.translate(frame_thickness(), frame_thickness());
+ painter.draw_line({ m_last_position.x(), 0 }, { m_last_position.x(), height() }, Color::Black);
+ painter.draw_line({ 0, m_last_position.y() }, { width(), m_last_position.y() }, Color::Black);
 }
 
 void CustomColorWidget::resize_event(ResizeEvent&)