DisplaySettings: Give the UI a facelift :^)

- Split the main UI into two tabs: "Background" and "Monitor".
- Use a GUI::IconView for selecting background pictures.
- Tweak layout, spacing, etc.

Userland/Applications/DisplaySettings/BackgroundSettingsWidget.h

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2019-2020, Jesse Buhagiar <jooster669@gmail.com>
+ * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include "MonitorWidget.h"
+#include <LibCore/Timer.h>
+#include <LibGUI/ColorInput.h>
+#include <LibGUI/ComboBox.h>
+#include <LibGUI/RadioButton.h>
+
+namespace DisplaySettings {
+
+class BackgroundSettingsWidget : public GUI::Widget {
+    C_OBJECT(BackgroundSettingsWidget);
+
+public:
+    virtual ~BackgroundSettingsWidget() override;
+
+    void apply_settings();
+
+private:
+    BackgroundSettingsWidget();
+
+    void create_frame();
+    void load_current_settings();
+
+    Vector<String> m_modes;
+
+    RefPtr<DisplaySettings::MonitorWidget> m_monitor_widget;
+    RefPtr<GUI::IconView> m_wallpaper_view;
+    RefPtr<GUI::ComboBox> m_mode_combo;
+    RefPtr<GUI::ColorInput> m_color_input;
+};
+
+}