[AlwaysOnTop] Proof of concept (#14360)

Co-authored-by: Niels Laute <niels.laute@live.nl>

src/modules/alwaysontop/AlwaysOnTop/Settings.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include <unordered_set>
+
+#include <common/SettingsAPI/FileWatcher.h>
+#include <common/SettingsAPI/settings_objects.h>
+
+#include <SettingsConstants.h>
+
+class SettingsObserver;
+
+// Needs to be kept in sync with src\settings-ui\Settings.UI.Library\AlwaysOnTopProperties.cs
+struct Settings
+{
+    PowerToysSettings::HotkeyObject hotkey = PowerToysSettings::HotkeyObject::from_settings(true, true, false, false, 84); // win + ctrl + T
+    bool enableFrame = true;
+    bool enableSound = true;
+    bool blockInGameMode = true;
+    float frameThickness = 15.0f;
+    COLORREF frameColor = RGB(0, 173, 239);
+    std::vector<std::wstring> excludedApps{};
+};
+
+class AlwaysOnTopSettings
+{
+public:
+    static AlwaysOnTopSettings& instance();
+    static inline const Settings& settings()
+    {
+        return instance().m_settings;
+    }
+
+    void InitFileWatcher();
+    static std::wstring GetSettingsFileName();
+
+    void AddObserver(SettingsObserver& observer);
+    void RemoveObserver(SettingsObserver& observer);
+
+    void LoadSettings();
+
+private:
+    AlwaysOnTopSettings();
+    ~AlwaysOnTopSettings() = default;
+
+    Settings m_settings;
+    std::unique_ptr<FileWatcher> m_settingsFileWatcher;
+    std::unordered_set<SettingsObserver*> m_observers;
+
+    void NotifyObservers(SettingId id) const;
+};