feat: add Preferences dialog for managing theme, rendering, and unit settings

app/gcompose/src/Settings.h

@@ -23,6 +23,11 @@ public:
         Dimensionless
     };
 
+    enum Theme {
+        Dark,
+        Bright
+    };
+
     void SetPreferredUnit(Dimension dim, const std::string& unit) {
         m_PreferredUnits[dim] = unit;
     }
@@ -64,9 +69,17 @@ public:
         return Dimensionless;
     }
 
+    bool GetThrottledRendering() const { return m_ThrottledRendering; }
+    void SetThrottledRendering(bool enabled) { m_ThrottledRendering = enabled; }
+
+    Theme GetTheme() const { return m_Theme; }
+    void SetTheme(Theme theme) { m_Theme = theme; }
+
 private:
-    Settings() {}
+    Settings() : m_ThrottledRendering(true), m_Theme(Dark) {}
     std::map<Dimension, std::string> m_PreferredUnits;
+    bool m_ThrottledRendering;
+    Theme m_Theme;
 };
 
 } // namespace Qt