add: rainbow_style.h

Signed-off-by: Collecting <collecting@noreply.localhost>

src/citron/util/rainbow_style.h

@@ -0,0 +1,27 @@
+// SPDX-FileCopyrightText: 2025 citron Emulator Project
+
+#pragma once
+
+#include <QProxyStyle>
+#include <QTimer>
+#include <QColor>
+
+class RainbowStyle : public QProxyStyle {
+    Q_OBJECT
+
+public:
+    explicit RainbowStyle(QStyle* baseStyle = nullptr);
+
+    // This intercepts palette requests from every widget in the app
+    QPalette standardPalette() const override;
+
+    // A helper for widgets that need the color directly
+    static QColor GetCurrentHighlightColor();
+
+private slots:
+    void UpdateHue();
+
+private:
+    QTimer* m_timer;
+    static float s_hue;
+};