Rename proto-palettes to color sets (copied from rsgbds)

include/gfx/color_set.hpp

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: MIT
+
+#ifndef RGBDS_GFX_COLOR_SET_HPP
+#define RGBDS_GFX_COLOR_SET_HPP
+
+#include <array>
+#include <stddef.h>
+#include <stdint.h>
+
+class ColorSet {
+public:
+	static constexpr size_t capacity = 4;
+
+private:
+	// Up to 4 colors, sorted, and where SIZE_MAX means the slot is empty
+	// (OK because it's not a valid color index)
+	// Sorting is done on the raw numerical values to lessen `compare`'s complexity
+	std::array<uint16_t, capacity> _colorIndices{UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX};
+
+public:
+	// Adds the specified color to the set, or **silently drops it** if the set is full.
+	void add(uint16_t color);
+
+	enum ComparisonResult {
+		NEITHER,
+		WE_BIGGER,
+		THEY_BIGGER = -1,
+	};
+	ComparisonResult compare(ColorSet const &other) const;
+
+	size_t size() const;
+	bool empty() const;
+
+	decltype(_colorIndices)::const_iterator begin() const;
+	decltype(_colorIndices)::const_iterator end() const;
+};
+
+#endif // RGBDS_GFX_COLOR_SET_HPP