Use colored/styled text output for diagnostics and usage info (#1775)

include/style.hpp

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: MIT
+
+#ifndef RGBDS_STYLE_HPP
+#define RGBDS_STYLE_HPP
+
+#include <stdio.h>
+
+#if defined(_MSC_VER) || defined(__MINGW32__) || defined(__CYGWIN__)
+	#define STYLE_ANSI 0
+#else
+	#define STYLE_ANSI 1
+#endif
+
+enum StyleColor {
+#if STYLE_ANSI
+	// Values analogous to ANSI foreground and background SGR colors
+	STYLE_BLACK,
+	STYLE_RED,
+	STYLE_GREEN,
+	STYLE_YELLOW,
+	STYLE_BLUE,
+	STYLE_MAGENTA,
+	STYLE_CYAN,
+	STYLE_GRAY,
+#else
+	// Values analogous to `FOREGROUND_*` constants from `windows.h`
+	STYLE_BLACK,
+	STYLE_BLUE,    // bit 0
+	STYLE_GREEN,   // bit 1
+	STYLE_CYAN,    // STYLE_BLUE | STYLE_GREEN
+	STYLE_RED,     // bit 2
+	STYLE_MAGENTA, // STYLE_BLUE | STYLE_RED
+	STYLE_YELLOW,  // STYLE_GREEN | STYLE_RED
+	STYLE_GRAY,    // STYLE_BLUE | STYLE_GREEN | STYLE_RED
+#endif
+};
+
+void style_Enable(bool enable);
+void style_Set(FILE *file, StyleColor color, bool bold);
+void style_Reset(FILE *file);
+
+#endif // RGBDS_STYLE_HPP