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

src/style.cpp

@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: MIT
+
+// This implementation was based on https://github.com/agauniyal/rang/
+// and adapted for RGBDS.
+
+#include "style.hpp"
+
+#include <stdlib.h> // getenv
+#include <string.h>
+
+#include "platform.hpp" // isatty
+
+#if !STYLE_ANSI
+// clang-format off: maintain `include` order
+	#define WIN32_LEAN_AND_MEAN // Include less from `windows.h`
+	#include <windows.h>
+// clang-format on
+#endif
+
+enum Tribool { TRI_NO, TRI_YES, TRI_MAYBE };
+
+#if !STYLE_ANSI
+static const HANDLE outHandle = GetStdHandle(STD_OUTPUT_HANDLE);
+static const HANDLE errHandle = GetStdHandle(STD_ERROR_HANDLE);
+
+static const WORD defaultAttrib = []() {
+	if (CONSOLE_SCREEN_BUFFER_INFO info; GetConsoleScreenBufferInfo(outHandle, &info)
+	                                     || GetConsoleScreenBufferInfo(errHandle, &info)) {
+		return info.wAttributes;
+	}
+	return static_cast<WORD>((STYLE_BLACK << 4) | (STYLE_GRAY | 8));
+}();
+
+static HANDLE getHandle(FILE *file) {
+	return file == stdout ? outHandle : file == stderr ? errHandle : INVALID_HANDLE_VALUE;
+}
+#endif // !STYLE_ANSI
+
+static Tribool forceStyle = []() {
+	if (char const *forceColor = getenv("FORCE_COLOR");
+	    forceColor && strcmp(forceColor, "") && strcmp(forceColor, "0")) {
+		return TRI_YES;
+	}
+	if (char const *noColor = getenv("NO_COLOR");
+	    noColor && strcmp(noColor, "") && strcmp(noColor, "0")) {
+		return TRI_NO;
+	}
+	return TRI_MAYBE;
+}();
+
+static bool isTerminal(FILE *file) {
+	static bool isOutTerminal = isatty(STDOUT_FILENO);
+	static bool isErrTerminal = isatty(STDERR_FILENO);
+
+	return (file == stdout && isOutTerminal) || (file == stderr && isErrTerminal);
+}
+
+static bool allowStyle(FILE *file) {
+	return forceStyle == TRI_YES || (forceStyle == TRI_MAYBE && isTerminal(file));
+}
+
+void style_Enable(bool enable) {
+	forceStyle = enable ? TRI_YES : TRI_NO;
+}
+
+void style_Set(FILE *file, StyleColor color, bool bold) {
+	if (!allowStyle(file)) {
+		return;
+	}
+
+	// LCOV_EXCL_START
+#if STYLE_ANSI
+	fprintf(file, "\033[%dm", static_cast<int>(color) + (bold ? 90 : 30));
+#else
+	if (HANDLE handle = getHandle(file); handle != INVALID_HANDLE_VALUE) {
+		fflush(file);
+		SetConsoleTextAttribute(handle, (defaultAttrib & ~0xF) | (color | (bold ? 8 : 0)));
+	}
+#endif
+	// LCOV_EXCL_STOP
+}
+
+void style_Reset(FILE *file) {
+	if (!allowStyle(file)) {
+		return;
+	}
+
+	// LCOV_EXCL_START
+#if STYLE_ANSI
+	fputs("\033[m", file);
+#else
+	if (HANDLE handle = getHandle(file); handle != INVALID_HANDLE_VALUE) {
+		fflush(file);
+		SetConsoleTextAttribute(handle, defaultAttrib);
+	}
+#endif
+	// LCOV_EXCL_STOP
+}