Add option for colored output

Default is --colors auto which detects if user runs from terminal and
no NO_COLOR env is set.
Argument always forces colors, never prevents them

src/util/cmdlineargs.cpp

@@ -1,29 +1,36 @@
+#include "util/cmdlineargs.h"
+
 #include <stdio.h>
+#include <unistd.h>
+#ifdef __WINDOWS__
+#include <io.h>
+#endif
 
+#include <QProcessEnvironment>
 #include <QStandardPaths>
 
-#include "util/cmdlineargs.h"
-#include "util/version.h"
-
 #include "sources/soundsourceproxy.h"
-
+#include "util/version.h"
 
 CmdlineArgs::CmdlineArgs()
-    : m_startInFullscreen(false), // Initialize vars
-      m_midiDebug(false),
-      m_developer(false),
-      m_safeMode(false),
-      m_debugAssertBreak(false),
-      m_settingsPathSet(false),
-      m_logLevel(mixxx::kLogLevelDefault),
-      m_logFlushLevel(mixxx::kLogFlushLevelDefault),
+        : m_startInFullscreen(false), // Initialize vars
+          m_midiDebug(false),
+          m_developer(false),
+          m_safeMode(false),
+          m_debugAssertBreak(false),
+          m_settingsPathSet(false),
+          m_useColors(false),
+          m_logLevel(mixxx::kLogLevelDefault),
+          m_logFlushLevel(mixxx::kLogFlushLevelDefault),
 // We are not ready to switch to XDG folders under Linux, so keeping $HOME/.mixxx as preferences folder. see lp:1463273
 #ifdef __LINUX__
-    m_settingsPath(QDir::homePath().append("/").append(SETTINGS_PATH)) {
+          m_settingsPath(QDir::homePath().append("/").append(SETTINGS_PATH)) {
 #else
-    // TODO(XXX) Trailing slash not needed anymore as we switches from String::append
-    // to QDir::filePath elsewhere in the code. This is candidate for removal.
-    m_settingsPath(QStandardPaths::writableLocation(QStandardPaths::DataLocation).append("/")) {
+          // TODO(XXX) Trailing slash not needed anymore as we switches from String::append
+          // to QDir::filePath elsewhere in the code. This is candidate for removal.
+          m_settingsPath(
+                  QStandardPaths::writableLocation(QStandardPaths::DataLocation)
+                          .append("/")) {
 #endif
 }
 
@@ -50,6 +57,7 @@ namespace {
 
 bool CmdlineArgs::Parse(int &argc, char **argv) {
     bool logLevelSet = false;
+    auto colorSettings = QString("auto");
     for (int i = 0; i < argc; ++i) {
         if (   argv[i] == QString("-h")
             || argv[i] == QString("--h")
@@ -103,10 +111,36 @@ when a critical error occurs unless this is set properly.\n", stdout);
             m_safeMode = true;
         } else if (QString::fromLocal8Bit(argv[i]).contains("--debugAssertBreak", Qt::CaseInsensitive)) {
             m_debugAssertBreak = true;
+        } else if (QString::fromLocal8Bit(argv[i]).contains(
+                           "--color", Qt::CaseInsensitive) &&
+                i + 1 < argc) {
+            colorSettings = QString::fromLocal8Bit(argv[i + 1]);
         } else {
             m_musicFiles += QString::fromLocal8Bit(argv[i]);
         }
     }
+    if (colorSettings.compare(QLatin1String("auto"), Qt::CaseInsensitive) == 0) {
+        // see https://no-color.org/
+        if (QProcessEnvironment::systemEnvironment().contains(QLatin1String("NO_COLOR"))) {
+            m_useColors = false;
+        } else {
+#ifndef __WINDOWS__
+            if (isatty(fileno(stderr))) {
+                m_useColors = true;
+            }
+#else
+            if (_isatty(_fileno(stderr))) {
+                m_useColors = true;
+            }
+#endif
+        }
+    } else if (colorSettings.compare(QLatin1String("always"), Qt::CaseInsensitive) == 0) {
+        m_useColors = true;
+    } else if (colorSettings.compare(QLatin1String("never"), Qt::CaseInsensitive) == 0) {
+        m_useColors = false;
+    } else {
+        qWarning() << "Unknown setting for color, ignoring";
+    }
 
     // If --logLevel was unspecified and --developer is enabled then set
     // logLevel to debug.
@@ -152,6 +186,8 @@ void CmdlineArgs::printUsage() {
                         and spinning vinyl widgets. Try this option if\n\
                         Mixxx is crashing on startup.\n\
 \n\
+--color auto            [auto|always|never] Use colors on the console output.\n\
+\n\
 --locale LOCALE         Use a custom locale for loading translations\n\
                         (e.g 'fr')\n\
 \n\
@@ -169,14 +205,15 @@ void CmdlineArgs::printUsage() {
                         defined at --logLevel above.\n\
 \n"
 #ifdef MIXXX_BUILD_DEBUG
-"\
+          "\
 --debugAssertBreak      Breaks (SIGINT) Mixxx, if a DEBUG_ASSERT\n\
                         evaluates to false. Under a debugger you can\n\
                         continue afterwards.\
 \n"
 #endif
-"\
--h, --help              Display this help message and exit", stdout);
+          "\
+-h, --help              Display this help message and exit",
+            stdout);
 
     fputs("\n\n(For more information, see http://mixxx.org/wiki/doku.php/command_line_options)\n",stdout);
 }

src/util/cmdlineargs.h

@@ -28,6 +28,9 @@ class CmdlineArgs final {
     bool getMidiDebug() const { return m_midiDebug; }
     bool getDeveloper() const { return m_developer; }
     bool getSafeMode() const { return m_safeMode; }
+    bool useColors() const {
+        return m_useColors;
+    }
     bool getDebugAssertBreak() const { return m_debugAssertBreak; }
     bool getSettingsPathSet() const { return m_settingsPathSet; }
     mixxx::LogLevel getLogLevel() const { return m_logLevel; }
@@ -50,6 +53,7 @@ class CmdlineArgs final {
     bool m_safeMode;
     bool m_debugAssertBreak;
     bool m_settingsPathSet; // has --settingsPath been set on command line ?
+    bool m_useColors;       // should colors be used
     mixxx::LogLevel m_logLevel; // Level of stderr logging message verbosity
     mixxx::LogLevel m_logFlushLevel; // Level of mixx.log file flushing
     QString m_locale;

src/util/logging.cpp

@@ -16,6 +16,7 @@
 
 #include "controllers/controllerdebug.h"
 #include "util/assert.h"
+#include "util/cmdlineargs.h"
 
 namespace {
 
@@ -36,6 +37,22 @@ const QString kThreadNamePattern = QStringLiteral("{{threadname}}");
 const QString kDefaultMessagePattern = QStringLiteral("%{type} [") +
         kThreadNamePattern + QStringLiteral("] %{message}");
 
+const QString kDefaultMessagePatternColor =
+        QStringLiteral(
+                "\033[32m%{time h:mm:ss.zzz}\033[0m "
+                "%{if-category}\033[35m %{category}:\033[35m%{endif}"
+                "[\033[97m") +
+        kThreadNamePattern +
+        QStringLiteral(
+                "\033[0m] "
+                "%{if-debug}\033[34m%{type} \033[36m%{function}%{endif}"
+                "%{if-info}\033[32m%{type}%{endif}"
+                "%{if-warning}\033[93m%{type}%{endif}"
+                "%{if-critical}\033[91m%{type}%{endif}"
+                "%{if-fatal}\033[97m\033[41m%{type} "
+                "\033[30m%{file}:%{line}%{endif}"
+                "\033[0m  %{message}");
+
 const QLoggingCategory kDefaultLoggingCategory = QLoggingCategory(nullptr);
 
 enum class WriteFlag {
@@ -319,7 +336,11 @@ void Logging::initialize(
     s_debugAssertBreak = debugAssertBreak;
 
     if (qEnvironmentVariableIsEmpty("QT_MESSAGE_PATTERN")) {
-        qSetMessagePattern(kDefaultMessagePattern);
+        if (CmdlineArgs::Instance().useColors()) {
+            qSetMessagePattern(kDefaultMessagePatternColor);
+        } else {
+            qSetMessagePattern(kDefaultMessagePattern);
+        }
     }
 
     // Install the Qt message handler.