From c63f2c72cd7b278584dcc70b8294063e89b01ca1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Barnab=C3=A1s=20P=C5=91cze?=
 <barnabas.pocze@ideasonboard.com>
Date: Thu, 18 Dec 2025 18:42:11 +0100
Subject: [PATCH] libcamera: base: log: Add `LIBCAMERA_LOG_COLOR` env var
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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Replace the `LIBCAMERA_NO_LOG_COLOR` env variable with another environment
variable that recognizes the "auto", "yes", "no" values. When set to "auto",
the messages are only colored if the standard error is a tty (as determined
by `isatty()`).

"auto" is the default value. This ensures that the ansi escape codes won't
litter the output if the stderr is redirected to a file, `tee`, etc.

Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 Documentation/runtime_configuration.rst | 12 +++++++-----
 src/libcamera/base/log.cpp              | 18 +++++++++++++-----
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/Documentation/runtime_configuration.rst b/Documentation/runtime_configuration.rst
index ce81ff25..e99ef2fb 100644
--- a/Documentation/runtime_configuration.rst
+++ b/Documentation/runtime_configuration.rst
@@ -98,8 +98,8 @@ LIBCAMERA_LOG_LEVELS
 
    Example value: ``*:DEBUG``
 
-LIBCAMERA_LOG_NO_COLOR
-   Disable coloring of log messages (`more <Notes about debugging_>`__).
+LIBCAMERA_LOG_COLOR
+   Control the coloring of log messages (`more <Notes about debugging_>`__).
 
 LIBCAMERA_IPA_CONFIG_PATH, ipa.config_paths
    Define custom search locations for IPA configurations (`more <IPA configuration_>`__).
@@ -174,12 +174,14 @@ Notes about debugging
 ~~~~~~~~~~~~~~~~~~~~~
 
 The environment variables ``LIBCAMERA_LOG_FILE``, ``LIBCAMERA_LOG_LEVELS`` and
-``LIBCAMERA_LOG_NO_COLOR`` are used to modify the default configuration of the
+``LIBCAMERA_LOG_COLOR`` are used to modify the default configuration of the
 libcamera logger.
 
 By default, libcamera logs all messages to the standard error (std::cerr).
-Messages are colored by default depending on the log level. Coloring can be
-disabled by setting the ``LIBCAMERA_LOG_NO_COLOR`` environment variable.
+The ``LIBCAMERA_LOG_COLOR`` environment variable can be used to control whether
+the messages will be colored or not. The possible values are: ``auto``, ``yes``,
+and ``no``. The default value is ``auto``, which enables coloring if the standard
+error is connected to a TTY.
 
 The default log destination can also be directed to a file by setting the
 ``LIBCAMERA_LOG_FILE`` environment variable to the log file name. This also
diff --git a/src/libcamera/base/log.cpp b/src/libcamera/base/log.cpp
index 81b550e2..6e6d2887 100644
--- a/src/libcamera/base/log.cpp
+++ b/src/libcamera/base/log.cpp
@@ -19,6 +19,7 @@
 #include <string_view>
 #include <syslog.h>
 #include <time.h>
+#include <unistd.h>
 #include <unordered_set>
 
 #include <libcamera/logging.h>
@@ -582,14 +583,21 @@ void Logger::logSetLevel(const char *category, const char *level)
 /**
  * \brief Construct a logger
  *
- * If the environment variable is not set, log to std::cerr. The log messages
- * are then colored by default. This can be overridden by setting the
- * LIBCAMERA_LOG_NO_COLOR environment variable to disable coloring.
+ * If the environment variable is not set, log to std::cerr. The coloring
+ * of log messages can be controlled using the LIBCAMERA_LOG_COLOR environment
+ * variable.
  */
 Logger::Logger()
 {
-	bool color = !utils::secure_getenv("LIBCAMERA_LOG_NO_COLOR");
-	logSetStream(&std::cerr, color);
+	const char *color = utils::secure_getenv("LIBCAMERA_LOG_COLOR");
+	bool wantColor = false;
+
+	if (!color || strcmp(color, "auto") == 0)
+		wantColor = isatty(STDERR_FILENO) == 1;
+	else if (strcmp(color, "yes") == 0)
+		wantColor = true;
+
+	logSetStream(&std::cerr, wantColor);
 
 	parseLogFile();
 	parseLogLevels();