Fix: common: improve color support handling

With this patch, terminal color codes are emitted by Babeltrace modules
if the `BABELTRACE_TERM_COLOR` environment variable is set to `ALWAYS`
or if all the following conditions are satisfied:

1. The `BABELTRACE_TERM_COLOR` environement variable is not set to
   `NEVER`.
2. The `TERM` environment variable starts with `xterm`, `rxvt`,
   `konsole`, `gnome`, `screen`, `tmux`, or `putty`.
3. For both the standard output and error streams: its file descriptor
   is a TTY.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/common/common.c b/common/common.c
index aa67b21f39528436b0d865f37428193ae9777c6e..3020b60ffd1a1bbd39d6fc1ba16f65736883b198 100644 (file)
--- a/common/common.c
+++ b/common/common.c
@@ -28,11 +28,13 @@
 #include <unistd.h>
 #include <string.h>
 #include <sys/types.h>
+#include <sys/stat.h>
 #include <unistd.h>
 #include <assert.h>
 #include <ctype.h>
 #include <glib.h>
 #include <stdlib.h>
+#include <stdbool.h>
 #include <babeltrace/babeltrace-internal.h>
 #include <babeltrace/common-internal.h>
 #include <babeltrace/compat/unistd-internal.h>
@@ -240,13 +242,37 @@ end:
        return ret;
 }
 
+static
+bool isarealtty(int fd)
+{
+       bool istty = false;
+       struct stat tty_stats;
+
+       if (!isatty(fd)) {
+               /* Not a TTY */
+               goto end;
+       }
+
+       if (fstat(fd, &tty_stats) == 0) {
+               if (!S_ISCHR(tty_stats.st_mode)) {
+                       /* Not a character device: not a TTY */
+                       goto end;
+               }
+       }
+
+       istty = true;
+
+end:
+       return istty;
+}
+
 BT_HIDDEN
 bool bt_common_colors_supported(void)
 {
        static bool supports_colors = false;
        static bool supports_colors_set = false;
-       const char *term;
-       const char *force;
+       const char *term_env_var;
+       const char *term_color_env_var;
 
        if (supports_colors_set) {
                goto end;
@@ -254,28 +280,39 @@ bool bt_common_colors_supported(void)
 
        supports_colors_set = true;
 
-       force = getenv("BABELTRACE_FORCE_COLORS");
-       if (force && strcmp(force, "1") == 0) {
-               supports_colors = true;
-               goto end;
+       /*
+        * `BABELTRACE_TERM_COLOR` environment variable always overrides
+        * the automatic color support detection.
+        */
+       term_color_env_var = getenv("BABELTRACE_TERM_COLOR");
+       if (term_color_env_var) {
+               if (g_ascii_strcasecmp(term_color_env_var, "always") == 0) {
+                       /* Force colors */
+                       supports_colors = true;
+               } else if (g_ascii_strcasecmp(term_color_env_var, "never") == 0) {
+                       /* Force no colors */
+                       goto end;
+               }
        }
 
-       term = getenv("TERM");
-       if (!term) {
+       /* We need a compatible, known terminal */
+       term_env_var = getenv("TERM");
+       if (!term_env_var) {
                goto end;
        }
 
-       if (strncmp(term, "xterm", 5) != 0 &&
-                       strncmp(term, "rxvt", 4) != 0 &&
-                       strncmp(term, "konsole", 7) != 0 &&
-                       strncmp(term, "gnome", 5) != 0 &&
-                       strncmp(term, "screen", 5) != 0 &&
-                       strncmp(term, "tmux", 4) != 0 &&
-                       strncmp(term, "putty", 5) != 0) {
+       if (strncmp(term_env_var, "xterm", 5) != 0 &&
+                       strncmp(term_env_var, "rxvt", 4) != 0 &&
+                       strncmp(term_env_var, "konsole", 7) != 0 &&
+                       strncmp(term_env_var, "gnome", 5) != 0 &&
+                       strncmp(term_env_var, "screen", 5) != 0 &&
+                       strncmp(term_env_var, "tmux", 4) != 0 &&
+                       strncmp(term_env_var, "putty", 5) != 0) {
                goto end;
        }
 
-       if (!isatty(1)) {
+       /* Both standard output and error streams need to be TTYs */
+       if (!isarealtty(STDOUT_FILENO) || !isarealtty(STDERR_FILENO)) {
                goto end;
        }