1 files changed, 135 insertions, 0 deletions
diff --git a/libgamma_list_methods.c b/libgamma_list_methods.c
new file mode 100644
index 0000000..6b912e1
--- /dev/null
+++ b/libgamma_list_methods.c
@@ -0,0 +1,135 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+/**
+ * Test whether a file descriptor refers to a VT
+ * 
+ * @param   fd  The file descriptor
+ * @return      Whether the file descriptor refers to a VT
+ */
+static int
+is_vt_proper(int fd)
+{
+	char buf[32], digit0;
+
+	/* Get TTY */
+	if (ttyname_r(fd, buf, sizeof(buf) / sizeof(char)))
+		return 0;
+
+	/* Validate TTY path */
+	if (!strcmp(buf, "/dev/console"))
+		return 1;
+	if (strncmp(buf, "/dev/tty", sizeof("/dev/tty") - 1))
+		return 0;
+
+	/* Validate TTY name */
+	digit0 = buf[sizeof("/dev/tty") - 1];
+	return '1' <= digit0 && digit0 <= '9';
+}
+
+
+/**
+ * Test the availability of an adjustment method
+ * 
+ * @param  method     The adjustment method
+ * @param  operation  Allowed values:
+ *                      0: Pass if the environment suggests it will work but is not fake
+ *                      1: Pass if the environment suggests it will work
+ *                      2: Pass if real and not fake
+ *                      3: Pass if real
+ *                      4: Always pass
+ *                    Other values invoke undefined behaviour
+ * @return            Whether the test passed
+ */
+static int
+list_method_test(int method, int operation)
+{
+	libgamma_method_capabilities_t caps;
+	int fd, r, saved_errno;
+
+	libgamma_method_capabilities(&caps, method);
+
+	switch (operation) {
+	case 0:
+		/* Methods that the environment suggests will work, excluding fake */
+		if (caps.fake)
+			return 0;
+		/* fall through */
+
+	case 1:
+		/* Methods that the environment suggests will work, including fake */
+		if (!caps.real)
+			return 0;
+#ifdef HAVE_LIBGAMMA_METHOD_LINUX_DRM
+		if (method == LIBGAMMA_METHOD_LINUX_DRM) {
+			saved_errno = errno;
+			if (is_vt_proper(STDIN_FILENO)) {
+				r = 1;
+			} else if (is_vt_proper(STDOUT_FILENO)) {
+				r = 1;
+			} else if (is_vt_proper(STDERR_FILENO)) {
+				r = 1;
+			} else {
+				r = 0;
+				fd = open("/dev/tty", O_RDONLY);
+				if (fd >= 0) {
+					r = is_vt_proper(fd);
+					close(fd);
+				}
+			}
+			errno = saved_errno;
+			return r;
+		}
+#endif
+#ifdef HAVE_LIBGAMMA_METHOD_DUMMY
+		if (method == LIBGAMMA_METHOD_DUMMY)
+			return 0;
+#endif
+		return caps.default_site_known;
+
+	case 2:
+		/* All real non-fake methods */
+		return caps.real && !caps.fake;
+
+	case 3:
+		/* All real methods */
+		return caps.real;
+
+	default:
+		/* All methods */
+		return 1;
+	}
+}
+
+
+/**
+ * List available adjustment methods by their order of preference based on the environment
+ * 
+ * @param  methods    Output array of methods, should be able to hold `LIBGAMMA_METHOD_COUNT` elements
+ * @param  buf_size   The number of elements that fits in `methods`, it should be `LIBGAMMA_METHOD_COUNT`,
+ *                    This is used to avoid writing outside the output buffer if this library adds new
+ *                    adjustment methods without the users of the library recompiling
+ * @param  operation  Allowed values:
+ *                      0: Methods that the environment suggests will work, excluding fake
+ *                      1: Methods that the environment suggests will work, including fake
+ *                      2: All real non-fake methods
+ *                      3: All real methods
+ *                      4: All methods
+ *                    Other values invoke undefined behaviour
+ * @return            The number of element that have been stored in `methods`, or should
+ *                    have been stored if the buffer was large enough
+ */
+size_t
+libgamma_list_methods(int *restrict methods, size_t buf_size, int operation)
+{
+	size_t n = 0;
+
+#define X(CONST, CNAME, DEPTH, RAMPS)\
+	if (list_method_test(CONST, operation) && n++ < buf_size)\
+		methods[n - 1] = CONST;
+	LIST_AVAILABLE_METHODS(X)
+#undef X
+
+	return n;
+}