sway/commands/output: Add command to set color profile

This makes it possible to render output buffers in a different color
space, by specifying an ICC profile for the output.

sway/commands/output.c

@@ -10,6 +10,7 @@ static const struct cmd_handler output_handlers[] = {
 	{ "adaptive_sync", output_cmd_adaptive_sync },
 	{ "background", output_cmd_background },
 	{ "bg", output_cmd_background },
+	{ "color_profile", output_cmd_color_profile },
 	{ "disable", output_cmd_disable },
 	{ "dpms", output_cmd_dpms },
 	{ "enable", output_cmd_enable },

sway/commands/output/color_profile.c

@@ -0,0 +1,101 @@
+#include <fcntl.h>
+#include <strings.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <wlr/render/color.h>
+#include "sway/commands.h"
+#include "sway/config.h"
+
+static bool read_file_into_buf(const char *path, void **buf, size_t *size) {
+	/* Why not use fopen/fread directly? glibc will succesfully open directories,
+	 * not just files, and supports seeking on them. Instead, we directly
+	 * work with file descriptors and use the more consistent open/fstat/read. */
+	int fd = open(path, O_RDONLY | O_NOCTTY | O_CLOEXEC);
+	if (fd == -1) {
+		return false;
+	}
+	char *b = NULL;
+	struct stat info;
+	if (fstat(fd, &info) == -1) {
+		goto fail;
+	}
+	// only regular files, to avoid issues with e.g. opening pipes
+	if (!S_ISREG(info.st_mode)) {
+		goto fail;
+	}
+	off_t s = info.st_size;
+	if (s <= 0) {
+		goto fail;
+	}
+	b = calloc(1, s);
+	if (!b) {
+		goto fail;
+	}
+	size_t nread = 0;
+	while (nread < (size_t)s) {
+		size_t to_read = (size_t)s - nread;
+		ssize_t r = read(fd, b + nread, to_read);
+		if ((r == -1 && errno != EINTR) || r == 0) {
+			goto fail;
+		}
+		nread += (size_t)r;
+	}
+	close(fd);
+	*buf = b;
+	*size = (size_t)s;
+	return true; // success
+fail:
+	free(b);
+	close(fd);
+	return false;
+}
+
+struct cmd_results *output_cmd_color_profile(int argc, char **argv) {
+	if (!config->handler_context.output_config) {
+		return cmd_results_new(CMD_FAILURE, "Missing output config");
+	}
+	if (!argc) {
+		return cmd_results_new(CMD_INVALID, "Missing color_profile first argument.");
+	}
+
+	if (strcmp(*argv, "srgb") == 0) {
+		wlr_color_transform_unref(config->handler_context.output_config->color_transform);
+		config->handler_context.output_config->color_transform = NULL;
+		config->handler_context.output_config->set_color_transform = true;
+
+		config->handler_context.leftovers.argc = argc - 1;
+		config->handler_context.leftovers.argv = argv + 1;
+	} else if (strcmp(*argv, "icc") == 0) {
+		if (argc < 2) {
+			return cmd_results_new(CMD_INVALID,
+				"Invalid color profile specification: icc type requires a file");
+		}
+		void *data = NULL;
+		size_t size = 0;
+		if (!read_file_into_buf(argv[1], &data, &size)) {
+			return cmd_results_new(CMD_FAILURE,
+				"Failed to load color profile: could not read ICC file");
+		}
+
+		struct wlr_color_transform *tmp =
+			wlr_color_transform_init_linear_to_icc(data, size);
+		if (!tmp) {
+			free(data);
+			return cmd_results_new(CMD_FAILURE,
+				"Failed to load color profile: failed to initialize transform from ICC");
+		}
+		free(data);
+
+		wlr_color_transform_unref(config->handler_context.output_config->color_transform);
+		config->handler_context.output_config->color_transform = tmp;
+		config->handler_context.output_config->set_color_transform = true;
+
+		config->handler_context.leftovers.argc = argc - 2;
+		config->handler_context.leftovers.argv = argv + 2;
+	} else {
+		return cmd_results_new(CMD_INVALID,
+			"Invalid color profile specification: first argument should be icc|srgb");
+	}
+
+	return NULL;
+}