Implement swaygrab for still images

sway.1.txt

@@ -81,4 +81,4 @@ source contributors. For more information about sway development, see
 See Also
 --------
 
-**sway**(5)
+**sway**(5) **swaymsg**(1) **swaygrab**(1)

swaygrab.1.txt

@@ -31,6 +31,15 @@ Options
 	Use the specified socket path. Otherwise, swaymsg will ask sway where the
 	socket is (which is the value of $SWAYSOCK, then of $I3SOCK).
 
+Examples
+--------
+
+swaygrab HDMI-A-1 output.png::
+	Grab the contents of HDMI-A-1 and write to output.png.
+
+swaygrab -c HDMI-A-1 output.webm::
+	Capture a webm of HDMI-A-1.
+
 Authors
 -------
 

swaygrab/main.c

@@ -1,5 +1,9 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+#include <getopt.h>
+#include <unistd.h>
+#include <math.h>
 #include "log.h"
 #include "ipc-client.h"
 
@@ -7,8 +11,42 @@ void sway_terminate(void) {
 	exit(1);
 }
 
-int main(int argc, const char **argv) {
-	int capture;
+int numlen(int n) {
+	if (n >= 1000000) return 7;
+	if (n >= 100000) return 6;
+	if (n >= 10000) return 5;
+	if (n >= 1000) return 4;
+	if (n >= 100) return 3;
+	if (n >= 10) return 2;
+	return 1;
+}
+
+void grab_and_apply_magick(const char *file, const char *output, int socketfd) {
+	uint32_t len = strlen(output);
+	char *pixels = ipc_single_command(socketfd,
+			IPC_SWAY_GET_PIXELS, output, &len);
+	uint32_t *u32pixels = (uint32_t *)(pixels + 1);
+	uint32_t width = u32pixels[0];
+	uint32_t height = u32pixels[1];
+	pixels += 9;
+
+	if (width == 0 || height == 0) {
+		sway_abort("Unknown output %s.", output);
+	}
+
+	const char *fmt = "convert -depth 8 -size %dx%d+0 rgba:- -flip %s";
+	char *cmd = malloc(strlen(fmt) - 6 /*args*/
+			+ numlen(width) + numlen(height) + strlen(file) + 1);
+	sprintf(cmd, fmt, width, height, file);
+
+	FILE *f = popen(cmd, "w");
+	fwrite(pixels, 1, len, f);
+	fflush(f);
+	fclose(f);
+}
+
+int main(int argc, char **argv) {
+	static int capture = 0;
 	char *socket_path = NULL;
 
 	init_log(L_INFO);
@@ -51,15 +89,21 @@ int main(int argc, const char **argv) {
 		}
 	}
 
-	if (optind >= argc) {
-		sway_abort("Expected output file on command line. See `man swaygrab`");
+	if (optind >= argc - 1) {
+		sway_abort("Expected output and file on command line. See `man swaygrab`");
 	}
 
-	char *out = argv[optind];
+	char *file = argv[optind + 1];
+	char *output = argv[optind];
 	int socketfd = ipc_open_socket(socket_path);
 	free(socket_path);
 
+	if (!capture) {
+		grab_and_apply_magick(file, output, socketfd);
+	} else {
+		sway_abort("Capture is not yet supported");
+	}
+
 	close(socketfd);
-	free(out);
 	return 0;
 }