Sway: Configuration: Support for escaping line breaks.

Escape line return in configuration file with the '\' character. Similar
to shell scripts.

Signed-off-by: Roosembert Palacios <roosembert.palacios@epfl.ch>

sway/config.c

@@ -455,10 +455,11 @@ bool load_include_configs(const char *path, struct sway_config *config) {
 
 bool read_config(FILE *file, struct sway_config *config) {
 	bool success = true;
+	bool multiline = false;
 	enum cmd_status block = CMD_BLOCK_END;
 
 	int line_number = 0;
-	char *line;
+	char *line, *mlinebuf = NULL;
 	while (!feof(file)) {
 		line = read_line(file);
 		line_number++;
@@ -467,6 +468,45 @@ bool read_config(FILE *file, struct sway_config *config) {
 			free(line);
 			continue;
 		}
+		size_t length = strlen(line);
+		if (line[length-1] == '\\') {
+			// Start of multiline
+			if (feof(file)){
+				sway_log(L_ERROR, "Error on line %i '%s': Unexpected EOF on "\
+						"multiline command", line_number, line);
+				free(line);
+				continue;
+			}
+			line[length-1] = '\0';
+			multiline = true;
+		} else
+			multiline = false;
+
+		if (multiline || mlinebuf){
+			size_t mlinebuf_length;
+			if (mlinebuf)
+				mlinebuf_length = strlen(mlinebuf);
+			else
+				mlinebuf_length = 0;
+
+			char *tmp = malloc(mlinebuf_length+length+1); // + '\0'
+			tmp[0]='\0'; // if mlinebuf_length==0 strncpy won't do anything. Make a null string.
+			strncpy(tmp, mlinebuf, mlinebuf_length);
+			tmp[mlinebuf_length]='\0'; // strncpy won't add '\0' at the end...
+			strcat(tmp, line);
+			if (mlinebuf)
+				free(mlinebuf);
+			free(line);
+			mlinebuf = tmp;
+			if (multiline) // The following line is part of a multi line config.
+				continue;
+			else {         // This is the last line of a multi line config.
+				line = mlinebuf;
+				sway_log(L_INFO, "Processing parsed multiline command '%s'", line);
+				mlinebuf = NULL;
+			}
+		}
+
 		struct cmd_results *res = config_command(line, block);
 		switch(res->status) {
 		case CMD_FAILURE:

sway/sway.5.txt

@@ -16,6 +16,12 @@ on startup.  These commands usually consist of setting your preferences and
 setting key bindings. An example config is likely present in /etc/sway/config
 for you to check out.
 
+Lines in the configuration file might be extended through multiple lines by
+adding a '\' character at the end of line. e.g.:
+
+	bindsym Shift+XF86AudioRaiseVolume exec pactl set-sink-volume \
+		$(pactl list sinks | grep -B 1 RUNNING | sed '1q;d' | sed 's/[^0-9]\+//g') +5%
+
 These commands can be executed in your config file, via **sway-msg**(1), or via
 the bindsym command.