Implement bar gaps

Adds the bar subcommand `gaps <amount>|<horizontal> <vertical>|<top>
<right> <bottom> <left>` to set gaps for swaybar. Due to restrictions on
margins for a layer_surface, only the sides that are anchored to an edge
of the screen can have gaps. Since there is support for per-side outer
gaps for workspaces, those should be able to be used instead for the
last side.

sway/commands/bar.c

@@ -14,6 +14,7 @@ static struct cmd_handler bar_handlers[] = {
 	{ "colors", bar_cmd_colors },
 	{ "context_button", bar_cmd_context_button },
 	{ "font", bar_cmd_font },
+	{ "gaps", bar_cmd_gaps },
 	{ "height", bar_cmd_height },
 	{ "hidden_state", bar_cmd_hidden_state },
 	{ "icon_theme", bar_cmd_icon_theme },

sway/commands/bar/gaps.c

@@ -0,0 +1,60 @@
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include "sway/commands.h"
+#include "sway/ipc-server.h"
+#include "log.h"
+
+struct cmd_results *bar_cmd_gaps(int argc, char **argv) {
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, "gaps", EXPECTED_AT_LEAST, 1))) {
+		return error;
+	}
+	if ((error = checkarg(argc, "gaps", EXPECTED_AT_MOST, 4))) {
+		return error;
+	}
+	if (!config->current_bar) {
+		return cmd_results_new(CMD_FAILURE, "bar gaps", "No bar defined.");
+	}
+
+	int top = 0, right = 0, bottom = 0, left = 0;
+
+	for (int i = 0; i < argc; i++) {
+		char *end;
+		int amount = strtol(argv[i], &end, 10);
+		if (strlen(end) && strcasecmp(end, "px") != 0) {
+			return cmd_results_new(CMD_INVALID, "bar gaps",
+					"Expected 'bar [<bar-id>] gaps <all> | <horizonal> "
+					"<vertical> | <top> <right> <bottom> <left>'");
+		}
+
+		if (i == 0) {
+			top = amount;
+		}
+		if (i == 0 || i == 1) {
+			right = amount;
+		}
+		if (i == 0 || i == 2) {
+			bottom = amount;
+		}
+		if (i == 0 || i == 1 || i == 3) {
+			left = amount;
+		}
+	}
+
+	config->current_bar->gaps.top = top;
+	config->current_bar->gaps.right = right;
+	config->current_bar->gaps.bottom = bottom;
+	config->current_bar->gaps.left = left;
+
+	wlr_log(WLR_DEBUG, "Setting bar gaps to %d %d %d %d on bar: %s",
+			config->current_bar->gaps.top, config->current_bar->gaps.right,
+			config->current_bar->gaps.bottom, config->current_bar->gaps.left,
+			config->current_bar->id);
+
+	if (!config->reading) {
+		ipc_event_barconfig_update(config->current_bar);
+	}
+
+	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+}

sway/ipc-json.c

@@ -638,6 +638,18 @@ json_object *ipc_json_describe_bar_config(struct bar_config *bar) {
 			json_object_new_string(bar->status_command) : NULL);
 	json_object_object_add(json, "font",
 			json_object_new_string((bar->font) ? bar->font : config->font));
+
+	json_object *gaps = json_object_new_object();
+	json_object_object_add(gaps, "top",
+			json_object_new_int(bar->gaps.top));
+	json_object_object_add(gaps, "right",
+			json_object_new_int(bar->gaps.right));
+	json_object_object_add(gaps, "bottom",
+			json_object_new_int(bar->gaps.bottom));
+	json_object_object_add(gaps, "left",
+			json_object_new_int(bar->gaps.left));
+	json_object_object_add(json, "gaps", gaps);
+
 	if (bar->separator_symbol) {
 		json_object_object_add(json, "separator_symbol",
 				json_object_new_string(bar->separator_symbol));

sway/meson.build

@@ -104,6 +104,7 @@ sway_sources = files(
 	'commands/bar/colors.c',
 	'commands/bar/context_button.c',
 	'commands/bar/font.c',
+	'commands/bar/gaps.c',
 	'commands/bar/height.c',
 	'commands/bar/hidden_state.c',
 	'commands/bar/icon_theme.c',

sway/sway-bar.5.scd

@@ -61,6 +61,13 @@ Sway allows configuring swaybar in the sway configuration file.
 *binding\_mode\_indicator* yes|no
 	Enable or disable binding mode indicator. Default is _yes_.
 
+*gaps* <all> | <horizontal> <vertical> | <top> <right> <bottom> <left>
+	Sets the gaps from the edge of the screen for the bar. Gaps can either be
+	set all at once, per direction, or per side. Note that only sides that
+	touch an edge of the screen can have gaps. For the side that does not
+	touch an edge of the screen, per-side outer gaps for workspaces may be of
+	use.
+
 *height* <height>
 	Sets the height of the bar. Default height will match the font size.