Implement swap command

include/sway/commands.h

@@ -144,6 +144,7 @@ sway_cmd cmd_splitt;
 sway_cmd cmd_splitv;
 sway_cmd cmd_sticky;
 sway_cmd cmd_swaybg_command;
+sway_cmd cmd_swap;
 sway_cmd cmd_title_format;
 sway_cmd cmd_unmark;
 sway_cmd cmd_workspace;

include/sway/tree/layout.h

@@ -69,4 +69,6 @@ struct sway_container *container_split(struct sway_container *child,
 void container_recursive_resize(struct sway_container *container,
 		double amount, enum resize_edge edge);
 
+void container_swap(struct sway_container *con1, struct sway_container *con2);
+
 #endif

sway/commands.c

@@ -186,6 +186,7 @@ static struct cmd_handler command_handlers[] = {
 	{ "splith", cmd_splith },
 	{ "splitt", cmd_splitt },
 	{ "splitv", cmd_splitv },
+	{ "swap", cmd_swap },
 	{ "title_format", cmd_title_format },
 	{ "unmark", cmd_unmark },
 };

sway/commands/swap.c

@@ -0,0 +1,80 @@
+#include <strings.h>
+#include <wlr/util/log.h>
+#include "sway/commands.h"
+#include "sway/tree/layout.h"
+#include "sway/tree/view.h"
+#include "stringop.h"
+
+static const char* EXPECTED_SYNTAX =
+	"Expected 'swap container with id|con_id|mark <arg>'";
+
+static bool test_con_id(struct sway_container *container, void *con_id) {
+	return container->id == (size_t)con_id;
+}
+
+static bool test_id(struct sway_container *container, void *id) {
+	xcb_window_t *wid = id;
+	return (container->type == C_VIEW
+			&& container->sway_view->type == SWAY_VIEW_XWAYLAND
+			&& container->sway_view->wlr_xwayland_surface->window_id == *wid);
+}
+
+static bool test_mark(struct sway_container *container, void *mark) {
+	if (container->type == C_VIEW && container->sway_view->marks->length) {
+		return !list_seq_find(container->sway_view->marks,
+				(int (*)(const void *, const void *))strcmp, mark);
+	}
+	return false;
+}
+
+struct cmd_results *cmd_swap(int argc, char **argv) {
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, "swap", EXPECTED_AT_LEAST, 4))) {
+		return error;
+	}
+
+	if (strcasecmp(argv[0], "container") || strcasecmp(argv[1], "with")) {
+		return cmd_results_new(CMD_INVALID, "swap", EXPECTED_SYNTAX);
+	}
+
+	struct sway_container *current = config->handler_context.current_container;
+	struct sway_container *other;
+
+	char *value = join_args(argv + 3, argc - 3);
+	if (strcasecmp(argv[2], "id") == 0) {
+		xcb_window_t id = strtol(value, NULL, 0);
+		other = container_find(&root_container, test_id, (void *)&id);
+	} else if (strcasecmp(argv[2], "con_id") == 0) {
+		size_t con_id = atoi(value);
+		other = container_find(&root_container, test_con_id, (void *)con_id);
+	} else if (strcasecmp(argv[2], "mark") == 0) {
+		other = container_find(&root_container, test_mark, (void *)value);
+	} else {
+		free(value);
+		return cmd_results_new(CMD_INVALID, "swap", EXPECTED_SYNTAX);
+	}
+
+	if (!other) {
+		error = cmd_results_new(CMD_FAILURE, "swap",
+				"Failed to find %s '%s'", argv[2], value);
+	} else if (current->type < C_CONTAINER || other->type < C_CONTAINER) {
+		error = cmd_results_new(CMD_FAILURE, "swap",
+				"Can only swap with containers and views");
+	} else if (container_has_anscestor(current, other)
+			|| container_has_anscestor(other, current)) {
+		error = cmd_results_new(CMD_FAILURE, "swap",
+				"Cannot swap ancestor and descendant");
+	} else if (current->layout == L_FLOATING || other->layout == L_FLOATING) {
+		error = cmd_results_new(CMD_FAILURE, "swap",
+				"Swapping with floating containers is not supported");
+	}
+
+	free(value);
+
+	if (error) {
+		return error;
+	}
+
+	container_swap(current, other);
+	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+}

sway/meson.build

@@ -63,6 +63,7 @@ sway_sources = files(
 	'commands/show_marks.c',
 	'commands/split.c',
 	'commands/swaybg_command.c',
+	'commands/swap.c',
 	'commands/title_format.c',
 	'commands/unmark.c',
 	'commands/workspace.c',

sway/sway.5.scd

@@ -167,6 +167,15 @@ They are expected to be used with *bindsym* or at runtime through *swaymsg*(1).
 	"Sticks" a floating window to the current output so that it shows up on all
 	workspaces.
 
+*swap* container with id|con\_id|mark <arg>
+	Swaps the position, geometry, and fullscreen status of two containers. The
+	first container can be selected either by criteria or focus. The second
+	container can be selected by _id_, _con\_id_, or _mark_. _id_ can only be
+	used with xwayland views. If the first container has focus, it will retain
+	focus unless it is moved to a different workspace or the second container
+	becomes fullscreen on the same workspace as the first container. In either
+	of those cases, the second container will gain focus.
+
 The following commands may be used either in the configuration file or at
 runtime.
 

sway/tree/layout.c

@@ -882,3 +882,127 @@ void container_recursive_resize(struct sway_container *container,
 		}
 	}
 }
+
+static void swap_places(struct sway_container *con1,
+		struct sway_container *con2) {
+	struct sway_container *temp = malloc(sizeof(struct sway_container));
+	temp->x = con1->x;
+	temp->y = con1->y;
+	temp->width = con1->width;
+	temp->height = con1->height;
+	temp->parent = con1->parent;
+
+	con1->x = con2->x;
+	con1->y = con2->y;
+	con1->width = con2->width;
+	con1->height = con2->height;
+
+	con2->x = temp->x;
+	con2->y = temp->y;
+	con2->width = temp->width;
+	con2->height = temp->height;
+
+	int temp_index = index_child(con1);
+	container_insert_child(con2->parent, con1, index_child(con2));
+	container_insert_child(temp->parent, con2, temp_index);
+
+	free(temp);
+}
+
+static void swap_focus(struct sway_container *con1,
+		struct sway_container *con2, struct sway_seat *seat,
+		struct sway_container *focus) {
+	if (focus == con1 || focus == con2) {
+		struct sway_container *ws1 = container_parent(con1, C_WORKSPACE);
+		struct sway_container *ws2 = container_parent(con2, C_WORKSPACE);
+		if (focus == con1 && (con2->parent->layout == L_TABBED
+					|| con2->parent->layout == L_STACKED)) {
+			if (workspace_is_visible(ws2)) {
+				seat_set_focus_warp(seat, con2, false);
+			}
+			seat_set_focus(seat, ws1 != ws2 ? con2 : con1);
+		} else if (focus == con2 && (con1->parent->layout == L_TABBED
+					|| con1->parent->layout == L_STACKED)) {
+			if (workspace_is_visible(ws1)) {
+				seat_set_focus_warp(seat, con1, false);
+			}
+			seat_set_focus(seat, ws1 != ws2 ? con1 : con2);
+		} else if (ws1 != ws2) {
+			seat_set_focus(seat, focus == con1 ? con2 : con1);
+		} else {
+			seat_set_focus(seat, focus);
+		}
+	} else {
+		seat_set_focus(seat, focus);
+	}
+}
+
+void container_swap(struct sway_container *con1, struct sway_container *con2) {
+	if (!sway_assert(con1 && con2, "Cannot swap with nothing")) {
+		return;
+	}
+	if (!sway_assert(con1->type >= C_CONTAINER && con2->type >= C_CONTAINER,
+				"Can only swap containers and views")) {
+		return;
+	}
+	if (!sway_assert(!container_has_anscestor(con1, con2)
+				&& !container_has_anscestor(con2, con1),
+				"Cannot swap anscestor and descendant")) {
+		return;
+	}
+	if (!sway_assert(con1->layout != L_FLOATING && con2->layout != L_FLOATING,
+				"Swapping with floating containers is not supported")) {
+		return;
+	}
+
+	wlr_log(L_DEBUG, "Swapping containers %zu and %zu", con1->id, con2->id);
+
+	int fs1 = con1->type == C_VIEW && con1->sway_view->is_fullscreen;
+	int fs2 = con2->type == C_VIEW && con2->sway_view->is_fullscreen;
+	if (fs1) {
+		view_set_fullscreen(con1->sway_view, false);
+	}
+	if (fs2) {
+		view_set_fullscreen(con2->sway_view, false);
+	}
+
+	struct sway_seat *seat = input_manager_get_default_seat(input_manager);
+	struct sway_container *focus = seat_get_focus(seat);
+	struct sway_container *vis1 = container_parent(
+			seat_get_focus_inactive(seat, container_parent(con1, C_OUTPUT)),
+			C_WORKSPACE);
+	struct sway_container *vis2 = container_parent(
+			seat_get_focus_inactive(seat, container_parent(con2, C_OUTPUT)),
+			C_WORKSPACE);
+
+	char *stored_prev_name = NULL;
+	if (prev_workspace_name) {
+		stored_prev_name = strdup(prev_workspace_name);
+	}
+
+	swap_places(con1, con2);
+
+	if (!workspace_is_visible(vis1)) {
+		seat_set_focus(seat, seat_get_focus_inactive(seat, vis1));
+	}
+	if (!workspace_is_visible(vis2)) {
+		seat_set_focus(seat, seat_get_focus_inactive(seat, vis2));
+	}
+
+	swap_focus(con1, con2, seat, focus);
+
+	if (stored_prev_name) {
+		free(prev_workspace_name);
+		prev_workspace_name = stored_prev_name;
+	}
+
+	arrange_children_of(con1->parent);
+	arrange_children_of(con2->parent);
+
+	if (fs1 && con2->type == C_VIEW) {
+		view_set_fullscreen(con2->sway_view, true);
+	}
+	if (fs2 && con1->type == C_VIEW) {
+		view_set_fullscreen(con1->sway_view, true);
+	}
+}