Move workspace moving code out of container_move_to

container_move_to handled moving containers to new parents, as well as
moving workspaces to new outputs.

This commit removes the workspace-moving code from this function and
introduces workspace_move_to_output. Moving workspaces using
container_move_to only happened from the move command, so it's been
implemented as a static function in that file.

Simplifying container_move_to makes it easier for me to fix some issues
in #2420.

sway/commands/move.c

@@ -8,6 +8,7 @@
 #include "sway/commands.h"
 #include "sway/input/cursor.h"
 #include "sway/input/seat.h"
+#include "sway/ipc-server.h"
 #include "sway/output.h"
 #include "sway/tree/arrange.h"
 #include "sway/tree/container.h"
@@ -15,6 +16,7 @@
 #include "sway/tree/workspace.h"
 #include "stringop.h"
 #include "list.h"
+#include "log.h"
 
 static const char* expected_syntax =
 	"Expected 'move <left|right|up|down> <[px] px>' or "
@@ -152,6 +154,46 @@ static struct cmd_results *cmd_move_container(struct sway_container *current,
 	return cmd_results_new(CMD_INVALID, "move", expected_syntax);
 }
 
+static void workspace_move_to_output(struct sway_container *workspace,
+		struct sway_container *output) {
+	if (!sway_assert(workspace->type == C_WORKSPACE, "Expected a workspace")) {
+		return;
+	}
+	if (!sway_assert(output->type == C_OUTPUT, "Expected an output")) {
+		return;
+	}
+	if (workspace->parent == output) {
+		return;
+	}
+	struct sway_container *old_output = container_remove_child(workspace);
+	struct sway_seat *seat = input_manager_get_default_seat(input_manager);
+	struct sway_container *new_output_focus =
+		seat_get_focus_inactive(seat, output);
+
+	container_add_child(output, workspace);
+	wl_signal_emit(&workspace->events.reparent, old_output);
+
+	// If moving the last workspace from the old output, create a new workspace
+	// on the old output
+	if (old_output->children->length == 0) {
+		char *ws_name = workspace_next_name(old_output->name);
+		struct sway_container *ws = workspace_create(old_output, ws_name);
+		free(ws_name);
+		seat_set_focus(seat, ws);
+	}
+
+	// Try to remove an empty workspace from the destination output.
+	container_reap_empty_recursive(new_output_focus);
+
+	container_sort_workspaces(output);
+	seat_set_focus(seat, output);
+	workspace_output_raise_priority(workspace, old_output, output);
+	ipc_event_workspace(NULL, workspace, "move");
+
+	container_notify_subtree_changed(old_output);
+	container_notify_subtree_changed(output);
+}
+
 static struct cmd_results *cmd_move_workspace(struct sway_container *current,
 		int argc, char **argv) {
 	struct cmd_results *error = NULL;
@@ -173,7 +215,7 @@ static struct cmd_results *cmd_move_workspace(struct sway_container *current,
 	if (current->type != C_WORKSPACE) {
 		current = container_parent(current, C_WORKSPACE);
 	}
-	container_move_to(current, destination);
+	workspace_move_to_output(current, destination);
 
 	arrange_windows(source);
 	arrange_windows(destination);

sway/tree/layout.c

@@ -142,6 +142,10 @@ struct sway_container *container_remove_child(struct sway_container *child) {
 
 void container_move_to(struct sway_container *container,
 		struct sway_container *destination) {
+	if (!sway_assert(container->type == C_CONTAINER ||
+				container->type == C_VIEW, "Expected a container or view")) {
+		return;
+	}
 	if (container == destination
 			|| container_has_ancestor(container, destination)) {
 		return;
@@ -154,11 +158,8 @@ void container_move_to(struct sway_container *container,
 	container->width = container->height = 0;
 	container->saved_width = container->saved_height = 0;
 
-	struct sway_container *new_parent, *new_parent_focus;
-	struct sway_seat *seat = input_manager_get_default_seat(input_manager);
+	struct sway_container *new_parent;
 
-	// Get the focus of the destination before we change it.
-	new_parent_focus = seat_get_focus_inactive(seat, destination);
 	if (destination->type == C_VIEW) {
 		new_parent = container_add_sibling(destination, container);
 	} else {
@@ -167,24 +168,7 @@ void container_move_to(struct sway_container *container,
 	}
 	wl_signal_emit(&container->events.reparent, old_parent);
 
-	if (container->type == C_WORKSPACE) {
-		// If moving a workspace to a new output, maybe create a new workspace
-		// on the previous output
-		if (old_parent->children->length == 0) {
-			char *ws_name = workspace_next_name(old_parent->name);
-			struct sway_container *ws = workspace_create(old_parent, ws_name);
-			free(ws_name);
-			seat_set_focus(seat, ws);
-		}
-
-		// Try to remove an empty workspace from the destination output.
-		container_reap_empty_recursive(new_parent_focus);
-
-		container_sort_workspaces(new_parent);
-		seat_set_focus(seat, new_parent);
-		workspace_output_raise_priority(container, old_parent, new_parent);
-		ipc_event_workspace(NULL, container, "move");
-	} else if (container->type == C_VIEW) {
+	if (container->type == C_VIEW) {
 		ipc_event_window(container, "move");
 	}
 	container_notify_subtree_changed(old_parent);