Implement scratchpad

Implements the following commands:

* move scratchpad
* scratchpad show
* [criteria] scratchpad show

Also fixes these:

* Fix memory leak when executing command with criteria
(use `list_free(views)` instead of `free(views)`)
* Fix crash when running `move to` with no further arguments

13 files changed, 290 insertions, 5 deletions

diff --git a/include/sway/scratchpad.h b/include/sway/scratchpad.h
new file mode 100644
index 00000000..5af5256f
--- /dev/null
+++ b/include/sway/scratchpad.h
@@ -0,0 +1,26 @@
+#ifndef _SWAY_SCRATCHPAD_H
+#define _SWAY_SCRATCHPAD_H
+
+#include "tree/container.h"
+
+/**
+ * Move a container to the scratchpad.
+ */
+void scratchpad_add_container(struct sway_container *con);
+
+/**
+ * Remove a container from the scratchpad.
+ */
+void scratchpad_remove_container(struct sway_container *con);
+
+/**
+ * Show or hide the next container on the scratchpad.
+ */
+void scratchpad_toggle_auto(void);
+
+/**
+ * Show or hide a specific container on the scratchpad.
+ */
+void scratchpad_toggle_container(struct sway_container *con);
+
+#endif
diff --git a/include/sway/server.h b/include/sway/server.h
index 70bde6d4..6cef2e58 100644
--- a/include/sway/server.h
+++ b/include/sway/server.h
@@ -48,6 +48,8 @@ struct sway_server {
 
         list_t *transactions;
         list_t *dirty_containers;
+
+        list_t *scratchpad; // struct sway_container
 };
 
 struct sway_server server;
diff --git a/include/sway/tree/container.h b/include/sway/tree/container.h
index 59c5b4c7..2a4be18c 100644
--- a/include/sway/tree/container.h
+++ b/include/sway/tree/container.h
@@ -135,6 +135,11 @@ struct sway_container {
 
         struct sway_container *parent;
 
+        // Indicates that the container is a scratchpad container.
+        // Both hidden and visible scratchpad containers have scratchpad=true.
+        // Hidden scratchpad containers have a NULL parent.
+        bool scratchpad;
+
         float alpha;
 
         struct wlr_texture *title_focused;
diff --git a/sway/commands.c b/sway/commands.c
index f40f0e9d..fdae1961 100644
--- a/sway/commands.c
+++ b/sway/commands.c
@@ -149,6 +149,7 @@ static struct cmd_handler command_handlers[] = {
         { "reload", cmd_reload },
         { "rename", cmd_rename },
         { "resize", cmd_resize },
+        { "scratchpad", cmd_scratchpad },
         { "split", cmd_split },
         { "splith", cmd_splith },
         { "splitt", cmd_splitt },
@@ -326,7 +327,7 @@ struct cmd_results *execute_command(char *_exec, struct sway_seat *seat) {
         } while(head);
 cleanup:
         free(exec);
-        free(views);
+        list_free(views);
         if (!results) {
                 results = cmd_results_new(CMD_SUCCESS, NULL, NULL);
         }
diff --git a/sway/commands/move.c b/sway/commands/move.c
index 6ec050a8..1940043d 100644
--- a/sway/commands/move.c
+++ b/sway/commands/move.c
@@ -9,6 +9,7 @@
 #include "sway/input/cursor.h"
 #include "sway/input/seat.h"
 #include "sway/output.h"
+#include "sway/scratchpad.h"
 #include "sway/tree/arrange.h"
 #include "sway/tree/container.h"
 #include "sway/tree/layout.h"
@@ -296,6 +297,19 @@ static struct cmd_results *move_to_position(struct sway_container *container,
         return cmd_results_new(CMD_SUCCESS, NULL, NULL);
 }
 
+static struct cmd_results *move_to_scratchpad(struct sway_container *con) {
+        if (con->type != C_CONTAINER && con->type != C_VIEW) {
+                return cmd_results_new(CMD_INVALID, "move",
+                                "Only views and containers can be moved to the scratchpad");
+        }
+        if (con->scratchpad) {
+                return cmd_results_new(CMD_INVALID, "move",
+                                "Container is already in the scratchpad");
+        }
+        scratchpad_add_container(con);
+        return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+}
+
 struct cmd_results *cmd_move(int argc, char **argv) {
         struct cmd_results *error = NULL;
         if ((error = checkarg(argc, "move", EXPECTED_AT_LEAST, 1))) {
@@ -317,10 +331,9 @@ struct cmd_results *cmd_move(int argc, char **argv) {
         } else if (strcasecmp(argv[0], "workspace") == 0) {
                 return cmd_move_workspace(current, argc, argv);
         } else if (strcasecmp(argv[0], "scratchpad") == 0
-                        || (strcasecmp(argv[0], "to") == 0
+                        || (strcasecmp(argv[0], "to") == 0 && argc == 2
                                 && strcasecmp(argv[1], "scratchpad") == 0)) {
-                // TODO: scratchpad
-                return cmd_results_new(CMD_FAILURE, "move", "Unimplemented");
+                return move_to_scratchpad(current);
         } else if (strcasecmp(argv[0], "position") == 0) {
                 return move_to_position(current, argc, argv);
         } else if (strcasecmp(argv[0], "absolute") == 0) {
diff --git a/sway/commands/scratchpad.c b/sway/commands/scratchpad.c
new file mode 100644
index 00000000..8a529cb4
--- /dev/null
+++ b/sway/commands/scratchpad.c
@@ -0,0 +1,37 @@
+#include "log.h"
+#include "sway/commands.h"
+#include "sway/config.h"
+#include "sway/scratchpad.h"
+#include "sway/server.h"
+#include "sway/tree/container.h"
+
+struct cmd_results *cmd_scratchpad(int argc, char **argv) {
+        struct cmd_results *error = NULL;
+        if ((error = checkarg(argc, "scratchpad", EXPECTED_EQUAL_TO, 1))) {
+                return error;
+        }
+        if (strcmp(argv[0], "show") != 0) {
+                return cmd_results_new(CMD_INVALID, "scratchpad",
+                                "Expected 'scratchpad show'");
+        }
+        if (!server.scratchpad->length) {
+                return cmd_results_new(CMD_INVALID, "scratchpad",
+                                "Scratchpad is empty");
+        }
+
+        if (config->handler_context.using_criteria) {
+                // If using criteria, this command is executed for every container which
+                // matches the criteria. If this container isn't in the scratchpad,
+                // we'll just silently return a success.
+                struct sway_container *con = config->handler_context.current_container;
+                wlr_log(WLR_INFO, "cmd_scratchpad(%s)", con->name);
+                if (!con->scratchpad) {
+                        return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+                }
+                scratchpad_toggle_container(con);
+        } else {
+                scratchpad_toggle_auto();
+        }
+
+        return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+}
diff --git a/sway/criteria.c b/sway/criteria.c
index e2b248de..6af97d5b 100644
--- a/sway/criteria.c
+++ b/sway/criteria.c
@@ -225,6 +225,14 @@ list_t *criteria_get_views(struct criteria *criteria) {
         };
         container_for_each_descendant_dfs(&root_container,
                 criteria_get_views_iterator, &data);
+
+        // Scratchpad items which are hidden are not in the tree.
+        for (int i = 0; i < server.scratchpad->length; ++i) {
+                struct sway_container *con = server.scratchpad->items[i];
+                if (!con->parent) {
+                        criteria_get_views_iterator(con, &data);
+                }
+        }
         return matches;
 }
 
diff --git a/sway/meson.build b/sway/meson.build
index f4fdc8ea..30c848e2 100644
--- a/sway/meson.build
+++ b/sway/meson.build
@@ -7,6 +7,7 @@ sway_sources = files(
         'debug-tree.c',
         'ipc-json.c',
         'ipc-server.c',
+        'scratchpad.c',
         'security.c',
 
         'desktop/desktop.c',
@@ -67,6 +68,7 @@ sway_sources = files(
         'commands/reload.c',
         'commands/rename.c',
         'commands/resize.c',
+        'commands/scratchpad.c',
         'commands/seat.c',
         'commands/seat/attach.c',
         'commands/seat/cursor.c',
diff --git a/sway/scratchpad.c b/sway/scratchpad.c
new file mode 100644
index 00000000..e1f931a4
--- /dev/null
+++ b/sway/scratchpad.c
@@ -0,0 +1,173 @@
+#define _XOPEN_SOURCE 700
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include "sway/scratchpad.h"
+#include "sway/input/seat.h"
+#include "sway/tree/arrange.h"
+#include "sway/tree/container.h"
+#include "sway/tree/view.h"
+#include "sway/tree/workspace.h"
+#include "list.h"
+#include "log.h"
+
+void scratchpad_add_container(struct sway_container *con) {
+        if (!sway_assert(!con->scratchpad, "Container is already in scratchpad")) {
+                return;
+        }
+        con->scratchpad = true;
+        list_add(server.scratchpad, con);
+
+        struct sway_container *parent = con->parent;
+        container_set_floating(con, true);
+        container_remove_child(con);
+        arrange_windows(parent);
+
+        struct sway_seat *seat = input_manager_current_seat(input_manager);
+        seat_set_focus(seat, seat_get_focus_inactive(seat, parent));
+}
+
+void scratchpad_remove_container(struct sway_container *con) {
+        if (!sway_assert(con->scratchpad, "Container is not in scratchpad")) {
+                return;
+        }
+        con->scratchpad = false;
+        for (int i = 0; i < server.scratchpad->length; ++i) {
+                if (server.scratchpad->items[i] == con) {
+                        list_del(server.scratchpad, i);
+                        break;
+                }
+        }
+}
+
+/**
+ * Show a single scratchpad container.
+ * The container might be visible on another workspace already.
+ */
+static void scratchpad_show(struct sway_container *con) {
+        struct sway_seat *seat = input_manager_current_seat(input_manager);
+        struct sway_container *ws = seat_get_focus(seat);
+        if (ws->type != C_WORKSPACE) {
+                ws = container_parent(ws, C_WORKSPACE);
+        }
+
+    // If the current con or any of its parents are in fullscreen mode, we
+    // first need to disable it before showing the scratchpad con.
+        if (ws->sway_workspace->fullscreen) {
+                view_set_fullscreen(ws->sway_workspace->fullscreen, false);
+        }
+
+        // Show the container
+        if (con->parent) {
+                container_remove_child(con);
+        }
+        container_add_child(ws->sway_workspace->floating, con);
+
+        // Make sure the container's center point overlaps this workspace
+        double center_lx = con->x + con->width / 2;
+        double center_ly = con->y + con->height / 2;
+
+        struct wlr_box workspace_box;
+        container_get_box(ws, &workspace_box);
+        if (!wlr_box_contains_point(&workspace_box, center_lx, center_ly)) {
+                // Maybe resize it
+                if (con->width > ws->width || con->height > ws->height) {
+                        // TODO: Do this properly once we can float C_CONTAINERs
+                        if (con->type == C_VIEW) {
+                                view_init_floating(con->sway_view);
+                                arrange_windows(con);
+                        }
+                }
+
+                // Center it
+                double new_lx = ws->x + (ws->width - con->width) / 2;
+                double new_ly = ws->y + (ws->height - con->height) / 2;
+                container_floating_move_to(con, new_lx, new_ly);
+        }
+
+        seat_set_focus(seat, con);
+
+        container_set_dirty(con->parent);
+}
+
+/**
+ * Hide a single scratchpad container.
+ * The container might not be the focused container (eg. when using criteria).
+ */
+static void scratchpad_hide(struct sway_container *con) {
+        struct sway_seat *seat = input_manager_current_seat(input_manager);
+        struct sway_container *focus = seat_get_focus(seat);
+        struct sway_container *ws = container_parent(con, C_WORKSPACE);
+
+        container_remove_child(con);
+        arrange_windows(ws);
+        if (con == focus) {
+                seat_set_focus(seat, seat_get_focus_inactive(seat, ws));
+        }
+        list_move_to_end(server.scratchpad, con);
+}
+
+void scratchpad_toggle_auto(void) {
+        struct sway_seat *seat = input_manager_current_seat(input_manager);
+        struct sway_container *focus = seat_get_focus(seat);
+        struct sway_container *ws = focus->type == C_WORKSPACE ?
+                focus : container_parent(focus, C_WORKSPACE);
+
+    // Check if the currently focused window is a scratchpad window and should
+    // be hidden again.
+        if (focus->scratchpad) {
+                wlr_log(WLR_DEBUG, "Focus is a scratchpad window - hiding %s",
+                                focus->name);
+                scratchpad_hide(focus);
+                return;
+        }
+
+    // Check if there is an unfocused scratchpad window on the current workspace
+    // and focus it.
+        for (int i = 0; i < ws->sway_workspace->floating->children->length; ++i) {
+                struct sway_container *floater =
+                        ws->sway_workspace->floating->children->items[i];
+                if (floater->scratchpad && focus != floater) {
+                        wlr_log(WLR_DEBUG,
+                                        "Focusing other scratchpad window (%s) in this workspace",
+                                        floater->name);
+                        scratchpad_show(floater);
+                        return;
+                }
+        }
+
+    // Check if there is a visible scratchpad window on another workspace.
+    // In this case we move it to the current workspace.
+        for (int i = 0; i < server.scratchpad->length; ++i) {
+                struct sway_container *con = server.scratchpad->items[i];
+                if (con->parent) {
+                        wlr_log(WLR_DEBUG,
+                                        "Moving a visible scratchpad window (%s) to this workspace",
+                                        con->name);
+                        scratchpad_show(con);
+                        return;
+                }
+        }
+
+        // Take the container at the bottom of the scratchpad list
+        if (!sway_assert(server.scratchpad->length, "Scratchpad is empty")) {
+                return;
+        }
+        struct sway_container *con = server.scratchpad->items[0];
+        wlr_log(WLR_DEBUG, "Showing %s from list", con->name);
+        scratchpad_show(con);
+}
+
+void scratchpad_toggle_container(struct sway_container *con) {
+        if (!sway_assert(con->scratchpad, "Container isn't in the scratchpad")) {
+                return;
+        }
+
+    // Check if it matches a currently visible scratchpad window and hide it.
+        if (con->parent) {
+                scratchpad_hide(con);
+                return;
+        }
+
+        scratchpad_show(con);
+}
diff --git a/sway/server.c b/sway/server.c
index 89dfbf8c..916e6b71 100644
--- a/sway/server.c
+++ b/sway/server.c
@@ -126,6 +126,8 @@ bool server_init(struct sway_server *server) {
         server->dirty_containers = create_list();
         server->transactions = create_list();
 
+        server->scratchpad = create_list();
+
         input_manager = input_manager_create(server);
         return true;
 }
@@ -135,6 +137,7 @@ void server_fini(struct sway_server *server) {
         wl_display_destroy(server->wl_display);
         list_free(server->dirty_containers);
         list_free(server->transactions);
+        list_free(server->scratchpad);
 }
 
 bool server_start_backend(struct sway_server *server) {
diff --git a/sway/tree/container.c b/sway/tree/container.c
index 42c1d024..4f743c40 100644
--- a/sway/tree/container.c
+++ b/sway/tree/container.c
@@ -17,6 +17,7 @@
 #include "sway/input/seat.h"
 #include "sway/ipc-server.h"
 #include "sway/output.h"
+#include "sway/scratchpad.h"
 #include "sway/server.h"
 #include "sway/tree/arrange.h"
 #include "sway/tree/layout.h"
@@ -328,6 +329,10 @@ static struct sway_container *container_destroy_noreaping(
         con->destroying = true;
         container_set_dirty(con);
 
+        if (con->scratchpad) {
+                scratchpad_remove_container(con);
+        }
+
         if (!con->parent) {
                 return NULL;
         }
@@ -955,6 +960,9 @@ void container_set_floating(struct sway_container *container, bool enable) {
                 container_reap_empty_recursive(workspace);
         } else {
                 // Returning to tiled
+                if (container->scratchpad) {
+                        scratchpad_remove_container(container);
+                }
                 container_remove_child(container);
                 container_add_child(workspace, container);
                 container->width = container->parent->width;
diff --git a/sway/tree/layout.c b/sway/tree/layout.c
index 533906fa..af37611f 100644
--- a/sway/tree/layout.c
+++ b/sway/tree/layout.c
@@ -135,6 +135,10 @@ void container_add_child(struct sway_container *parent,
         list_add(parent->children, child);
         child->parent = parent;
         container_handle_fullscreen_reparent(child, old_parent);
+        if (old_parent) {
+                container_set_dirty(old_parent);
+        }
+        container_set_dirty(child);
 }
 
 struct sway_container *container_remove_child(struct sway_container *child) {
@@ -153,6 +157,9 @@ struct sway_container *container_remove_child(struct sway_container *child) {
         child->parent = NULL;
         container_notify_subtree_changed(parent);
 
+        container_set_dirty(parent);
+        container_set_dirty(child);
+
         return parent;
 }
 
diff --git a/sway/tree/view.c b/sway/tree/view.c
index 89150a69..9d88d7aa 100644
--- a/sway/tree/view.c
+++ b/sway/tree/view.c
@@ -1065,7 +1065,7 @@ void view_update_marks_textures(struct sway_view *view) {
 }
 
 bool view_is_visible(struct sway_view *view) {
-        if (!view->swayc || view->swayc->destroying) {
+        if (!view->swayc || view->swayc->destroying || !view->swayc->parent) {
                 return false;
         }
         struct sway_container *workspace =