Add a button in Settings that opens the config folder

Shows the folder with config.ini, the saved settings and the cached
characters and songs in the system's file manager.

Closes #45

popups/SettingsPopup.tscn

@@ -158,6 +158,21 @@ focus_mode = 0
 action_mode = 0
 text = "Count plays in statistics"
 
+[node name="ConfigFolderRow" type="HBoxContainer" parent="SettingsPanel/VBoxContainer"]
+layout_mode = 2
+
+[node name="Title" type="Label" parent="SettingsPanel/VBoxContainer/ConfigFolderRow"]
+layout_mode = 2
+size_flags_horizontal = 3
+theme_type_variation = &"SettingsRowLabel"
+text = "Settings and cached files"
+
+[node name="OpenConfigFolderButton" type="Button" parent="SettingsPanel/VBoxContainer/ConfigFolderRow"]
+unique_name_in_owner = true
+layout_mode = 2
+focus_mode = 0
+text = "Open folder"
+
 [node name="FolderDialog" type="FileDialog" parent="."]
 unique_name_in_owner = true
 title = "Choose a music folder"

popups/settings_popup.gd

@@ -2,7 +2,8 @@ class_name SettingsPopup
 extends BasePopup
 ## The application settings: which MusicServer or music folder to play from, fullscreen,
 ## how many songs to download ahead, whether to prefer less played soundtracks and whether
-## plays count in the statistics. Opened from the Settings button in the top bar.
+## plays count in the statistics, and a button that opens the folder the settings are
+## kept in. Opened from the Settings button in the top bar.
 ##
 ## A music folder (see [MusicFolder]) is used instead of the server until Use server is
 ## pressed or the game is closed. The settings that need the server are off meanwhile.
@@ -32,6 +33,11 @@ const PADDING: Vector2 = Vector2(20, 12)
 @onready var play_order_row: HBoxContainer = %PlayOrderRow
 @onready var play_order_button: OptionButton = %PlayOrderButton
 @onready var folder_dialog: FileDialog = %FolderDialog
+@onready var open_config_folder_button: Button = %OpenConfigFolderButton
+
+## Shows a folder in the system's file manager. The tests replace it, so no file manager
+## opens while they run.
+var show_folder: Callable = _show_in_file_manager
 
 # Where the panel's middle is, so it stays centred when rows are shown or hidden
 var _panel_middle_y: float = 0.0
@@ -48,6 +54,8 @@ func _ready() -> void:
 	choose_folder_button.pressed.connect(folder_dialog.popup_centered)
 	folder_dialog.dir_selected.connect(use_music_folder)
 	use_server_button.pressed.connect(use_server)
+	open_config_folder_button.pressed.connect(open_config_folder)
+	open_config_folder_button.tooltip_text = Settings.config_dir()
 	play_order_button.item_selected.connect(_on_play_order_selected)
 	lower_cache_button.pressed.connect(lower_cache)
 	increase_cache_button.pressed.connect(increase_cache)
@@ -88,6 +96,14 @@ func use_server() -> void:
 	server_changed.emit()
 
 
+## Shows the folder with the config file, the saved settings and the cached characters
+## and songs in the system's file manager.
+func open_config_folder() -> void:
+	var dir: String = Settings.config_dir()
+	DirAccess.make_dir_recursive_absolute(dir)
+	show_folder.call(dir)
+
+
 func lower_cache() -> void:
 	Playlist.number_of_tracks_to_preload = maxi(Playlist.number_of_tracks_to_preload - 1, 1)
 	cache_label.text = str(Playlist.number_of_tracks_to_preload)
@@ -160,5 +176,14 @@ func _fit_to_rows() -> void:
 	rows.size = Vector2(settings_panel.size.x - PADDING.x * 2, height - PADDING.y * 2)
 
 
+func _show_in_file_manager(dir: String) -> void:
+	var error: Error = OS.shell_show_in_file_manager(dir)
+	if error != OK:
+		# Not every platform has a file manager to show a folder in; open it instead
+		error = OS.shell_open(dir)
+	if error != OK:
+		GameLog.warning("Could not open %s: %s" % [dir, error_string(error)])
+
+
 func _update_fullscreen_button() -> void:
 	fullscreen_button.set_pressed_no_signal(Settings.fullscreen)