Open the About popup the first time a new version starts

The last version the About popup was shown for is saved as last_seen_version in
settings.cfg. When the game starts with another version, About opens to show
what is new.

data/settings.gd

@@ -26,6 +26,7 @@ const SAVED_SETTINGS: Dictionary[String, Array] = {
 		&"inspiration_list_speed",
 	],
 	"window": [&"fullscreen"],
+	"app": [&"last_seen_version"],
 }
 ## When this environment variable is set, the settings files are kept in that folder
 ## instead of the user's config folder. The tests set it so they never touch the real files.
@@ -83,6 +84,9 @@ var character_select_open: bool = false
 ## [code]MusicServerClient[/code]. Saved in the [code][queues][/code] section of
 ## [method saved_settings_path], so the game goes on with the same queue after a restart.
 var queue_ids: Dictionary[String, String] = {}
+## The version the game last showed the About popup for. When it is not [member version],
+## this version is new and the main window opens the About popup to show what is new.
+var last_seen_version: String = ""
 
 ## The game version, set in Project Settings > Application > Config > Version.
 ## Releases are made from it, see RELEASING.md.

main/main_window.gd

@@ -43,6 +43,16 @@ func _ready() -> void:
 	statistics_view.soundtrack_selected.connect(soundtrack_stats_popup.show_soundtrack)
 
 	search_popup.get_list_of_soundtracks()
+	show_about_if_new_version()
+
+
+## Opens the About popup, with what is new, the first time this version starts.
+func show_about_if_new_version() -> void:
+	if Settings.last_seen_version == Settings.version:
+		return
+	Settings.last_seen_version = Settings.version
+	Settings.save_settings()
+	show_about()
 
 
 func _input(event: InputEvent) -> void:

tests/fakes/main_window_test_suite.gd

@@ -24,6 +24,8 @@ func before_test() -> void:
 	Settings.hide_next_track = true
 	Settings.use_low_played_mode = false
 	Settings.winning_score = 20
+	# Otherwise the About popup opens at start, as for a new version
+	Settings.last_seen_version = Settings.version
 
 	_server = FakeHttpTransport.new().install()
 	var mp3: PackedByteArray = FileAccess.get_file_as_bytes("res://tests/data/short.mp3")

tests/fakes/ui_tour.gd

@@ -170,6 +170,7 @@ static func prepare_autoloads() -> void:
 	Settings.hide_next_track = true
 	Settings.use_low_played_mode = false
 	Settings.winning_score = 20
+	Settings.last_seen_version = Settings.version
 	# The inspiration list scrolls by itself, which would make every picture different
 	Settings.inspiration_list_speed = 0
 

tests/integration/test_about_on_new_version.gd

@@ -0,0 +1,58 @@
+extends MainWindowTestSuite
+## The About popup opens by itself the first time a new version starts, to show what is
+## new.
+
+var _last_seen_before_start: String = "1.0.0"
+
+
+func _before_window_starts() -> void:
+	Settings.last_seen_version = _last_seen_before_start
+
+
+func _about() -> AboutPopup:
+	return _window.get_node("%AboutPopup")
+
+
+func test_new_version_opens_about_at_start() -> void:
+	assert_bool(_about().visible).is_true()
+
+
+func test_new_version_is_remembered_and_saved() -> void:
+	assert_str(Settings.last_seen_version).is_equal(Settings.version)
+	var saved: ConfigFile = ConfigFile.new()
+	assert_int(saved.load(Settings.saved_settings_path())).is_equal(OK)
+	assert_str(saved.get_value("app", "last_seen_version")).is_equal(Settings.version)
+
+
+func test_about_opens_only_once_per_version() -> void:
+	_about().close()
+
+	_window.show_about_if_new_version()
+
+	assert_bool(_about().visible).is_false()
+
+
+func test_about_can_be_closed_like_any_popup() -> void:
+	await _click_at(Vector2(5, 1075))
+
+	assert_bool(_about().visible).is_false()
+
+
+@warning_ignore("unused_parameter")
+func test_first_start_opens_about_too(
+		last_seen: String, test_parameters: Array = [[""], ["0.1.0"]]) -> void:
+	_about().close()
+	Settings.last_seen_version = last_seen
+
+	_window.show_about_if_new_version()
+
+	assert_bool(_about().visible).is_true()
+
+
+func test_same_version_does_not_open_about() -> void:
+	_about().close()
+	Settings.last_seen_version = Settings.version
+
+	_window.show_about_if_new_version()
+
+	assert_bool(_about().visible).is_false()

tests/integration/test_about_on_new_version.gd.uid

@@ -0,0 +1 @@
+uid://davke6pxkvvw3

tests/unit/test_settings_files.gd

@@ -6,7 +6,7 @@ const SAVED_VALUES: Dictionary = {
 	&"auto_repeat_song": false, &"stop_after_current": false, &"hide_next_track": false,
 	&"hide_beginning": true, &"hide_for_seconds": 7.0, &"hide_length": true,
 	&"hide_ticks": true, &"winning_score": 13, &"inspiration_list_speed": 4,
-	&"fullscreen": true,
+	&"fullscreen": true, &"last_seen_version": "1.2.3",
 }
 
 var _snapshot: AutoloadSnapshot