Show in the top bar when a newer version is available

At start and after switching server, the game asks the server for the newest
MusicPlayer release and shows "Version X is available" in the top bar when it
is newer than this one.

tests/integration/test_scene_split.gd

@@ -29,7 +29,7 @@ const LOCKED_BY_SYNC: Array[String] = [
 
 const TOP_BAR_CHILDREN: Array[String] = [
 	"TopPanelContainer", "Title", "SyncButton", "SettingsButton", "ShortcutsButton",
-	"DebugLabel",
+	"DebugLabel", "UpdateLabel",
 	"AboutButton", "QRButton", "QuizTab", "StatisticsTab",
 ]
 

tests/integration/test_update_notice.gd

@@ -0,0 +1,74 @@
+extends MainWindowTestSuite
+## The top bar tells the user when the server has a newer MusicPlayer release.
+
+var _top_bar: TopBar
+
+
+func before_test() -> void:
+	super()
+	_top_bar = _window.get_node("TopBar")
+
+
+func test_no_message_when_this_is_the_newest_version() -> void:
+	assert_bool(_top_bar.update_label.visible).is_false()
+	assert_int(_server.count("/download")).is_equal(1)
+
+
+func test_newer_release_shows_a_message() -> void:
+	_server.respond_json("/download", "99.0.0")
+
+	_top_bar.check_for_update()
+
+	assert_bool(_top_bar.update_label.is_visible_in_tree()).is_true()
+	assert_str(_top_bar.update_label.text).is_equal("Version 99.0.0 is available")
+	assert_str(_top_bar.update_label.tooltip_text).contains(Settings.version)
+
+
+func test_message_fits_between_the_tabs_and_the_buttons() -> void:
+	_server.respond_json("/download", "99.10.10")
+	_top_bar.check_for_update()
+	await _runner.simulate_frames(1)
+
+	var label: Rect2 = _top_bar.update_label.get_global_rect()
+	var text_width: float = _top_bar.update_label.get_minimum_size().x
+	assert_float(text_width).is_less_equal(label.size.x)
+	assert_float(label.position.x).is_greater(
+			(_top_bar.get_node("StatisticsTab") as Control).get_global_rect().end.x)
+	assert_float(label.end.x).is_less(
+			(_top_bar.get_node("SyncButton") as Control).get_global_rect().position.x)
+
+
+func test_message_stays_on_the_statistics_tab() -> void:
+	_server.respond_json("/download", "99.0.0")
+	_top_bar.check_for_update()
+
+	_window.show_tab(&"statistics")
+
+	assert_bool(_top_bar.update_label.is_visible_in_tree()).is_true()
+
+
+func test_server_change_checks_again() -> void:
+	_server.respond_json("/download", "99.0.0")
+
+	_quiz.on_server_changed()
+
+	assert_bool(_top_bar.update_label.visible).is_true()
+
+
+func test_failed_check_shows_nothing() -> void:
+	_server.respond_json("/download", "error", 502)
+
+	_top_bar.check_for_update()
+
+	assert_bool(_top_bar.update_label.visible).is_false()
+
+
+func test_version_comparison() -> void:
+	assert_bool(TopBar.is_newer_version("2.0.1", "2.0.0")).is_true()
+	assert_bool(TopBar.is_newer_version("1.10.0", "1.9.0")).is_true()
+	assert_bool(TopBar.is_newer_version("v3.0", "2.9.9")).is_true()
+	assert_bool(TopBar.is_newer_version("2.1", "2.0.5")).is_true()
+	assert_bool(TopBar.is_newer_version("2.0.0", "2.0.0")).is_false()
+	assert_bool(TopBar.is_newer_version("2.0", "2.0.0")).is_false()
+	assert_bool(TopBar.is_newer_version("1.9.0", "2.0.0")).is_false()
+	assert_bool(TopBar.is_newer_version("1.9.9", "1.10.0")).is_false()

tests/integration/test_update_notice.gd.uid

@@ -0,0 +1 @@
+uid://dmm31450qjd8v