Update check: version feed from the git server's releases, title-screen banner, clearer version refusals

scripts/ui/title_screen.gd

@@ -85,6 +85,7 @@ func _ready() -> void:
 	var spacer := Control.new()
 	spacer.custom_minimum_size = Vector2(0, 24)
 	col.add_child(spacer)
+	_build_update_banner(root)
 
 	_pages["main"] = _main_page()
 	_pages["new"] = _new_page()
@@ -498,7 +499,7 @@ func _on_join_failed(reason: String) -> void:
 		_on_host_status(reason, true)
 		return
 	_join_btn.disabled = false
-	_join_msg.text = reason
+	_join_msg.text = reason + version_advice(reason)
 	_join_msg.add_theme_color_override("font_color", UITheme.BAD)
 
 func _on_left(reason: String) -> void:
@@ -697,3 +698,74 @@ func _play_tutorial() -> void:
 func _play(id: String) -> void:
 	Saves.current_id = id
 	get_tree().change_scene_to_file(WORLD_SCENE)
+
+# --- updates (scripts/core/updates.gd) ------------------------------------------------
+
+## Asked once per run of the game, not every time you come back to the title.
+static var _update_asked := false
+var update_banner: PanelContainer
+var _update_text: Label
+var _update_btn: Button
+var version_label: Label
+
+## The version, bottom left; and a card bottom right when a newer one is out.
+func _build_update_banner(root: Control) -> void:
+	version_label = UITheme.label("Emberwild %s" % Updates.version, 13, UITheme.TEXT_DIM)
+	version_label.set_anchors_and_offsets_preset(Control.PRESET_BOTTOM_LEFT)
+	version_label.offset_left = 16
+	version_label.offset_top = -30
+	root.add_child(version_label)
+	update_banner = UITheme.panel()
+	update_banner.set_anchors_and_offsets_preset(Control.PRESET_BOTTOM_RIGHT)
+	update_banner.grow_horizontal = Control.GROW_DIRECTION_BEGIN
+	update_banner.grow_vertical = Control.GROW_DIRECTION_BEGIN
+	update_banner.offset_right = -24
+	update_banner.offset_bottom = -24
+	update_banner.visible = false
+	root.add_child(update_banner)
+	var v := VBoxContainer.new()
+	v.add_theme_constant_override("separation", 8)
+	v.custom_minimum_size = Vector2(360, 0)
+	update_banner.add_child(v)
+	_update_text = UITheme.label("", 16)
+	_update_text.autowrap_mode = TextServer.AUTOWRAP_WORD_SMART
+	_update_text.custom_minimum_size = Vector2(360, 0)
+	v.add_child(_update_text)
+	var h := HBoxContainer.new()
+	h.add_theme_constant_override("separation", 8)
+	v.add_child(h)
+	_update_btn = _button("Download", _on_update_download, 170)
+	h.add_child(_update_btn)
+	h.add_child(_button("Not now", func(): update_banner.visible = false, 120))
+	Updates.checked.connect(_on_update_checked)
+	if Updates.state == "available":
+		_on_update_checked("available")
+	elif not _update_asked:
+		_update_asked = true
+		Updates.check()
+
+func _on_update_checked(s: String) -> void:
+	if s != "available" or update_banner == null:
+		return
+	var notes := String(Updates.latest.get("notes", ""))
+	var how := "" if Updates.packaged() else "\nRunning from the source: git pull in the game folder, then restart."
+	_update_text.text = "Emberwild %s is out (you have %s).%s%s" % [Updates.latest_version(), Updates.version,
+		("\n" + notes) if not notes.is_empty() else "", how]
+	_update_btn.text = "Download" if Updates.packaged() and not String(Updates.download().get("url", "")).is_empty() else "Release page"
+	_update_btn.disabled = Updates.download_url().is_empty()
+	update_banner.visible = true
+
+func _on_update_download() -> void:
+	var u := Updates.download_url()
+	if not u.is_empty():
+		OS.shell_open(u)
+
+## Extra words for a "Different game version" refusal: what to do about it.
+static func version_advice(reason: String) -> String:
+	if not reason.begins_with("Different game version"):
+		return ""
+	if Updates.state == "available":
+		return "\nEmberwild %s is out: Download is on the title page." % Updates.latest_version()
+	if reason.ends_with("Update the game to join."):
+		return "\nThere's no newer release yet: the server may be running a newer copy from the source."
+	return ""