Adrien Ufferte
67 lines
2.7 KiB
GDScript
67 lines
2.7 KiB
GDScript
extends Node
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## Scene changer that keeps peak memory low on low-end devices.
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##
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## [method SceneTree.change_scene_to_file] loads the new scene while the old
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## one is still fully resident, so transitions between heavy scenes (gardens,
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## minigames) momentarily need the memory of both — enough to OOM-crash old
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## tablets. This helper frees the current scene first, then streams the new
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## scene from disk on a background thread so the main thread keeps rendering
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## frames instead of freezing.
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##
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## Callers are expected to have covered the screen (OpeningCurtain closed)
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## before calling [method change_scene]; the curtain stays visible while the
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## tree has no current scene.
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## Scene shown if the requested scene fails to load, so the player is never
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## stuck on a black screen.
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const FALLBACK_SCENE_PATH: String = "res://sources/menus/main/main_menu.tscn"
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var _is_changing: bool = false
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func change_scene(scene_path: String) -> void:
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if _is_changing:
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Log.warn("SceneLoader: Change to %s requested while another change is in progress; ignoring" % scene_path)
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return
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if not ResourceLoader.exists(scene_path):
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Log.error("SceneLoader: Scene does not exist: %s" % scene_path)
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return
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_is_changing = true
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# Defer so the calling scene is never freed while one of its methods is
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# still on the stack.
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_change_scene_deferred.call_deferred(scene_path)
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func _change_scene_deferred(scene_path: String) -> void:
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var tree: SceneTree = get_tree()
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# Free the old scene before loading the new one: this roughly halves the
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# memory peak of the transition.
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if tree.current_scene:
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tree.unload_current_scene()
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var error: Error = ResourceLoader.load_threaded_request(scene_path)
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if error != OK:
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Log.error("SceneLoader: Could not start loading %s (error %s)" % [scene_path, error_string(error)])
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_finish_with_fallback(tree, scene_path)
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return
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var status: ResourceLoader.ThreadLoadStatus = ResourceLoader.load_threaded_get_status(scene_path)
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while status == ResourceLoader.THREAD_LOAD_IN_PROGRESS:
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await tree.process_frame
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status = ResourceLoader.load_threaded_get_status(scene_path)
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if status != ResourceLoader.THREAD_LOAD_LOADED:
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Log.error("SceneLoader: Failed to load %s (status %d)" % [scene_path, status])
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_finish_with_fallback(tree, scene_path)
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return
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var packed_scene: PackedScene = ResourceLoader.load_threaded_get(scene_path) as PackedScene
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if not packed_scene:
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Log.error("SceneLoader: %s is not a PackedScene" % scene_path)
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_finish_with_fallback(tree, scene_path)
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return
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_is_changing = false
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tree.change_scene_to_packed(packed_scene)
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func _finish_with_fallback(tree: SceneTree, failed_scene_path: String) -> void:
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_is_changing = false
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if failed_scene_path != FALLBACK_SCENE_PATH:
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tree.change_scene_to_file(FALLBACK_SCENE_PATH)
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