Add CharacterAnimationPlayerBehavior

Similar to CharacterSpriteBehavior, this behavior node can control an
AnimationPlayer to play idle, walk and run animations depending on the
velocity of a CharacterBody2D.

Resolve #1225

Author: manuq

scenes/game_logic/character_animation_player_behavior.gd

@@ -0,0 +1,69 @@
+# SPDX-FileCopyrightText: The Threadbare Authors
+# SPDX-License-Identifier: MPL-2.0
+@tool
+class_name CharacterAnimationPlayerBehavior
+extends Node2D
+## @experimental
+##
+## Play animations in [member animation_player] according
+## to the velocity of [member character].
+## [br][br]
+## For creating simple characters, consider using [CharacterSpriteBehavior] instead.
+
+## The [member CharacterBody2D.velocity] is used to change the [member animation_player].
+## [br][br]
+## [b]Note:[/b] If the grandparent node is a CharacterBody2D and this isn't set,
+## the grandparent node will be automatically assigned to this variable.
+@export var character: CharacterBody2D
+
+## The controlled animation player.
+## [br][br]
+## [b]Note:[/b] If the parent node is an AnimationPlayer and this isn't set,
+## the parent node will be automatically assigned to this variable.
+@export var animation_player: AnimationPlayer:
+	set = _set_animation_player
+
+var _is_character_running: bool = false
+
+
+func _enter_tree() -> void:
+	if not animation_player and get_parent() is AnimationPlayer:
+		animation_player = get_parent()
+	if not character and get_parent() and get_parent().get_parent() is CharacterBody2D:
+		character = get_parent().get_parent()
+
+
+func _set_animation_player(new_animation_player: AnimationPlayer) -> void:
+	animation_player = new_animation_player
+	update_configuration_warnings()
+
+
+func _get_configuration_warnings() -> PackedStringArray:
+	var warnings: PackedStringArray
+	if animation_player is not AnimationPlayer:
+		warnings.append("Animation Player must be set.")
+	return warnings
+
+
+func _ready() -> void:
+	if Engine.is_editor_hint():
+		set_process(false)
+		return
+
+
+func _process(_delta: float) -> void:
+	if not character:
+		return
+
+	if character.velocity.is_zero_approx():
+		animation_player.play(&"idle")
+	else:
+		if _is_character_running:
+			animation_player.play(&"run")
+		else:
+			animation_player.play(&"walk")
+
+
+## You can connect this callback to a [member InputWalkBehavior.running_changed] signal.
+func on_running_changed(is_running: bool) -> void:
+	_is_character_running = is_running

scenes/game_logic/character_animation_player_behavior.gd.uid

@@ -0,0 +1 @@
+uid://b3hx1n2yl88qr