Move even more code away from Global and Project to AnimationTimeline

This time related to layer buttons

src/Autoload/Global.gd

@@ -489,14 +489,6 @@ var cel_button_scene: PackedScene = load("res://src/UI/Timeline/CelButton.tscn")
 @onready var cel_vbox: VBoxContainer = animation_timeline.find_child("CelVBox")
 ## The container of animation tags.
 @onready var tag_container: Control = animation_timeline.find_child("TagContainer")
-## Remove layer button.
-@onready var remove_layer_button: BaseButton = animation_timeline.find_child("RemoveLayer")
-## Move layer up button.
-@onready var move_up_layer_button: BaseButton = animation_timeline.find_child("MoveUpLayer")
-## Move layer down button.
-@onready var move_down_layer_button: BaseButton = animation_timeline.find_child("MoveDownLayer")
-## Merge with layer below button.
-@onready var merge_down_layer_button: BaseButton = animation_timeline.find_child("MergeDownLayer")
 
 ## The brushes popup dialog used to display brushes.
 ## It has the [param BrushesPopup.gd] script attached.

src/Classes/Project.gd

@@ -178,7 +178,6 @@ func change_project() -> void:
 	Global.animation_timeline.project_changed()
 
 	Global.current_frame_mark_label.text = "%s/%s" % [str(current_frame + 1), frames.size()]
-	toggle_layer_buttons()
 	animation_tags = animation_tags
 
 	# Change the guides
@@ -516,7 +515,6 @@ func change_cel(new_frame: int, new_layer := -1) -> void:
 
 	if new_layer != current_layer:  # If the layer has changed
 		current_layer = new_layer
-		toggle_layer_buttons()
 
 	Global.transparent_checker.update_rect()
 	Global.cel_changed.emit()
@@ -527,31 +525,6 @@ func change_cel(new_frame: int, new_layer := -1) -> void:
 	Global.canvas.queue_redraw()
 
 
-func toggle_layer_buttons() -> void:
-	if layers.is_empty() or current_layer >= layers.size():
-		return
-	var child_count: int = layers[current_layer].get_child_count(true)
-
-	Global.disable_button(
-		Global.remove_layer_button,
-		layers[current_layer].is_locked_in_hierarchy() or layers.size() == child_count + 1
-	)
-	Global.disable_button(Global.move_up_layer_button, current_layer == layers.size() - 1)
-	Global.disable_button(
-		Global.move_down_layer_button,
-		current_layer == child_count and not is_instance_valid(layers[current_layer].parent)
-	)
-	Global.disable_button(
-		Global.merge_down_layer_button,
-		(
-			current_layer == child_count
-			or layers[current_layer] is GroupLayer
-			or layers[current_layer - 1] is GroupLayer
-			or layers[current_layer - 1] is Layer3D
-		)
-	)
-
-
 func _animation_tags_changed(value: Array[AnimationTag]) -> void:
 	animation_tags = value
 	for child in Global.tag_container.get_children():
@@ -866,4 +839,3 @@ func _update_layer_ui() -> void:
 		for f in frames.size():
 			cel_hbox.get_child(f).layer = l
 			cel_hbox.get_child(f).button_setup()
-	toggle_layer_buttons()

src/UI/Timeline/AnimationTimeline.gd

@@ -20,15 +20,19 @@ var future_above_canvas := true
 @onready var layer_settings_container := %LayerSettingsContainer as VBoxContainer
 @onready var layer_container := %LayerContainer as VBoxContainer
 @onready var add_layer_list := %AddLayerList as MenuButton
+@onready var remove_layer := %RemoveLayer as Button
+@onready var move_up_layer := %MoveUpLayer as Button
+@onready var move_down_layer := %MoveDownLayer as Button
+@onready var merge_down_layer := %MergeDownLayer as Button
 @onready var blend_modes_button := %BlendModes as OptionButton
 @onready var opacity_slider: ValueSlider = %OpacitySlider
 @onready var frame_scroll_container := %FrameScrollContainer as Control
 @onready var frame_scroll_bar := %FrameScrollBar as HScrollBar
 @onready var tag_scroll_container := %TagScroll as ScrollContainer
 @onready var layer_frame_h_split := %LayerFrameHSplit as HSplitContainer
-@onready var delete_frame: Button = %DeleteFrame
+@onready var delete_frame := %DeleteFrame as Button
-@onready var move_frame_left: Button = %MoveFrameLeft
+@onready var move_frame_left := %MoveFrameLeft as Button
-@onready var move_frame_right: Button = %MoveFrameRight
+@onready var move_frame_right := %MoveFrameRight as Button
 @onready var play_backwards := %PlayBackwards as Button
 @onready var play_forward := %PlayForward as Button
 @onready var fps_spinbox := %FPSValue as ValueSlider
@@ -993,6 +997,7 @@ func _on_onion_skinning_settings_visibility_changed() -> void:
 
 func _cel_changed() -> void:
 	_toggle_frame_buttons()
+	_toggle_layer_buttons()
 	var project := Global.current_project
 	var cel_opacity := project.get_current_cel().opacity
 	opacity_slider.value = cel_opacity * 100
@@ -1009,9 +1014,36 @@ func _toggle_frame_buttons() -> void:
 	Global.disable_button(move_frame_right, project.current_frame == project.frames.size() - 1)
 
 
+func _toggle_layer_buttons() -> void:
+	var project := Global.current_project
+	if project.layers.is_empty() or project.current_layer >= project.layers.size():
+		return
+	var layer := project.layers[project.current_layer]
+	var child_count := layer.get_child_count(true)
+
+	Global.disable_button(
+		remove_layer, layer.is_locked_in_hierarchy() or project.layers.size() == child_count + 1
+	)
+	Global.disable_button(move_up_layer, project.current_layer == project.layers.size() - 1)
+	Global.disable_button(
+		move_down_layer,
+		project.current_layer == child_count and not is_instance_valid(layer.parent)
+	)
+	Global.disable_button(
+		merge_down_layer,
+		(
+			project.current_layer == child_count
+			or layer is GroupLayer
+			or project.layers[project.current_layer - 1] is GroupLayer
+			or project.layers[project.current_layer - 1] is Layer3D
+		)
+	)
+
+
 func project_changed() -> void:
 	var project := Global.current_project
 	_toggle_frame_buttons()
+	_toggle_layer_buttons()
 	# These must be removed from tree immediately to not mess up the indices of
 	# the new buttons, so use either free or queue_free + parent.remove_child
 	for layer_button in Global.layer_vbox.get_children():

src/UI/Timeline/AnimationTimeline.tscn

@@ -254,6 +254,7 @@ offset_bottom = 6.0
 texture = ExtResource("10")
 
 [node name="RemoveLayer" type="Button" parent="TimelineContainer/TimelineButtons/LayerTools/LayerSettingsContainer/LayerButtons" groups=["UIButtons"]]
+unique_name_in_owner = true
 custom_minimum_size = Vector2(24, 24)
 layout_mode = 2
 size_flags_horizontal = 3
@@ -279,6 +280,7 @@ size_flags_vertical = 0
 texture = ExtResource("6")
 
 [node name="MoveUpLayer" type="Button" parent="TimelineContainer/TimelineButtons/LayerTools/LayerSettingsContainer/LayerButtons" groups=["UIButtons"]]
+unique_name_in_owner = true
 custom_minimum_size = Vector2(24, 24)
 layout_mode = 2
 size_flags_horizontal = 3
@@ -304,6 +306,7 @@ size_flags_vertical = 0
 texture = ExtResource("4")
 
 [node name="MoveDownLayer" type="Button" parent="TimelineContainer/TimelineButtons/LayerTools/LayerSettingsContainer/LayerButtons" groups=["UIButtons"]]
+unique_name_in_owner = true
 custom_minimum_size = Vector2(24, 24)
 layout_mode = 2
 size_flags_horizontal = 3
@@ -353,6 +356,7 @@ size_flags_vertical = 0
 texture = ExtResource("7")
 
 [node name="MergeDownLayer" type="Button" parent="TimelineContainer/TimelineButtons/LayerTools/LayerSettingsContainer/LayerButtons" groups=["UIButtons"]]
+unique_name_in_owner = true
 custom_minimum_size = Vector2(24, 24)
 layout_mode = 2
 size_flags_horizontal = 3