Implement basic clipping masks

A very simple implementation, not as complex as something like #768 yet, but it can be done in the future.

The main current limitation is that it doesn't work with group layers as of right now.

assets/graphics/layers/clipping_mask.png.import

@@ -0,0 +1,34 @@
+[remap]
+
+importer="texture"
+type="CompressedTexture2D"
+uid="uid://ieo8fsapcgsy"
+path="res://.godot/imported/clipping_mask.png-735677b4fff2e062e79993566d07bdd3.ctex"
+metadata={
+"vram_texture": false
+}
+
+[deps]
+
+source_file="res://assets/graphics/layers/clipping_mask.png"
+dest_files=["res://.godot/imported/clipping_mask.png-735677b4fff2e062e79993566d07bdd3.ctex"]
+
+[params]
+
+compress/mode=0
+compress/high_quality=false
+compress/lossy_quality=0.7
+compress/hdr_compression=1
+compress/normal_map=0
+compress/channel_pack=0
+mipmaps/generate=false
+mipmaps/limit=-1
+roughness/mode=0
+roughness/src_normal=""
+process/fix_alpha_border=true
+process/premult_alpha=false
+process/normal_map_invert_y=false
+process/hdr_as_srgb=false
+process/hdr_clamp_exposure=false
+process/size_limit=0
+detect_3d/compress_to=1

src/Autoload/DrawingAlgos.gd

@@ -26,9 +26,10 @@ func blend_layers(
 	only_selected_layers := false,
 ) -> void:
 	var textures: Array[Image] = []
-	# Nx3 texture, where N is the number of layers and the first row are the blend modes,
-	# the second are the opacities and the third are the origins
-	var metadata_image := Image.create(project.layers.size(), 3, false, Image.FORMAT_R8)
+	# Nx4 texture, where N is the number of layers and the first row are the blend modes,
+	# the second are the opacities, the third are the origins and the fourth are the
+	# clipping mask booleans.
+	var metadata_image := Image.create(project.layers.size(), 4, false, Image.FORMAT_R8)
 	var frame_index := project.frames.find(frame)
 	var previous_ordered_layers: Array[int] = project.ordered_layers
 	project.order_layers(frame_index)
@@ -51,14 +52,7 @@ func blend_layers(
 		var cel := frame.cels[ordered_index]
 		var cel_image := layer.display_effects(cel)
 		textures.append(cel_image)
-		# Store the blend mode
-		metadata_image.set_pixel(ordered_index, 0, Color(layer.blend_mode / 255.0, 0.0, 0.0, 0.0))
-		# Store the opacity
-		if include:
-			var opacity := cel.get_final_opacity(layer)
-			metadata_image.set_pixel(ordered_index, 1, Color(opacity, 0.0, 0.0, 0.0))
-		else:
-			metadata_image.set_pixel(ordered_index, 1, Color())
+		set_layer_metadata_image(layer, cel, metadata_image, ordered_index, include)
 	var texture_array := Texture2DArray.new()
 	texture_array.create_from_images(textures)
 	var params := {
@@ -73,6 +67,24 @@ func blend_layers(
 	project.ordered_layers = previous_ordered_layers
 
 
+func set_layer_metadata_image(
+	layer: BaseLayer, cel: BaseCel, image: Image, index: int, include := true
+) -> void:
+	# Store the blend mode
+	image.set_pixel(index, 0, Color(layer.blend_mode / 255.0, 0.0, 0.0, 0.0))
+	# Store the opacity
+	if layer.is_visible_in_hierarchy() and include:
+		var opacity := cel.get_final_opacity(layer)
+		image.set_pixel(index, 1, Color(opacity, 0.0, 0.0, 0.0))
+	else:
+		image.set_pixel(index, 1, Color())
+	# Store the clipping mask boolean
+	if layer.clipping_mask:
+		image.set_pixel(index, 3, Color.WHITE)
+	else:
+		image.set_pixel(index, 3, Color.BLACK)
+
+
 ## Algorithm based on http://members.chello.at/easyfilter/bresenham.html
 func get_ellipse_points(pos: Vector2i, size: Vector2i) -> Array[Vector2i]:
 	var array: Array[Vector2i] = []

src/Classes/Layers/BaseLayer.gd

@@ -36,6 +36,7 @@ var visible := true  ## Sets visibility of the layer.
 var locked := false  ## Images of a locked layer won't be overritten.
 var new_cels_linked := false  ## Determines if new cel of the layer should be linked or not.
 var blend_mode := BlendModes.NORMAL  ## Blend mode of the current layer.
+var clipping_mask := false  ## If [code]true[/code], the layer acts as a clipping mask.
 var opacity := 1.0  ## The opacity of the layer, affects all frames that belong to that layer.
 var cel_link_sets: Array[Dictionary] = []  ## Each Dictionary represents a cel's "link set"
 var effects: Array[LayerEffect]  ## An array for non-destructive effects of the layer.
@@ -215,6 +216,7 @@ func serialize() -> Dictionary:
 		"visible": visible,
 		"locked": locked,
 		"blend_mode": blend_mode,
+		"clipping_mask": clipping_mask,
 		"opacity": opacity,
 		"parent": parent.index if is_instance_valid(parent) else -1,
 		"effects": effect_data
@@ -233,13 +235,12 @@ func serialize() -> Dictionary:
 
 ## Sets the layer data according to a curated [Dictionary] obtained from [method serialize].
 func deserialize(dict: Dictionary) -> void:
-	name = dict.name
-	visible = dict.visible
-	locked = dict.locked
-	if dict.has("blend_mode"):
-		blend_mode = dict.blend_mode
-	if dict.has("opacity"):
-		opacity = dict.opacity
+	name = dict.get("name", "")
+	visible = dict.get("visible", true)
+	locked = dict.get("locked", false)
+	blend_mode = dict.get("blend_mode", BlendModes.NORMAL)
+	clipping_mask = dict.get("clipping_mask", false)
+	opacity = dict.get("opacity", 1.0)
 	if dict.get("parent", -1) != -1:
 		parent = project.layers[dict.parent]
 	if dict.has("linked_cels") and not dict["linked_cels"].is_empty():  # Backwards compatibility

src/Shaders/BlendLayers.gdshader

@@ -5,8 +5,9 @@ const float HCV_EPSILON = 1e-10;
 const float HSL_EPSILON = 1e-10;
 
 uniform sampler2DArray layers : filter_nearest;
-// Nx3 texture, where N is the number of layers and the first row are the blend modes,
-// the second are the opacities and the third are the origins
+// Nx4 texture, where N is the number of layers and the first row are the blend modes,
+// the second are the opacities, the third are the origins and the fourth are the
+// clipping mask booleans.
 uniform sampler2D metadata : filter_nearest;
 uniform bool origin_x_positive = true;
 uniform bool origin_y_positive = true;
@@ -153,9 +154,9 @@ void fragment() {
 		first_origin.y = -first_origin.y;
 	}
 	float first_opacity = texture(metadata, vec2(0.0, 1.0 / float(metadata_size.y))).r;
-	vec4 col = texture(layers, vec3(UV - first_origin, 0.0));
-	col.a = border_trim(col, UV - first_origin);
-	col.a *= first_opacity;
+	vec4 result_color = texture(layers, vec3(UV - first_origin, 0.0));
+	result_color.a = border_trim(result_color, UV - first_origin);
+	result_color.a *= first_opacity;
 	for(int i = 1; i < metadata_size.x + 1; i++) // Loops through every layer
 	{
 		float blend_mode_float = texture(metadata, vec2(float(i) / float(metadata_size.x), 0.0)).r;
@@ -171,9 +172,12 @@ void fragment() {
 		}
 		float current_opacity = texture(metadata, vec2(float(i) / float(metadata_size.x), 1.0 / float(metadata_size.y))).r;
 		vec2 uv = UV - current_origin;
-		vec4 texture_color = texture(layers, vec3(uv, float(i)));
-		texture_color.a = border_trim(texture_color, uv);
-		col = blend(current_blend_mode, texture_color, col, current_opacity);
+		vec4 layer_color = texture(layers, vec3(uv, float(i)));
+		vec4 prev_layer_color = texture(layers, vec3(uv, float(i - 1)));
+		float clipping_mask = texture(metadata, vec2(float(i) / float(metadata_size.x), 3.0 / float(metadata_size.y))).r;
+		layer_color.a *= prev_layer_color.a * step(0.5, clipping_mask) + 1.0 * step(clipping_mask, 0.5);
+		layer_color.a = border_trim(layer_color, uv);
+		result_color = blend(current_blend_mode, layer_color, result_color, current_opacity);
 	}
-	COLOR = col;
+	COLOR = result_color;
 }

src/UI/Canvas/Canvas.gd

@@ -148,9 +148,10 @@ func draw_layers() -> void:
 	if recreate_texture_array:
 		var textures: Array[Image] = []
 		textures.resize(project.layers.size())
-		# Nx3 texture, where N is the number of layers and the first row are the blend modes,
-		# the second are the opacities and the third are the origins
-		layer_metadata_image = Image.create(project.layers.size(), 3, false, Image.FORMAT_RG8)
+		# Nx4 texture, where N is the number of layers and the first row are the blend modes,
+		# the second are the opacities, the third are the origins and the fourth are the
+		# clipping mask booleans.
+		layer_metadata_image = Image.create(project.layers.size(), 4, false, Image.FORMAT_RG8)
 		# Draw current frame layers
 		for i in project.layers.size():
 			var ordered_index := project.ordered_layers[i]
@@ -162,16 +163,7 @@ func draw_layers() -> void:
 			else:
 				cel_image = cel.get_image()
 			textures[ordered_index] = cel_image
-			# Store the blend mode
-			layer_metadata_image.set_pixel(
-				ordered_index, 0, Color(layer.blend_mode / 255.0, 0.0, 0.0, 0.0)
-			)
-			# Store the opacity
-			if layer.is_visible_in_hierarchy():
-				var opacity := cel.get_final_opacity(layer)
-				layer_metadata_image.set_pixel(ordered_index, 1, Color(opacity, 0.0, 0.0, 0.0))
-			else:
-				layer_metadata_image.set_pixel(ordered_index, 1, Color())
+			DrawingAlgos.set_layer_metadata_image(layer, cel, layer_metadata_image, ordered_index)
 			# Store the origin
 			if [project.current_frame, i] in project.selected_cels:
 				var origin := Vector2(move_preview_location).abs() / Vector2(cel_image.get_size())
@@ -199,14 +191,10 @@ func draw_layers() -> void:
 				else:
 					cel_image = cel.get_image()
 				layer_texture_array.update_layer(cel_image, ordered_index)
-				layer_metadata_image.set_pixel(
-					ordered_index, 0, Color(layer.blend_mode / 255.0, 0.0, 0.0, 0.0)
+				DrawingAlgos.set_layer_metadata_image(
+					layer, cel, layer_metadata_image, ordered_index
 				)
-				if layer.is_visible_in_hierarchy():
-					var opacity := cel.get_final_opacity(layer)
-					layer_metadata_image.set_pixel(ordered_index, 1, Color(opacity, 0.0, 0.0, 0.0))
-				else:
-					layer_metadata_image.set_pixel(ordered_index, 1, Color())
+				# Update the origin
 				var origin := Vector2(move_preview_location).abs() / Vector2(cel_image.get_size())
 				layer_metadata_image.set_pixel(
 					ordered_index, 2, Color(origin.x, origin.y, 0.0, 0.0)

src/UI/Canvas/CanvasPreview.gd

@@ -76,9 +76,10 @@ func _draw_layers() -> void:
 	var current_frame := project.frames[frame_index]
 	var current_cels := current_frame.cels
 	var textures: Array[Image] = []
-	# Nx3 texture, where N is the number of layers and the first row are the blend modes,
-	# the second are the opacities and the third are the origins
-	var metadata_image := Image.create(project.layers.size(), 3, false, Image.FORMAT_R8)
+	# Nx4 texture, where N is the number of layers and the first row are the blend modes,
+	# the second are the opacities, the third are the origins and the fourth are the
+	# clipping mask booleans.
+	var metadata_image := Image.create(project.layers.size(), 4, false, Image.FORMAT_R8)
 	# Draw current frame layers
 	for i in project.ordered_layers:
 		var cel := current_cels[i]
@@ -91,12 +92,7 @@ func _draw_layers() -> void:
 		else:
 			cel_image = cel.get_image()
 		textures.append(cel_image)
-		metadata_image.set_pixel(i, 0, Color(layer.blend_mode / 255.0, 0.0, 0.0, 0.0))
-		if layer.is_visible_in_hierarchy():
-			var opacity := cel.get_final_opacity(layer)
-			metadata_image.set_pixel(i, 1, Color(opacity, 0.0, 0.0, 0.0))
-		else:
-			metadata_image.set_pixel(i, 1, Color(0.0, 0.0, 0.0, 0.0))
+		DrawingAlgos.set_layer_metadata_image(layer, cel, metadata_image, i)
 	var texture_array := Texture2DArray.new()
 	texture_array.create_from_images(textures)
 	material.set_shader_parameter("layers", texture_array)

src/UI/Timeline/AnimationTimeline.gd

@@ -940,13 +940,11 @@ func _on_MergeDownLayer_pressed() -> void:
 		var top_image := top_layer.display_effects(top_cel)
 		var bottom_cel := frame.cels[bottom_layer.index]
 		var textures: Array[Image] = []
-		var metadata_image := Image.create(2, 3, false, Image.FORMAT_R8)
 		textures.append(bottom_cel.get_image())
-		metadata_image.set_pixel(0, 1, Color(1.0, 0.0, 0.0, 0.0))
 		textures.append(top_image)
-		metadata_image.set_pixel(1, 0, Color(top_layer.blend_mode / 255.0, 0.0, 0.0, 0.0))
-		var opacity := frame.cels[top_layer.index].get_final_opacity(top_layer)
-		metadata_image.set_pixel(1, 1, Color(opacity, 0.0, 0.0, 0.0))
+		var metadata_image := Image.create(2, 4, false, Image.FORMAT_R8)
+		DrawingAlgos.set_layer_metadata_image(bottom_layer, bottom_cel, metadata_image, 0)
+		DrawingAlgos.set_layer_metadata_image(top_layer, top_cel, metadata_image, 1)
 		var texture_array := Texture2DArray.new()
 		texture_array.create_from_images(textures)
 		var params := {

src/UI/Timeline/LayerButton.gd

@@ -12,6 +12,8 @@ var layer_index := 0
 @onready var line_edit := %LayerNameLineEdit as LineEdit
 @onready var hierarchy_spacer := %HierarchySpacer as Control
 @onready var linked_button := %LinkButton as BaseButton
+@onready var clipping_mask_icon := %ClippingMask as TextureRect
+@onready var popup_menu := $PopupMenu as PopupMenu
 
 
 func _ready() -> void:
@@ -71,6 +73,8 @@ func update_buttons() -> void:
 
 	visibility_button.modulate.a = 1
 	lock_button.modulate.a = 1
+	popup_menu.set_item_checked(0, layer.clipping_mask)
+	clipping_mask_icon.visible = layer.clipping_mask
 	if is_instance_valid(layer.parent):
 		if not layer.parent.is_visible_in_hierarchy():
 			visibility_button.modulate.a = 0.33
@@ -108,7 +112,9 @@ func _input(event: InputEvent) -> void:
 func _on_LayerContainer_gui_input(event: InputEvent) -> void:
 	var project := Global.current_project
 
-	if event is InputEventMouseButton and event.button_index == MOUSE_BUTTON_LEFT:
+	if not event is InputEventMouseButton:
+		return
+	if event.button_index == MOUSE_BUTTON_LEFT:
 		Global.canvas.selection.transform_content_confirm()
 		var prev_curr_layer := project.current_layer
 		if Input.is_action_pressed(&"shift"):
@@ -135,6 +141,10 @@ func _on_LayerContainer_gui_input(event: InputEvent) -> void:
 			line_edit.visible = true
 			line_edit.editable = true
 			line_edit.grab_focus()
+	elif event.button_index == MOUSE_BUTTON_RIGHT and event.pressed:
+		var layer := Global.current_project.layers[layer_index]
+		if not layer is GroupLayer:
+			popup_menu.popup(Rect2(get_global_mouse_position(), Vector2.ONE))
 
 
 func _on_LineEdit_focus_exited() -> void:
@@ -368,3 +378,12 @@ func _get_region_rect(y_begin: float, y_end: float) -> Rect2:
 	rect.position.y += rect.size.y * y_begin
 	rect.size.y *= y_end - y_begin
 	return rect
+
+
+func _on_popup_menu_id_pressed(id: int) -> void:
+	var layer := Global.current_project.layers[layer_index]
+	if id == 0:
+		layer.clipping_mask = not layer.clipping_mask
+		popup_menu.set_item_checked(0, layer.clipping_mask)
+		clipping_mask_icon.visible = layer.clipping_mask
+		Global.canvas.draw_layers()

src/UI/Timeline/LayerButton.tscn

@@ -1,10 +1,11 @@
-[gd_scene load_steps=6 format=3 uid="uid://bai814sqvk68f"]
+[gd_scene load_steps=7 format=3 uid="uid://bai814sqvk68f"]
 
 [ext_resource type="Script" path="res://src/UI/Timeline/LayerButton.gd" id="1_6hlpe"]
 [ext_resource type="Texture2D" uid="uid://c2b3htff5yox8" path="res://assets/graphics/layers/layer_visible.png" id="2_ef6fb"]
 [ext_resource type="Texture2D" uid="uid://dndlglvqc7v6a" path="res://assets/graphics/layers/group_expanded.png" id="2_enrtd"]
 [ext_resource type="Texture2D" uid="uid://dhc0pnnqojd2m" path="res://assets/graphics/layers/unlock.png" id="3_ah1my"]
 [ext_resource type="Texture2D" uid="uid://cofw1x6chh4i" path="res://assets/graphics/layers/unlinked_layer.png" id="4_058qm"]
+[ext_resource type="Texture2D" uid="uid://ieo8fsapcgsy" path="res://assets/graphics/layers/clipping_mask.png" id="6_73j5q"]
 
 [node name="LayerButton" type="Button"]
 offset_right = 200.0
@@ -147,6 +148,13 @@ unique_name_in_owner = true
 layout_mode = 2
 mouse_filter = 2
 
+[node name="ClippingMask" type="TextureRect" parent="HBoxContainer/LayerName"]
+unique_name_in_owner = true
+visible = false
+layout_mode = 2
+texture = ExtResource("6_73j5q")
+stretch_mode = 5
+
 [node name="LayerNameLabel" type="Label" parent="HBoxContainer/LayerName"]
 unique_name_in_owner = true
 layout_mode = 2
@@ -169,9 +177,17 @@ caret_blink_interval = 0.5
 layout_mode = 2
 mouse_filter = 2
 
+[node name="PopupMenu" type="PopupMenu" parent="."]
+disable_3d = true
+item_count = 1
+item_0/text = "Clipping mask"
+item_0/checkable = 1
+item_0/id = 0
+
 [connection signal="gui_input" from="." to="." method="_on_LayerContainer_gui_input"]
 [connection signal="pressed" from="HBoxContainer/LayerButtons/ExpandButton" to="." method="_on_ExpandButton_pressed"]
 [connection signal="pressed" from="HBoxContainer/LayerButtons/VisibilityButton" to="." method="_on_VisibilityButton_pressed"]
 [connection signal="pressed" from="HBoxContainer/LayerButtons/LockButton" to="." method="_on_LockButton_pressed"]
 [connection signal="pressed" from="HBoxContainer/LayerButtons/LinkButton" to="." method="_on_LinkButton_pressed"]
 [connection signal="focus_exited" from="HBoxContainer/LayerName/LayerNameLineEdit" to="." method="_on_LineEdit_focus_exited"]
+[connection signal="id_pressed" from="PopupMenu" to="." method="_on_popup_menu_id_pressed"]