Implement support for group layer blending (#1077)

* Blend group layers on `DrawingAlgos.blend_layers()` * Support group layer blending on the canvas * Allow editing of group layer properties * Fix issues with group layer blending in canvas, and unite common code * Group layers can now be used as clipping masks * Make move tool preview work on child layers * Change OffsetImage's `blend_layers()` to support group layer blending * Support group layer blending in the canvas preview * Fix layer blending mode, clipping mask opacity and cel opacity not being updated automatically if the layer/cel changed is not selected * Add a pass through blending mode to layer groups Fingers crossed that no bugs were introduced * Fix issue with layers that belong to pass through groups not updating their textures on the canvas automatically on undo
2025-01-18 17:19:50 +00:00 · 2024-08-15 15:52:55 +03:00 · 2024-08-15 15:52:55 +03:00 · 077c57c53a
parent f6f40e03e5
commit 077c57c53a
12 changed files with 332 additions and 115 deletions
--- a/Translations/Translations.pot
+++ b/Translations/Translations.pot
@ -2143,6 +2143,10 @@ msgstr ""
 msgid "Blend mode:"
 msgstr ""

+#. Found in the layer's section of the timeline, as a blend mode option, only available for group layers. If enabled, group blending is disabled and the group simply acts as a way to organize layers instead of affecting blending.
+msgid "Pass through"
+msgstr ""
+
 #. Adjective, refers to something usual/regular, such as the normal blend mode.
 msgid "Normal"
 msgstr ""
--- a/src/Autoload/DrawingAlgos.gd
+++ b/src/Autoload/DrawingAlgos.gd
@ -52,9 +52,19 @@ func blend_layers(
 		var cel := frame.cels[ordered_index]
 		if DisplayServer.get_name() == "headless":
 			blend_layers_headless(image, project, layer, cel, origin)
+		else:
+			if layer is GroupLayer and layer.blend_mode != BaseLayer.BlendModes.PASS_THROUGH:
+				var cel_image := (layer as GroupLayer).blend_children(frame)
+				textures.append(cel_image)
 			else:
 				var cel_image := layer.display_effects(cel)
 				textures.append(cel_image)
+			if (
+				layer.is_blended_by_ancestor()
+				and not only_selected_cels
+				and not only_selected_layers
+			):
+				include = false
 			set_layer_metadata_image(layer, cel, metadata_image, ordered_index, include)
 	if DisplayServer.get_name() != "headless":
 		var texture_array := Texture2DArray.new()
@ -84,9 +94,14 @@ func set_layer_metadata_image(
 		image.set_pixel(index, 1, Color())
 	# Store the clipping mask boolean
 	if layer.clipping_mask:
-		image.set_pixel(index, 3, Color.WHITE)
+		image.set_pixel(index, 3, Color.RED)
 	else:
 		image.set_pixel(index, 3, Color.BLACK)
+	if not include:
+		# Store a small red value as a way to indicate that this layer should be skipped
+		# Used for layers such as child layers of a group, so that the group layer itself can
+		# sucessfuly be used as a clipping mask with the layer below it.
+		image.set_pixel(index, 3, Color(0.2, 0.0, 0.0, 0.0))


 func blend_layers_headless(
--- a/src/Classes/Layers/BaseLayer.gd
+++ b/src/Classes/Layers/BaseLayer.gd
@ -1,3 +1,4 @@
+# gdlint: ignore=max-public-methods
 class_name BaseLayer
 extends RefCounted
 ## Base class for layer properties. Different layer types extend from this class.
@ -9,7 +10,8 @@ signal visibility_changed  ## Emits when [member visible] is changed.
 ## is the blend layer, and the bottom layer is the base layer.
 ## For more information, refer to: [url]https://en.wikipedia.org/wiki/Blend_modes[/url]
 enum BlendModes {
-	NORMAL,  ## The blend layer colors are simply placed on top of the base colors.
+	PASS_THROUGH = -2,  ## Only for group layers. Ignores group blending, like it doesn't exist.
+	NORMAL = 0,  ## The blend layer colors are simply placed on top of the base colors.
 	DARKEN,  ## Keeps the darker colors between the blend and the base layers.
 	MULTIPLY,  ## Multiplies the numerical values of the two colors, giving a darker result.
 	COLOR_BURN,  ## Darkens by increasing the contrast between the blend and base colors.
@ -124,6 +126,17 @@ func is_locked_in_hierarchy() -> bool:
 	return locked


+## Returns [code]true[/code] if the layer has at least one ancestor
+## that does not have its blend mode set to pass through.
+func is_blended_by_ancestor() -> bool:
+	var is_blended := false
+	for ancestor in get_ancestors():
+		if ancestor.blend_mode != BlendModes.PASS_THROUGH:
+			is_blended = true
+			break
+	return is_blended
+
+
 ## Returns an [Array] of [BaseLayer]s that are ancestors of this layer.
 ## If there are no ancestors, returns an empty array.
 func get_ancestors() -> Array[BaseLayer]:
@ -141,6 +154,20 @@ func get_hierarchy_depth() -> int:
 	return 0


+## Returns the layer's top most parent that is responsible for its blending.
+## For example, if a layer belongs in a group with its blend mode set to anything but pass through,
+## and that group has no parents of its own, then that group gets returned.
+## If that group is a child of another non-pass through group,
+## then the grandparent group is returned, and so on.
+## If the layer has no ancestors, or if they are set to pass through mode, it returns self.
+func get_blender_ancestor() -> BaseLayer:
+	var blender := self
+	for ancestor in get_ancestors():
+		if ancestor.blend_mode != BlendModes.PASS_THROUGH:
+			blender = ancestor
+	return blender
+
+
 ## Returns the path of the layer in the timeline as a [String].
 func get_layer_path() -> String:
 	if is_instance_valid(parent):
@ -189,8 +216,11 @@ func link_cel(cel: BaseCel, link_set = null) -> void:
 ## Returns a copy of the [param cel]'s [Image] with all of the effects applied to it.
 ## This method is not destructive as it does NOT change the data of the image,
 ## it just returns a copy.
-func display_effects(cel: BaseCel) -> Image:
+func display_effects(cel: BaseCel, image_override: Image = null) -> Image:
 	var image := Image.new()
+	if is_instance_valid(image_override):
+		image.copy_from(image_override)
+	else:
 		image.copy_from(cel.get_image())
 	if not effects_enabled:
 		return image
@ -200,8 +230,10 @@ func display_effects(cel: BaseCel) -> Image:
 			continue
 		var shader_image_effect := ShaderImageEffect.new()
 		shader_image_effect.generate_image(image, effect.shader, effect.params, image_size)
-	# Inherit effects from the parents
+	# Inherit effects from the parents, if their blend mode is set to pass through
 	for ancestor in get_ancestors():
+		if ancestor.blend_mode != BlendModes.PASS_THROUGH:
+			break
 		if not ancestor.effects_enabled:
 			continue
 		for effect in ancestor.effects:
--- a/src/Classes/Layers/GroupLayer.gd
+++ b/src/Classes/Layers/GroupLayer.gd
@ -11,42 +11,128 @@ func _init(_project: Project, _name := "") -> void:


 ## Blends all of the images of children layer of the group layer into a single image.
-func blend_children(frame: Frame, origin := Vector2i.ZERO) -> Image:
+func blend_children(frame: Frame, origin := Vector2i.ZERO, apply_effects := true) -> Image:
 	var image := Image.create(project.size.x, project.size.y, false, Image.FORMAT_RGBA8)
 	var children := get_children(false)
 	if children.size() <= 0:
 		return image
-	var blend_rect := Rect2i(Vector2i.ZERO, project.size)
 	var textures: Array[Image] = []
-	var metadata_image := Image.create(children.size(), 4, false, Image.FORMAT_R8)
+	var metadata_image := Image.create(children.size(), 4, false, Image.FORMAT_RG8)
+	var current_child_index := 0
 	for i in children.size():
 		var layer := children[i]
 		if not layer.is_visible_in_hierarchy():
+			current_child_index += 1
 			continue
-		var cel := frame.cels[layer.index]
 		if layer is GroupLayer:
-			var blended_children: Image = layer.blend_children(frame, origin)
+			current_child_index = _blend_child_group(
+				image,
+				layer,
+				frame,
+				textures,
+				metadata_image,
+				current_child_index,
+				origin,
+				apply_effects
+			)
+		else:
+			_include_child_in_blending(
+				image,
+				layer,
+				frame,
+				textures,
+				metadata_image,
+				current_child_index,
+				origin,
+				apply_effects
+			)
+		current_child_index += 1
+
+	if DisplayServer.get_name() != "headless" and textures.size() > 0:
+		var texture_array := Texture2DArray.new()
+		texture_array.create_from_images(textures)
+		var params := {
+			"layers": texture_array,
+			"metadata": ImageTexture.create_from_image(metadata_image),
+			"origin_x_positive": origin.x > 0,
+			"origin_y_positive": origin.y > 0,
+		}
+		var gen := ShaderImageEffect.new()
+		gen.generate_image(image, DrawingAlgos.blend_layers_shader, params, project.size)
+		if apply_effects:
+			image = display_effects(frame.cels[index], image)
+	return image
+
+
+func _include_child_in_blending(
+	image: Image,
+	layer: BaseLayer,
+	frame: Frame,
+	textures: Array[Image],
+	metadata_image: Image,
+	i: int,
+	origin: Vector2i,
+	apply_effects: bool
+) -> void:
+	var cel := frame.cels[layer.index]
+	if DisplayServer.get_name() == "headless":
+		DrawingAlgos.blend_layers_headless(image, project, layer, cel, origin)
+	else:
+		var cel_image: Image
+		if apply_effects:
+			cel_image = layer.display_effects(cel)
+		else:
+			cel_image = cel.get_image()
+		textures.append(cel_image)
+		DrawingAlgos.set_layer_metadata_image(layer, cel, metadata_image, i)
+		if origin != Vector2i.ZERO:
+			# Only used as a preview for the move tool, when used on a group's children
+			var test_array := [project.frames.find(frame), project.layers.find(layer)]
+			if test_array in project.selected_cels:
+				var origin_fixed := Vector2(origin).abs() / Vector2(cel_image.get_size())
+				metadata_image.set_pixel(i, 2, Color(origin_fixed.x, origin_fixed.y, 0.0, 0.0))
+
+
+## Include a child group in the blending process.
+## If the child group is set to pass through mode, loop through its children
+## and include them as separate images, instead of blending them all together.
+## Gets called recursively if the child group has children groups of its own,
+## and they are also set to pass through mode.
+func _blend_child_group(
+	image: Image,
+	layer: BaseLayer,
+	frame: Frame,
+	textures: Array[Image],
+	metadata_image: Image,
+	i: int,
+	origin: Vector2i,
+	apply_effects: bool
+) -> int:
+	var new_i := i
+	var blend_rect := Rect2i(Vector2i.ZERO, project.size)
+	var cel := frame.cels[layer.index]
+	if layer.blend_mode == BlendModes.PASS_THROUGH:
+		var children := layer.get_children(false)
+		for j in children.size():
+			var child := children[j]
+			if child is GroupLayer:
+				new_i = _blend_child_group(
+					image, child, frame, textures, metadata_image, i + j, origin, apply_effects
+				)
+			else:
+				new_i += j
+				metadata_image.crop(metadata_image.get_width() + 1, metadata_image.get_height())
+				_include_child_in_blending(
+					image, child, frame, textures, metadata_image, new_i, origin, apply_effects
+				)
+	else:
+		var blended_children := (layer as GroupLayer).blend_children(frame, origin)
 		if DisplayServer.get_name() == "headless":
 			image.blend_rect(blended_children, blend_rect, origin)
 		else:
 			textures.append(blended_children)
 			DrawingAlgos.set_layer_metadata_image(layer, cel, metadata_image, i)
-		else:
-			if DisplayServer.get_name() == "headless":
-				DrawingAlgos.blend_layers_headless(image, project, layer, cel, origin)
-			else:
-				textures.append(layer.display_effects(cel))
-				DrawingAlgos.set_layer_metadata_image(layer, cel, metadata_image, i)
-
-	if DisplayServer.get_name() != "headless":
-		var texture_array := Texture2DArray.new()
-		texture_array.create_from_images(textures)
-		var params := {
-			"layers": texture_array, "metadata": ImageTexture.create_from_image(metadata_image)
-		}
-		var gen := ShaderImageEffect.new()
-		gen.generate_image(image, DrawingAlgos.blend_layers_shader, params, project.size)
-	return image
+	return new_i


 # Overridden Methods:
--- a/src/Shaders/BlendLayers.gdshader
+++ b/src/Shaders/BlendLayers.gdshader
@ -144,6 +144,20 @@ float border_trim(vec4 color, vec2 uv) {
 }


+int find_previous_opaque_layer(int index, vec2 metadata_size_float) {
+	for (int i = index - 1; i > 0; i--) {
+		float layer_index = float(i) / metadata_size_float.x;
+		float clipping_mask = texture(metadata, vec2(layer_index, 3.0 / metadata_size_float.y)).r;
+		// If the red value is ~0.2, it means that it should be skipped.
+		// Otherwise, return the index.
+		if (clipping_mask > 0.25 || clipping_mask < 0.15) {
+			return i;
+		}
+	}
+	return 0;
+}
+
+
 void fragment() {
 	ivec2 metadata_size = textureSize(metadata, 0) - 1;
 	vec2 metadata_size_float = vec2(metadata_size);
@ -173,7 +187,8 @@ void fragment() {
 			current_origin.y = -current_origin.y;
 		}
 		// get origin of previous layer (used for clipping masks to work correctly)
-		vec2 prev_origin = texture(metadata, vec2(float(i - 1), 2.0 / metadata_size_float.y)).rg;
+		float clipping_mask_index = float(find_previous_opaque_layer(i, metadata_size_float));
+		vec2 prev_origin = texture(metadata, vec2(clipping_mask_index, 2.0 / metadata_size_float.y)).rg;
 		if (!origin_x_positive) {
 			prev_origin.x = -prev_origin.x;
 		}
@ -183,7 +198,7 @@ void fragment() {
 		float current_opacity = texture(metadata, vec2(layer_index, 1.0 / metadata_size_float.y)).r;
 		vec2 uv = UV - current_origin;
 		vec4 layer_color = texture(layers, vec3(uv, float(i)));
-		vec4 prev_layer_color = texture(layers, vec3(UV - prev_origin, float(i - 1)));
+		vec4 prev_layer_color = texture(layers, vec3(UV - prev_origin, clipping_mask_index));
 		float clipping_mask = texture(metadata, vec2(layer_index, 3.0 / metadata_size_float.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);
--- a/src/UI/Canvas/Canvas.gd
+++ b/src/UI/Canvas/Canvas.gd
@ -117,8 +117,13 @@ func update_texture(layer_i: int, frame_i := -1, project := Global.current_proje
 		if frame_i != project.current_frame:
 			# Don't update if the cel is on a different frame (can happen with undo/redo)
 			return
-		var layer := project.layers[layer_i]
+		var layer := project.layers[layer_i].get_blender_ancestor()
 		var cel_image: Image
+		if layer is GroupLayer:
+			cel_image = layer.blend_children(
+				project.frames[project.current_frame], Vector2i.ZERO, Global.display_layer_effects
+			)
+		else:
 			if Global.display_layer_effects:
 				cel_image = layer.display_effects(current_cel)
 			else:
@ -127,7 +132,7 @@ func update_texture(layer_i: int, frame_i := -1, project := Global.current_proje
 			cel_image.get_size()
 			== Vector2i(layer_texture_array.get_width(), layer_texture_array.get_height())
 		):
-			layer_texture_array.update_layer(cel_image, project.ordered_layers[layer_i])
+			layer_texture_array.update_layer(cel_image, project.ordered_layers[layer.index])


 func update_selected_cels_textures(project := Global.current_project) -> void:
@ -141,7 +146,6 @@ func update_selected_cels_textures(project := Global.current_project) -> void:

 func draw_layers(force_recreate := false) -> void:
 	var project := Global.current_project
-	var current_cels := project.frames[project.current_frame].cels
 	var recreate_texture_array := (
 		layer_texture_array.get_layers() != project.layers.size()
 		or layer_texture_array.get_width() != project.size.x
@ -157,16 +161,11 @@ func draw_layers(force_recreate := false) -> void:
 		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]
 			var layer := project.layers[i]
-			var cel := current_cels[i]
-			var cel_image: Image
-			if Global.display_layer_effects:
-				cel_image = layer.display_effects(cel)
-			else:
-				cel_image = cel.get_image()
+			var ordered_index := project.ordered_layers[layer.index]
+			var cel_image := Image.new()
+			_update_texture_array_layer(project, layer, cel_image, false)
 			textures[ordered_index] = cel_image
-			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())
@ -185,18 +184,14 @@ func draw_layers(force_recreate := false) -> void:
 					var test_array := [project.current_frame, i]
 					if not test_array in project.selected_cels:
 						continue
-				var ordered_index := project.ordered_layers[i]
 				var layer := project.layers[i]
-				var cel := current_cels[i]
-				var cel_image: Image
-				if Global.display_layer_effects:
-					cel_image = layer.display_effects(cel)
-				else:
-					cel_image = cel.get_image()
-				layer_texture_array.update_layer(cel_image, ordered_index)
-				DrawingAlgos.set_layer_metadata_image(
-					layer, cel, layer_metadata_image, ordered_index
-				)
+				var ordered_index := project.ordered_layers[layer.index]
+				var cel_image := Image.new()
+				_update_texture_array_layer(project, layer, cel_image, true)
+				var parent_layer := layer.get_blender_ancestor()
+				if layer != parent_layer:
+					# True when the layer has parents. In that case, update its top-most parent.
+					_update_texture_array_layer(project, parent_layer, Image.new(), true)
 				# Update the origin
 				var origin := Vector2(move_preview_location).abs() / Vector2(cel_image.get_size())
 				layer_metadata_image.set_pixel(
@ -209,6 +204,32 @@ func draw_layers(force_recreate := false) -> void:
 	update_all_layers = false


+func _update_texture_array_layer(
+	project: Project, layer: BaseLayer, cel_image: Image, update_layer: bool
+) -> void:
+	var ordered_index := project.ordered_layers[layer.index]
+	var cel := project.frames[project.current_frame].cels[layer.index]
+	var include := true
+	if layer is GroupLayer and layer.blend_mode != BaseLayer.BlendModes.PASS_THROUGH:
+		cel_image.copy_from(
+			layer.blend_children(
+				project.frames[project.current_frame],
+				move_preview_location,
+				Global.display_layer_effects
+			)
+		)
+	else:
+		if Global.display_layer_effects:
+			cel_image.copy_from(layer.display_effects(cel))
+		else:
+			cel_image.copy_from(cel.get_image())
+	if layer.is_blended_by_ancestor():
+		include = false
+	if update_layer:
+		layer_texture_array.update_layer(cel_image, ordered_index)
+	DrawingAlgos.set_layer_metadata_image(layer, cel, layer_metadata_image, ordered_index, include)
+
+
 func refresh_onion() -> void:
 	onion_past.queue_redraw()
 	onion_future.queue_redraw()
--- a/src/UI/Canvas/CanvasPreview.gd
+++ b/src/UI/Canvas/CanvasPreview.gd
@ -83,10 +83,13 @@ func _draw_layers() -> void:
 	# Draw current frame layers
 	for i in project.ordered_layers:
 		var cel := current_cels[i]
-		if current_cels[i] is GroupCel:
-			continue
 		var layer := project.layers[i]
 		var cel_image: Image
+		if layer is GroupLayer and layer.blend_mode != BaseLayer.BlendModes.PASS_THROUGH:
+			cel_image = layer.blend_children(
+				current_frame, Vector2i.ZERO, Global.display_layer_effects
+			)
+		else:
 			if Global.display_layer_effects:
 				cel_image = layer.display_effects(cel)
 			else:
--- a/src/UI/Dialogs/ImageEffects/OffsetImage.gd
+++ b/src/UI/Dialogs/ImageEffects/OffsetImage.gd
@ -66,7 +66,7 @@ func recalculate_preview(params: Dictionary) -> void:


 ## Altered version of blend_layers() located in DrawingAlgos.gd
-## This function is REQUIRED in order for offset effect to work correctly with cliping masks
+## This function is REQUIRED in order for offset effect to work correctly with clipping masks
 func blend_layers(
 	image: Image,
 	frame: Frame,
@ -101,8 +101,14 @@ func blend_layers(
 			if not layer_is_selected:
 				include = false
 		var cel := frame.cels[ordered_index]
-		var cel_image := layer.display_effects(cel)
-		if include:  ## apply offset effect to it
+		var cel_image: Image
+		if layer is GroupLayer and layer.blend_mode != BaseLayer.BlendModes.PASS_THROUGH:
+			cel_image = (layer as GroupLayer).blend_children(frame)
+		else:
+			cel_image = layer.display_effects(cel)
+		if layer.is_blended_by_ancestor() and not only_selected_cels and not only_selected_layers:
+			include = false
+		if include:  # Apply offset effect to it
 			gen.generate_image(cel_image, shader, effect_params, project.size)
 		textures.append(cel_image)
 		DrawingAlgos.set_layer_metadata_image(layer, cel, metadata_image, ordered_index, include)
--- a/src/UI/Timeline/AnimationTimeline.gd
+++ b/src/UI/Timeline/AnimationTimeline.gd
@ -65,34 +65,7 @@ func _ready() -> void:
 	frame_scroll_bar.value_changed.connect(_frame_scroll_changed)
 	Global.animation_timer.wait_time = 1 / Global.current_project.fps
 	fps_spinbox.value = Global.current_project.fps
-
-	# Fill the blend modes OptionButton with items
-	blend_modes_button.add_item("Normal", BaseLayer.BlendModes.NORMAL)
-	blend_modes_button.add_separator("Darken")
-	blend_modes_button.add_item("Darken", BaseLayer.BlendModes.DARKEN)
-	blend_modes_button.add_item("Multiply", BaseLayer.BlendModes.MULTIPLY)
-	blend_modes_button.add_item("Color burn", BaseLayer.BlendModes.COLOR_BURN)
-	blend_modes_button.add_item("Linear burn", BaseLayer.BlendModes.LINEAR_BURN)
-	blend_modes_button.add_separator("Lighten")
-	blend_modes_button.add_item("Lighten", BaseLayer.BlendModes.LIGHTEN)
-	blend_modes_button.add_item("Screen", BaseLayer.BlendModes.SCREEN)
-	blend_modes_button.add_item("Color dodge", BaseLayer.BlendModes.COLOR_DODGE)
-	blend_modes_button.add_item("Add", BaseLayer.BlendModes.ADD)
-	blend_modes_button.add_separator("Contrast")
-	blend_modes_button.add_item("Overlay", BaseLayer.BlendModes.OVERLAY)
-	blend_modes_button.add_item("Soft light", BaseLayer.BlendModes.SOFT_LIGHT)
-	blend_modes_button.add_item("Hard light", BaseLayer.BlendModes.HARD_LIGHT)
-	blend_modes_button.add_separator("Inversion")
-	blend_modes_button.add_item("Difference", BaseLayer.BlendModes.DIFFERENCE)
-	blend_modes_button.add_item("Exclusion", BaseLayer.BlendModes.EXCLUSION)
-	blend_modes_button.add_item("Subtract", BaseLayer.BlendModes.SUBTRACT)
-	blend_modes_button.add_item("Divide", BaseLayer.BlendModes.DIVIDE)
-	blend_modes_button.add_separator("Component")
-	blend_modes_button.add_item("Hue", BaseLayer.BlendModes.HUE)
-	blend_modes_button.add_item("Saturation", BaseLayer.BlendModes.SATURATION)
-	blend_modes_button.add_item("Color", BaseLayer.BlendModes.COLOR)
-	blend_modes_button.add_item("Luminosity", BaseLayer.BlendModes.LUMINOSITY)
-
+	_fill_blend_modes_option_button()
 	# Config loading
 	layer_frame_h_split.split_offset = Global.config_cache.get_value("timeline", "layer_size", 0)
 	cel_size = Global.config_cache.get_value("timeline", "cel_size", cel_size)  # Call setter
@ -220,6 +193,48 @@ func _cel_size_changed(value: int) -> void:
 		tag_c.update_position_and_size()


+## Fill the blend modes OptionButton with items
+func _fill_blend_modes_option_button() -> void:
+	blend_modes_button.clear()
+	var selected_layers_are_groups := true
+	if Global.current_project.layers.size() == 0:
+		selected_layers_are_groups = false
+	else:
+		for idx_pair in Global.current_project.selected_cels:
+			var layer := Global.current_project.layers[idx_pair[1]]
+			if not layer is GroupLayer:
+				selected_layers_are_groups = false
+				break
+	if selected_layers_are_groups:
+		# Special blend mode that appears only when group layers are selected
+		blend_modes_button.add_item("Pass through", BaseLayer.BlendModes.PASS_THROUGH)
+	blend_modes_button.add_item("Normal", BaseLayer.BlendModes.NORMAL)
+	blend_modes_button.add_separator("Darken")
+	blend_modes_button.add_item("Darken", BaseLayer.BlendModes.DARKEN)
+	blend_modes_button.add_item("Multiply", BaseLayer.BlendModes.MULTIPLY)
+	blend_modes_button.add_item("Color burn", BaseLayer.BlendModes.COLOR_BURN)
+	blend_modes_button.add_item("Linear burn", BaseLayer.BlendModes.LINEAR_BURN)
+	blend_modes_button.add_separator("Lighten")
+	blend_modes_button.add_item("Lighten", BaseLayer.BlendModes.LIGHTEN)
+	blend_modes_button.add_item("Screen", BaseLayer.BlendModes.SCREEN)
+	blend_modes_button.add_item("Color dodge", BaseLayer.BlendModes.COLOR_DODGE)
+	blend_modes_button.add_item("Add", BaseLayer.BlendModes.ADD)
+	blend_modes_button.add_separator("Contrast")
+	blend_modes_button.add_item("Overlay", BaseLayer.BlendModes.OVERLAY)
+	blend_modes_button.add_item("Soft light", BaseLayer.BlendModes.SOFT_LIGHT)
+	blend_modes_button.add_item("Hard light", BaseLayer.BlendModes.HARD_LIGHT)
+	blend_modes_button.add_separator("Inversion")
+	blend_modes_button.add_item("Difference", BaseLayer.BlendModes.DIFFERENCE)
+	blend_modes_button.add_item("Exclusion", BaseLayer.BlendModes.EXCLUSION)
+	blend_modes_button.add_item("Subtract", BaseLayer.BlendModes.SUBTRACT)
+	blend_modes_button.add_item("Divide", BaseLayer.BlendModes.DIVIDE)
+	blend_modes_button.add_separator("Component")
+	blend_modes_button.add_item("Hue", BaseLayer.BlendModes.HUE)
+	blend_modes_button.add_item("Saturation", BaseLayer.BlendModes.SATURATION)
+	blend_modes_button.add_item("Color", BaseLayer.BlendModes.COLOR)
+	blend_modes_button.add_item("Luminosity", BaseLayer.BlendModes.LUMINOSITY)
+
+
 func _on_blend_modes_item_selected(index: int) -> void:
 	var project := Global.current_project
 	var current_mode := blend_modes_button.get_item_id(index)
@ -231,13 +246,18 @@ func _on_blend_modes_item_selected(index: int) -> void:
 		project.undo_redo.add_undo_property(layer, "blend_mode", previous_mode)
 	project.undo_redo.add_do_method(Global.undo_or_redo.bind(false))
 	project.undo_redo.add_do_method(_update_layer_ui)
-	project.undo_redo.add_do_method(Global.canvas.draw_layers)
+	project.undo_redo.add_do_method(_update_layers)
 	project.undo_redo.add_undo_method(Global.undo_or_redo.bind(true))
 	project.undo_redo.add_undo_method(_update_layer_ui)
-	project.undo_redo.add_undo_method(Global.canvas.draw_layers)
+	project.undo_redo.add_undo_method(_update_layers)
 	project.undo_redo.commit_action()


+func _update_layers() -> void:
+	Global.canvas.update_all_layers = true
+	Global.canvas.draw_layers()
+
+
 func add_frame() -> void:
 	var project := Global.current_project
 	var frame_add_index := project.current_frame + 1
@ -1068,6 +1088,7 @@ func _on_timeline_settings_visibility_changed() -> void:
 func _cel_switched() -> void:
 	_toggle_frame_buttons()
 	_toggle_layer_buttons()
+	_fill_blend_modes_option_button()
 	# Temporarily disconnect it in order to prevent layer opacity changing
 	# in the rest of the selected layers, if there are any.
 	opacity_slider.value_changed.disconnect(_on_opacity_slider_value_changed)
@ -1077,10 +1098,9 @@ func _cel_switched() -> void:

 func _update_layer_ui() -> void:
 	var project := Global.current_project
-	opacity_slider.value = project.layers[project.current_layer].opacity * 100
-	var blend_mode_index := blend_modes_button.get_item_index(
-		project.layers[project.current_layer].blend_mode
-	)
+	var layer := project.layers[project.current_layer]
+	opacity_slider.value = layer.opacity * 100
+	var blend_mode_index := blend_modes_button.get_item_index(layer.blend_mode)
 	blend_modes_button.selected = blend_mode_index


--- a/src/UI/Timeline/CelProperties.gd
+++ b/src/UI/Timeline/CelProperties.gd
@ -37,6 +37,7 @@ func _on_opacity_slider_value_changed(value: float) -> void:
 	for cel_index in cel_indices:
 		var cel := Global.current_project.frames[cel_index[0]].cels[cel_index[1]]
 		cel.opacity = value / 100.0
+	Global.canvas.update_all_layers = true
 	Global.canvas.queue_redraw()


--- a/src/UI/Timeline/LayerButton.gd
+++ b/src/UI/Timeline/LayerButton.gd
@ -145,8 +145,6 @@ func _on_main_button_gui_input(event: InputEvent) -> void:
 			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_on_parent(Rect2(get_global_mouse_position(), Vector2.ONE))


@ -222,6 +220,7 @@ func _on_popup_menu_id_pressed(id: int) -> void:
 		layer.clipping_mask = not layer.clipping_mask
 		popup_menu.set_item_checked(id, layer.clipping_mask)
 		clipping_mask_icon.visible = layer.clipping_mask
+		Global.canvas.update_all_layers = true
 		Global.canvas.draw_layers()


--- a/src/UI/Timeline/LayerProperties.gd
+++ b/src/UI/Timeline/LayerProperties.gd
@ -10,8 +10,34 @@ var layer_indices: PackedInt32Array
@onready var user_data_text_edit := $GridContainer/UserDataTextEdit as TextEdit


-func _ready() -> void:
-	# Fill the blend modes OptionButton with items
+func _on_visibility_changed() -> void:
+	if layer_indices.size() == 0:
+		return
+	Global.dialog_open(visible)
+	var first_layer := Global.current_project.layers[layer_indices[0]]
+	if visible:
+		_fill_blend_modes_option_button()
+		name_line_edit.text = first_layer.name
+		opacity_slider.value = first_layer.opacity * 100.0
+		var blend_mode_index := blend_modes_button.get_item_index(first_layer.blend_mode)
+		blend_modes_button.selected = blend_mode_index
+		user_data_text_edit.text = first_layer.user_data
+	else:
+		layer_indices = []
+
+
+## Fill the blend modes OptionButton with items
+func _fill_blend_modes_option_button() -> void:
+	blend_modes_button.clear()
+	var selected_layers_are_groups := true
+	for layer_index in layer_indices:
+		var layer := Global.current_project.layers[layer_index]
+		if not layer is GroupLayer:
+			selected_layers_are_groups = false
+			break
+	if selected_layers_are_groups:
+		# Special blend mode that appears only when group layers are selected
+		blend_modes_button.add_item("Pass through", BaseLayer.BlendModes.PASS_THROUGH)
 	blend_modes_button.add_item("Normal", BaseLayer.BlendModes.NORMAL)
 	blend_modes_button.add_item("Darken", BaseLayer.BlendModes.DARKEN)
 	blend_modes_button.add_item("Multiply", BaseLayer.BlendModes.MULTIPLY)
@ -34,20 +60,6 @@ func _ready() -> void:
 	blend_modes_button.add_item("Luminosity", BaseLayer.BlendModes.LUMINOSITY)


-func _on_visibility_changed() -> void:
-	if layer_indices.size() == 0:
-		return
-	Global.dialog_open(visible)
-	var first_layer := Global.current_project.layers[layer_indices[0]]
-	if visible:
-		name_line_edit.text = first_layer.name
-		opacity_slider.value = first_layer.opacity * 100.0
-		blend_modes_button.selected = first_layer.blend_mode
-		user_data_text_edit.text = first_layer.user_data
-	else:
-		layer_indices = []
-
-
 func _on_name_line_edit_text_changed(new_text: String) -> void:
 	if layer_indices.size() == 0:
 		return
@ -63,18 +75,21 @@ func _on_opacity_slider_value_changed(value: float) -> void:
 		var layer := Global.current_project.layers[layer_index]
 		layer.opacity = value / 100.0
 	_emit_layer_property_signal()
+	Global.canvas.update_all_layers = true
 	Global.canvas.queue_redraw()


 func _on_blend_mode_option_button_item_selected(index: BaseLayer.BlendModes) -> void:
 	if layer_indices.size() == 0:
 		return
+	Global.canvas.update_all_layers = true
 	var project := Global.current_project
+	var current_mode := blend_modes_button.get_item_id(index)
 	project.undo_redo.create_action("Set Blend Mode")
 	for layer_index in layer_indices:
 		var layer := project.layers[layer_index]
 		var previous_mode := layer.blend_mode
-		project.undo_redo.add_do_property(layer, "blend_mode", index)
+		project.undo_redo.add_do_property(layer, "blend_mode", current_mode)
 		project.undo_redo.add_undo_property(layer, "blend_mode", previous_mode)
 	project.undo_redo.add_do_method(Global.undo_or_redo.bind(false))
 	project.undo_redo.add_do_method(Global.canvas.draw_layers)