Implement alpha lock as a global tool option

assets/graphics/misc/alpha_lock_off.png.import

@@ -0,0 +1,34 @@
+[remap]
+
+importer="texture"
+type="CompressedTexture2D"
+uid="uid://j8eywwy082a4"
+path="res://.godot/imported/alpha_lock_off.png-2b88d446a40bc5d304eb489a1531dbc7.ctex"
+metadata={
+"vram_texture": false
+}
+
+[deps]
+
+source_file="res://assets/graphics/misc/alpha_lock_off.png"
+dest_files=["res://.godot/imported/alpha_lock_off.png-2b88d446a40bc5d304eb489a1531dbc7.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

assets/graphics/misc/alpha_lock_on.png.import

@@ -0,0 +1,34 @@
+[remap]
+
+importer="texture"
+type="CompressedTexture2D"
+uid="uid://cecc5pdyv1qqc"
+path="res://.godot/imported/alpha_lock_on.png-b504142d180d946e470db4c9a8a68837.ctex"
+metadata={
+"vram_texture": false
+}
+
+[deps]
+
+source_file="res://assets/graphics/misc/alpha_lock_on.png"
+dest_files=["res://.godot/imported/alpha_lock_on.png-b504142d180d946e470db4c9a8a68837.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/Tools.gd

@@ -8,6 +8,7 @@ var picking_color_for := MOUSE_BUTTON_LEFT
 var horizontal_mirror := false
 var vertical_mirror := false
 var pixel_perfect := false
+var alpha_locked := false
 
 # Dynamics
 var stabilizer_enabled := false
@@ -568,6 +569,12 @@ func handle_draw(position: Vector2i, event: InputEvent) -> void:
 	Global.cursor_position_label.text = text
 
 
+## Returns [code]true[/code] if [member alpha_locked] is [code]true[/code]
+## and the [param image]'s pixel at [param position] is transparent.
+func check_alpha_lock(image: Image, position: Vector2i) -> bool:
+	return alpha_locked and is_zero_approx(image.get_pixelv(position).a)
+
+
 func get_alpha_dynamic(strength := 1.0) -> float:
 	if dynamics_alpha == Dynamics.PRESSURE:
 		strength *= lerpf(alpha_min, alpha_max, pen_pressure)

src/Classes/Drawers.gd

@@ -67,12 +67,13 @@ func reset() -> void:
 
 func set_pixel(image: Image, position: Vector2i, color: Color, ignore_mirroring := false) -> void:
 	var project := Global.current_project
-	drawers[0].set_pixel(image, position, color, color_op)
+	if not Tools.check_alpha_lock(image, position):
+		drawers[0].set_pixel(image, position, color, color_op)
 	if ignore_mirroring:
 		return
 	# Handle mirroring
-	var i := 1
+	var mirrored_positions := Tools.get_mirrored_positions(position, project)
-	for mirror_pos in Tools.get_mirrored_positions(position, project):
+	for i in mirrored_positions.size():
-		if project.can_pixel_get_drawn(mirror_pos):
+		var mirror_pos := mirrored_positions[i]
-			drawers[i].set_pixel(image, mirror_pos, color, color_op)
+		if project.can_pixel_get_drawn(mirror_pos) && not Tools.check_alpha_lock(image, mirror_pos):
-		i += 1
+			drawers[i + 1].set_pixel(image, mirror_pos, color, color_op)

src/Tools/DesignTools/Bucket.gd

@@ -182,6 +182,8 @@ func fill_in_color(pos: Vector2i) -> void:
 	var project := Global.current_project
 	var images := _get_selected_draw_images()
 	for image in images:
+		if Tools.check_alpha_lock(image, pos):
+			continue
 		var color: Color = image.get_pixelv(pos)
 		var pattern_image: Image
 		if _fill_with == FillWith.COLOR or _pattern == null:
@@ -296,11 +298,11 @@ func _add_new_segment(y := 0) -> void:
 ## Fill an horizontal segment around the specified position, and adds it to the
 ## list of segments filled. Returns the first x coordinate after the part of the
 ## line that has been filled.
+## Τhis method is called by [method _flood_fill] after the required data structures
+## have been initialized.
 func _flood_line_around_point(
 	pos: Vector2i, project: Project, image: Image, src_color: Color
 ) -> int:
-	# this method is called by `_flood_fill` after the required data structures
-	# have been initialized
 	if not image.get_pixelv(pos).is_equal_approx(src_color):
 		return pos.x + 1
 	var west := pos
@@ -382,6 +384,8 @@ func _flood_fill(pos: Vector2i) -> void:
 	var project := Global.current_project
 	var images := _get_selected_draw_images()
 	for image in images:
+		if Tools.check_alpha_lock(image, pos):
+			continue
 		var color: Color = image.get_pixelv(pos)
 		if _fill_with == FillWith.COLOR or _pattern == null:
 			# end early if we are filling with the same color

src/Tools/DesignTools/Pencil.gd

@@ -196,12 +196,20 @@ func draw_end(pos: Vector2i) -> void:
 	_spacing_mode = _old_spacing_mode
 
 
-func _draw_brush_image(image: Image, src_rect: Rect2i, dst: Vector2i) -> void:
+func _draw_brush_image(brush_image: Image, src_rect: Rect2i, dst: Vector2i) -> void:
 	_changed = true
 	var images := _get_selected_draw_images()
 	if _overwrite:
 		for draw_image in images:
-			draw_image.blit_rect(image, src_rect, dst)
+			if Tools.alpha_locked:
+				var mask := draw_image.get_region(Rect2i(dst, brush_image.get_size()))
+				draw_image.blit_rect_mask(brush_image, mask, src_rect, dst)
+			else:
+				draw_image.blit_rect(brush_image, src_rect, dst)
 	else:
 		for draw_image in images:
-			draw_image.blend_rect(image, src_rect, dst)
+			if Tools.alpha_locked:
+				var mask := draw_image.get_region(Rect2i(dst, brush_image.get_size()))
+				draw_image.blend_rect_mask(brush_image, mask, src_rect, dst)
+			else:
+				draw_image.blend_rect(brush_image, src_rect, dst)

src/UI/GlobalToolOptions/GlobalToolOptions.gd

@@ -8,6 +8,7 @@ enum { ALPHA, SIZE }
 @onready var horizontal_mirror: BaseButton = grid_container.get_node("Horizontal")
 @onready var vertical_mirror: BaseButton = grid_container.get_node("Vertical")
 @onready var pixel_perfect: BaseButton = grid_container.get_node("PixelPerfect")
+@onready var alpha_lock: BaseButton = grid_container.get_node("AlphaLock")
 @onready var dynamics: Button = $"%Dynamics"
 
 @onready var dynamics_panel: PopupPanel = $DynamicsPanel
@@ -100,6 +101,16 @@ func _on_PixelPerfect_toggled(button_pressed: bool) -> void:
 	Global.change_button_texturerect(texture_button, file_name)
 
 
+func _on_alpha_lock_toggled(toggled_on: bool) -> void:
+	Tools.alpha_locked = toggled_on
+	Global.config_cache.set_value("preferences", "alpha_locked", toggled_on)
+	var texture_button: TextureRect = alpha_lock.get_node("TextureRect")
+	var file_name := "alpha_lock_on.png"
+	if not toggled_on:
+		file_name = "alpha_lock_off.png"
+	Global.change_button_texturerect(texture_button, file_name)
+
+
 func _on_Dynamics_pressed() -> void:
 	var pos := dynamics.global_position + Vector2(0, 32)
 	dynamics_panel.popup(Rect2(pos, dynamics_panel.size))

src/UI/GlobalToolOptions/GlobalToolOptions.tscn

@@ -1,10 +1,11 @@
-[gd_scene load_steps=20 format=3 uid="uid://wo0hqxkst808"]
+[gd_scene load_steps=21 format=3 uid="uid://wo0hqxkst808"]
 
 [ext_resource type="Texture2D" uid="uid://cjrokejjsp5dm" path="res://assets/graphics/misc/horizontal_mirror_off.png" id="1"]
 [ext_resource type="Texture2D" uid="uid://hiduvaa73fr6" path="res://assets/graphics/misc/vertical_mirror_off.png" id="2"]
 [ext_resource type="Script" path="res://src/UI/GlobalToolOptions/GlobalToolOptions.gd" id="3"]
 [ext_resource type="Texture2D" uid="uid://22h12g8p3jtd" path="res://assets/graphics/misc/pixel_perfect_off.png" id="4"]
 [ext_resource type="Script" path="res://src/UI/Nodes/ValueSlider.gd" id="5"]
+[ext_resource type="Texture2D" uid="uid://j8eywwy082a4" path="res://assets/graphics/misc/alpha_lock_off.png" id="5_jv20x"]
 [ext_resource type="Texture2D" uid="uid://dg3dumyfj1682" path="res://assets/graphics/misc/dynamics.png" id="6"]
 [ext_resource type="Texture2D" uid="uid://di8au2u87jgv5" path="res://assets/graphics/misc/uncheck.png" id="7"]
 [ext_resource type="PackedScene" uid="uid://bmsc0s03pwji4" path="res://src/UI/Nodes/MaxMinEdit.tscn" id="8"]
@@ -62,7 +63,7 @@ size_flags_vertical = 3
 [node name="GridContainer" type="GridContainer" parent="ScrollContainer/CenterContainer"]
 layout_mode = 2
 size_flags_vertical = 0
-columns = 4
+columns = 5
 
 [node name="Horizontal" type="Button" parent="ScrollContainer/CenterContainer/GridContainer" groups=["UIButtons"]]
 custom_minimum_size = Vector2(32, 32)
@@ -125,6 +126,27 @@ offset_right = 11.0
 offset_bottom = 10.0
 texture = ExtResource("4")
 
+[node name="AlphaLock" type="Button" parent="ScrollContainer/CenterContainer/GridContainer"]
+custom_minimum_size = Vector2(32, 32)
+layout_mode = 2
+tooltip_text = "Pixel Perfect
+Makes lines smooth by removing the extra pixels on the edges"
+mouse_default_cursor_shape = 2
+toggle_mode = true
+shortcut = SubResource("Shortcut_vcyug")
+
+[node name="TextureRect" type="TextureRect" parent="ScrollContainer/CenterContainer/GridContainer/AlphaLock"]
+layout_mode = 0
+anchor_left = 0.5
+anchor_top = 0.5
+anchor_right = 0.5
+anchor_bottom = 0.5
+offset_left = -11.0
+offset_top = -10.0
+offset_right = 11.0
+offset_bottom = 10.0
+texture = ExtResource("5_jv20x")
+
 [node name="Dynamics" type="Button" parent="ScrollContainer/CenterContainer/GridContainer" groups=["UIButtons"]]
 unique_name_in_owner = true
 custom_minimum_size = Vector2(32, 32)
@@ -149,10 +171,10 @@ canvas_item_default_texture_filter = 0
 size = Vector2i(300, 334)
 
 [node name="VBoxContainer" type="VBoxContainer" parent="DynamicsPanel"]
-offset_left = 8.0
+offset_left = 4.0
-offset_top = 8.0
+offset_top = 4.0
-offset_right = 292.0
+offset_right = 296.0
-offset_bottom = 326.0
+offset_bottom = 330.0
 
 [node name="StabilizerContainer" type="HBoxContainer" parent="DynamicsPanel/VBoxContainer"]
 layout_mode = 2
@@ -436,6 +458,7 @@ offset_bottom = 23.0
 [connection signal="toggled" from="ScrollContainer/CenterContainer/GridContainer/Horizontal" to="." method="_on_Horizontal_toggled"]
 [connection signal="toggled" from="ScrollContainer/CenterContainer/GridContainer/Vertical" to="." method="_on_Vertical_toggled"]
 [connection signal="toggled" from="ScrollContainer/CenterContainer/GridContainer/PixelPerfect" to="." method="_on_PixelPerfect_toggled"]
+[connection signal="toggled" from="ScrollContainer/CenterContainer/GridContainer/AlphaLock" to="." method="_on_alpha_lock_toggled"]
 [connection signal="pressed" from="ScrollContainer/CenterContainer/GridContainer/Dynamics" to="." method="_on_Dynamics_pressed"]
 [connection signal="toggled" from="DynamicsPanel/VBoxContainer/StabilizerContainer/EnableStabilizer" to="." method="_on_enable_stabilizer_toggled"]
 [connection signal="value_changed" from="DynamicsPanel/VBoxContainer/StabilizerContainer/StabilizerValue" to="." method="_on_stabilizer_value_value_changed"]