Make bucket fill "Whole Selection" option work with patterns

Also fix issue with similar area and color fill where if the selected color is the same as the pixel's color in mouse position, the operation stops even if there are other cels selected.

src/Shaders/PatternFill.gdshader

@@ -0,0 +1,17 @@
+shader_type canvas_item;
+render_mode unshaded;
+
+uniform sampler2D selection;
+uniform sampler2D pattern;
+uniform vec2 size;
+uniform vec2 pattern_size;
+uniform vec2 pattern_uv_offset;
+
+void fragment() {
+	vec4 original_color = texture(TEXTURE, UV);
+	vec4 selection_color = texture(selection, UV); 
+	vec4 col = original_color; 
+	col = textureLod(pattern, UV * (size / pattern_size) + pattern_uv_offset, 0.0);
+
+	COLOR = mix(original_color, col, selection_color.a);
+}

src/Tools/Bucket.gd

@@ -4,6 +4,7 @@ enum FillArea { AREA, COLORS, SELECTION }
 enum FillWith { COLOR, PATTERN }
 
 const COLOR_REPLACE_SHADER := preload("res://src/Shaders/ColorReplace.shader")
+const PATTERN_FILL_SHADER := preload("res://src/Shaders/PatternFill.gdshader")
 
 var _prev_mode := 0
 var _pattern: Patterns.Pattern
@@ -180,13 +181,13 @@ func draw_end(position: Vector2) -> void:
 
 func fill_in_color(position: Vector2) -> void:
 	var project: Project = Global.current_project
-	var color: Color = _get_draw_image().get_pixelv(position)
 	var images := _get_selected_draw_images()
 	for image in images:
+		var color: Color = image.get_pixelv(position)
 		var pattern_image: Image
 		if _fill_with == FillWith.COLOR or _pattern == null:
 			if tool_slot.color.is_equal_approx(color):
-				return
+				continue
 		else:
 			# End early if we are filling with an empty pattern
 			pattern_image = _pattern.image
@@ -250,6 +251,7 @@ func fill_in_area(position: Vector2) -> void:
 func fill_in_selection() -> void:
 	var project: Project = Global.current_project
 	var images := _get_selected_draw_images()
+	if _fill_with == FillWith.COLOR or _pattern == null:
 		if project.has_selection:
 			var filler := Image.new()
 			filler.create(project.size.x, project.size.y, false, Image.FORMAT_RGBA8)
@@ -264,11 +266,45 @@ func fill_in_selection() -> void:
 		else:
 			for image in images:
 				image.fill(tool_slot.color)
+	else:
+		# End early if we are filling with an empty pattern
+		var pattern_image: Image = _pattern.image
+		var pattern_size := pattern_image.get_size()
+		if pattern_size.x == 0 or pattern_size.y == 0:
+			return
+
+		var selection: Image
+		var selection_tex := ImageTexture.new()
+		if project.has_selection:
+			selection = project.selection_map
+		else:
+			selection = Image.new()
+			selection.create(project.size.x, project.size.y, false, Image.FORMAT_RGBA8)
+			selection.fill(Color(1, 1, 1, 1))
+
+		selection_tex.create_from_image(selection)
+
+		var pattern_tex := ImageTexture.new()
+		if _pattern and pattern_image:
+			pattern_tex.create_from_image(pattern_image)
+
+		var params := {
+			"selection": selection_tex,
+			"size": project.size,
+			"pattern": pattern_tex,
+			"pattern_size": pattern_tex.get_size(),
+			# pixel offset converted to pattern uv offset
+			"pattern_uv_offset":
+			Vector2.ONE / pattern_tex.get_size() * Vector2(_offset_x, _offset_y),
+		}
+		for image in images:
+			var gen := ShaderImageEffect.new()
+			gen.generate_image(image, PATTERN_FILL_SHADER, params, project.size)
 
 
 # Add a new segment to the array
 func _add_new_segment(y: int = 0) -> void:
-	var segment = {}
+	var segment := {}
 	segment.flooding = false
 	segment.todo_above = false
 	segment.todo_below = false
@@ -374,7 +410,7 @@ func _flood_fill(position: Vector2) -> void:
 		if _fill_with == FillWith.COLOR or _pattern == null:
 			# end early if we are filling with the same color
 			if tool_slot.color.is_equal_approx(color):
-				return
+				continue
 		else:
 			# end early if we are filling with an empty pattern
 			var pattern_size := _pattern.image.get_size()