[Experimental] When using tool, redraw the pixel with new size if it's changed via pressure

src/Autoload/Tools.gd

@@ -33,6 +33,8 @@ var pen_pressure_min := 0.2
 var pen_pressure_max := 0.8
 var pressure_buf := [0, 0]  # past pressure value buffer
 var pen_inverted := false
+## Checks if pen pressure caused a change in brush size in the current frame.
+var pressure_changed_size := false
 var mouse_velocity := 0.0
 var mouse_velocity_min_thres := 0.2
 var mouse_velocity_max_thres := 0.8
@@ -832,6 +834,7 @@ func handle_draw(position: Vector2i, event: InputEvent) -> void:
 		active_button = -1
 
 	if event is InputEventMouseMotion:
+		var last_pressure_increment := roundi(lerpf(0, brush_size_max_increment, pen_pressure))
 		pen_pressure = event.pressure
 		# Workaround https://github.com/godotengine/godot/issues/53033#issuecomment-930409407
 		# If a pressure value of 1 is encountered, "correct" the value by
@@ -857,7 +860,11 @@ func handle_draw(position: Vector2i, event: InputEvent) -> void:
 			mouse_velocity = 1.0
 		if active_button == -1:  # there is no meaning of velocity without an active tool
 			mouse_velocity = 0.0
-		if not position == _last_position:
+		# Check if we should update with new brush size if pressure is changed enough, or if the
+		# mouse was moved by an entire pixel
+		var dynamic_pressure_increment := roundi(lerpf(0, brush_size_max_increment, pen_pressure))
+		pressure_changed_size = last_pressure_increment != dynamic_pressure_increment
+		if not position == _last_position or pressure_changed_size:
 			_last_position = position
 			_slots[MOUSE_BUTTON_LEFT].tool_node.cursor_move(position)
 			_slots[MOUSE_BUTTON_RIGHT].tool_node.cursor_move(position)

src/Tools/DesignTools/Eraser.gd

@@ -1,6 +1,6 @@
 extends BaseDrawTool
 
-var _last_position := Vector2.INF
+var _last_position := Vector2i(Vector2.INF)
 var _clear_image: Image
 var _changed := false
 
@@ -83,7 +83,13 @@ func draw_move(pos_i: Vector2i) -> void:
 		cursor_text = d.text
 		update_line_polylines(_line_start, _line_end)
 	else:
-		draw_fill_gap(_last_position, pos)
+		# If the tool moved, fill the middle points between last (exclusive)
+		# and new (inclusive) pixel position.
+		if _last_position != Vector2i(pos):
+			draw_fill_gap(_last_position, pos)
+		# If tool didn't move but pressure changed we still need to re-draw with new size
+		elif Tools.pressure_changed_size:
+			draw_tool(pos)
 		_last_position = pos
 		cursor_text = ""
 		Global.canvas.sprite_changed_this_frame = true

src/Tools/DesignTools/Pencil.gd

@@ -154,7 +154,13 @@ func draw_move(pos_i: Vector2i) -> void:
 		cursor_text = d.text
 		update_line_polylines(_line_start, _line_end)
 	else:
-		draw_fill_gap(_last_position, pos)
+		# If the tool moved, fill the middle points between last (exclusive)
+		# and new (inclusive) pixel position.
+		if _last_position != Vector2i(pos):
+			draw_fill_gap(_last_position, pos)
+		# If tool didn't move but pressure changed we still need to re-draw with new size
+		elif Tools.pressure_changed_size:
+			draw_tool(pos)
 		_last_position = pos
 		cursor_text = ""
 		Global.canvas.sprite_changed_this_frame = true