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The back end can both move the origin and the current point from which the next line is going to start. Boxes.py hides this by using Turtle Graphics commands that also move the origin to the end of the last line. Other drawing commands restore the current position after they are finished.

Moving the origin like this allows ignoring the absolute coordinates and for all movement and drawing to be relative to the current position. The current position not only consists of a point on the drawing canvas but also a direction.

To move the origin to a different location there are these two methods:

Boxes.moveTo(x, y=0.0, degrees=0)

Move coordinate system to given point

Parameters:

• x

• y – (Default value = 0.0)

• degrees – (Default value = 0)

Boxes.moveArc(angle, r=0.0)

Parameters:

• angle

• r – (Default value = 0.0)

Often it is necessary to return to a position e.g. after placing a row of parts. This can be done with the following context manager:

Boxes.saved_context()

Generator: for saving and restoring contexts.

It can be used with the following code pattern:

with self.saved_context():
    self.rectangularWall(x, h, move="right")
    self.rectangularWall(y, h, move="right")
    self.rectangularWall(y, h, move="right")
    self.rectangularWall(x, h, move="right")
self.rectangularWall(x, h, move="up only")

# continue above the row

Parts of the code still directly use the back end primitives Boxes.ctx.save() and Boxes.ctx.restore(). But this has several disadvantages and is discouraged. For one it requires matching calls. It also does not reset the starting point of the next line. This is “healed” by a follow up .moveTo(). Use .moveTo(0, 0) if in doubt.