django_schevo_comparison.py

class Canvas(m.Model):
    """A canvas for turtle(s) to draw on.

    The origin of a canvas is the bottom left of the plane.

    A heading of 0 degrees points upward.
    """

    class Meta:
        verbose_name_plural = 'canvases'

    title = m.CharField(max_length=100)
    width = m.IntegerField('width (pixels)')
    height = m.IntegerField('height (pixels)')

    def initial_state(self):
        return CanvasState.objects.filter(
            canvas=self, previous_state=None).get()

    def __unicode__(self):
        return self.title

    def save(self, *args, **kw):
        # Prevent alteration of width and height.
        if self.pk is not None:
            other = Canvas.objects.get(pk=self.pk)
            if other.width != self.width or other.height != self.height:
                raise ValueError('width and height cannot be altered')
        # Save object.
        m.Model.save(self)
        # Store initial canvas state with centered turtle.
        initial_state = CanvasState(
            canvas=self,
            previous_state=None,
            turtle_x=float(self.width) / 2,
            turtle_y=float(self.height) / 2,
            turtle_heading=0.0,
        )
        initial_state.save()



class Canvas(E.Entity):
    """A canvas for turtle(s) to draw on.

    The origin of a canvas is the bottom left of the plane.

    A heading of 0 degrees points upward.
    """

    _plural = 'Canvases'

    title = f.string()
    width = f.integer(units='pixels')
    height = f.integer(units='pixels')
    @f.entity('CanvasState')
    def initial_state(self):
        return db.CanvasState.findone(canvas=self, previous_state=UNASSIGNED)

    def __unicode__(self):
        return self.title

    class _Create(T.Create):

        def _after_execute(self, db, canvas):
            db.execute(db.CanvasState.t.create(
                canvas=canvas,
                previous_state=UNASSIGNED,
                turtle_x=float(canvas.width) / 2,
                turtle_y=float(canvas.height) / 2,
                turtle_heading=0.0,
            ))

    class _Update(T.Update):

        def _setup(self):
            self.f.width.readonly = True
            self.f.height.readonly = True