Support rotation/scale/flip for Actor

[lordmauve]

Originally reported by: Daniel Pope (Bitbucket: lordmauve, GitHub: lordmauve)

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Pygame supports somewhat slow rotation, scale and flip operations in software.

We should expose these for the Actor class.

May depend on issue #2, which allows users to specify an "anchor point" around which the actor will rotate.

Open questions: how should these operations affect the actor's bounding rect?

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• Bitbucket: https://bitbucket.org/lordmauve/pgzero/issue/3

[lordmauve]

Original comment by Daniel Pope (Bitbucket: lordmauve, GitHub: lordmauve):

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I had it in mind that this would be a property, eg:

actor.rotation = 1.5 * math.pi
actor.flip_x = True

However this has the drawback of needing an implied order for the transform. Maybe it could be CSS3 transform style?:

alien = Actor('alien')
alien.transform = 'rotate(5deg) scaleX(-1)'

[dryabov]

+1

My son asked me how to flip the alien image (to move it in the opposite direction), and the only solution I found (in addition to pre-creation of flipping image in an image editor) is:

from pygame.transform import flip

def draw():
    if direction > 0:
        alien.draw()
    else:
        screen.blit(flip(alien._surf, True, False), alien.topleft)

It would be nice to get it in a simpler way out of the box.

[lordmauve]

@a96tudor has been working on scale/flip at the recent Europython sprints.

The proposed API is to set alien.scale_x = -1 - I wonder if that's what your son would guess?

[dryabov]

Exactly. Currently he uses direction variable to move the alien with alien.left += 2 * direction, so that alien.scale_x = direction seems to be an ideal and clear solution.