bulletml/impl.py

   1 """BulletML implementation."""
   2
   3 from __future__ import division
   4
   5 from math import atan2, sin, cos
   6
   7 from bulletml import parser
   8
   9 __all__ = ["Action", "Bullet"]
  10
  11 class Action(object):
  12     """Running action implementation.
  13
  14     To implement new actions, add a new element/class pair to
  15     parser.ActionDef.CONSTRUCTORS.  It should support FromXML,
  16     __getstate__, and __setstate__, and 5-ary __call__:
  17
  18         def __call__(self, owner, action, params, rank, created)
  19
  20     Which will be called to execute it. This function should modify
  21     owner, action, and created in-place, and return true if action
  22     execution should stop for this bullet this frame.
  23
  24     """
  25
  26     def __init__(self, parent, actions, params, rank, repeat=1):
  27         self.actions = actions
  28         self.parent = parent
  29         self.repeat = repeat
  30         self.wait_frames = 0
  31         self.speed = 0
  32         self.speed_frames = 0
  33         self.direction = 0
  34         self.direction_frames = 0
  35         self.aiming = False
  36         self.mx = 0
  37         self.my = 0
  38         self.accel_frames = 0
  39         self.previous_fire_direction = 0
  40         self.previous_fire_speed = 0
  41         self.params = params
  42         self.pc = -1
  43         self.finished = False
  44         if parent:
  45             self.copy_state(parent)
  46
  47     def __repr__(self):
  48         return "%s(pc=%r, actions=%r)" % (
  49             type(self).__name__, self.pc, self.actions)
  50
  51     def Child(self, actions, params, rank, repeat=1):
  52         return type(self)(self, actions, params, rank, repeat)
  53
  54     def vanish(self):
  55         """End this action and its parents."""
  56         if self.parent:
  57             self.parent.vanish()
  58         self.pc = None
  59         self.finished = True
  60
  61     def copy_state(self, other):
  62         """Copy fire/movement state from other to self."""
  63         self.direction_frames = other.direction_frames
  64         self.direction = other.direction
  65         self.aiming = other.aiming
  66         self.speed_frames = other.speed_frames
  67         self.speed = other.speed
  68         self.accel_frames = other.accel_frames
  69         self.mx = other.mx
  70         self.my = other.my
  71         self.previous_fire_direction = other.previous_fire_direction
  72         self.previous_fire_speed = other.previous_fire_speed
  73
  74     def step(self, owner, created):
  75         """Advance by one frame."""
  76         s_params = self.params
  77         rank = owner.rank
  78
  79         if self.speed_frames > 0:
  80             self.speed_frames -= 1
  81             owner.speed += self.speed
  82
  83         if self.direction_frames > 0:
  84             # I'm still not sure what the aim check is supposed to do.
  85             self.direction_frames -= 1
  86             if self.aiming and self.direction_frames <= 0:
  87                 owner.direction += owner.aim
  88             else:
  89                 owner.direction += self.direction
  90
  91         if self.accel_frames > 0:
  92             self.accel_frames -= 1
  93             owner.mx += self.mx
  94             owner.my += self.my
  95
  96         if self.pc is None:
  97             return
  98
  99         if self.wait_frames > 0:
 100             self.wait_frames -= 1
 101             return
 102
 103         while True:
 104             self.pc += 1
 105
 106             try:
 107                 action = self.actions[self.pc]
 108             except IndexError:
 109                 self.repeat -= 1
 110                 if self.repeat <= 0:
 111                     self.pc = None
 112                     self.finished = True
 113                     if self.parent is not None:
 114                         self.parent.copy_state(self)
 115                         owner.replace(self, self.parent)
 116                     break
 117                 else:
 118                     self.pc = 0
 119                     action = self.actions[self.pc]
 120
 121             if isinstance(action, (parser.ActionDef, parser.ActionRef)):
 122                 actions, params = action(s_params, rank)
 123                 child = self.__class__(self, actions, params, rank)
 124                 owner.replace(self, child)
 125                 child.step(owner, created)
 126                 break
 127
 128             elif action(owner, self, s_params, rank, created):
 129                 break
 130
 131 class Bullet(object):
 132     """Simple bullet implementation.
 133
 134     Attributes:
 135     x, y - current X/Y position
 136     px, py - X/Y position prior to the last step
 137     mx, my - X/Y axis-oriented speed modifier ("acceleration")
 138     direction - direction of movement, in radians
 139     speed - speed of movement, in units per frame
 140     target - object with .x and .y fields for "aim" directions
 141     vanished - set to true by a <vanish> action
 142     rank - game difficulty, 0 to 1, default 0.5
 143     tags - string tags set by the running actions
 144     appearance - string used to set bullet appearance
 145
 146     Contructor Arguments:
 147     x, y, direction, speed, target, rank, tags, appearance
 148         - same as the above attributes
 149     actions - internal action list
 150     Action - custom Action constructor
 151
 152     """
 153
 154     def __init__(self, x=0, y=0, direction=0, speed=0, target=None,
 155                  actions=(), rank=0.5, tags=(), appearance=None,
 156                  Action=Action):
 157         self.x = self.px = x
 158         self.y = self.py = y
 159         self.mx = 0
 160         self.my = 0
 161         self.direction = direction
 162         self.speed = speed
 163         self.vanished = False
 164         self.target = target
 165         self.rank = rank
 166         self.tags = set(tags)
 167         self.appearance = appearance
 168         # New bullets reset the parent hierarchy.
 169         self.actions = [Action(None, action, params, rank)
 170                          for action, params in actions]
 171
 172     @classmethod
 173     def FromDocument(cls, doc, x=0, y=0, direction=0, speed=0, target=None,
 174                      params=(), rank=0.5, Action=Action):
 175         """Construct a new Bullet from a loaded BulletML document."""
 176         actions = [a(params, rank) for a in doc.actions]
 177         return cls(x=x, y=y, direction=direction, speed=speed,
 178                    target=target, actions=actions, rank=rank, Action=Action)
 179
 180     def __repr__(self):
 181         return ("%s(%r, %r, accel=%r, direction=%r, speed=%r, "
 182                 "actions=%r, target=%r, appearance=vanished=%r)") % (
 183             type(self).__name__, self.x, self.y, (self.mx, self.my),
 184             self.direction, self.speed, self.actions, self.target,
 185             self.appearance, self.vanished)
 186
 187     @property
 188     def aim(self):
 189         """Angle to the target, in radians.
 190
 191         If the target does not exist or cannot be found, return 0.
 192         """
 193         try:
 194             target_x = self.target.x
 195             target_y = self.target.y
 196         except AttributeError:
 197             return 0
 198         else:
 199             return atan2(target_x - self.x, target_y - self.y)
 200
 201     @property
 202     def finished(self):
 203         """Check if this bullet is finished running.
 204
 205         A bullet is finished when it has vanished, and all its
 206         actions have finished.
 207
 208         If this is true, the bullet should be removed from the screen.
 209         (You will probably want to cull it under other circumstances
 210         as well).
 211         """
 212         if not self.vanished:
 213             return False
 214         for action in self.actions:
 215             if not action.finished:
 216                 return False
 217         return True
 218
 219     def vanish(self):
 220         """Vanish this bullet and stop all actions."""
 221         self.vanished = True
 222         for action in self.actions:
 223             action.vanish()
 224         self.actions = []
 225
 226     def replace(self, old, new):
 227         """Replace an active action with another.
 228
 229         This is mostly used by actions internally to queue children.
 230         """
 231         try:
 232             idx = self.actions.index(old)
 233         except ValueError:
 234             pass
 235         else:
 236             self.actions[idx] = new
 237
 238     def step(self):
 239         """Advance by one frame.
 240
 241         This updates the position and velocity, and may also set the
 242         vanished flag.
 243
 244         It returns any new bullets this bullet spawned during this step.
 245         """
 246         created = []
 247
 248         for action in self.actions:
 249             action.step(self, created)
 250
 251         self.px = self.x
 252         self.py = self.y
 253         self.x += self.mx + sin(self.direction) * self.speed
 254         self.y += -self.my + cos(self.direction) * self.speed
 255
 256         return created