destination prototype

also ship bounds resets

vacuum_gambit.p8

@@ -466,9 +466,7 @@ ship_m = mknew{
  -- xmin, xmax, ymin, ymax:
  --   movement constraints
  --   enforced by `constrain`.
- xmin = 0, xmax = 104,
+ xmin = 0, xmax = 104, ymin = 0, ymax = 120
- -- ymin, ymax default to nil
- --   pship needs more constraint 
 }
 
 function ship_m:die()
@@ -510,6 +508,10 @@ function ship_m:brake_dist(v0)
  return (chunk_zone + overage * (tri_frames + 1)) * sgn(v0), (overage > 0) and tri_frames + 1 or tri_frames
 end
 
+function ship_m:reset_bounds()
+ self.xmin, self.xmax, self.ymin, self.ymax = 0, 104, 0, 120
+end
+
 function ship_m:constrain(p, dp, pmin, pmax, want)
  if (not pmin) return want
  local v1, bd, bf, bp
@@ -615,6 +617,54 @@ function ship_m:refresh_shield()
  self.shield_refresh_ready = gframe + self.shieldcooldown
 end
 
+-->8
+-- paths
+
+-- destination: a point the
+-- center of a ship approaches
+destination = mknew{
+ -- 0..1: a point on a line
+ -- segment from the ship's
+ -- flotilla spot to the player;
+ -- -1 means center of play area
+ anchor_frac=0,
+
+ -- (0, 1]: relative to max
+ -- acceleration, how quickly
+ -- should the ship accelerate
+ -- to its destination?
+ -- 0: park here instead, using
+ -- constraint following
+ accel_frac=1,
+
+ -- how far to lerp between the
+ -- anchor and the screen bounds.
+ -- this is the "destination"-y
+ -- part of a destination.
+ x_off_frac = 0,
+ y_off_frac = 0
+}
+
+function lerp(a, b, f)
+ return (1-f)*a+b*f
+end
+
+function destination:anchor(fx, fy)
+ local af = self.anchor_frac
+ if (af == -1) return 55,63
+ return lerp(fx, primary_ship.x + 4, af), lerp(fy, primary_ship.y + 4, af)
+end
+
+function destination:target_from(fx, fy)
+ local rx, ry = self:anchor(fx, fy)
+ local xf, yf = self.x_off_frac, self.y_off_frac
+ if (xf < 0) rx = lerp(rx, 0, -xf)
+ if (xf > 0) rx = lerp(rx, 112, xf)
+ if (yf < 0) ry = lerp(ry, 0, -yf)
+ if (yf > 0) ry = lerp(ry, 128, yf)
+ return rx, ry
+end
+
 -->8
 -- bullet and gun behaviors
 
@@ -1089,7 +1139,6 @@ player = mknew(ship_m.new{
  ymomentum = 0,
  maxspd = 1.5, -- momentum cap
  thrust = 0.1875, -- momentum added from button
- ymin = 0, ymax = 120, -- stay on screen
  drag = 0.0625, -- momentum lost per frame
  act = function(self)  -- fetch buttons
   local b,th = btn(),self.thrust
@@ -1329,8 +1378,14 @@ ship_skirmisher = mknew(ship_f.new{
  sparks = smokespark,
  sparkodds = 3,
  fire_off_y = 7,
+ xmin = -8,
+ xmax = 112,
 })
 
+function ship_skirmisher:reset_bounds()
+ self.xmin, self.xmax, self.ymin, self.ymax = -8, 112, 0, 120
+end
+
 function rnd_spawn_loc()
  local x,y = flr(rnd(304)), flr(rnd(32))
  if (x<184) return x-40,-y-8