Add Animator

animator.lua

@@ -0,0 +1,89 @@
+local Object = require "lib/classic"
+
+---@alias AnimationFinishBehavior
+---| '"loop"' Loop the animation over from the beginning.
+---| '"stop"' Freeze the animation on the last frame.
+---| '"goto"' Go to another state.
+
+---@class State
+---@field animation Animation The animation frames for this state.
+---@field on_finish? AnimationFinishBehavior What to do after this state's animation finishes. Defaults to "loop".
+---@field next? string The next state to go to in the case of "goto" on_finish.
+
+local Animator = Object:extend()
+
+---Creates a new animator.
+---@param states { [string]: State } A dictionary of all states in this animator.
+---@param first_state string The first state of this animator.
+function Animator:new(states, first_state)
+  ---The states in this animator.
+  self.states = states
+
+  ---The current state.
+  self.state = first_state
+
+  ---The timestep of the current frame.
+  self.step = 0
+
+  ---The current frame in the current animation.
+  self.frame = 1
+
+  --- The next state to progress to.
+  self.next_state = nil
+end
+
+function Animator:update(dt)
+  local state = self.states[self.state]
+  local frames = state.animation.frames
+
+  --Step the current timestep and return if the frame hasn't changed.
+  self.step = self.step + dt
+  if self.step <= frames[self.frame].duration then
+    return
+  end
+
+  --Step the current frame and return if there are more.
+  self.step = 0
+  self.frame = self.frame + 1
+  if self.frame <= #frames then
+    return
+  end
+
+  --We've reached the end of the current state.
+  if self.next_state then
+    self.state = self.next_state
+    self.frame = 1
+    self.next_state = nil
+  elseif state.on_finish == "goto" then
+    self.state = state.next
+    self.frame = 1
+  elseif state.on_finish == "stop" then
+    self.frame = #frames
+  elseif state.on_finish == "loop" or state.on_finish == nil then
+    self.frame = 1
+  else
+    error("Invalid state on_finish " .. state.on_finish)
+  end
+end
+
+function Animator:draw(x, y)
+  local state = self.states[self.state]
+  state.animation:draw(self.frame, x, y)
+end
+
+---Sets the state of this animator.
+---@param state string The name of the state to set.
+---@param queue? boolean If true, queues the state change for after the current state.
+function Animator:setState(state, queue)
+  if not self.states[state] then
+    error("Invalid state " .. state)
+  elseif queue then
+    self.next_state = state
+  else
+    self.state = state
+    self.step = 0
+    self.frame = 1
+  end
+end
+
+return Animator

main.lua

@@ -1,4 +1,5 @@
 local Animation = require "animation"
+local Animator = require "animator"
 local Atlas = require "atlas"
 local Font = require "font"
 local MultiMenu = require "multimenu"
@@ -31,38 +32,31 @@ function love.load()
   local leafRangerSprites = love.graphics.newImage("assets/leaf-ranger.png")
   local leafRangerAtlas = Atlas(leafRangerSprites, 288, 128)
 
-  local function sprites(row, len)
+  local function sprites(row, len, on_finish, next)
     local start = (row - 1) * 22 + 1
-    return Animation:new_spanned(leafRangerAtlas, start, start + len - 1)
+    local anim = Animation:new_spanned(leafRangerAtlas, start, start + len - 1)
+    return { animation = anim, on_finish = on_finish, next = next }
   end
 
-  LeafRangerAnimations = {
+  local states = {
     idle = sprites(1, 12),
     run = sprites(2, 10),
-    hurt = sprites(16, 6),
-    death = sprites(17, 20),
+    hurt = sprites(16, 6, "goto", "idle"),
+    death = sprites(17, 19, "stop"),
   }
 
+  LeafRanger = Animator(states, "idle")
+
   local options = {}
 
-  for name, anim in pairs(LeafRangerAnimations) do
+  for name, state in pairs(states) do
     options[#options + 1] = {
       text = name,
-      callback = function()
-        LeafRanger.animation = anim
-        LeafRanger.step = 0
-        LeafRanger.frame = 1
-      end,
+      callback = function() LeafRanger:setState(name) end,
     }
   end
 
   Menu = MultiMenu(BlockyFont, options)
-
-  LeafRanger = {
-    animation = LeafRangerAnimations.idle,
-    step = 0,
-    frame = 1,
-  }
 end
 
 function love.draw()
@@ -70,22 +64,13 @@ function love.draw()
 
   Menu:draw()
   BlockyFont:draw("Hello, world!")
-
-  LeafRanger.animation:draw(LeafRanger.frame, 0, 0)
+  LeafRanger:draw(0, 0)
 
   push:finish()
 end
 
 function love.update(dt)
-  LeafRanger.step = LeafRanger.step + dt
-
-  if LeafRanger.step > LeafRanger.animation.frames[LeafRanger.frame].duration then
-    LeafRanger.step = 0
-    LeafRanger.frame = LeafRanger.frame + 1
-    if LeafRanger.frame > #LeafRanger.animation.frames then
-      LeafRanger.frame = 1
-    end
-  end
+  LeafRanger:update(dt)
 end
 
 function love.keypressed(key)