Add luacheck support and fix identified issues

.luacheckrc

@@ -0,0 +1,5 @@
+stds.easypattern = require "luacheck/Luacheck"
+
+std = "lua54+playdate+easypattern"
+
+operators = {"+=", "-=", "*=", "/="}

EasyPattern.lua

@@ -11,7 +11,7 @@ local CACHE_EXP <const> = 1 / 60 -- max FPS
 
 -- Animated patterns with easing, made easy.
 --
--- SAMPLE USAGE: 
+-- SAMPLE USAGE:
 --
 --     local checkerboard = {0xF0F0, 0xF0F0, 0xF0F0, 0xF0F0, 0x0F0F, 0x0F0F, 0x0F0F, 0x0F0F}
 --     local easyCheckerboard = EasyPattern {
@@ -197,12 +197,12 @@ function EasyPattern:init(params)
     self:updatePatternImage()
 end
 
-function setColor(color)
+function EasyPattern:setColor(color)
     self.color = color
     self:updatePatternImage()
 end
 
-function setBackgroundColor(color)
+function EasyPattern:setBackgroundColor(color)
     self.bgColor = color
     self:updatePatternImage()
 end
@@ -242,8 +242,8 @@ function EasyPattern:getPhases()
     end
 
     -- calculate the effective time param for each axis accounting for offsets, speed scaling, and looping
-    tx = (t * self.xSpeed + self.xPhaseOffset) % self.xPhaseDuration
-    ty = (t * self.ySpeed + self.yPhaseOffset) % self.yPhaseDuration
+    local tx = (t * self.xSpeed + self.xPhaseOffset) % self.xPhaseDuration
+    local ty = (t * self.ySpeed + self.yPhaseOffset) % self.yPhaseDuration
 
     -- handle animation reversal when crossing the animation duration bounds
     if self.xReverses and self._ptx > tx then
@@ -270,7 +270,7 @@ function EasyPattern:getPhases()
     if self.yReversed then yPhase = PTTRN_SIZE - yPhase - 1 end
 
     -- determine if we're dirty and cache the computed phase values along with a timestamp
-    dirty = xPhase ~= self._xPhase or yPhase ~= self._yPhase
+    local dirty = xPhase ~= self._xPhase or yPhase ~= self._yPhase
     self._xPhase = xPhase
     self._yPhase = yPhase
     self._pt = t

luacheck/Luacheck.lua

@@ -0,0 +1,34 @@
+-- EasyPattern globals
+--
+-- This file can also be used with toyboxpy (https://toyboxpy.io):
+--
+-- 1. Add this to your project's .luacheckrc:
+--    require "toyboxes/luacheck" (stds, files)
+--
+-- 2. Add 'toyboxes' to your std:
+--    std = "lua54+playdate+toyboxes"
+
+return {
+    globals = {
+        EasyPattern = {
+            fields = {
+                super = {
+                    fields = {
+                        className = {},
+                        init = {}
+                    },
+                },
+                className = {},
+                init = {},
+                setColor = {},
+                setBackgroundColor = {},
+                setPattern = {},
+                setDitherPattern = {},
+                updatePatternImage = {},
+                getPhases = {},
+                isDirty = {},
+                apply = {}
+            }
+        },
+    }
+}