Online Json to lua table converter: JSON Lua table converter - MAGEDDO
I use this for static level data. I put the lua files in my source folder and load the resulting pdz that pdc automatically creates with file.run
3 Likes
Here's a lightweight drop-in replacement for playdate.graphics.image that adds support for animated images: Lightweight AnimatedImage Library
Based on a conversation in the Playdate Squad Discord earlier I came up with some functions for drawing bezier curves in the Playdate Lua SDK by using line segments. Both quadratic beziers (3-point) and cubic beziers (4-point, the kind you'd find in most vector drawing apps) are supported!
This site has a nice interactive demo to compare both kinds of curves and the step parameter: A Primer on Bézier Curves
9 Likes
I'll add this here too in case the announcement thread falls by the way side. I'm working on a little Amiga mod player, blast from the past but could be very useful given the memory constraints if we can get it to run fast enough on real hardware.
2 Likes
You may want to check for overflow when implementing calloc. It's one of the reason it's best to use calloc versus malloc with a total size to avoid buffer overruns (although on PlayDate it probably will not be an issue given the lack of user input on these calls).
Something like this:
void* pd_calloc(size_t nb_of_items, size_t item_size)
{
if (item_size && (nb_of_items > (SIZE_MAX / item_size))) {
return NULL;
}
size_t size = nb_of_items * item_size;
void* memory = pd_malloc(size);
if(memory != NULL) {
memset(memory, 0, size);
}
return memory;
}
2 Likes
I built a dependency/package manager for Playdate: GitHub - jm/toybox: A dependency management system for Lua on the Playdate. Just got the binary releases up (accessible at Release First release! · jm/toybox · GitHub) so I hope folks can give it a spin. I'm working on getting it published in package managers etc so it's easier to upgrade.
I also published a repo of examples for things that don't currently have single file examples so that they have focused example scripts to learn from: GitHub - jm/playdate_examples: Examples for the Playdate SDK I'll be adding to this as I experiment with more of the APIs for sure. 
8 Likes
Amazing! I'm working on a little eurorack modular synth app for the Playdate, but I love trackers. My Polyend Tracker is my fav piece of gear!
10 Likes
Mentioned in a discussion thread I created, but wanted to drop this here in case it's useful to anyone checking this thread in the future. I started work on a tool to more easily view and choose dither patterns directly on device:
Thanks!
2 Likes
Show Toast message (temporary text that pop up on the screen) code:
local function showToast(text, duration)
local t = playdate.frameTimer.new(duration)
t.updateCallback = function()
Graphics.drawTextAligned(text, 200, 70, kTextAlignment.center)
end
end
Feel free to change text position (200, 70)
10 Likes
I love how simple and useful it is.
Really nice function!
1 Like
Here's a function I wrote to draw an image tiled within bounds with an optional offset. The built-in image:drawTiled(...) does not take a draw offset, so the tiled image is always tiled from 0, 0 of the destination rect. Ehh, it appears to work! 
function drawTiledImage(img, bounds, offset_x, offset_y)
offset_x = offset_x or 0
offset_y = offset_y or 0
-- Take easy route when no offset is specified.
if offset_x == 0 and offset_y == 0 then
img:drawTiled(bounds)
return
end
local iw, ih = img:getSize()
local sx = math.abs(offset_x % iw) - iw + bounds.x
local sy = math.abs(offset_y % ih) - ih + bounds.y
local cx, cy, cw, ch = playdate.graphics.getClipRect()
playdate.graphics.setClipRect(bounds)
img:drawTiled(sx, sy, bounds.width - sx, bounds.height - sy)
playdate.graphics.setClipRect(cx, cy, cw, ch)
end
1 Like
Converted the Roomy scene manager lib over to be useable with playdate
::edit::
Finally added a read me 
7 Likes
Here's a simple class I made to make a scrolling parallax background simple
local pd <const> = playdate
local gfx <const> = pd.graphics
class("Parallax").extends(gfx.sprite)
function Parallax:init()
Parallax.super.init(self)
self.layers = {}
end
function Parallax:draw(...)
gfx.setClipRect(...)
for _, layer in ipairs(self.layers) do
local img = layer.image
-- lock offset to steps of 2 to reduce flashing
local offset = layer.offset - (layer.offset % 2)
local w = layer.width
img:draw(self.x+offset, self.y)
if offset < 0 or offset > w - self.width then
if offset > 0 then
img:draw(self.x+offset-w, self.y)
else
img:draw(self.x+offset+w, self.y)
end
end
end
gfx.clearClipRect()
end
function Parallax:addLayer(img, depth)
local w, _ = img:getSize()
local layer = {}
layer.image = img
layer.depth = depth
layer.offset = 0
layer.width = w
table.push(self.layers, layer)
end
function Parallax:scroll(delta)
for _, layer in ipairs(self.layers) do
layer.offset = math.ring(
layer.offset + (delta * layer.depth),
-layer.width, 0
)
end
self:markDirty()
end
it also uses the math.ring function that was posted is this thread somewhere (I can't find it atm)
function math.ring(a, min, max)
if min > max then
min, max = max, min
end
return min + (a-min)%(max-min)
end
It's simple to use:
img_1 = gfx.image.new("images/parallax-1")
img_2 = gfx.image.new("images/parallax-2")
-- create
local parallax = Parallax()
parallax:setSize(400,240)
parallax:addLayer(img_1, 0.2)
parallax:addLayer(img_2, 0.6)
parallax:add()
-- scroll
parallax:scroll(10)
11 Likes
Pulled code from Lua SDK to read cranks ticks and wrapped it in an object. The reason for this is that the SDK code uses a local global vars which can be an issue if you want to read the number of ticks, or even with a different ticksPerRevolution value. Each reading resets the sampler.
So, with this code you simply create a Ticker, and sample each frame or whatever. You can reset it too during periods where you don't need samples.
You can of course create multiple Tickers each with their own ticksPerRevolution values to sample at different rates.
local ticker = Ticker.new(20)
-- elsewhere:
function update()
local ticks = ticker:sample()
end
Anyway, I've found it helpful so thought you may too.
Ticker = {}
Ticker.__index = Ticker
function Ticker.new(ticks_per_revolution)
local ticker = {}
setmetatable(ticker, Ticker)
ticker.ticks_per_revolution = ticks_per_revolution
ticker.last_reading = nil
return ticker
end
function Ticker:setTicksPerRevolution(ticks_per_revolution)
self.ticks_per_revolution = ticks_per_revolution
end
function Ticker:reset()
self.last_reading = nil
end
function Ticker:sample()
local totalSegments = self.ticks_per_revolution
local degreesPerSegment = 360 / self.ticks_per_revolution
local thisCrankReading = playdate.getCrankPosition()
local lastCrankReading = self.last_reading
if lastCrankReading == nil then
lastCrankReading = thisCrankReading
end
-- if it seems we've gone more than halfway around the circle, that probably means we're seeing:
-- 1) a reversal in directiotn, not that the player is really cranking that fast. (a good assumption if fps is 20 or higher; maybe not as good if we're at 2 fps or similar.)
-- 2) a crossing of the 359->0 border, which gives the appearance of a massive crank change, but is really very small.
-- both these cases can be treated identically.
local difference = thisCrankReading - lastCrankReading
if difference > 180 or difference < -180 then
if lastCrankReading >= 180 then
-- move tick_lastCrankReading back 360 degrees so it's < 0. It's the same location, just it is unequivocally lower than thisCrankReading
lastCrankReading -= 360
else
-- move tick_lastCrankReading ahead 360 degrees so it's > 0. It's the same location, just now it is unequivocally greater than thisCrankReading.
lastCrankReading += 360
end
end
-- which segment is thisCrankReading in?
local thisSegment = math.ceil(thisCrankReading / degreesPerSegment)
local lastSegment = math.ceil(lastCrankReading / degreesPerSegment)
local segmentBoundariesCrossed = thisSegment - lastSegment
-- save off value
self.last_reading = thisCrankReading
return segmentBoundariesCrossed
end
2 Likes
Determine tilt angle from reference point using accelerometer.
Spent a bit of time trying to figure this out so thought I'd just share here. If you want to determine the angle a player has tilted the device vertically (along the Y), I've so far found this to work pretty well:
-- Store reference position which to measure tilt from.
local _, ay, az = playdate.readAccelerometer()
local start_v = geometry.vector2D.new(ay, az)
-- Elsewhere, measure angle off reference position
local _, ay, az = playdate.readAccelerometer()
local current_v = geometry.vectory2D.new(ay, az)
local tilt_angle = start_v:angleBetween(current_v)
I think that's it. Though I haven't tried it, it seems you'd be able to measure tilt along the X axis by replacing ay with ax (the first value off readAccelerometer that I'm ignoring in this example).
OK! Happy, um, accelerating?
7 Likes
Cheat Codes
I've been working on adding some cheats to my game, figured I'd share the class here incase anyone else would like it.
local keys = {
a = playdate.kButtonA,
b = playdate.kButtonB,
up = playdate.kButtonUp,
down = playdate.kButtonDown,
left = playdate.kButtonLeft,
right = playdate.kButtonRight
}
class("CheatCode").extends()
function CheatCode:init(...)
local seq = {}
for _, key in ipairs({...}) do
local v = keys[key]
assert(v, "CheatCode: unknown key given => "..tostring(key))
table.insert(seq, v)
end
self._seq = seq
self.progress = 1
self.completed = false
self.run_once = true
self:setTimerDelay(400)
end
function CheatCode:update()
-- exit early if complete
if self.run_once and self.completed then return end
local _, pressed, _ = playdate.getButtonState()
-- exit early if no button currently pressed
if pressed == 0 then return end
if pressed == self._seq[self.progress] then
self.progress += 1
self._timer:reset()
if self.progress > #self._seq then
self.completed = true
if type(self.onComplete) == "function" then
self.onComplete()
end
end
else
self:reset()
end
end
function CheatCode:reset()
self.progress = 1
self._timer:reset()
self._timer:pause()
end
function CheatCode:setTimerDelay(ms)
if self._timer then
self._timer:remove()
end
self._timer = playdate.timer.new(ms, function() self:reset() end)
self._timer:pause()
self._timer.discardOnCompletion = false
end
function CheatCode:nextIs(key)
return keys[key] == self._seq[self.progress]
end
Using it is simple enough
-- initialize
local cheat = CheatCode("up", "up", "down", "down", "left", "right", "left", "right", "b", "a")
cheat.onComplete = function() print("cheat") end
-- in update function
playdate.timer.updateTimers() -- uses timers so make sure you call this
cheat:update()
By default it'll only trigger the first time the sequence is called, can be changed by setting run_once to false
CheatCode:nextIs([key]) is a helper to allow you to avoid triggering other effects while the code is being entered. eg:
if not cheat:nextIs("a") then
-- do something else
end
8 Likes
This is very helpful! Have you put this in a github repo with some documentation by any chance?
@dustin , I am quite interested in using this model as it could make reusing some cutscenes or parts of them quite easy (probably in conjunction with the Sequence lib also posted on the page here).
Nonetheless, could you clarify where does the dt param come from in your example? I assume it means time difference, but I am a bit confused by it.
I am hoping to achieve nicer animations on cutscenes with the use of these 2 libs, but please let me know if there is an easier way
Thanks for the help
The easiest way to calculate the time delta between frames is just to assume it's the current frame rate. You could just use:
local dt <const> = 1.0 / playdate.display.getRefreshRate()
Or if you want to be more accurate, you could do something like:
local previous_time = nil
function playdate.update()
local dt = 0
local current_time <const> = playdate.getCurrentTimeMilliseconds()
if previous_time ~= nil then
dt = (current_time - previous_time) / 1000.0
end
previous_time = current_time
if dt == 0 then
return
end
end
3 Likes
Simple just works object pooling function.
---Add objectToAdd into list
---@param list table table list
---@param objectToAdd table needs a "enabled" key
function ObjectPooling(list, objectToAdd)
local found = false
for i = 1, #list, 1 do
local o = list[i]
if not o.enabled then
list[i] = objectToAdd
found = true
break
end
end
if not found then
list[#list+1] = objectToAdd
end
end
2 Likes