snowkittykira [Lexaloffle Blog Feed]

picotron error explorer 0.0.6 - interactive stack trace on error

Fri, 26 Apr 2024 17:36:36 UTC

hi, i wrote an interactive error screen for picotron! on error, it lets you explore the stack, local variables, and shows the source location where the error occurred. use arrows to go up and down the stack, the mouse wheel to scroll, and click on table variables to expand them. you can also press space or x to toggle small-font mode.

error_explorer_example

by snowkittykira

[Click to Play]

download: https://github.com/snowkittykira/picotron-error-explorer

to use it, download error_explorer.lua and include it after defining your _init, _update and _draw functions.

it replaces these functions which wrappers that call them in a coroutine, so that when errors happen the coroutine can be inspected. on error, it does its best to reset the graphics state, but there might still be cases where this fails so let me know if you run into any issues!

it relies on the following functions from lua's debug library, so i hope they will continue to be available:

debug.traceback
debug.getinfo
debug.getlocal
debug.getupvalue

(note: please use the github version and not the one in the example cart, as it'll be more up to date)

minor bug report: calling clip() during _init() crashes picotron

Fri, 26 Apr 2024 17:12:11 UTC

this crashes picotron when run:

function _init ()
  clip()
end

coroutine.resume weirdness

Tue, 23 Apr 2024 22:47:18 UTC

hi, i'm loving picotron so far! i just wanted to report some issues using coroutines.

when using coroutine.resume, it can sometimes return early when the coroutine runs for a while due to how picotron does timeslicing. from reading head.lua, i learned that using coresume instead of coroutine.resume fixes this, which makes me think maybe coroutine.resume should be replaced with it. another more minor issue is that coresume only returns the first value of a multiple-value return/yield from the coroutine, and not any more.

here's a simple test case:

local function long_running_coroutine ()
  for i = 1, 100 do
    cls()
  end
  return 1, 2
end

function working ()
  local c = coroutine.create (long_running_coroutine)
  coresume (c)
  assert (coroutine.status(c) == 'dead', 'this works')
end

function not_working ()
  local c = coroutine.create (long_running_coroutine)
  coroutine.resume (c)
  assert (coroutine.status(c) == 'dead', 'this doesn\'t work')
end

function also_not_working ()
  local c = coroutine.create (long_running_coroutine)
  local a, b, c = coresume (c)
  assert (a)
  assert (b)
  assert (c, 'only one coroutine return value returned')
end

function _draw ()
  working ()
  not_working ()
  also_not_working ()
end

globals set in terminal.lua

Sun, 21 Apr 2024 17:21:35 UTC

hi! when i use lua i usually use a library that prevents me from accidentally using/setting globals that aren't already defined, in order to cut down on typos. i've collected a small whitelist of globals that need to be available for picotron. i noticed in terminal.lua there's a comment saying it's not supposed to set any globals, so i thought i'd report them in case they should be fixed.

here's what i have so far in my whitelist:

-- terminal.lua
cproj_draw
cproj_update
_
_is_terminal_command
k
res
-- gui.lua
drag_t

and here's the full script i'm using to protect globals in case it's helpful:

-- if you're using include(), include this after including everything else,
-- since most included modules will need to assign global variables on load

-- these globals are needed by picotron
_init = _init or false
_draw = _draw or false
_update = _update or false
-- these are used by the picotron terminal
cproj_draw = cproj_draw or false
cproj_update = cproj_update or false
_ = _ or false
_is_terminal_command = _is_terminal_command or false
k = k or false
res = res or false
-- gui needs these
drag_t = drag_t or false

local function unknown_variable (t, k)
  error (debug.traceback ('unknown variable ' .. tostring (k), 2))
end

setmetatable (_G, {
  __index = unknown_variable,
  __newindex = unknown_variable,
})

it's probably a good idea not to use it in finished carts because then changes to picotron might break them

picobloc - userdata-based ecs library

Sat, 20 Apr 2024 00:13:54 UTC

I've been writing an archetype-based ecs (entity-component-system) library for picotron and i put it up on github!

https://github.com/snowkittykira/picobloc

It keeps component values in picotron userdata so that for simple cases like velocity / acceleration, you can use userdata operations to make it very fast! As a result it is probably slightly harder to use than the other ecs libraries available for picotron right now (which use tables to represent entities), but should allow some pretty good optimizations.

you can see the example from the readme running here:

https://www.lexaloffle.com/bbs/?tid=141824

and my plink cart also uses it, though it doesn't really need the optimization:

https://www.lexaloffle.com/bbs/?tid=141789

waterfall demo

Fri, 19 Apr 2024 19:29:26 UTC

ecs_waterfall

by snowkittykira

[Click to Play]

a little demo of an ecs system i'm working on that uses userdata to store component fields

it's 4k particles, hold the '`' key to see cpu usage for update and draw (edit: oops this key only works on desktop apparently, but it's currently at 16% update and 33% draw)

plink

Wed, 17 Apr 2024 21:54:22 UTC

plink

by snowkittykira

[Click to Play]

playing around with physics and note()

~~(sound is pretty borked on the bbs, so download it with load #plink)~~ sound seems fixed yay!

userdata:copy issues

Tue, 16 Apr 2024 21:53:16 UTC

i'm trying to use :copy when growing a userdata:

local a = vec(1, 1)
local b = vec(0, 0, 0)
a:copy (b)
print(b)
-- b is still zero

i figured maybe the vectors needed to be the same size but neither of these work either:

local a = vec(1, 1)
local b = vec(0, 0)
local c = vec(0, 0)
a:add (0, b)
a:copy (c)
print(a)
print(b)
print(c)

segmentation fault on left-multiplying userdata

Sun, 31 Mar 2024 20:44:47 UTC

just noting that the following crashes picotron:

function _draw ()
    print (tostring (1 * vec(1, 1, 1)))
end

color table indices swapped?

Sat, 30 Mar 2024 17:00:09 UTC

not sure if this is a bug in picotron or just in the docs, but in the gfx pipeline doc it says that the colour tables are accessed like this:

out_col = peek(0x8000+coltab*0x1000 + target_col*64 + draw_col)

but to get the colour table working properly in practice i have to swap the target and draw colours like this:

function c_set_table (draw_color, target_color, result)
  poke (0x8000 + 64 * draw_color + target_color, result)
end

simple dither patterns

Sat, 30 Mar 2024 16:39:31 UTC

simple_dither

by snowkittykira

[Click to Play]

thought i'd post a demonstration of generating simple dither patterns for fillp in case it was useful to anyone!

feel free to use under the CC license or mit license or public domain

dither.lua:

-- threshold map from https://en.wikipedia.org/wiki/Ordered_dithering
local threshold_map = {
   0,  8,  2, 10,
  12,  4, 14,  6,
   3, 11,  1,  9,
  15,  7, 13,  5,
}

local function make_mask (value)
  local mask = 0
  for i = 1, 16 do
    mask = mask * 2
    if threshold_map [i] >= value then
      mask = mask + 1
    end
  end
  return mask
end

local dither_masks = {}
for i = 0, 16 do
  dither_masks[i] = make_mask (i)
end

-- value 0-1
function dither_mask (value)
  return dither_masks [mid (0, math.floor (value * 16 + 0.5), 16)]
end

main.lua:

include 'dither.lua'

local W, H = 480, 270

local color1 = 9
local color2 = 30

function _draw ()
  for i = 0, H-1 do
    fillp (dither_mask (i/H))
    rectfill (0, i, W, i, (color1 << 8) | color2)
  end
  fillp ()
end