I've stumbled across a rather bizarre memory leak. I don't fully understand what's going on, but I think it must be a bug under the hood. Here's a simple repro:
import "CoreLibs/graphics"
-- commenting out sprites import resolves leak, regardless of below
import "CoreLibs/sprites"
function playdate.update()
-- must have at least 3 calls to drawTextAligned()
playdate.graphics.drawTextAligned("Some", 42, 198, kTextAlignment.center )
playdate.graphics.drawTextAligned("Stuff", 42, 210, kTextAlignment.center )
playdate.graphics.drawTextAligned("Here", 42, 222, kTextAlignment.center )
end
My device after a few minutes of running the above snippet:
I modified the code in the following way and it appears to no longer eat memory, although if you comment out the last drawTextAligned it will start eating again.
import "CoreLibs/sprites"
import "CoreLibs/graphics"
local GFX <const> = playdate.graphics;
local line1 <const> = "Some"
local line2 <const> = "Stuff"
local line3 <const> = "Here"
local line4 <const> = "Extra!"
function playdate.update()
GFX.drawTextAligned(line1, 200, 10, kTextAlignment.center )
GFX.drawTextAligned(line2, 200, 30, kTextAlignment.center )
GFX.drawTextAligned(line3, 200, 50, kTextAlignment.center )
GFX.drawTextAligned(line4, 200, 70, kTextAlignment.center )
end
I spent a while trying to narrow down the problem, but it seems a little inconsistent. From what I have seen, it looks like playdate.graphics.drawTextAligned makes use of str:gmatch, which generates a lot of garbage every frame. Normally the garbage collector will clean it up, but sometimes it seems to get out of control and will continue generating garbage very quickly.
I tried to change the align to left, guessing that that would be the simplest to place and it was still slowly eating memory. I removed all rendered text and even it still was ever so slowly eating memory, I removed the FPS counter, which is also text, memory leak stopped. It's gotta be the text.
If I put collectgarbage() in the update loop it does prevent it from eating ram, and craters the FPS to 26.
Ahh I hadn't realized the Lua source was in the SDK folder!
You seem to be correct, gmatch is creating garbage every frame as compiling with this modifications to graphics.lua fixes the leak:
function playdate.graphics.drawTextAligned(str, x, y, textAlignment, lineHeightAdjustment)
local font = g.getFont()
if font == nil then print('error: no font set!') return 0, 0 end
local lineHeight = font:getHeight() + font:getLeading() + math.floor(lineHeightAdjustment or 0)
local ox = x
str = ""..str -- if a number was passed in, convert it to a string
local styleCharacterForNewline = ""
-- gmatch create garbage!
-- for line in str:gmatch("[^\r\n]*") do -- split into hard-coded lines
local line = str
line = _addStyleToLine(styleCharacterForNewline, line)
local width = g.getTextSize(line)
if textAlignment == kTextAlignment.right then
x = ox - width
elseif textAlignment == kTextAlignment.center then
x = ox - (width / 2)
end
g.drawText(line, x, y)
y += lineHeight
styleCharacterForNewline = _styleCharacterForNewline(line)
-- end
end
It's not garbage collection as the collection is never occurring. Here's a screen shot of a longer session. Garbage hasn't been collected yet and the RAM is 50% used.
okay, I think I see what's happening. We're asking dlmalloc for the # of bytes allocated to decide how hard we want to push the allocator, and it turns out that can take a bit of time when there are a lot of small allocations. I didn't realize it was walking a list, had assumed it kept a tally. So by the time it's figured out how long it needs to run the collector it's already used up all the time available. I'll add a memory tally to dlmalloc and I'll also look at why drawTextAligned is generating so much garbage.
I've been experiencing a similar issue using drawLocalizedTextInRect, though it was a lot more extreme; if i called it in update without a conditional, memory would run out extremely quickly. i've modified it to only call when absolutely needed, but i still lose about .5% of memory for each text box generated. Not much, but could be an issue in the future, especially on repeat playthroughs
So by the time it's figured out how long it needs to run the collector it's already used up all the time available. I'll add a memory tally to dlmalloc and I'll also look at why drawTextAligned is generating so much garbage.