Rendering to a Window hangs in linux

[goldenratio]

Hey,

when I try to run below code snippet, in Fedora 42 (i3wm, uses x11 display server) - terminal becomes unresponsive. I have to Ctrl + C to kill the process.

Searching the issues list, #159 sounds similar. I have no warning or error messages.

import { Window } from 'skia-canvas'

let win = new Window(300, 300, { fit: 'none' })
win.title = "Canvas Window"
win.on("draw", e => {
  let ctx = e.target.canvas.getContext("2d")
  ctx.lineWidth = 25 + 25 * Math.cos(e.frame / 10)
  ctx.beginPath()
  ctx.arc(150, 150, 50, 0, 2 * Math.PI)
  ctx.stroke()

  ctx.beginPath()
  ctx.arc(150, 150, 10, 0, 2 * Math.PI)
  ctx.stroke()
  ctx.fill()
})

 node ./main.js

skia-canvas-demo tree -L 2
.
├── main.js
├── node_modules
│   ├── agent-base
│   ├── debug
│   ├── detect-libc
│   ├── follow-redirects
│   ├── https-proxy-agent
│   ├── ms
│   ├── parenthesis
│   ├── skia-canvas
│   └── string-split-by
├── package.json
├── package-lock.json
└── rainbox.png

11 directories, 4 files

[samizdatco]

Out of curiosity, does it work if you run under Wayland rather than X11?

[goldenratio]

yeah, I used another computer with Fedora 42 sway. It works. Please note: this computer has no discrete graphics card.

CPU: Intel(R) Core(TM) i5-6200U (4) @ 2.80 GHz
GPU: Intel HD Graphics 520 @ 1.00 GHz [Integrated]

My X11 machine has Nvidia 755m graphics card (quite old) may be it's related too that, that being said raylib-rs, bevy works fine.. I think they also use winit.

Below is vulkaninfo log, not sure who useful it is:
https://gist.github.com/goldenratio/436cb442977b148fcb3ffd782fa656b5

[samizdatco]

I've found nvidia support to be extremely driver-version dependent, so that's another possible wrinkle here. On the system that's hanging, what output do you get for:

import {Canvas} from 'skia-canvas'
let c = new Canvas()
console.log(c.engine)

[goldenratio]

{
  renderer: 'GPU',
  api: 'Vulkan',
  device: 'Discrete GPU (NVIDIA GeForce GT 755M)',
  driver: 'NvidiaProprietary (470.256.02)',
  threads: 8,
  textContrast: 0,
  textGamma: 1.4
}

[samizdatco]

Interesting... Are you able to call toFile or toBuffer successfully with the gpu enabled? If so it seems like it's initializing the Vulkan context successfully, but tripping up on the just windowing.

[goldenratio]

ya, I can draw stuff to file and stuff. I think, just windowing is the issue

[samizdatco]

I'm wondering if you're actually encountering a hang or if the window is rendering, but invisible/offscreen. Could you try running this and see if it prints anything out after launching?

import {App, Window} from 'skia-canvas'

async function main(){
  App.fps = 2
  App.eventLoop = "node"
  let win = new Window()
  win.on('frame', e => console.log(`frame ${e.frame}`))
  setTimeout(() => win.close(), 2000)

  console.log('launching')
  await App.launch()
  console.log('exiting')
}

main()

[goldenratio]

with above code snippet window launches and prints log,

 node ./main.js
launching
frame 2
frame 3
frame 4
frame 5
frame 6
frame 7
frame 8
frame 9
frame 10
frame 11
frame 12
frame 13
frame 14
frame 15

attached video

recording_2025-08-28_22.13.29.mp4

[samizdatco]

I'm a little confused. In your video it looks like it's also successfully opening a window. But weren't you saying that that didn't happen in your original bug report?

Or is this running on the (working) Intel-GPU system? If so, could you try running the script on the X11/Nvidia system so we can figure out what's happening when it's becoming unresponsive?

[goldenratio]

I am confused too. But with the below code form README, it hangs,
thinking should I use App to launch the window?

import { Window } from 'skia-canvas'

let win = new Window(300, 300, { fit: 'none' })
win.title = "Canvas Window"
win.on("draw", e => {
  let ctx = e.target.canvas.getContext("2d")
  ctx.lineWidth = 25 + 25 * Math.cos(e.frame / 10)
  ctx.beginPath()
  ctx.arc(150, 150, 50, 0, 2 * Math.PI)
  ctx.stroke()

  ctx.beginPath()
  ctx.arc(150, 150, 10, 0, 2 * Math.PI)
  ctx.stroke()
  ctx.fill()
})

video, (green forest/plant is my wallpaper.. basically a window with hole appears, and it's not responsive, I have to force kill it)

recording_2025-08-28_22.17.17.mp4

Both the videos (from previous post) are from X11/Nvidia

[goldenratio]

@samizdatco Hey, I think I found the root cause of the issue (not quite technical).

To sum it up, hang happens when I draw something using context when the Window is open. Please note: I can draw directly to file, without any issues, since there is no Window involved.

For frame event:

• I found a workaround, If I skip first 2 frames and then start drawing. It works.

For draw event:

• Skipping first 2 frame doesn't to the trick.

Attaching video. Please let me know If you need more details. This was tested on X11 / Nvidia proprietary driver 470.xx.

recording_2025-08-30_10.48.00.mp4

maybe this issue can be closed. Since it's X11/Nvidia only issue and we have a workaround for it.