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benoitlahoz/child.html

Created April 29, 2025 16:28
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'paint' event not triggered if window is created via 'setWindowOpenHandler'
Raw
child.html
<!DOCTYPE html>
<html style="width: 100vw; height: 100vh;">
<head>
<meta charset="UTF-8">
<!-- https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP -->
<meta http-equiv="Content-Security-Policy" content="default-src 'unsafe-inline'; script-src 'self' 'unsafe-inline'">
<title>Hello World!</title>
</head>
<body style="width: 100%; height: 100%; margin: 0;">
<canvas id="my-canvas" style="background-color: black; width: 100%; height: 100%;" />
</body>
</html>
Raw
index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<!-- https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP -->
<meta http-equiv="Content-Security-Policy" content="default-src 'unsafe-inline'; script-src 'self' 'unsafe-inline'">
<title>Hello World!</title>
</head>
<body>
<h1>Hello World!</h1>
We are using Node.js <span id="node-version"></span>,
Chromium <span id="chrome-version"></span>,
and Electron <span id="electron-version"></span>.
<canvas id="my-canvas" style="background-color: black; width: 320px; height: 240px;" />
<!-- You can also require other files to run in this process -->
<script src="./renderer.js"></script>
</body>
</html>
Raw
main.js
// Modules to control application life and create native browser window
const { app, BrowserWindow, shell } = require('electron')
const path = require('node:path')
function createWindow () {
// Create the browser window.
const mainWindow = new BrowserWindow({
width: 800,
height: 600,
webPreferences: {
contextIsolation: true, // Doesn't work with false either.
sandbox: false,
backgroundThrottling: false,
nodeIntegrationInWorker: true,
preload: path.join(__dirname, 'preload.js')
}
})
// and load the index.html of the app.
mainWindow.loadFile('index.html')
mainWindow.webContents.setWindowOpenHandler(({ url, frameName, features }) => {
if (frameName.startsWith('syphon_')) {
return {
action: 'allow',
createWindow(options) {
const newOptions = {
...options,
// --------------------------------------------
show: false, // Change this to see the window.
// --------------------------------------------
webPreferences: {
...options.webPreferences,
offscreen: {
useSharedTexture: true,
},
contextIsolation: true,
nodeIntegrationInWorker: true,
preload: path.join(__dirname, 'preload.js'),
},
};
const subwindow = new BrowserWindow(newOptions);
const handlePaint = (event) => {
const texture = event.texture;
console.log('--- SHOULD LOG PAINT ---');
if (texture) {
const handle = texture.textureInfo.sharedTextureHandle;
// Here: node-syphon publishes handle.
texture.release();
}
};
subwindow.webContents.on('paint', handlePaint);
return subwindow.webContents;
}
}
}
shell.openExternal(url);
return { action: 'deny' };
});
// Open the DevTools.
// mainWindow.webContents.openDevTools()
}
// This method will be called when Electron has finished
// initialization and is ready to create browser windows.
// Some APIs can only be used after this event occurs.
app.whenReady().then(() => {
createWindow()
app.on('activate', function () {
// On macOS it's common to re-create a window in the app when the
// dock icon is clicked and there are no other windows open.
if (BrowserWindow.getAllWindows().length === 0) createWindow()
})
})
// Quit when all windows are closed, except on macOS. There, it's common
// for applications and their menu bar to stay active until the user quits
// explicitly with Cmd + Q.
app.on('window-all-closed', function () {
if (process.platform !== 'darwin') app.quit()
})
// In this file you can include the rest of your app's specific main process
// code. You can also put them in separate files and require them here.
Raw
preload.js
/**
* The preload script runs before `index.html` is loaded
* in the renderer. It has access to web APIs as well as
* Electron's renderer process modules and some polyfilled
* Node.js functions.
*
* https://www.electronjs.org/docs/latest/tutorial/sandbox
*/
window.addEventListener('DOMContentLoaded', () => {
const replaceText = (selector, text) => {
const element = document.getElementById(selector)
if (element) element.innerText = text
}
for (const type of ['chrome', 'node', 'electron']) {
replaceText(`${type}-version`, process.versions[type])
}
})
Raw
renderer.js
/**
* This file is loaded via the <script> tag in the index.html file and will
* be executed in the renderer process for that window. No Node.js APIs are
* available in this process because `nodeIntegration` is turned off and
* `contextIsolation` is turned on. Use the contextBridge API in `preload.js`
* to expose Node.js functionality from the main process.
*/
let canvas;
let child;
const draw = (timestamp) => {
const hue = (timestamp / 10) % 360;
if (canvas) {
const width = canvas.width;
const height = canvas.height;
const ctx = canvas.getContext('2d');
ctx.fillStyle = `hsl(${hue}, 100%, 50%)`;
ctx.fillRect(0, 0, width, height);
if (child) {
// Draw on child window canvas.
const winCanvas = child.document.getElementById('my-canvas');
if (winCanvas) {
const winCtx = winCanvas.getContext('2d');
winCtx.drawImage(canvas, 0, 0);
}
}
}
requestAnimationFrame(draw);
}
window.addEventListener('DOMContentLoaded', () => {
canvas = document.getElementById('my-canvas');
draw();
child = window.open('child.html', 'syphon_0', 'width=800,height=600');
})
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