Attaching a glfw window to an electron handle freezes the electron window - c++

Question

I'm trying to attach a glfw window to an electron one.
I've succesfully retrieved the electron window handle (electronWindow.getNativeWindowHandle()) in my glfw app, and then used win32 api to try and attach them to one another :
GLFWwindow* createWindow(HWND parentWindow)
{
// Create an invisible window
fprintf(stdout, "Creating window as child of window 0x%016x\n", parentWindow);
glfwDefaultWindowHints();
glfwWindowHint(GLFW_RESIZABLE, FALSE);
glfwWindowHint(GLFW_DECORATED, GLFW_FALSE);
glfwWindowHint(GLFW_VISIBLE, GLFW_TRUE);
GLFWwindow* window = glfwCreateWindow(800, 600, "", nullptr, nullptr);
// That we attach as a child to an other one
HWND hw = glfwGetWin32Window(window);
HWND previousParent = SetParent(hw, parentWindow);
if (!previousParent) {
fprintf(stderr, "Couldn't set window parent: %s\n", lastWindowsError().c_str());
glfwDestroyWindow(window);
return nullptr;
}
ShowWindow(hw, SW_SHOW);
return window;
}
The SetParent call doesn't fail so I'm assuming the connection is made.
Then I have my (very classical) main glfw loop like this :
while (!glfwWindowShouldClose(window))
{
glClearColor(0.3, 0.4, 0.8, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glfwPollEvents();
glfwSwapBuffers(window);
}
So the "faulty" behavior I've got is the following :
The electron app freezes. Nothing moves, the process is "not responding"
My glfw window doesn't show up anywhere
I haven't done an win32 event handling on glfw side, could this be the issue ? Like some specific event I have to take care of ?
Is this an issue with the electron app not passing events to the glfw window, hence blocking everything ?
Note: I'm doing this because I want to display native opengl using a pre-existing engine we've got.
I've tried naively doing glfwSetWindowPos each time the electron window moves, but it's sluggish as hell (probably Windows preventing this behavior) so I'm trying other approaches (here : attaching the opengl window as a child of electron).

Answer 1

So it seems it's not a very good idea haha + I'm not that good with win32 api so I can't really tell what's not working (cf. #iinspectable comments)
I delved into this issue on electron's github : https://github.com/electron/electron/issues/10547 and found a way to display an OpenGL frame on top of an Electron window.
I circumvented the issue by creating the window as a child process of the electron app with the HWND as startup argument :
const { app, BrowserWindow } = require('electron')
const { endianness } = require('os')
const { spawn } = require('child_process')
const nativeExecutablePath = 'src/overlay/build/Release/kf-overlay.exe'
const indexPath = 'src/ui/html/index.html'
const startChildProcess = (hwnd, target) => {
const data = endianness() == 'LE'
? hwnd.readInt32LE()
: hwnd.readInt32BE()
const p = spawn(target, [data], { cwd: process.cwd() })
p.stdout.on('data', data => console.log(`[native] ${data}`))
p.stderr.on('data', data => console.log(`[native] ${data}`))
}
const createWindow = () => {
const win = new BrowserWindow({
width: 800,
height: 600
})
// win.loadFile(indexPath)
win.loadURL('https://www.google.com')
win.webContents.setFrameRate(60)
console.log(`Starting child process ${nativeExecutablePath}`)
const hwnd = win.getNativeWindowHandle()
startChildProcess(hwnd, nativeExecutablePath)
}
app.whenReady().then(() => {
createWindow()
})
Then creating the window as a child from C++ side :
HWND createChildWindow(HWND parent)
{
RECT rect;
GetWindowRect(parent, &rect);
int parentWidth = rect.right - rect.left;
int parentHeight = rect.bottom - rect.top;
DWORD style = WS_VISIBLE | WS_CHILD | WS_POPUP;
auto child = CreateWindowEx(
WS_EX_LAYERED | WS_EX_TOPMOST | WS_EX_TRANSPARENT | WS_EX_COMPOSITED,
WINDOW_CLASS_NAME,
nullptr,
style,
parentWidth / 2 - 512,
parentHeight / 2 - 512,
512,
512,
parent,
nullptr,
nullptr,
nullptr
);
SetParent(child, parent);
return child;
}
Finally I could create the OpenGL context through wglCreateContext calls, and render a frame with OpenGL calls :)