C++ Windows application menus stop responding - c++

Question

I'm an electrical engineer and am creating my first C++ Windows 10 application in Visual Studio.
When I start the app that I've created, and my application window starts with its menus, I can open a file and start processing that file. This processing takes several minutes and
can't be interrupted for too long (less than a millisecond - hopefully).
The problem I'm having is that when the file processing is underway my window's menus don't respond. This is tolerable when I'm running under the Visual Studio IDE, but when I run the standalone app's .exe file then the app's graphics soon stops rendering and Windows posts a "Not responding" error message.
Can someone please point me in the right direction to solve these related problems. There must be a simple way to temporarily give control back to WinMain or window_callback.
Here's a simplified structure of the code:
LRESULT CALLBACK window_callback(HWND hwnd, UINT uMsg, ...) {
switch (uMsg) {
case WM_CREATE:
AddMenus(hwnd);
break;
case MY_FILE_OPEN:
open_file(hwnd);
break;
...
}
}
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, ...) {
// Create Window Class
...
// Register Class
...
// Create Window
HWND window = CreateWindow(window_class.lpszClassName, L"My Window NAME", ...);
hdc = GetDC(window);
// My application's initialization code
...
while (running) {
MSG message;
while (PeekMessage(&message, window, ...) {
TranslateMessage(&message);
DispatchMessage(&message);
}
}
}
void open_file(HWND hwnd) {
here's where I call the file processing code (a several-minute loop);
}

Answer 1

If your application is not running the main message processing loop of PeekMessage, TranslateMessage, and DispatchMessage then it will become completely non-responsive as you have noticed. That's the nature of message-driven event loops such as used by Windows.
You either need to run open_file in a different thread, or segment it in some way that it can process a small piece at a time and return and get called again to process another piece.
E.g.
while (running) {
MSG message;
while (PeekMessage(&message, window, ...) {
TranslateMessage(&message);
DispatchMessage(&message);
}
open_file_piece();
}