How to detect the window has been maximized?

Question

I have my application and third-party application. And I need to know that the window of third-party application has been maximized. Is there any way to know it?
At first, I thought that I could use my own callback function for handling events of this window.

SetWindowLong(hwnd, GWL_WNDPROC, (LONG)WindowProc);

But this function fails with error "Access denied". And this happens for a reason. It's not very wise to change something in the window that you don't own.

So what should I do?

Answer 1

Use GetWindowPlacement function. Make sure you set the length member of WINDOWPLACEMENT to sizeof(WINDOWPLACEMENT) before calling GetWindowPlacement.

The showCmd field of the returned WINDOWPLACEMENT structure should be equal to SW_MAXIMIZE (3) if the window is maximized.