Problem when maximizing window in C++

Question

My program needs to arbitrarily maximize any window on the current desktop. I achieve this by calling ShowWindow(hWnd, SW_MAXIMIZE), where hWnd is the HWND of the window I want to maximize. When that line of code executes, the window in question (here, Notepad) looks like this:

Everything seems fine, except for the fact that the window has not been positioned correctly, i.e. the window seems to be a few pixels to low, and the title bar does not look "squashed" like it should. Compared to how it should look when the maximize button is clicked, the problem is clearly visible:

Does anyone know why this behaviour occurs, and what I can do to fix it?

Answer 1

Telling the window to maximize itself might bypass some internal adjustments that the program makes when it maximizes via a system menu command. To emulate clicking on the maximize button, send it a SC_MAXIMIZE command:

SendMessage(hwnd, WM_SYSCOMMAND, SC_MAXIMIZE, 0);