What is WM_KEYDOWN in c++

Question

I'm new to c++ and wondering what "WM_KEYDOWN" is? And how to use it.

Thank you.

Answer 1

WM_KEYDOWN is defined in Microsoft Docs :

#define WM_KEYDOWN  0x0100

While I don't have a better explanation than Microsoft's, I'll post what the doc says:

Posted to the window with the keyboard focus when a nonsystem key is pressed. A nonsystem key is a key that is pressed when the Alt key is not pressed.

Simply put, it is a value returned by Windows in a program when a key on the keyboard is pressed (and when Alt isn't). The opposite is WM_KEYUP , which will be emitted when you release the key.

Answer 2

A message flag produced by your window when your key is pressed. You can use it in the message handler function like

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

Then register it to your WNDCLASS

WNDCLASS ws;
ws.lpfnWndProc = WndProc; 

See http://msdn.microsoft.com/en-us/library/gg153546(v=VS.85).aspx for more information about how to dual with WM_KEYDOWN in WndProc.