Question

Is there a way to handle wm_print message in a CWnd (using MFC) ?. I’m trying to intercept this message and prevent printing of a child control. Adding ON_WM_PRINT() to my message map throws compilation errors.

Answer 1

MFC only defines ON_WM_XXXX() macros for the commonest messages, but there is also a general ON_MESSAGE() macro to allow you to handle other cases. Add

ON_MESSAGE(WM_PRINT, OnPrint)

to your message map, and then declare and implement a member function

afx_msg LRESULT OnPrint(WPARAM, LPARAM);

The device context is passed in the WPARAM, so you need something like this in your implementation:

LRESULT MyWindowClass::OnPrint(WPARAM wp, LPARAM)
{
  CDC* dc = CDC::FromHandle((HDC)wp);

  // Do custom logic here ...

  // Only call Default() if you want the default processing for this message too ...
  return Default();
}