L_BN_CLICKED

When received, this message indicates that the window was clicked with the left mouse button.

The L_BITMAPCLASS window's parent window receives this code through a WM_COMMAND message from the L_BITMAPCLASS window.

Parameter	Description
wParam	Contains the wParam parameter of the WM_COMMAND message, and specifies the child-window ID.
lParam	Contains the L_BITMAPCLASS window handle in its low-order word and the L_BN_CLICKED code in its high-order word.