The window procedure for the predefined button control window class carries out default processing for all messages that the button control procedure does not process. When the button control procedure returns FALSE for any message, the predefined window procedure checks the messages and performs the default actions listed in the following table.
| Message | Default action |
|---|---|
| BM_CLICK | Sends the button a WM_LBUTTONDOWN and a WM_LBUTTONUP message, and sends the parent window a BN_CLICKED notification message. |
| BM_GETCHECK | Returns the check state of the button. |
| BM_GETIMAGE | Returns a handle to the bitmap or icon associated with the button or NULL if the button has no bitmap or icon. |
| BM_GETSTATE | Returns the current check state, push state, and focus state of the button. |
| BM_SETCHECK | Sets the check state for all styles of radio buttons and check boxes. If the wParam parameter is greater than zero for radio buttons, the button is given the WS_TABSTOP style. |
| BM_SETIMAGE | Associates the specified bitmap or icon handle with the button and returns a handle to the previous bitmap or icon. |
| BM_SETSTATE | Sets the push state of the button. For owner-drawn buttons, a WM_DRAWITEM message is sent to the parent window if the state of the button has changed. |
| BM_SETSTYLE | Sets the button style. If the low-order word of the lParam parameter is TRUE, the button is redrawn. |
| WM_CHAR | Checks a check box or automatic check box when the user presses the plus (+) or equal (=) keys. Unchecks a check box or automatic check box when the user presses the minus (–) key. |
| WM_ENABLE | Paints the button. |
| WM_ERASEBKGND | Erases the background for owner-drawn buttons. The backgrounds of other buttons are erased as part of the WM_PAINT and WM_ENABLE processing. |
| WM_GETDLGCODE | Returns values indicating the type of input processed by the default button procedure, as shown in the following table. |
| Button style | Returns | |
|---|---|---|
| BS_AUTOCHECKBOX | ||
| DLGC_WANTCHARS | DLGC_BUTTON | ||
| BS_AUTORADIOBUTTON | ||
| DLGC_RADIOBUTTON | ||
| BS_CHECKBOX | ||
| DLGC_WANTCHARS | DLGC_BUTTON | ||
| BS_DEFPUSHBUTTON | ||
| DLGC_DEFPUSHBUTTON | ||
| BS_GROUPBOX | ||
| DLGC_STATIC | ||
| BS_PUSHBUTTON | ||
| DLGC_UNDEFPUSHBUTTON | ||
| BS_RADIOBUTTON | ||
| DLGC_RADIOBUTTON | ||
| WM_GETFONT | Returns a handle to the current font. |
| WM_KEYDOWN | Pushes the button if the user presses the spacebar. |
| WM_KEYUP | Releases the mouse capture for all cases except the tab key. |
| WM_KILLFOCUS | Removes the focus rectangle from a button. For push buttons and default push buttons, the focus rectangle is invalidated. If the button has the mouse capture, the capture is released, the button is not clicked, and any push state is removed. |
| WM_LBUTTONDBLCLK | Sends a BN_DBLCLK notification message to the parent window for radio buttons and owner-drawn buttons. For other buttons, a double-click is processed as a WM_LBUTTONDOWN message. |
| WM_LBUTTONDOWN | Highlights the button if the position of the mouse cursor is within the button's client rectangle. |
| WM_LBUTTONUP | Releases the mouse capture if the button had the mouse capture. |
| WM_MOUSEMOVE | Performs the same action as WM_LBUTTONDOWN, if the button has the mouse capture. Otherwise, no action is performed. |
| WM_NCCREATE | Turns any BS_OWNERDRAW button into a BS_PUSHBUTTON button. |
| WM_NCHITTEST | Returns HTTRANSPARENT, if the button control is a group box. |
| WM_PAINT | Draws the button according to its style and current state. |
| WM_SETFOCUS | Draws a focus rectangle on the button getting the focus. For radio buttons and automatic radio buttons, the parent window is sent a BN_CLICKED notification message. |
| WM_SETFONT | Sets a new font and optionally updates the window. |
| WM_SETTEXT | Sets the text of the button. In the case of a group box, the message paints over the preexisting text before repainting the group box with the new text. |
| WM_SYSKEYUP | Releases the mouse capture for all cases except the tab key. |
The predefined window procedure passes all other messages to the DefWindowProc function for default processing.