msgs12.hlp (Topic list)
BM_QUERYCHECKINDEX (1.2)
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#define INCL_WINBUTTONS
 
BM_QUERYCHECKINDEX
mp1 = 0L;    /* not used, must be zero */
mp2 = 0L;    /* not used, must be zero */
 
An application sends the BM_QUERYCHECKINDEX message to determine the
zero-based index of a checked radio button. It can be sent to any radio
button or auto-radio button within a group. The button window responds to
this message by returning the zero-based index of the checked radio button.
 
This message does not use any parameters.
 
Return Value
 
The return value is the radio-button index if the operation is successful or
-1 if no radio button in the group is checked or if the button control does
not have the style BS_RADIOBUTTON or BS_AUTORADIOBUTTON.
 
See Also
 
BM_QUERYCHECK