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MM_ACM_FORMATCHOOSE

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The MM_ACM_FORMATCHOOSE message notifies an acmFormatChoose dialog hook function before adding an element to one of the three drop-down list boxes. This message allows an application to further customize the selections available through the user interface.

MM_ACM_FORMATCHOOSE 
wParam = (WPARAM) wDropDown 
lParam = (LONG) lCustom

Parameters

wDropDown

Drop-down list box being initialized and a verify or add operation.

FORMATCHOOSE_CUSTOM_VERIFY The lParam parameter is a pointer to a WAVEFORMATEX structure to be added to the custom Name drop-down list box.
FORMATCHOOSE_FORMAT_ADD The lParam parameter is a pointer to a buffer that will accept a WAVEFORMATEX structure to be added to the Format drop-down list box. The application must copy the format structure to be added into this buffer.
FORMATCHOOSE_FORMAT_VERIFY The lParam parameter is a pointer to a WAVEFORMATEX structure to be added to the Format drop-down list box.
FORMATCHOOSE_FORMATTAG_ADD The lParam parameter is a pointer to a variable that will accept a waveform-audio format tag to be added to the Format Tag drop-down list box.
FORMATCHOOSE_FORMATTAG_VERIFY The lParam parameter is a waveform-audio format tag to be listed in the Format Tag drop-down list box.

lCustom

Value defined by the listbox specified in the wParam parameter.

Return Values

Returns TRUE if an application handles this message or FALSE otherwise.

Remarks

If the application processes the FILTERCHOOSE_FORMAT_ADD operation, the size of the memory buffer supplied in lParam will be determined from the acmMetrics function.

If your application is processing a verify operation, it can prevent the dialog box from listing this selection by calling the SetWindowLong function with nIndex set to DWL_MSGRESULT and lNewLong set to FALSE (cast to a LONG data type). To allow the dialog box to list this selection, call this function with lNewLong set to TRUE.

If your application is processing an add operation, it can indicate that no more additions are required by calling the SetWindowLong function with nIndex set to DWL_MSGRESULT and lNewLong set to FALSE (cast to a LONG data type). To indicate more additions are required, call this function with lNewLong set to TRUE.

Requirements

**  Windows NT/2000/XP:** Included in Windows NT 3.1 and later.
**  Windows 95/98/Me:** Included in Windows 95 and later.
**  Header:** Declared in Msacm.h.

See Also

Audio Compression Manager, Audio Compression Messages, acmFormatChoose, acmMetrics, SetWindowLong, WAVEFORMATEX