生成用于选择筛选器的对话框

应用程序允许用户选择任意筛选操作并将其应用于波形音频数据。 在以下示例中，应用程序分配一个缓冲区来保存筛选器，然后使用 acmFilterChoose 函数选择筛选器。 此示例中的函数必须使用相应的筛选器或筛选器标记调用。

MMRESULT        mmr; 
ACMFILTERCHOOSE afc; 
PWAVEFILTER     pwfltr; 
DWORD           cbwfltr; 
 
// Determine the maximum size required for any valid filter 
// for which the ACM has a driver installed and enabled. 
mmr = acmMetrics(NULL, ACM_METRIC_MAX_SIZE_FILTER, &cbwfltr); 
if (MMSYSERR_NOERROR != mmr) { 
 
    // The ACM probably has no drivers installed and 
    // enabled for filter operations. 
    return (mmr); 
} 
 
// Dynamically allocate a structure large enough to hold the 
// maximum sized filter enabled in the system. 
pwfltr = (PWAVEFILTER)LocalAlloc(LPTR, (UINT)cbwfltr); 
if (NULL == pwfltr) { 
    return (MMSYSERR_NOMEM); 
} 
 
// Initialize the ACMFILTERCHOOSE members. 
memset(&afc, 0, sizeof(afc)); 
 
afc.cbStruct    = sizeof(afc); 
afc.fdwStyle    = 0L;               // no special style flags 
afc.hwndOwner   = hwnd;             // hwnd of parent window 
afc.pwfltr      = pwfltr;           // wfltr to receive selection 
afc.cbwfltr     = cbwfltr;          // size of wfltr buffer 
afc.pszTitle    = TEXT("Any Filter Selection"); 
 
// Call the ACM to bring up the filter-selection dialog box. 
mmr = acmFilterChoose(&afc); 
if (MMSYSERR_NOERROR == mmr) { 
    // The user selected a valid filter. The pwfltr buffer, 
    // allocated above, contains the complete filter description. 
} 
 
// Clean up and exit. 
LocalFree((HLOCAL)pwfltr); 
return (mmr);