ACMFORMATCHOOSE structure (msacm.h)
The ACMFORMATCHOOSE structure contains information the ACM uses to initialize the system-defined waveform-audio format selection dialog box. After the user closes the dialog box, the system returns information about the user's selection in this structure.
Syntax
typedef struct tACMFORMATCHOOSE {
DWORD cbStruct;
DWORD fdwStyle;
HWND hwndOwner;
LPWAVEFORMATEX pwfx;
DWORD cbwfx;
LPCSTR pszTitle;
char szFormatTag[ACMFORMATTAGDETAILS_FORMATTAG_CHARS];
char szFormat[ACMFORMATDETAILS_FORMAT_CHARS];
LPSTR pszName;
DWORD cchName;
DWORD fdwEnum;
LPWAVEFORMATEX pwfxEnum;
HINSTANCE hInstance;
LPCSTR pszTemplateName;
LPARAM lCustData;
ACMFORMATCHOOSEHOOKPROC pfnHook;
} ACMFORMATCHOOSE, *PACMFORMATCHOOSE, *LPACMFORMATCHOOSE;
Members
cbStruct
Size, in bytes, of the ACMFORMATCHOOSE structure. This member must be initialized before an application calls the acmFormatChoose function. The size specified in this member must be large enough to contain the base ACMFORMATCHOOSE structure.
fdwStyle
Optional style flags for the acmFormatChoose function. This member must be initialized to a valid combination of the following flags before an application calls the acmFormatChoose function:
| Name | Description |
|---|---|
|
Context-sensitive help will be available in the dialog box. To use this feature, an application must register the ACMHELPMSGCONTEXTMENU and ACMHELPMSGCONTEXTHELP constants, using the RegisterWindowMessage function. When the user invokes help, the registered message will be posted to the owning window. The message will contain the wParam and lParam parameters from the original WM_CONTEXTMENU or WM_CONTEXTHELP message. |
|
Enables the hook function pointed to by the pfnHook member. An application can use hook functions for a variety of customizations, including answering the MM_ACM_FORMATCHOOSE message. |
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Causes the ACM to create the dialog box template identified by hInstance and pszTemplateName. |
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The hInstance member identifies a data block that contains a preloaded dialog box template. If this flag is specified, the ACM ignores the pszTemplateName member. |
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The buffer pointed to by pwfx contains a valid WAVEFORMATEX structure that the dialog box will use as the initial selection. |
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A help button will appear in the dialog box. To use a custom Help file, an application must register the ACMHELPMSGSTRING constant with the RegisterWindowMessage function. When the user presses the help button, the registered message will be posted to the owner. |
hwndOwner
Handle to the window that owns the dialog box. This member can be any valid window handle, or NULL if the dialog box has no owner. This member must be initialized before calling the acmFormatChoose function.
pwfx
Pointer to a WAVEFORMATEX structure. If the ACMFORMATCHOOSE_STYLEF_INITTOWFXSTRUCT flag is specified in the fdwStyle member, this structure must be initialized to a valid format. When the acmFormatChoose function returns, this buffer contains the selected format. If the user cancels the dialog box, no changes will be made to this buffer.
cbwfx
Size, in bytes, of the buffer pointed to by pwfx. If the buffer is too small to contain the format information, the acmFormatChoose function returns ACMERR_NOTPOSSIBLE. Also, the ACM copies the required size into this member. An application can use the acmMetrics and acmFormatTagDetails functions to determine the largest size required for this buffer.
pszTitle
Pointer to a string to be placed in the title bar of the dialog box. If this member is NULL, the ACM uses the default title (that is, "Sound Selection").
szFormatTag[ACMFORMATTAGDETAILS_FORMATTAG_CHARS]
Buffer containing a null-terminated string describing the format tag of the format selection when the ACMFORMATTAGDETAILS structure returned by the acmFormatTagDetails function. If the user cancels the dialog box, this member will contain a null-terminated string.
szFormat[ACMFORMATDETAILS_FORMAT_CHARS]
Buffer containing a null-terminated string describing the format attributes of the format selection when the ACMFORMATDETAILS structure returned by the acmFormatDetails function. If the user cancels the dialog box, this member will contain a null-terminated string.
pszName
Pointer to a string for a user-defined format name. If this is a non-null-terminated string, the ACM will attempt to match the name with a previously saved user-defined format name. If a match is found, the dialog box is initialized to that format. If a match is not found or this member is a null-terminated string, this member is ignored on input. When the acmFormatChoose function returns, this buffer contains a null-terminated string describing the user-defined format. If the format name is untitled (that is, the user has not given a name for the format), this member will be a null-terminated string on return. If the user cancels the dialog box, no changes will be made to this buffer.
cchName
Size, in characters, of the buffer identified by the pszName member. This buffer should be at least 128 characters long. If the pszName member is NULL, this member is ignored.
fdwEnum
Optional flags for restricting the type of formats listed in the dialog box. These flags are identical to the fdwEnum flags for the acmFormatEnum function. If pwfxEnum is NULL, this member should be zero. The following values are defined:
| Name | Description |
|---|---|
|
The WAVEFORMATEX structure pointed to by the pwfxEnum member is valid. The enumerator will enumerate only destination formats that can be converted from the given pwfxEnum format. |
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The enumerator should enumerate only formats that are supported in hardware by one or more of the installed waveform-audio devices. This flag provides a way for an application to choose only formats native to an installed waveform-audio device. |
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The enumerator should enumerate only formats that are supported for input (recording). |
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The nChannels member of the WAVEFORMATEX structure pointed to by the pwfxEnum member is valid. The enumerator will enumerate only a format that conforms to this attribute. |
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The nSamplesPerSec member of the WAVEFORMATEX structure pointed to by the pwfxEnum member is valid. The enumerator will enumerate only a format that conforms to this attribute. |
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The enumerator should enumerate only formats that are supported for output (playback). |
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The WAVEFORMATEX structure pointed to by the pwfxEnum member is valid. The enumerator will enumerate all suggested destination formats for the given pwfxEnum format. |
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The wBitsPerSample member of the WAVEFORMATEX structure pointed to by the pwfxEnum member is valid. The enumerator will enumerate only a format that conforms to this attribute. |
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The wFormatTag member of the WAVEFORMATEX structure pointed to by the pwfxEnum member is valid. The enumerator will enumerate only a format that conforms to this attribute. |
pwfxEnum
Pointer to a WAVEFORMATEX structure that will be used to restrict the formats listed in the dialog box. The fdwEnum member defines the members of the structure pointed to by pwfxEnum that should be used for the enumeration restrictions. If no special restrictions are desired, this member can be NULL. For other requirements associated with the pwfxEnum member, see the description for the acmFormatEnum function.
hInstance
Handle to a data block that contains a dialog box template specified by the pszTemplateName member. This member is used only if the fdwStyle member specifies the ACMFORMATCHOOSE_STYLEF_ENABLETEMPLATE or ACMFORMATCHOOSE_STYLEF_ENABLETEMPLATEHANDLE flag; otherwise, this member should be NULL on input.
pszTemplateName
Pointer to a null-terminated string that specifies the name of the resource file for the dialog box template that is to be substituted for the dialog box template in the ACM. An application can use the MAKEINTRESOURCE macro for numbered dialog box resources. This member is used only if the fdwStyle member specifies the ACMFORMATCHOOSE_STYLEF_ENABLETEMPLATE flag; otherwise, this member should be NULL on input.
lCustData
Application-defined data that the ACM passes to the hook function identified by the pfnHook member. The system passes the data in the lParam parameter of the WM_INITDIALOG message.
pfnHook
Pointer to a callback function that processes messages intended for the dialog box. An application must specify the ACMFORMATCHOOSE_STYLEF_ENABLEHOOK flag in the fdwStyle member to enable the hook; otherwise, this member should be NULL. The hook function should return FALSE to pass a message to the standard dialog box procedure or TRUE to discard the message. The callback function type is acmFormatChooseHookProc.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows 2000 Professional [desktop apps only] |
| Minimum supported server | Windows 2000 Server [desktop apps only] |
| Header | msacm.h |
See also
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