A window can place more than one object on the clipboard, each representing the same information in a different clipboard format. Users need not be aware of the clipboard formats used for an object on the clipboard.
The following topics describe the clipboard formats.
Standard Clipboard Formats
The clipboard formats defined by the system are called
standard clipboard formats. These clipboard formats are described in the following table.
| Value | Meaning |
|---|
| CF_BITMAP | A handle to a bitmap (HBITMAP). |
| CF_DIB | A memory object containing a BITMAPINFO structure followed by the bitmap bits. |
| CF_DIBV5 | Windows 2000/XP: A memory object containing a BITMAPV5HEADER structure followed by the bitmap color space information and the bitmap bits. |
| CF_DIF | Software Arts' Data Interchange Format. |
| CF_DSPBITMAP | Bitmap display format associated with a private format. The
hMem parameter must be a handle to data that can be displayed in bitmap format in lieu of the privately formatted data. |
| CF_DSPENHMETAFILE | Enhanced metafile display format associated with a private format. The
hMem parameter must be a handle to data that can be displayed in enhanced metafile format in lieu of the privately formatted data. |
| CF_DSPMETAFILEPICT | Metafile-picture display format associated with a private format. The
hMem parameter must be a handle to data that can be displayed in metafile-picture format in lieu of the privately formatted data. |
| CF_DSPTEXT | Text display format associated with a private format. The
hMem parameter must be a handle to data that can be displayed in text format in lieu of the privately formatted data. |
| CF_ENHMETAFILE | A handle to an enhanced metafile (HENHMETAFILE). |
| CF_GDIOBJFIRST through CF_GDIOBJLAST | Range of integer values for application-defined Microsoft Windows Graphics Device Interface (GDI) object clipboard formats. Handles associated with clipboard formats in this range are not automatically deleted using the GlobalFree function when the clipboard is emptied. Also, when using values in this range, the
hMem parameter is not a handle to a GDI object, but is a handle allocated by the GlobalAlloc function with the GMEM_MOVEABLE flag. |
| CF_HDROP | A handle to type
HDROP that identifies a list of files. An application can retrieve information about the files by passing the handle to the
DragQueryFile functions. |
| CF_LOCALE | The data is a handle to the locale identifier associated with text in the clipboard. When you close the clipboard, if it contains CF_TEXT data but no CF_LOCALE data, the system automatically sets the CF_LOCALE format to the current input language. You can use the CF_LOCALE format to associate a different locale with the clipboard text. An application that pastes text from the clipboard can retrieve this format to determine which character set was used to generate the text. Note that the clipboard does not support plain text in multiple character sets. To achieve this, use a formatted text data type such as Rich Text Format (RTF) instead. Windows NT/2000/XP: The system uses the code page associated with CF_LOCALE to implicitly convert from CF_TEXT to CF_UNICODETEXT. Therefore, the correct code page table is used for the conversion. |
| CF_METAFILEPICT | Handle to a metafile picture format as defined by the METAFILEPICT structure. When passing a CF_METAFILEPICT handle by means of Dynamic Data Exchange (DDE), the application responsible for deleting
hMem should also free the metafile referred to by the CF_METAFILEPICT handle. |
| CF_OEMTEXT | Text format containing characters in the OEM character set. Each line ends with a carriage return/linefeed (CR-LF) combination. A null character signals the end of the data. |
| CF_OWNERDISPLAY | Owner-display format. The clipboard owner must display and update the clipboard viewer window, and receive the WM_ASKCBFORMATNAME, WM_HSCROLLCLIPBOARD, WM_PAINTCLIPBOARD, WM_SIZECLIPBOARD, and WM_VSCROLLCLIPBOARD messages. The
hMem parameter must be NULL. |
| CF_PALETTE | Handle to a color palette. Whenever an application places data in the clipboard that depends on or assumes a color palette, it should place the palette on the clipboard as well. |
| | If the clipboard contains data in the CF_PALETTE (logical color palette) format, the application should use the SelectPalette and RealizePalette functions to realize (compare) any other data in the clipboard against that logical palette. When displaying clipboard data, the clipboard always uses as its current palette any object on the clipboard that is in the CF_PALETTE format. |
| CF_PENDATA | Data for the pen extensions to the Microsoft Windows for Pen Computing. |
| CF_PRIVATEFIRST through CF_PRIVATELAST | Range of integer values for private clipboard formats. Handles associated with private clipboard formats are not freed automatically; the clipboard owner must free such handles, typically in response to the WM_DESTROYCLIPBOARD message. |
| CF_RIFF | Represents audio data more complex than can be represented in a CF_WAVE standard wave format. |
| CF_SYLK | Microsoft Symbolic Link (SYLK) format. |
| CF_TEXT | Text format. Each line ends with a carriage return/linefeed (CR-LF) combination. A null character signals the end of the data. Use this format for ANSI text. |
| CF_WAVE | Represents audio data in one of the standard wave formats, such as 11 kHz or 22 kHz Pulse Code Modulation (PCM). |
| CF_TIFF | Tagged-image file format. |
| CF_UNICODETEXT | Windows NT/2000/XP: Unicode text format. Each line ends with a carriage return/linefeed (CR-LF) combination. A null character signals the end of the data. |
Registered Clipboard Formats
Many applications work with data that cannot be translated into a standard clipboard format without loss of information. These applications can create their own clipboard formats. A clipboard format that is defined by an application, is called a registered clipboard format. For example, if a word-processing application copied formatted text to the clipboard using a standard text format, the formatting information would be lost. The solution would be to register a new clipboard format, such as RTF.
To register a new clipboard format, use the RegisterClipboardFormat function. This function takes the name of the format and returns and unsigned integer value that represents the registered clipboard format. To retrieve the name of the registered clipboard format, pass the unsigned integer value to the GetClipboardFormatName function.
If more than one application registers a clipboard format with exactly the same name, the clipboard format is registered only once. Both calls to the RegisterClipboardFormat function return the same value. In this way, two different applications can share data by using a registered clipboard format.
Private Clipboard Formats
An application can identify a private clipboard format by defining a value in the range CF_PRIVATEFIRST through CF_PRIVATELAST. An application can use a private clipboard format for an application-defined data format that does not need to be registered with the system.
Data handles associated with private clipboard formats are automatically freed by the system. Windows that use private clipboard formats can use the WM_DESTROYCLIPBOARD message to free any related resources that are no longer needed.
For more information about the WM_DESTROYCLIPBOARD message, see Clipboard Ownership.
An application can place data handles on the clipboard by defining a private format in the range CF_GDIOBJFIRST through CF_GDIOBJLAST. When using values in this range, the data handle is not a handle to a GDI object, but is a handle allocated by the GlobalAlloc function with the GMEM_MOVEABLE flag. When the clipboard is emptied the system automatically deletes the object using the GlobalFree function.
Multiple Clipboard Formats
A window can place more than one clipboard object on the clipboard, each representing the same information in a different clipboard format. When placing information on the clipboard, the window should provide data in as many formats as possible. To find out how many formats are currently used on the clipboard, call the CountClipboardFormats function.
Clipboard formats that contain the most information should be placed on the clipboard first, followed by less descriptive formats. A window pasting information from the clipboard typically retrieves a clipboard object in the first format it recognizes. Because clipboard formats are enumerated in the order they are placed on the clipboard, the first recognized format is also the most descriptive.
For example, suppose a user copies styled text from a word-processing document. The window containing the document might first place data on the clipboard in a registered format, such as RTF. Subsequently, the window would place data on the clipboard in a less descriptive format, such as text (CF_TEXT).
When the content of the clipboard is pasted into another window, the window retrieves data in the most descriptive format it recognizes. If the window recognizes RTF, the corresponding data is pasted into the document. Otherwise, the text data is pasted into the document and the formatting information is lost.
Synthesized Clipboard Formats
The system implicitly converts data between certain clipboard formats: if a window requests data in a format that is not on the clipboard, the system converts an available format to the requested format. The system can convert data as indicated in the following table.
| Clipboard Format | Conversion Format | Platform Support |
|---|
| CF_BITMAP | CF_DIB | Microsoft Windows NT/Windows 2000, Windows 95/Windows 98/Windows Millennium Edition (Windows Me) |
| CF_BITMAP | CF_DIBV5 | Windows 2000/XP |
| CF_DIB | CF_BITMAP | Windows NT/Windows 2000, Windows 95/Windows 98/Windows Me |
| CF_DIB | CF_PALETTE | Windows NT/Windows 2000, Windows 95/Windows 98/Windows Me |
| CF_DIB | CF_DIBV5 | Windows 2000 |
| CF_DIBV5 | CF_BITMAP | Windows 2000 |
| CF_DIBV5 | CF_DIB | Windows 2000 |
| CF_DIBV5 | CF_PALETTE | Windows 2000 |
| CF_ENHMETAFILE | CF_METAFILEPICT | Windows NT/Windows 2000, Windows 95/Windows 98/Windows Me |
| CF_METAFILEPICT | CF_ENHMETAFILE | Windows NT/Windows 2000, Windows 95/Windows 98/Windows Me |
| CF_OEMTEXT | CF_TEXT | Windows NT/Windows 2000, Windows 95/Windows 98/Windows Me |
| CF_OEMTEXT | CF_UNICODETEXT | Windows NT/Windows 2000 |
| CF_TEXT | CF_OEMTEXT | Windows NT/Windows 2000, Windows 95/Windows 98/Windows Me |
| CF_TEXT | CF_UNICODETEXT | Windows NT/Windows 2000 |
| CF_UNICODETEXT | CF_OEMTEXT | Windows NT/Windows 2000 |
| CF_UNICODETEXT | CF_TEXT | Windows NT/Windows 2000 |
If the system provides an automatic type conversion for a particular clipboard format, there is no advantage to placing the conversion format(s) on the clipboard.
If the system provides an automatic type conversion for a particular clipboard format, and you call EnumClipboardFormats to enumerate the clipboard data formats, the system first enumerates the format that is on the clipboard, followed by the formats to which it can be converted.
When copying bitmaps, it is best to place the CF_DIB or CF_DIBV5 format on the clipboard. This is because the colors in a device-dependent bitmap (CF_BITMAP) are relative to the system palette, which may change before the bitmap is pasted. If the CF_DIB or CF_DIBV5 format is on the clipboard and a window requests the CF_BITMAP format, the system renders the device-independent bitmap (DIB) using the current palette at that time.
If you place the CF_BITMAP format on the clipboard (and not CF_DIB), the system renders the CF_DIB or CF_DIBV5 clipboard format as soon as the clipboard is closed. This ensures that the correct palette is used to generate the DIB. If you place the CF_DIBV5 format with the bitmap color space information in the clipboard, the system will convert the bitmap bits from the bitmap color space to the sRGB color space when CF_DIB or CF_DIBV5 is requested. If CF_DIBV5 is requested when there is no color space information in the clipboard, the system returns sRGB color space information in the BITMAPV5HEADER structure. Conversions between other clipboard formats occur upon demand.
If the clipboard contains data in the CF_PALETTE format, the application should use the SelectPalette and RealizePalette functions to realize any other data in the clipboard against that logical palette.
There are two clipboard formats for metafiles: CF_ENHMETAFILE and CF_METAFILEPICT. Specify CF_ENHMETAFILE for enhanced metafiles and CF_METAFILEPICT for Windows metafiles.