- Qt 6.9
- Qt GUI
- C++ Classes
- QWindowsMimeConverter
- Qt 6.9.3 Reference Documentation

# QWindowsMimeConverter Class

The QWindowsMimeConverter class maps open-standard MIME to Window Clipboard formats. More...

Header: | `#include <QWindowsMimeConverter>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Gui)` `target_link_libraries(mytarget PRIVATE Qt6::Gui)`
qmake: | `QT += gui`

- List of all members, including inherited members

## Public Functions

| QWindowsMimeConverter()
virtual | ~QWindowsMimeConverter()
virtual bool | canConvertFromMime(const FORMATETC &formatetc, const QMimeData *mimeData) const = 0
virtual bool | canConvertToMime(const QString &mimeType, IDataObject *pDataObj) const = 0
virtual bool | convertFromMime(const FORMATETC &formatetc, const QMimeData *mimeData, STGMEDIUM *pmedium) const = 0
virtual QVariant | convertToMime(const QString &mimeType, IDataObject *pDataObj, QMetaType preferredType) const = 0
virtual QList<FORMATETC> | formatsForMime(const QString &mimeType, const QMimeData *mimeData) const = 0
virtual QString | mimeForFormat(const FORMATETC &formatetc) const = 0

## Static Public Members

int | registerMimeType(const QString &mimeType)

## Detailed Description

Qt's drag-and-drop and clipboard facilities use the MIME standard. On X11, this maps trivially to the Xdnd protocol, but on Windows although some applications use MIME types to describe clipboard formats, others use arbitrary non-standardized naming conventions, or unnamed built-in formats of Windows.

By instantiating subclasses of QWindowsMimeConverter that provide conversions between Windows Clipboard and MIME formats, you can convert proprietary clipboard formats to MIME formats.

Construct an instance of your converter implementation after instantiating QGuiApplication:

     int main(int argc, char **argv)
     {
         QGuiApplication app(argc, argv);
         JsonMimeConverter jsonConverter;
     }

Destroying the instance will unregister the converter and remove support for the conversion. It is also valid to heap-allocate the converter instance; Qt takes ownership and will delete the converter object during QGuiApplication shut-down.

Qt has predefined support for the following Windows Clipboard formats:

Windows Format | Equivalent MIME type
--- | ---
`CF_UNICODETEXT` | `text/plain`
`CF_TEXT` | `text/plain`
`CF_DIB` | `image/xyz`, where `xyz` is a Qt image format
`CF_HDROP` | `text/uri-list`
`CF_INETURL` | `text/uri-list`
`CF_HTML` | `text/html`

An example use of this class would be to map the Windows Metafile clipboard format (`CF_METAFILEPICT`) to and from the MIME type `image/x-wmf`. This conversion might simply be adding or removing a header, or even just passing on the data. See Drag and Drop for more information on choosing and definition MIME types.

You can check if a MIME type is convertible using canConvertFromMime() and can perform conversions with convertToMime() and convertFromMime().

## Member Function Documentation

### QWindowsMimeConverter::QWindowsMimeConverter()

Constructs a QWindowsMimeConverter instance.

The instance is automatically registered, and will be called to convert data during clipboard or drag'n'drop operations.

Call this constructor after QGuiApplication has been created.

### `[virtual noexcept]` QWindowsMimeConverter::~QWindowsMimeConverter()

Constructs a QWindowsMimeConverter instance.

The instance is automatically unregistered.

### `[pure virtual]` bool QWindowsMimeConverter::canConvertFromMime(const FORMATETC &formatetc, const QMimeData *mimeData) const

Returns `true` if the converter can convert from the mimeData to the format specified in formatetc.

All subclasses must reimplement this pure virtual function.

### `[pure virtual]` bool QWindowsMimeConverter::canConvertToMime(const QString &mimeType, IDataObject *pDataObj) const

Returns `true` if the converter can convert to the mimeType from the available formats in pDataObj.

All subclasses must reimplement this pure virtual function.

### `[pure virtual]` bool QWindowsMimeConverter::convertFromMime(const FORMATETC &formatetc, const QMimeData *mimeData, STGMEDIUM *pmedium) const

Convert the mimeData to the format specified in formatetc. The converted data should then be placed in pmedium structure.

Return true if the conversion was successful.

All subclasses must reimplement this pure virtual function.

### `[pure virtual]` QVariant QWindowsMimeConverter::convertToMime(const QString &mimeType, IDataObject *pDataObj, QMetaType preferredType) const

Returns a QVariant containing the converted data for mimeType from pDataObj. If possible the QVariant should be of the preferredType to avoid needless conversions.

All subclasses must reimplement this pure virtual function.

### `[pure virtual]` QList<FORMATETC> QWindowsMimeConverter::formatsForMime(const QString &mimeType, const QMimeData *mimeData) const

Returns a QList of FORMATETC structures representing the different windows clipboard formats that can be provided for the mimeType from the mimeData.

All subclasses must reimplement this pure virtual function.

### `[pure virtual]` QString QWindowsMimeConverter::mimeForFormat(const FORMATETC &formatetc) const

Returns the mime type that will be created form the format specified in formatetc, or an empty string if this converter does not support formatetc.

All subclasses must reimplement this pure virtual function.

### `[static]` int QWindowsMimeConverter::registerMimeType(const QString &mimeType)

Registers the MIME type mimeType, and returns an ID number identifying the format on Windows.

A mime type `application/x-qt-windows-mime;value="WindowsType"` will be registered as the clipboard format for `WindowsType`.