Detailed Description

wxDataObjectComposite is the simplest wxDataObject derivation which may be used to support multiple formats.

It contains several wxDataObjectSimple objects and supports any format supported by at least one of them. Only one of these data objects is preferred (the first one if not explicitly changed by using the second parameter of Add()) and its format determines the preferred format of the composite data object as well.

See wxDataObject documentation for the reasons why you might prefer to use wxDataObject directly instead of wxDataObjectComposite for efficiency reasons.

This example shows how a composite data object capable of storing either bitmaps or file names (presumably of bitmap files) can be initialized and used:

MyDropTarget::MyDropTarget()
{
    wxDataObjectComposite* dataobj = new wxDataObjectComposite();
    dataobj->Add(new wxBitmapDataObject(), true);
    dataobj->Add(new wxFileDataObject());
    SetDataObject(dataobj);
}
 
wxDragResult MyDropTarget::OnData(wxCoord x, wxCoord y,
                                  wxDragResult defaultDragResult)
{
    if ( !GetData() )
        return wxDragNone;
 
    wxDataObjectComposite *
        dataobjComp = static_cast<wxDataObjectComposite *>(GetDataObject());
 
    wxDataFormat format = dataobjComp->GetReceivedFormat();
    wxDataObject *dataobj = dataobjComp->GetObject(format);
    switch ( format.GetType() )
    {
        case wxDF_BITMAP:
            {
                wxBitmapDataObject *
                    dataobjBitmap = static_cast<wxBitmapDataObject *>(dataobj);
 
                ... use dataobj->GetBitmap() ...
            }
            break;
 
        case wxDF_FILENAME:
            {
                wxFileDataObject *
                    dataobjFile = static_cast<wxFileDataObject *>(dataobj);
 
                ... use dataobj->GetFilenames() ...
            }
            break;
 
        default:
            wxFAIL_MSG( "unexpected data object format" );
    }
 
    return defaultDragResult;
}

Library: wxCore

Category: Clipboard and Drag & Drop

See also: Drag and Drop Overview, wxDataObject, wxDataObjectSimple, wxFileDataObject, wxTextDataObject, wxBitmapDataObject

Public Member Functions
	wxDataObjectComposite ()
	The default constructor. More...

void	Add (wxDataObjectSimple *dataObject, bool preferred=false)
	Adds the dataObject to the list of supported objects and it becomes the preferred object if preferred is true. More...

wxDataFormat	GetReceivedFormat () const
	Report the format passed to the SetData() method. More...

wxDataObjectSimple *	GetObject (const wxDataFormat &format, wxDataObject::Direction dir=wxDataObject::Get) const
	Returns the pointer to the object which supports the passed format for the specified direction. More...

Public Member Functions inherited from wxDataObject
	wxDataObject ()
	Constructor. More...

virtual	~wxDataObject ()
	Destructor. More...

virtual void	GetAllFormats (wxDataFormat *formats, Direction dir=Get) const =0
	Copies all formats supported in the given direction dir to the array pointed to by formats. More...

virtual bool	GetDataHere (const wxDataFormat &format, void *buf) const =0
	The method will write the data of the format format to the buffer buf. More...

virtual size_t	GetDataSize (const wxDataFormat &format) const =0
	Returns the data size of the given format format. More...

virtual size_t	GetFormatCount (Direction dir=Get) const =0
	Returns the number of available formats for rendering or setting the data. More...

virtual wxDataFormat	GetPreferredFormat (Direction dir=Get) const =0
	Returns the preferred format for either rendering the data (if dir is `Get`, its default value) or for setting it. More...

virtual bool	SetData (const wxDataFormat &format, size_t len, const void *buf)
	Set the data in the format format of the length len provided in the buffer buf. More...

bool	IsSupported (const wxDataFormat &format, Direction dir=Get) const
	Returns true if this format is supported. More...

Additional Inherited Members
Public Types inherited from wxDataObject
enum	Direction { Get = 0x01 , Set = 0x02 , Both = 0x03 }

Constructor & Destructor Documentation

◆ wxDataObjectComposite()

wxDataObjectComposite::wxDataObjectComposite ( )

The default constructor.

Member Function Documentation

◆ Add()

void wxDataObjectComposite::Add	(	wxDataObjectSimple *	dataObject,
		bool	preferred = `false`
	)

Adds the dataObject to the list of supported objects and it becomes the preferred object if preferred is true.

◆ GetObject()

wxDataObjectSimple* wxDataObjectComposite::GetObject	(	const wxDataFormat &	format,
		wxDataObject::Direction	dir = `wxDataObject::Get`
	)		const

Returns the pointer to the object which supports the passed format for the specified direction.

NULL is returned if the specified format is not supported for this direction dir. The returned pointer is owned by wxDataObjectComposite itself and shouldn't be deleted by caller.

Since: 2.9.1

◆ GetReceivedFormat()

wxDataFormat wxDataObjectComposite::GetReceivedFormat ( ) const

Report the format passed to the SetData() method.

This should be the format of the data object within the composite that received data from the clipboard or the DnD operation. You can use this method to find out what kind of data object was received.