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wxWidgets/interface/wx/dataobj.h

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/////////////////////////////////////////////////////////////////////////////
// Name: dataobj.h
// Purpose: interface of wx*DataObject
// Author: wxWidgets team
// Licence: wxWindows licence
/////////////////////////////////////////////////////////////////////////////
/**
@class wxDataFormat
A wxDataFormat is an encapsulation of a platform-specific format handle
which is used by the system for the clipboard and drag and drop operations.
The applications are usually only interested in, for example, pasting data
from the clipboard only if the data is in a format the program understands
and a data format is something which uniquely identifies this format.
On the system level, a data format is usually just a number (@c CLIPFORMAT
under Windows or @c Atom under X11, for example) and the standard formats
are, indeed, just numbers which can be implicitly converted to wxDataFormat.
The standard formats are:
@beginDefList
@itemdef{wxDF_INVALID,
An invalid format - used as default argument for functions taking
a wxDataFormat argument sometimes.}
@itemdef{wxDF_TEXT,
Text format (wxString).}
@itemdef{wxDF_BITMAP,
A bitmap (wxBitmap).}
@itemdef{wxDF_METAFILE,
A metafile (wxMetafile, Windows only).}
@itemdef{wxDF_UNICODETEXT,
Unicode text format (wxString).}
@itemdef{wxDF_FILENAME,
A list of filenames.}
@itemdef{wxDF_HTML,
An HTML string. This is currently only valid on Mac and MSW.}
@itemdef{wxDF_PNG,
A PNG file. This is valid only on MSW. This constant is available
since wxWidgets 3.1.5.}
@endDefList
As mentioned above, these standard formats may be passed to any function
taking wxDataFormat argument because wxDataFormat has an implicit
conversion from them (or, to be precise from the type
@c wxDataFormat::NativeFormat which is the type used by the underlying
platform for data formats).
Aside the standard formats, the application may also use custom formats
which are identified by their names (strings) and not numeric identifiers.
Although internally custom format must be created (or @e registered) first,
you shouldn't care about it because it is done automatically the first time
the wxDataFormat object corresponding to a given format name is created.
The only implication of this is that you should avoid having global
wxDataFormat objects with non-default constructor because their
constructors are executed before the program has time to perform all
necessary initialisations and so an attempt to do clipboard format
registration at this time will usually lead to a crash!
@library{wxcore}
@category{dnd}
@see @ref overview_dnd, @ref page_samples_dnd, wxDataObject
*/
class wxDataFormat
{
public:
/**
Constructs a data format object for one of the standard data formats or
an empty data object (use SetType() or SetId() later in this case).
@beginWxPerlOnly
In wxPerl use Wx::Bitmap->newNative(format).
@endWxPerlOnly
*/
wxDataFormat(wxDataFormatId format = wxDF_INVALID);
/**
Constructs a data format object for a custom format identified by its
name @a format.
@beginWxPerlOnly
In wxPerl use Wx::Bitmap->newUser(format).
@endWxPerlOnly
*/
wxDataFormat(const wxString& format);
/**
Returns the name of a custom format (this function will fail for a
standard format).
*/
wxString GetId() const;
/**
Returns the platform-specific number identifying the format.
*/
wxDataFormatId GetType() const;
/**
Sets the format to be the custom format identified by the given name.
*/
void SetId(const wxString& format);
/**
Sets the format to the given value, which should be one of wxDF_XXX
constants.
*/
void SetType(wxDataFormatId type);
/**
Returns @true if the formats are different.
*/
bool operator !=(const wxDataFormat& format) const;
/**
Returns @true if the formats are different.
*/
bool operator !=(wxDataFormatId format) const;
/**
Returns @true if the formats are equal.
*/
bool operator ==(const wxDataFormat& format) const;
/**
Returns @true if the formats are equal.
*/
bool operator ==(wxDataFormatId format) const;
};
const wxDataFormat wxFormatInvalid;
/**
@class wxDataObject
A wxDataObject represents data that can be copied to or from the clipboard,
or dragged and dropped. The important thing about wxDataObject is that this
is a 'smart' piece of data unlike 'dumb' data containers such as memory
buffers or files. Being 'smart' here means that the data object itself
should know what data formats it supports and how to render itself in each
of its supported formats.
A supported format, incidentally, is exactly the format in which the data
can be requested from a data object or from which the data object may be
set. In the general case, an object may support different formats on
'input' and 'output', i.e. it may be able to render itself in a given
format but not be created from data on this format or vice versa.
wxDataObject defines the wxDataObject::Direction enumeration type which
distinguishes between them.
See wxDataFormat documentation for more about formats.
Not surprisingly, being 'smart' comes at a price of added complexity. This
is reasonable for the situations when you really need to support multiple
formats, but may be annoying if you only want to do something simple like
cut and paste text.
To provide a solution for both cases, wxWidgets has two predefined classes
which derive from wxDataObject: wxDataObjectSimple and
wxDataObjectComposite. wxDataObjectSimple is the simplest wxDataObject
possible and only holds data in a single format (such as HTML or text) and
wxDataObjectComposite is the simplest way to implement a wxDataObject that
does support multiple formats because it achieves this by simply holding
several wxDataObjectSimple objects.
So, you have several solutions when you need a wxDataObject class (and you
need one as soon as you want to transfer data via the clipboard or drag and
drop):
-# Use one of the built-in classes.
- You may use wxTextDataObject, wxBitmapDataObject wxFileDataObject,
wxURLDataObject in the simplest cases when you only need to support
one format and your data is either text, bitmap or list of files.
-# Use wxDataObjectSimple
- Deriving from wxDataObjectSimple is the simplest solution for custom
data - you will only support one format and so probably won't be able
to communicate with other programs, but data transfer will work in
your program (or between different instances of it).
-# Use wxDataObjectComposite
- This is a simple but powerful solution which allows you to support
any number of formats (either standard or custom if you combine it
with the previous solution).
-# Use wxDataObject directly
- This is the solution for maximum flexibility and efficiency, but it
is also the most difficult to implement.
Please note that the easiest way to use drag and drop and the clipboard
with multiple formats is by using wxDataObjectComposite, but it is not the
most efficient one as each wxDataObjectSimple would contain the whole data
in its respective formats. Now imagine that you want to paste 200 pages of
text in your proprietary format, as well as Word, RTF, HTML, Unicode and
plain text to the clipboard and even today's computers are in trouble. For
this case, you will have to derive from wxDataObject directly and make it
enumerate its formats and provide the data in the requested format on
demand.
Note that neither the GTK+ data transfer mechanisms for clipboard and drag
and drop, nor OLE data transfer, @e copies any data until another application
actually requests the data. This is in contrast to the 'feel' offered to
the user of a program who would normally think that the data resides in the
clipboard after having pressed 'Copy' - in reality it is only declared to
be @e available.
You may also derive your own data object classes from wxCustomDataObject
for user-defined types. The format of user-defined data is given as a
mime-type string literal, such as "application/word" or "image/png". These
strings are used as they are under Unix (so far only GTK+) to identify a
format and are translated into their Windows equivalent under Win32 (using
the OLE IDataObject for data exchange to and from the clipboard and for
drag and drop). Note that the format string translation under Windows is
not yet finished.
Each class derived directly from wxDataObject must override and implement
all of its functions which are pure virtual in the base class. The data
objects which only render their data or only set it (i.e. work in only one
direction), should return 0 from GetFormatCount().
@beginWxPerlOnly
This class is not currently usable from wxPerl; you may use
Wx::PlDataObjectSimple instead.
@endWxPerlOnly
@library{wxcore}
@category{dnd}
@see @ref overview_dnd, @ref page_samples_dnd, wxFileDataObject,
wxTextDataObject, wxBitmapDataObject, wxCustomDataObject,
wxDropTarget, wxDropSource, wxTextDropTarget, wxFileDropTarget
*/
class wxDataObject
{
public:
enum Direction
{
/** Format is supported by GetDataHere() */
Get = 0x01,
/** Format is supported by SetData() */
Set = 0x02,
/**
Format is supported by both GetDataHere() and SetData()
(unused currently)
*/
Both = 0x03
};
/**
Constructor.
*/
wxDataObject();
/**
Destructor.
*/
virtual ~wxDataObject();
/**
Copies all formats supported in the given direction @a dir to the array
pointed to by @a formats.
There must be enough space for GetFormatCount(dir) formats in it.
@beginWxPerlOnly
In wxPerl this method only takes the @a dir parameter. In scalar
context it returns the first format in the list, in list
context it returns a list containing all the supported
formats.
@endWxPerlOnly
*/
virtual void GetAllFormats(wxDataFormat* formats,
Direction dir = Get) const = 0;
/**
The method will write the data of the format @a format to the buffer
@a buf. In other words, copy the data from this object in the given
format to the supplied buffer. Returns @true on success, @false on
failure.
*/
virtual bool GetDataHere(const wxDataFormat& format, void* buf) const = 0;
/**
Returns the data size of the given format @a format.
*/
virtual size_t GetDataSize(const wxDataFormat& format) const = 0;
/**
Returns the number of available formats for rendering or setting the
data.
*/
virtual size_t GetFormatCount(Direction dir = Get) const = 0;
/**
Returns the preferred format for either rendering the data (if @a dir
is @c Get, its default value) or for setting it. Usually this will be
the native format of the wxDataObject.
*/
virtual wxDataFormat GetPreferredFormat(Direction dir = Get) const = 0;
/**
Set the data in the format @a format of the length @a len provided in
the buffer @a buf. In other words, copy length bytes of data from the
buffer to this data object.
@param format
The format for which to set the data.
@param len
The size of data in bytes.
@param buf
Non-@NULL pointer to the data.
@return
@true on success, @false on failure.
*/
virtual bool SetData(const wxDataFormat& format, size_t len, const void* buf);
/**
Returns true if this format is supported.
*/
bool IsSupported(const wxDataFormat& format, Direction dir = Get) const;
};
/**
@class wxCustomDataObject
wxCustomDataObject is a specialization of wxDataObjectSimple for some
application-specific data in arbitrary (either custom or one of the
standard ones). The only restriction is that it is supposed that this data
can be copied bitwise (i.e. with @c memcpy()), so it would be a bad idea to
make it contain a C++ object (though C struct is fine).
By default, wxCustomDataObject stores the data inside in a buffer. To put
the data into the buffer you may use either SetData() or TakeData()
depending on whether you want the object to make a copy of data or not.
This class may be used as is, but if you don't want store the data inside
the object but provide it on demand instead, you should override GetSize(),
GetData() and SetData() (or may be only the first two or only the last one
if you only allow reading/writing the data).
@library{wxcore}
@category{dnd}
@see wxDataObject
*/
class wxCustomDataObject : public wxDataObjectSimple
{
public:
/**
The constructor accepts a @a format argument which specifies the
(single) format supported by this object. If it isn't set here,
wxDataObjectSimple::SetFormat() should be used.
*/
wxCustomDataObject(const wxDataFormat& format = wxFormatInvalid);
/**
The destructor will free the data held by the object. Notice that
although it calls the virtual Free() function, the base class version
will always be called (C++ doesn't allow calling virtual functions from
constructors or destructors), so if you override Free(), you should
override the destructor in your class as well (which would probably
just call the derived class' version of Free()).
*/
virtual ~wxCustomDataObject();
/**
This function is called to allocate @a size bytes of memory from
SetData(). The default version just uses the operator new.
*/
virtual void* Alloc(size_t size);
/**
This function is called when the data is freed, you may override it to
anything you want (or may be nothing at all). The default version calls
operator delete[] on the data.
*/
virtual void Free();
/**
Returns a pointer to the data.
*/
virtual void* GetData() const;
/**
Returns the data size in bytes.
*/
virtual size_t GetSize() const;
/**
Set the data. The data object will make an internal copy.
*/
virtual bool SetData(size_t size, const void* data);
/**
Like SetData(), but doesn't copy the data - instead the object takes
ownership of the pointer.
*/
void TakeData(size_t size, void* data);
};
/**
@class wxDataObjectComposite
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 @e 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:
@code
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;
}
@endcode
@library{wxcore}
@category{dnd}
@see @ref overview_dnd, wxDataObject, wxDataObjectSimple, wxFileDataObject,
wxTextDataObject, wxBitmapDataObject
*/
class wxDataObjectComposite : public wxDataObject
{
public:
/**
The default constructor.
*/
wxDataObjectComposite();
/**
Adds the @a dataObject to the list of supported objects and it becomes
the preferred object if @a preferred is @true.
*/
void Add(wxDataObjectSimple* dataObject, bool preferred = false);
/**
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.
*/
wxDataFormat GetReceivedFormat() const;
/**
Returns the pointer to the object which supports the passed format for
the specified direction.
@NULL is returned if the specified @a format is not supported for this
direction @a dir. The returned pointer is owned by wxDataObjectComposite
itself and shouldn't be deleted by caller.
@since 2.9.1
*/
wxDataObjectSimple *GetObject(const wxDataFormat& format,
wxDataObject::Direction dir = wxDataObject::Get) const;
};
/**
@class wxDataObjectSimple
This is the simplest possible implementation of the wxDataObject class.
The data object of (a class derived from) this class only supports
<strong>one format</strong>, so the number of virtual functions to
be implemented is reduced.
Notice that this is still an abstract base class and cannot be used
directly, it must be derived. The objects supporting rendering the data
must override GetDataSize() and GetDataHere() while the objects which may
be set must override SetData(). Of course, the objects supporting both
operations must override all three methods.
@beginWxPerlOnly
In wxPerl, you need to derive your data object class from
Wx::PlDataObjectSimple.
@endWxPerlOnly
@library{wxcore}
@category{dnd}
@see @ref overview_dnd, @ref page_samples_dnd, wxFileDataObject,
wxTextDataObject, wxBitmapDataObject
*/
class wxDataObjectSimple : public wxDataObject
{
public:
/**
Constructor accepts the supported format (none by default) which may
also be set later with SetFormat().
*/
wxDataObjectSimple(const wxDataFormat& format = wxFormatInvalid);
/**
Copy the data to the buffer, return @true on success.
Must be implemented in the derived class if the object supports rendering
its data.
*/
virtual bool GetDataHere(void* buf) const;
/**
Gets the size of our data. Must be implemented in the derived class if
the object supports rendering its data.
*/
virtual size_t GetDataSize() const;
/**
Returns the (one and only one) format supported by this object.
It is assumed that the format is supported in both directions.
*/
const wxDataFormat& GetFormat() const;
/**
Copy the data from the buffer, return @true on success.
Must be implemented in the derived class if the object supports setting
its data.
*/
virtual bool SetData(size_t len, const void* buf);
/**
Sets the supported format.
*/
void SetFormat(const wxDataFormat& format);
};
/**
@class wxBitmapDataObject
wxBitmapDataObject is a specialization of wxDataObject for bitmap data. It
can be used without change to paste data into the wxClipboard or a
wxDropSource. A user may wish to derive a new class from this class for
providing a bitmap on-demand in order to minimize memory consumption when
offering data in several formats, such as a bitmap and GIF.
This class may be used as is, but GetBitmap() may be overridden to increase
efficiency.
@library{wxcore}
@category{dnd}
@see @ref overview_dnd, wxDataObject, wxDataObjectSimple, wxFileDataObject,
wxTextDataObject, wxDataObject
*/
class wxBitmapDataObject : public wxDataObjectSimple
{
public:
/**
Constructor, optionally passing a bitmap (otherwise use SetBitmap()
later).
*/
wxBitmapDataObject(const wxBitmap& bitmap = wxNullBitmap);
/**
Returns the bitmap associated with the data object. You may wish to
override this method when offering data on-demand, but this is not
required by wxWidgets' internals. Use this method to get data in bitmap
form from the wxClipboard.
*/
virtual wxBitmap GetBitmap() const;
/**
Sets the bitmap associated with the data object. This method is called
when the data object receives data. Usually there will be no reason to
override this function.
*/
virtual void SetBitmap(const wxBitmap& bitmap);
};
/**
@class wxImageDataObject
wxImageDataObject is a specialization of wxDataObject for image data.
It can be used e.g. when you need to put on and retrieve from the clipboard
a wxImage with its metadata (like image resolution).
@since 3.1.5
@library{wxcore}
@category{dnd}
@see @ref overview_dnd, wxDataObject, wxCustomDataObject, wxBitmapDataObject
*/
class wxImageDataObject : public wxCustomDataObject
{
public:
/**
Constructor, optionally passing an image (otherwise use SetImage()
later).
*/
explicit wxImageDataObject(const wxImage& image = wxNullImage);
/**
Returns the image associated with the data object.
*/
wxImage GetImage() const;
/**
Sets the image stored by the data object.
*/
void SetImage(const wxImage& image);
};
/**
@class wxURLDataObject
wxURLDataObject is a wxDataObject containing an URL and can be used e.g.
when you need to put an URL on or retrieve it from the clipboard:
@code
wxTheClipboard->SetData(new wxURLDataObject(url));
@endcode
@note The actual base class of this class is not always wxDataObject
itself, but rather either wxDataObjectComposite in wxMSW and wxGTK or
wxTextDataObject in the other ports. Please don't rely on the exact
base class, it is not guaranteed that it won't change in the future.
@library{wxcore}
@category{dnd}
@see @ref overview_dnd, wxDataObject
*/
class wxURLDataObject: public wxDataObject
{
public:
/**
Constructor, may be used to initialize the URL. If @a url is empty,
SetURL() can be used later.
*/
wxURLDataObject(const wxString& url = wxEmptyString);
/**
Returns the URL stored by this object, as a string.
*/
wxString GetURL() const;
/**
Sets the URL stored by this object.
*/
void SetURL(const wxString& url);
};
/**
@class wxTextDataObject
wxTextDataObject is a specialization of wxDataObjectSimple for text data.
It can be used without change to paste data into the wxClipboard or a
wxDropSource. A user may wish to derive a new class from this class for
providing text on-demand in order to minimize memory consumption when
offering data in several formats, such as plain text and RTF because by
default the text is stored in a string in this class, but it might as well
be generated when requested. For this, GetTextLength() and GetText() will
have to be overridden.
Note that if you already have the text inside a string, you will not
achieve any efficiency gain by overriding these functions because copying
wxStrings is already a very efficient operation (data is not actually
copied because wxStrings are reference counted).
@library{wxcore}
@category{dnd}
@see @ref overview_dnd, wxDataObject, wxDataObjectSimple, wxFileDataObject,
wxBitmapDataObject
*/
class wxTextDataObject : public wxDataObjectSimple
{
public:
/**
Constructor, may be used to initialise the text (otherwise SetText()
should be used later).
*/
wxTextDataObject(const wxString& text = wxEmptyString);
/**
Returns the text associated with the data object. You may wish to
override this method when offering data on-demand, but this is not
required by wxWidgets' internals. Use this method to get data in text
form from the wxClipboard.
*/
virtual wxString GetText() const;
/**
Returns the data size. By default, returns the size of the text data
set in the constructor or using SetText(). This can be overridden to
provide text size data on-demand. It is recommended to return the text
length plus 1 for a trailing zero, but this is not strictly required.
*/
virtual size_t GetTextLength() const;
/**
Returns 2 under wxMac and wxGTK, where text data coming from the
clipboard may be provided as ANSI (@c wxDF_TEXT) or as Unicode text
(@c wxDF_UNICODETEXT, but only when @c wxUSE_UNICODE==1).
Returns 1 under other platforms (e.g. wxMSW) or when building in ANSI mode
(@c wxUSE_UNICODE==0).
*/
virtual size_t GetFormatCount(wxDataObject::Direction dir = wxDataObject::Get) const;
/**
Returns the preferred format supported by this object.
This is @c wxDF_TEXT or @c wxDF_UNICODETEXT depending on the platform
and from the build mode (i.e. from @c wxUSE_UNICODE).
*/
const wxDataFormat& GetFormat() const;
/**
Returns all the formats supported by wxTextDataObject.
Under wxMac and wxGTK they are @c wxDF_TEXT and @c wxDF_UNICODETEXT,
under other ports returns only one of the two, depending on the build mode.
*/
virtual void GetAllFormats(wxDataFormat* formats,
wxDataObject::Direction dir = wxDataObject::Get) const;
/**
Sets the text associated with the data object. This method is called
when the data object receives the data and, by default, copies the text
into the member variable. If you want to process the text on the fly
you may wish to override this function.
*/
virtual void SetText(const wxString& strText);
};
/**
@class wxFileDataObject
wxFileDataObject is a specialization of wxDataObject for file names. The
program works with it just as if it were a list of absolute file names, but
internally it uses the same format as Explorer and other compatible
programs under Windows or GNOME/KDE file manager under Unix which makes it
possible to receive files from them using this class.
@library{wxcore}
@category{dnd}
@see wxDataObject, wxDataObjectSimple, wxTextDataObject,
wxBitmapDataObject, wxDataObject
*/
class wxFileDataObject : public wxDataObjectSimple
{
public:
/**
Constructor.
*/
wxFileDataObject();
/**
Adds a file to the file list represented by this data object (Windows only).
*/
void AddFile(const wxString& file);
/**
Returns the array of file names.
*/
const wxArrayString& GetFilenames() const;
};
/**
@class wxHTMLDataObject
wxHTMLDataObject is used for working with HTML-formatted text.
@library{wxcore}
@category{dnd}
@see wxDataObject, wxDataObjectSimple
*/
class wxHTMLDataObject : public wxDataObjectSimple
{
public:
/**
Constructor.
*/
wxHTMLDataObject(const wxString& html = wxEmptyString);
/**
Returns the HTML string.
*/
virtual wxString GetHTML() const;
/**
Sets the HTML string.
*/
virtual void SetHTML(const wxString& html);
};
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