wxDataObject - Functions for wxDataObject class
Please see following description for synopsis
wxDataObject(3) Erlang Module Definition wxDataObject(3)
NAME
wxDataObject - Functions for wxDataObject class
DESCRIPTION
A wxDataObject represents data that can be copied to or from the clip-
board, 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 ren-
der 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 for-
mats 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 (not implemented in
wx) enumeration type which distinguishes between them.
See wxDataFormat (not implemented in wx) 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 (not imple-
mented in wx) and wxDataObjectComposite (not implemented in wx).
wxDataObjectSimple (not implemented in wx) is the simplest wxDataObject
possible and only holds data in a single format (such as HTML or text)
and wxDataObjectComposite (not implemented in wx) is the simplest way
to implement a wxDataObject that does support multiple formats because
it achieves this by simply holding several wxDataObjectSimple (not
implemented in wx) 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):
Please note that the easiest way to use drag and drop and the clipboard
with multiple formats is by using wxDataObjectComposite (not imple-
mented in wx), but it is not the most efficient one as each wxDataOb-
jectSimple (not implemented in wx) 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 trou-
ble. 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, 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 available.
You may also derive your own data object classes from wxCustomDataOb-
ject (not implemented in wx) 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 fin-
ished.
Each class derived directly from wxDataObject must override and imple-
ment 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() (not imple-
mented in wx).
See: Overview dnd, Examples, wxFileDataObject, wxTextDataObject,
wxBitmapDataObject, wxCustomDataObject (not implemented in wx), wxDrop-
Target (not implemented in wx), wxDropSource (not implemented in wx),
wxTextDropTarget (not implemented in wx), wxFileDropTarget (not imple-
mented in wx)
wxWidgets docs: wxDataObject
DATA TYPES
wxDataObject() = wx:wx_object()
wxWidgets team. wx 2.1.1 wxDataObject(3)