# `wxDataObject`
[🔗](https://github.com/erlang/otp/blob/OTP-29.0.1/lib/wx/src/gen/wxDataObject.erl#L58)

A `m:wxDataObject` represents data that can be copied to or from the clipboard, or
dragged and dropped.

The important thing about `m: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. `m: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 `m:wxDataObject`: `wxDataObjectSimple` (not implemented in wx) and `wxDataObjectComposite`
(not implemented in wx). `wxDataObjectSimple` (not implemented in wx) is the simplest `m: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 `m: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 `m: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 implemented in wx), but it is not the
most efficient one as each `wxDataObjectSimple` (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 trouble. For this case, you will have to
derive from `m: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 `wxCustomDataObject` (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 finished.

Each class derived directly from `m: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()`
(not implemented in wx).

See:
* [Overview dnd](https://docs.wxwidgets.org/3.2/overview_dnd.html#overview_dnd)

* [Examples](https://docs.wxwidgets.org/3.2/page_samples.html#page_samples_dnd)

* `m:wxFileDataObject`

* `m:wxTextDataObject`

* `m:wxBitmapDataObject`

wxWidgets docs: [wxDataObject](https://docs.wxwidgets.org/3.2/classwx_data_object.html)

# `wxDataObject`

```erlang
-type wxDataObject() :: wx:wx_object().
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*
