1wxDataObject(3) Erlang Module Definition wxDataObject(3)
2
6 wxDataObject - Functions for wxDataObject class
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9 A wxDataObject represents data that can be copied to or from the clip‐
10 board, or dragged and dropped. The important thing about wxDataObject
11 is that this is a 'smart' piece of data unlike 'dumb' data containers
12 such as memory buffers or files. Being 'smart' here means that the data
13 object itself should know what data formats it supports and how to ren‐
14 der itself in each of its supported formats.
15 A supported format, incidentally, is exactly the format in which the
17 data can be requested from a data object or from which the data object
18 may be set. In the general case, an object may support different for‐
19 mats on 'input' and 'output', i.e. it may be able to render itself in a
20 given format but not be created from data on this format or vice versa.
21 wxDataObject defines the wxDataObject::Direction (not implemented in
22 wx) enumeration type which distinguishes between them.
23 See wxDataFormat (not implemented in wx) documentation for more about
25 formats.
26 Not surprisingly, being 'smart' comes at a price of added complexity.
28 This is reasonable for the situations when you really need to support
29 multiple formats, but may be annoying if you only want to do something
30 simple like cut and paste text.
31 To provide a solution for both cases, wxWidgets has two predefined
33 classes which derive from wxDataObject: wxDataObjectSimple (not imple‐
34 mented in wx) and wxDataObjectComposite (not implemented in wx). wx‐
35 DataObjectSimple (not implemented in wx) is the simplest wxDataObject
36 possible and only holds data in a single format (such as HTML or text)
37 and wxDataObjectComposite (not implemented in wx) is the simplest way
38 to implement a wxDataObject that does support multiple formats because
39 it achieves this by simply holding several wxDataObjectSimple (not im‐
40 plemented in wx) objects.
41 So, you have several solutions when you need a wxDataObject class (and
43 you need one as soon as you want to transfer data via the clipboard or
44 drag and drop):
45 Please note that the easiest way to use drag and drop and the clipboard
47 with multiple formats is by using wxDataObjectComposite (not imple‐
48 mented in wx), but it is not the most efficient one as each wxDataOb‐
49 jectSimple (not implemented in wx) would contain the whole data in its
50 respective formats. Now imagine that you want to paste 200 pages of
51 text in your proprietary format, as well as Word, RTF, HTML, Unicode
52 and plain text to the clipboard and even today's computers are in trou‐
53 ble. For this case, you will have to derive from wxDataObject directly
54 and make it enumerate its formats and provide the data in the requested
55 format on demand.
56 Note that neither the GTK+ data transfer mechanisms for clipboard and
58 drag and drop, nor OLE data transfer, copies any data until another ap‐
59 plication actually requests the data. This is in contrast to the 'feel'
60 offered to the user of a program who would normally think that the data
61 resides in the clipboard after having pressed 'Copy' - in reality it is
62 only declared to be available.
63 You may also derive your own data object classes from wxCustomDataOb‐
65 ject (not implemented in wx) for user-defined types. The format of
66 user-defined data is given as a mime-type string literal, such as "ap‐
67 plication/word" or "image/png". These strings are used as they are un‐
68 der Unix (so far only GTK+) to identify a format and are translated
69 into their Windows equivalent under Win32 (using the OLE IDataObject
70 for data exchange to and from the clipboard and for drag and drop).
71 Note that the format string translation under Windows is not yet fin‐
72 ished.
73 Each class derived directly from wxDataObject must override and imple‐
75 ment all of its functions which are pure virtual in the base class. The
76 data objects which only render their data or only set it (i.e. work in
77 only one direction), should return 0 from GetFormatCount() (not imple‐
78 mented in wx).
79 See: Overview dnd, Examples, wxFileDataObject, wxTextDataObject,
81 wxBitmapDataObject, wxCustomDataObject (not implemented in wx), wxDrop‐
82 Target (not implemented in wx), wxDropSource (not implemented in wx),
83 wxTextDropTarget (not implemented in wx), wxFileDropTarget (not imple‐
84 mented in wx)
85 wxWidgets docs: wxDataObject
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89 wxDataObject() = wx:wx_object()
90wxWidgets team. wx 2.3.1 wxDataObject(3)