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1%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
2%% Name: dataobj.tex
3%% Purpose: wxDataObject documentation
4%% Author: Vadim Zeitlin
5%% Modified by:
6%% Created: 18.10.99
7%% RCS-ID: $Id$
8%% Copyright: (c) wxWindows team
f6bcfd97 9%% License: wxWindows license
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10%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
11
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12\section{\class{wxDataObject}}\label{wxdataobject}
13
14A wxDataObject represents data that can be copied to or from the clipboard, or
717a57c2 15dragged and dropped. The important thing about wxDataObject is that this is a
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16'smart' piece of data unlike usual 'dumb' data containers such as memory
17buffers or files. Being 'smart' here means that the data object itself should
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18know what data formats it supports and how to render itself in each of
19supported formats.
20
21A supported format, incidentally, is exactly the format in which the data can
22be requested from a data object or from which the data object may be set. In
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23the general case, an object may support different formats on 'input' and
24'output', i.e. it may be able to render itself in a given format but not be
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25created from data on this format or vice versa. wxDataObject defines an
26enumeration type
27
28\begin{verbatim}
29enum Direction
30{
31 Get = 0x01, // format is supported by GetDataHere()
32 Set = 0x02 // format is supported by SetData()
33};
34\end{verbatim}
35
fa482912 36which allows to distinguish between them. See
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37\helpref{wxDataFormat}{wxdataformat} documentation for more about formats.
38
407f3681 39Not surprizingly, being 'smart' comes at a price of added complexity. This is
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40reasonable for the situations when you really need to support multiple formats,
41but may be annoying if you only want to do something simple like cut and paste
42text.
43
44To provide a solution for both cases, wxWindows has two predefined classes
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45which derive from wxDataObject: \helpref{wxDataObjectSimple}{wxdataobjectsimple} and
46\helpref{wxDataObjectComposite}{wxdataobjectcomposite}.
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47\helpref{wxDataObjectSimple}{wxdataobjectsimple} is
48the simplest wxDataObject possible and only holds data in a single format (such
49as HTML or text) and \helpref{wxDataObjectComposite}{wxdataobjectcomposite} is
50the simplest way to implement wxDataObject which does support multiple formats
51because it achievs this by simply holding several wxDataObjectSimple objects.
52
53So, you have several solutions when you need a wxDataObject class (and you need
54one as soon as you want to transfer data via the clipboard or drag and drop):
55
c03648c2 56\begin{twocollist}\itemsep=1cm
fa482912 57\twocolitem{{\bf 1. Use one of the built-in classes}}{You may use wxTextDataObject,
717a57c2 58wxBitmapDataObject or wxFileDataObject in the simplest cases when you only need
407f3681 59to support one format and your data is either text, bitmap or list of files.}
fa482912 60\twocolitem{{\bf 2. Use wxDataObjectSimple}}{Deriving from wxDataObjectSimple is the simplest
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61solution for custom data - you will only support one format and so probably
62won't be able to communicate with other programs, but data transfer will work
63in your program (or between different copies of it).}
fa482912 64\twocolitem{{\bf 3. Use wxDataObjectComposite}}{This is a simple but powerful
407f3681 65solution which allows you to support any number of formats (either
717a57c2 66standard or custom if you combine it with the previous solution).}
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67\twocolitem{{\bf 4. Use wxDataObject directly}}{This is the solution for
68maximal flexibility and efficiency, but it is also is the most difficult to
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69implement.}
70\end{twocollist}
71
407f3681 72Please note that the easiest way to use drag and drop and the clipboard with
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73multiple formats is by using wxDataObjectComposite, but it is not the most
74efficient one as each wxDataObjectSimple would contain the whole data in its
f59d80ca 75respective formats. Now imagine that you want to paste 200 pages of text in
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76your proprietary format, as well as Word, RTF, HTML, Unicode and plain text to
77the clipboard and even today's computers are in trouble. For this case, you
78will have to derive from wxDataObject directly and make it enumerate its
79formats and provide the data in the requested format on demand.
80
81Note that neither the GTK data transfer mechanisms for the clipboard and
f59d80ca 82drag and drop, nor the OLE data transfer copy any data until another application
407f3681 83actually requests the data. This is in contrast to the 'feel' offered to the
717a57c2 84user of a program who would normally think that the data resides in the
407f3681 85clipboard after having pressed 'Copy' - in reality it is only declared to be
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86available.
87
88There are several predefined data object classes derived from
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89wxDataObjectSimple: \helpref{wxFileDataObject}{wxfiledataobject},
90\helpref{wxTextDataObject}{wxtextdataobject} and
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91\helpref{wxBitmapDataObject}{wxbitmapdataobject} which can be used without
92change.
93
fa482912 94You may also derive your own data object classes from
0a2017e0 95\helpref{wxCustomDataObject}{wxcustomdataobject} for user-defined types. The
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96format of user-defined data is given as mime-type string literal, such as
97"application/word" or "image/png". These strings are used as they are under
98Unix (so far only GTK) to identify a format and are translated into their
99Windows equivalent under Win32 (using the OLE IDataObject for data exchange to
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100and from the clipboard and for drag and drop). Note that the format string
101translation under Windows is not yet finished.
717a57c2 102
874a1686 103\pythonnote{At this time this class is not directly usable from wxPython.
fa482912 104Derive a class from \helpref{wxPyDataObjectSimple}{wxdataobjectsimple}
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105instead.}
106
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107\wxheading{Virtual functions to override}
108
109Each class derived directly from wxDataObject must override and implement all
110of its functions which are pure virtual in the base class.
111
112The data objects which only render their data or only set it (i.e. work in
fa482912 113only one direction), should return 0 from
717a57c2 114\helpref{GetFormatCount}{wxdataobjectgetformatcount}.
f37615d7 115
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116\wxheading{Derived from}
117
717a57c2 118None
dface61c 119
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120\wxheading{Include files}
121
122<wx/dataobj.h>
123
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124\wxheading{See also}
125
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126\helpref{Clipboard and drag and drop overview}{wxdndoverview},
127\helpref{DnD sample}{samplednd},
128\helpref{wxFileDataObject}{wxfiledataobject},
129\helpref{wxTextDataObject}{wxtextdataobject},
130\helpref{wxBitmapDataObject}{wxbitmapdataobject},
131\helpref{wxCustomDataObject}{wxcustomdataobject},
132\helpref{wxDropTarget}{wxdroptarget},
133\helpref{wxDropSource}{wxdropsource},
134\helpref{wxTextDropTarget}{wxtextdroptarget},
717a57c2 135\helpref{wxFileDropTarget}{wxfiledroptarget}
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136
137\latexignore{\rtfignore{\wxheading{Members}}}
138
139\membersection{wxDataObject::wxDataObject}\label{wxdataobjectwxdataobject}
140
141\func{}{wxDataObject}{\void}
142
143Constructor.
144
145\membersection{wxDataObject::\destruct{wxDataObject}}\label{wxdataobjectdtor}
146
147\func{}{\destruct{wxDataObject}}{\void}
148
149Destructor.
150
717a57c2 151\membersection{wxDataObject::GetAllFormats}\label{wxdataobjectgetallformats}
fc9c7c09 152
407f3681 153\constfunc{virtual void}{GetAllFormats}{ \param{wxDataFormat *}{formats}, \param{Direction}{ dir = Get}}
fc9c7c09 154
fa482912 155Copy all supported formats in the given direction to the array pointed to by
407f3681 156{\it formats}. There is enough space for GetFormatCount(dir) formats in it.
fc9c7c09 157
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158\perlnote{In wxPerl this method only takes the {\tt dir} parameter.
159In scalar context it returns the first format,
160in list context it returns a list containing all the supported formats.}
161
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162\membersection{wxDataObject::GetDataHere}\label{wxdataobjectgetdatahere}
163
717a57c2 164\constfunc{virtual bool}{GetDataHere}{\param{const wxDataFormat\&}{ format}, \param{void }{*buf} }
fc9c7c09 165
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166The method will write the data of the format {\it format} in the buffer {\it
167buf} and return TRUE on success, FALSE on failure.
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168
169\membersection{wxDataObject::GetDataSize}\label{wxdataobjectgetdatasize}
170
171\constfunc{virtual size\_t}{GetDataSize}{\param{const wxDataFormat\&}{ format} }
172
173Returns the data size of the given format {\it format}.
174
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175\membersection{wxDataObject::GetFormatCount}\label{wxdataobjectgetformatcount}
176
177\constfunc{virtual size\_t}{GetFormatCount}{\param{Direction}{ dir = Get}}
178
407f3681 179Returns the number of available formats for rendering or setting the data.
717a57c2 180
fc9c7c09 181\membersection{wxDataObject::GetPreferredFormat}\label{wxdataobjectgetpreferredformat}
f37615d7 182
717a57c2 183\constfunc{virtual wxDataFormat}{GetPreferredFormat}{\param{Direction}{ dir = Get}}
f37615d7 184
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185Returns the preferred format for either rendering the data (if {\it dir} is {\tt Get},
186its default value) or for setting it. Usually this will be the
717a57c2 187native format of the wxDataObject.
f37615d7 188
fc9c7c09 189\membersection{wxDataObject::SetData}\label{wxdataobjectsetdata}
f37615d7 190
407f3681 191\func{virtual bool}{SetData}{ \param{const wxDataFormat\&}{ format}, \param{size\_t}{ len}, \param{const void }{*buf} }
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192
193Set the data in the format {\it format} of the length {\it len} provided in the
194buffer {\it buf}.
dface61c 195
407f3681 196Returns TRUE on success, FALSE on failure.
dface61c 197