make it explicitly clear that the len parameter of SetData() is in bytes
[wxWidgets.git] / interface / wx / dataobj.h
1 /////////////////////////////////////////////////////////////////////////////
2 // Name: dataobj.h
3 // Purpose: interface of wx*DataObject
4 // Author: wxWidgets team
5 // RCS-ID: $Id$
6 // Licence: wxWindows license
7 /////////////////////////////////////////////////////////////////////////////
8
9
10 /**
11 @class wxDataFormat
12
13 A wxDataFormat is an encapsulation of a platform-specific format handle
14 which is used by the system for the clipboard and drag and drop operations.
15 The applications are usually only interested in, for example, pasting data
16 from the clipboard only if the data is in a format the program understands
17 and a data format is something which uniquely identifies this format.
18
19 On the system level, a data format is usually just a number (@c CLIPFORMAT
20 under Windows or @c Atom under X11, for example) and the standard formats
21 are, indeed, just numbers which can be implicitly converted to wxDataFormat.
22 The standard formats are:
23
24 @beginDefList
25 @itemdef{wxDF_INVALID,
26 An invalid format - used as default argument for functions taking
27 a wxDataFormat argument sometimes.}
28 @itemdef{wxDF_TEXT,
29 Text format (wxString).}
30 @itemdef{wxDF_BITMAP,
31 A bitmap (wxBitmap).}
32 @itemdef{wxDF_METAFILE,
33 A metafile (wxMetafile, Windows only).}
34 @itemdef{wxDF_FILENAME,
35 A list of filenames.}
36 @itemdef{wxDF_HTML,
37 An HTML string. This is only valid when passed to
38 wxSetClipboardData when compiled with Visual C++ in non-Unicode
39 mode.}
40 @endDefList
41
42 As mentioned above, these standard formats may be passed to any function
43 taking wxDataFormat argument because wxDataFormat has an implicit
44 conversion from them (or, to be precise from the type
45 @c wxDataFormat::NativeFormat which is the type used by the underlying
46 platform for data formats).
47
48 Aside the standard formats, the application may also use custom formats
49 which are identified by their names (strings) and not numeric identifiers.
50 Although internally custom format must be created (or @e registered) first,
51 you shouldn't care about it because it is done automatically the first time
52 the wxDataFormat object corresponding to a given format name is created.
53 The only implication of this is that you should avoid having global
54 wxDataFormat objects with non-default constructor because their
55 constructors are executed before the program has time to perform all
56 necessary initialisations and so an attempt to do clipboard format
57 registration at this time will usually lead to a crash!
58
59 @library{wxbase}
60 @category{dnd}
61
62 @see @ref overview_dnd, @ref page_samples_dnd, wxDataObject
63 */
64 class wxDataFormat
65 {
66 public:
67 /**
68 Constructs a data format object for one of the standard data formats or
69 an empty data object (use SetType() or SetId() later in this case).
70 */
71 wxDataFormat(wxDataFormatId format = wxDF_INVALID);
72
73 /**
74 Constructs a data format object for a custom format identified by its
75 name @a format.
76 */
77 wxDataFormat(const wxString& format);
78
79 /**
80 Returns the name of a custom format (this function will fail for a
81 standard format).
82 */
83 wxString GetId() const;
84
85 /**
86 Returns the platform-specific number identifying the format.
87 */
88 wxDataFormatId GetType() const;
89
90 /**
91 Sets the format to be the custom format identified by the given name.
92 */
93 void SetId(const wxString& format);
94
95 /**
96 Sets the format to the given value, which should be one of wxDF_XXX
97 constants.
98 */
99 void SetType(wxDataFormatId type);
100
101 /**
102 Returns @true if the formats are different.
103 */
104 bool operator !=(wxDataFormatId format) const;
105
106 /**
107 Returns @true if the formats are equal.
108 */
109 bool operator ==(wxDataFormatId format) const;
110 };
111
112
113
114 /**
115 @class wxDataObject
116
117 A wxDataObject represents data that can be copied to or from the clipboard,
118 or dragged and dropped. The important thing about wxDataObject is that this
119 is a 'smart' piece of data unlike 'dumb' data containers such as memory
120 buffers or files. Being 'smart' here means that the data object itself
121 should know what data formats it supports and how to render itself in each
122 of its supported formats.
123
124 A supported format, incidentally, is exactly the format in which the data
125 can be requested from a data object or from which the data object may be
126 set. In the general case, an object may support different formats on
127 'input' and 'output', i.e. it may be able to render itself in a given
128 format but not be created from data on this format or vice versa.
129 wxDataObject defines the wxDataObject::Direction enumeration type which
130 distinguishes between them.
131
132 See wxDataFormat documentation for more about formats.
133
134 Not surprisingly, being 'smart' comes at a price of added complexity. This
135 is reasonable for the situations when you really need to support multiple
136 formats, but may be annoying if you only want to do something simple like
137 cut and paste text.
138
139 To provide a solution for both cases, wxWidgets has two predefined classes
140 which derive from wxDataObject: wxDataObjectSimple and
141 wxDataObjectComposite. wxDataObjectSimple is the simplest wxDataObject
142 possible and only holds data in a single format (such as HTML or text) and
143 wxDataObjectComposite is the simplest way to implement a wxDataObject that
144 does support multiple formats because it achieves this by simply holding
145 several wxDataObjectSimple objects.
146
147 So, you have several solutions when you need a wxDataObject class (and you
148 need one as soon as you want to transfer data via the clipboard or drag and
149 drop):
150
151 -# Use one of the built-in classes.
152 - You may use wxTextDataObject, wxBitmapDataObject wxFileDataObject,
153 wxURLDataObject in the simplest cases when you only need to support
154 one format and your data is either text, bitmap or list of files.
155 -# Use wxDataObjectSimple
156 - Deriving from wxDataObjectSimple is the simplest solution for custom
157 data - you will only support one format and so probably won't be able
158 to communicate with other programs, but data transfer will work in
159 your program (or between different instances of it).
160 -# Use wxDataObjectComposite
161 - This is a simple but powerful solution which allows you to support
162 any number of formats (either standard or custom if you combine it
163 with the previous solution).
164 -# Use wxDataObject directly
165 - This is the solution for maximum flexibility and efficiency, but it
166 is also the most difficult to implement.
167
168 Please note that the easiest way to use drag and drop and the clipboard
169 with multiple formats is by using wxDataObjectComposite, but it is not the
170 most efficient one as each wxDataObjectSimple would contain the whole data
171 in its respective formats. Now imagine that you want to paste 200 pages of
172 text in your proprietary format, as well as Word, RTF, HTML, Unicode and
173 plain text to the clipboard and even today's computers are in trouble. For
174 this case, you will have to derive from wxDataObject directly and make it
175 enumerate its formats and provide the data in the requested format on
176 demand.
177
178 Note that neither the GTK+ data transfer mechanisms for clipboard and drag
179 and drop, nor OLE data transfer, @e copies any data until another application
180 actually requests the data. This is in contrast to the 'feel' offered to
181 the user of a program who would normally think that the data resides in the
182 clipboard after having pressed 'Copy' - in reality it is only declared to
183 be @e available.
184
185 You may also derive your own data object classes from wxCustomDataObject
186 for user-defined types. The format of user-defined data is given as a
187 mime-type string literal, such as "application/word" or "image/png". These
188 strings are used as they are under Unix (so far only GTK+) to identify a
189 format and are translated into their Windows equivalent under Win32 (using
190 the OLE IDataObject for data exchange to and from the clipboard and for
191 drag and drop). Note that the format string translation under Windows is
192 not yet finished.
193
194 Each class derived directly from wxDataObject must override and implement
195 all of its functions which are pure virtual in the base class. The data
196 objects which only render their data or only set it (i.e. work in only one
197 direction), should return 0 from GetFormatCount().
198
199 @beginWxPythonOnly
200 At this time this class is not directly usable from wxPython. Derive a
201 class from wxPyDataObjectSimple() instead.
202 @endWxPythonOnly
203
204 @beginWxPerlOnly
205 This class is not currently usable from wxPerl; you may use
206 Wx::PlDataObjectSimple instead.
207 @endWxPerlOnly
208
209 @library{wxcore}
210 @category{dnd}
211
212 @see @ref overview_dnd, @ref page_samples_dnd, wxFileDataObject,
213 wxTextDataObject, wxBitmapDataObject, wxCustomDataObject,
214 wxDropTarget, wxDropSource, wxTextDropTarget, wxFileDropTarget
215 */
216 class wxDataObject
217 {
218 public:
219 enum Direction
220 {
221 /** Format is supported by GetDataHere() */
222 Get = 0x01,
223
224 /** Format is supported by SetData() */
225 Set = 0x02,
226
227 /**
228 Format is supported by both GetDataHere() and SetData()
229 (unused currently)
230 */
231 Both = 0x03
232 };
233
234 /**
235 Constructor.
236 */
237 wxDataObject();
238
239 /**
240 Destructor.
241 */
242 virtual ~wxDataObject();
243
244 /**
245 Copies all formats supported in the given direction @a dir to the array
246 pointed to by @a formats.
247 There must be enough space for GetFormatCount(dir) formats in it.
248 */
249 virtual void GetAllFormats(wxDataFormat* formats,
250 Direction dir = Get) const = 0;
251
252 /**
253 The method will write the data of the format @a format in the buffer
254 @a buf and return @true on success, @false on failure.
255 */
256 virtual bool GetDataHere(const wxDataFormat& format, void* buf) const = 0;
257
258 /**
259 Returns the data size of the given format @a format.
260 */
261 virtual size_t GetDataSize(const wxDataFormat& format) const = 0;
262
263 /**
264 Returns the number of available formats for rendering or setting the
265 data.
266 */
267 virtual size_t GetFormatCount(Direction dir = Get) const = 0;
268
269 /**
270 Returns the preferred format for either rendering the data (if @a dir
271 is @c Get, its default value) or for setting it. Usually this will be
272 the native format of the wxDataObject.
273 */
274 virtual wxDataFormat GetPreferredFormat(Direction dir = Get) const = 0;
275
276 /**
277 Set the data in the format @a format of the length @a len provided in
278 the buffer @a buf.
279
280 @param format
281 The format for which to set the data.
282 @param len
283 The size of data in bytes.
284 @param buf
285 Non-@NULL pointer to the data.
286 @return
287 @true on success, @false on failure.
288 */
289 virtual bool SetData(const wxDataFormat& format, size_t len, const void* buf);
290
291 /**
292 Returns true if this format is supported.
293 */
294 bool IsSupported(const wxDataFormat& format, Direction dir = Get) const;
295 };
296
297
298 /**
299 @class wxCustomDataObject
300
301 wxCustomDataObject is a specialization of wxDataObjectSimple for some
302 application-specific data in arbitrary (either custom or one of the
303 standard ones). The only restriction is that it is supposed that this data
304 can be copied bitwise (i.e. with @c memcpy()), so it would be a bad idea to
305 make it contain a C++ object (though C struct is fine).
306
307 By default, wxCustomDataObject stores the data inside in a buffer. To put
308 the data into the buffer you may use either SetData() or TakeData()
309 depending on whether you want the object to make a copy of data or not.
310
311 This class may be used as is, but if you don't want store the data inside
312 the object but provide it on demand instead, you should override GetSize(),
313 GetData() and SetData() (or may be only the first two or only the last one
314 if you only allow reading/writing the data).
315
316 @library{wxcore}
317 @category{dnd}
318
319 @see wxDataObject
320 */
321 class wxCustomDataObject : public wxDataObjectSimple
322 {
323 public:
324 /**
325 The constructor accepts a @a format argument which specifies the
326 (single) format supported by this object. If it isn't set here,
327 wxDataObjectSimple::SetFormat() should be used.
328 */
329 wxCustomDataObject(const wxDataFormat& format = wxFormatInvalid);
330
331 /**
332 The destructor will free the data held by the object. Notice that
333 although it calls the virtual Free() function, the base class version
334 will always be called (C++ doesn't allow calling virtual functions from
335 constructors or destructors), so if you override Free(), you should
336 override the destructor in your class as well (which would probably
337 just call the derived class' version of Free()).
338 */
339 virtual ~wxCustomDataObject();
340
341 /**
342 This function is called to allocate @a size bytes of memory from
343 SetData(). The default version just uses the operator new.
344 */
345 virtual void* Alloc(size_t size);
346
347 /**
348 This function is called when the data is freed, you may override it to
349 anything you want (or may be nothing at all). The default version calls
350 operator delete[] on the data.
351 */
352 virtual void Free();
353
354 /**
355 Returns a pointer to the data.
356 */
357 virtual void* GetData() const;
358
359 /**
360 Returns the data size in bytes.
361 */
362 virtual size_t GetSize() const;
363
364 /**
365 Set the data. The data object will make an internal copy.
366
367 @beginWxPythonOnly
368 This method expects a string in wxPython. You can pass nearly any
369 object by pickling it first.
370 @endWxPythonOnly
371 */
372 virtual bool SetData(size_t size, const void* data);
373
374 /**
375 Like SetData(), but doesn't copy the data - instead the object takes
376 ownership of the pointer.
377
378 @beginWxPythonOnly
379 This method expects a string in wxPython. You can pass nearly any
380 object by pickling it first.
381 @endWxPythonOnly
382 */
383 void TakeData(size_t size, void* data);
384 };
385
386
387
388 /**
389 @class wxDataObjectComposite
390
391 wxDataObjectComposite is the simplest wxDataObject derivation which may be
392 used to support multiple formats. It contains several wxDataObjectSimple
393 objects and supports any format supported by at least one of them. Only one
394 of these data objects is @e preferred (the first one if not explicitly
395 changed by using the second parameter of Add()) and its format determines
396 the preferred format of the composite data object as well.
397
398 See wxDataObject documentation for the reasons why you might prefer to use
399 wxDataObject directly instead of wxDataObjectComposite for efficiency
400 reasons.
401
402 @library{wxcore}
403 @category{dnd}
404
405 @see @ref overview_dnd, wxDataObject, wxDataObjectSimple, wxFileDataObject,
406 wxTextDataObject, wxBitmapDataObject
407 */
408 class wxDataObjectComposite : public wxDataObject
409 {
410 public:
411 /**
412 The default constructor.
413 */
414 wxDataObjectComposite();
415
416 /**
417 Adds the @a dataObject to the list of supported objects and it becomes
418 the preferred object if @a preferred is @true.
419 */
420 void Add(wxDataObjectSimple* dataObject, bool preferred = false);
421
422 /**
423 Report the format passed to the SetData() method. This should be the
424 format of the data object within the composite that recieved data from
425 the clipboard or the DnD operation. You can use this method to find
426 out what kind of data object was recieved.
427 */
428 wxDataFormat GetReceivedFormat() const;
429 };
430
431
432
433 /**
434 @class wxDataObjectSimple
435
436 This is the simplest possible implementation of the wxDataObject class.
437 The data object of (a class derived from) this class only supports
438 <strong>one format</strong>, so the number of virtual functions to
439 be implemented is reduced.
440
441 Notice that this is still an abstract base class and cannot be used
442 directly, it must be derived. The objects supporting rendering the data
443 must override GetDataSize() and GetDataHere() while the objects which may
444 be set must override SetData(). Of course, the objects supporting both
445 operations must override all three methods.
446
447 @beginWxPythonOnly
448 If you wish to create a derived wxDataObjectSimple class in wxPython you
449 should derive the class from wxPyDataObjectSimple in order to get
450 Python-aware capabilities for the various virtual methods.
451 @endWxPythonOnly
452
453 @beginWxPerlOnly
454 In wxPerl, you need to derive your data object class from
455 Wx::PlDataObjectSimple.
456 @endWxPerlOnly
457
458 @library{wxcore}
459 @category{dnd}
460
461 @see @ref overview_dnd, @ref page_samples_dnd, wxFileDataObject,
462 wxTextDataObject, wxBitmapDataObject
463 */
464 class wxDataObjectSimple : public wxDataObject
465 {
466 public:
467 /**
468 Constructor accepts the supported format (none by default) which may
469 also be set later with SetFormat().
470 */
471 wxDataObjectSimple(const wxDataFormat& format = wxFormatInvalid);
472
473 /**
474 Copy the data to the buffer, return @true on success.
475 Must be implemented in the derived class if the object supports rendering
476 its data.
477
478 @beginWxPythonOnly
479 When implementing this method in wxPython, no additional parameters are
480 required and the data should be returned from the method as a string.
481 @endWxPythonOnly
482 */
483 virtual bool GetDataHere(void* buf) const;
484
485 /**
486 Gets the size of our data. Must be implemented in the derived class if
487 the object supports rendering its data.
488 */
489 virtual size_t GetDataSize() const;
490
491 /**
492 Returns the (one and only one) format supported by this object.
493 It is assumed that the format is supported in both directions.
494 */
495 const wxDataFormat& GetFormat() const;
496
497 /**
498 Copy the data from the buffer, return @true on success.
499 Must be implemented in the derived class if the object supports setting
500 its data.
501
502 @beginWxPythonOnly
503 When implementing this method in wxPython, the data comes as a single
504 string parameter rather than the two shown here.
505 @endWxPythonOnly
506 */
507 virtual bool SetData(size_t len, const void* buf);
508
509 /**
510 Sets the supported format.
511 */
512 void SetFormat(const wxDataFormat& format);
513 };
514
515
516
517 /**
518 @class wxBitmapDataObject
519
520 wxBitmapDataObject is a specialization of wxDataObject for bitmap data. It
521 can be used without change to paste data into the wxClipboard or a
522 wxDropSource. A user may wish to derive a new class from this class for
523 providing a bitmap on-demand in order to minimize memory consumption when
524 offering data in several formats, such as a bitmap and GIF.
525
526 This class may be used as is, but GetBitmap() may be overridden to increase
527 efficiency.
528
529 @beginWxPythonOnly
530 If you wish to create a derived wxBitmapDataObject class in wxPython you
531 should derive the class from wxPyBitmapDataObject in order to get
532 Python-aware capabilities for the various virtual methods.
533 @endWxPythonOnly
534
535 @library{wxcore}
536 @category{dnd}
537
538 @see @ref overview_dnd, wxDataObject, wxDataObjectSimple, wxFileDataObject,
539 wxTextDataObject, wxDataObject
540 */
541 class wxBitmapDataObject : public wxDataObjectSimple
542 {
543 public:
544 /**
545 Constructor, optionally passing a bitmap (otherwise use SetBitmap()
546 later).
547 */
548 wxBitmapDataObject(const wxBitmap& bitmap = wxNullBitmap);
549
550 /**
551 Returns the bitmap associated with the data object. You may wish to
552 override this method when offering data on-demand, but this is not
553 required by wxWidgets' internals. Use this method to get data in bitmap
554 form from the wxClipboard.
555 */
556 virtual wxBitmap GetBitmap() const;
557
558 /**
559 Sets the bitmap associated with the data object. This method is called
560 when the data object receives data. Usually there will be no reason to
561 override this function.
562 */
563 virtual void SetBitmap(const wxBitmap& bitmap);
564 };
565
566
567
568 /**
569 @class wxURLDataObject
570
571 wxURLDataObject is a wxDataObject containing an URL and can be used e.g.
572 when you need to put an URL on or retrieve it from the clipboard:
573
574 @code
575 wxTheClipboard->SetData(new wxURLDataObject(url));
576 @endcode
577
578 @note This class is derived from wxDataObjectComposite on Windows rather
579 than wxTextDataObject on all other platforms.
580
581 @library{wxcore}
582 @category{dnd}
583
584 @see @ref overview_dnd, wxDataObject
585 */
586 class wxURLDataObject: public wxTextDataObject
587 {
588 public:
589 /**
590 Constructor, may be used to initialize the URL. If @a url is empty,
591 SetURL() can be used later.
592 */
593 wxURLDataObject(const wxString& url = wxEmptyString);
594
595 /**
596 Returns the URL stored by this object, as a string.
597 */
598 wxString GetURL() const;
599
600 /**
601 Sets the URL stored by this object.
602 */
603 void SetURL(const wxString& url);
604 };
605
606
607 /**
608 @class wxTextDataObject
609
610 wxTextDataObject is a specialization of wxDataObjectSimple for text data.
611 It can be used without change to paste data into the wxClipboard or a
612 wxDropSource. A user may wish to derive a new class from this class for
613 providing text on-demand in order to minimize memory consumption when
614 offering data in several formats, such as plain text and RTF because by
615 default the text is stored in a string in this class, but it might as well
616 be generated when requested. For this, GetTextLength() and GetText() will
617 have to be overridden.
618
619 Note that if you already have the text inside a string, you will not
620 achieve any efficiency gain by overriding these functions because copying
621 wxStrings is already a very efficient operation (data is not actually
622 copied because wxStrings are reference counted).
623
624 @beginWxPythonOnly
625 If you wish to create a derived wxTextDataObject class in wxPython you
626 should derive the class from wxPyTextDataObject in order to get
627 Python-aware capabilities for the various virtual methods.
628 @endWxPythonOnly
629
630 @library{wxcore}
631 @category{dnd}
632
633 @see @ref overview_dnd, wxDataObject, wxDataObjectSimple, wxFileDataObject,
634 wxBitmapDataObject
635 */
636 class wxTextDataObject : public wxDataObjectSimple
637 {
638 public:
639 /**
640 Constructor, may be used to initialise the text (otherwise SetText()
641 should be used later).
642 */
643 wxTextDataObject(const wxString& text = wxEmptyString);
644
645 /**
646 Returns the text associated with the data object. You may wish to
647 override this method when offering data on-demand, but this is not
648 required by wxWidgets' internals. Use this method to get data in text
649 form from the wxClipboard.
650 */
651 virtual wxString GetText() const;
652
653 /**
654 Returns the data size. By default, returns the size of the text data
655 set in the constructor or using SetText(). This can be overridden to
656 provide text size data on-demand. It is recommended to return the text
657 length plus 1 for a trailing zero, but this is not strictly required.
658 */
659 virtual size_t GetTextLength() const;
660
661 /**
662 Returns 2 under wxMac and wxGTK, where text data coming from the
663 clipboard may be provided as ANSI (@c wxDF_TEXT) or as Unicode text
664 (@c wxDF_UNICODETEXT, but only when @c wxUSE_UNICODE==1).
665
666 Returns 1 under other platforms (e.g. wxMSW) or when building in ANSI mode
667 (@c wxUSE_UNICODE==0).
668 */
669 virtual size_t GetFormatCount(Direction dir = Get);
670
671 /**
672 Returns the preferred format supported by this object.
673
674 This is @c wxDF_TEXT or @c wxDF_UNICODETEXT depending on the platform
675 and from the build mode (i.e. from @c wxUSE_UNICODE).
676 */
677 const wxDataFormat& GetFormat() const;
678
679 /**
680 Returns all the formats supported by wxTextDataObject.
681
682 Under wxMac and wxGTK they are @c wxDF_TEXT and @c wxDF_UNICODETEXT,
683 under other ports returns only one of the two, depending on the build mode.
684 */
685 virtual void GetAllFormats(wxDataFormat* formats,
686 Direction dir = Get) const = 0;
687
688 /**
689 Sets the text associated with the data object. This method is called
690 when the data object receives the data and, by default, copies the text
691 into the member variable. If you want to process the text on the fly
692 you may wish to override this function.
693 */
694 virtual void SetText(const wxString& strText);
695 };
696
697
698
699 /**
700 @class wxFileDataObject
701
702 wxFileDataObject is a specialization of wxDataObject for file names. The
703 program works with it just as if it were a list of absolute file names, but
704 internally it uses the same format as Explorer and other compatible
705 programs under Windows or GNOME/KDE filemanager under Unix which makes it
706 possible to receive files from them using this class.
707
708 @warning Under all non-Windows platforms this class is currently
709 "input-only", i.e. you can receive the files from another
710 application, but copying (or dragging) file(s) from a wxWidgets
711 application is not currently supported. PS: GTK2 should work as
712 well.
713
714 @library{wxcore}
715 @category{dnd}
716
717 @see wxDataObject, wxDataObjectSimple, wxTextDataObject,
718 wxBitmapDataObject, wxDataObject
719 */
720 class wxFileDataObject : public wxDataObjectSimple
721 {
722 public:
723 /**
724 Constructor.
725 */
726 wxFileDataObject();
727
728 /**
729 Adds a file to the file list represented by this data object (Windows only).
730 */
731 void AddFile(const wxString& file);
732
733 /**
734 Returns the array of file names.
735 */
736 const wxArrayString& GetFilenames() const;
737 };
738
739