interface/dataobj.h

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