interface/dataobj.h

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