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