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 wxURLDataObject
 280
 281     wxURLDataObject is a wxDataObject containing an URL and can be used e.g.
 282     when you need to put an URL on or retrieve it from the clipboard:
 283
 284     @code
 285     wxTheClipboard->SetData(new wxURLDataObject(url));
 286     @endcode
 287
 288     @note This class is derived from wxDataObjectComposite on Windows rather
 289           than wxTextDataObject on all other platforms.
 290
 291     @library{wxcore}
 292     @category{dnd}
 293
 294     @see @ref overview_dnd, wxDataObject
 295 */
 296 class wxURLDataObject: public wxTextDataObject
 297 {
 298 public:
 299     /**
 300         Constructor, may be used to initialize the URL. If @a url is empty,
 301         SetURL() can be used later.
 302     */
 303     wxURLDataObject(const wxString& url = wxEmptyString);
 304
 305     /**
 306         Returns the URL stored by this object, as a string.
 307     */
 308     wxString GetURL() const;
 309
 310     /**
 311         Sets the URL stored by this object.
 312     */
 313     void SetURL(const wxString& url);
 314 };
 315
 316
 317 /**
 318     @class wxTextDataObject
 319
 320     wxTextDataObject is a specialization of wxDataObject for text data. It can
 321     be used without change to paste data into the wxClipboard or a
 322     wxDropSource. A user may wish to derive a new class from this class for
 323     providing text on-demand in order to minimize memory consumption when
 324     offering data in several formats, such as plain text and RTF because by
 325     default the text is stored in a string in this class, but it might as well
 326     be generated when requested. For this, GetTextLength() and GetText() will
 327     have to be overridden.
 328
 329     Note that if you already have the text inside a string, you will not
 330     achieve any efficiency gain by overriding these functions because copying
 331     wxStrings is already a very efficient operation (data is not actually
 332     copied because wxStrings are reference counted).
 333
 334     @beginWxPythonOnly
 335     If you wish to create a derived wxTextDataObject class in wxPython you
 336     should derive the class from wxPyTextDataObject in order to get
 337     Python-aware capabilities for the various virtual methods.
 338     @endWxPythonOnly
 339
 340     @library{wxcore}
 341     @category{dnd}
 342
 343     @see @ref overview_dnd, wxDataObject, wxDataObjectSimple, wxFileDataObject,
 344          wxBitmapDataObject
 345 */
 346 class wxTextDataObject : public wxDataObjectSimple
 347 {
 348 public:
 349     /**
 350         Constructor, may be used to initialise the text (otherwise SetText()
 351         should be used later).
 352     */
 353     wxTextDataObject(const wxString& text = wxEmptyString);
 354
 355     /**
 356         Returns the text associated with the data object. You may wish to
 357         override this method when offering data on-demand, but this is not
 358         required by wxWidgets' internals. Use this method to get data in text
 359         form from the wxClipboard.
 360     */
 361     virtual wxString GetText() const;
 362
 363     /**
 364         Returns the data size. By default, returns the size of the text data
 365         set in the constructor or using SetText(). This can be overridden to
 366         provide text size data on-demand. It is recommended to return the text
 367         length plus 1 for a trailing zero, but this is not strictly required.
 368     */
 369     virtual size_t GetTextLength() const;
 370
 371     /**
 372         Sets the text associated with the data object. This method is called
 373         when the data object receives the data and, by default, copies the text
 374         into the member variable. If you want to process the text on the fly
 375         you may wish to override this function.
 376     */
 377     virtual void SetText(const wxString& strText);
 378 };
 379
 380
 381
 382 /**
 383     @class wxFileDataObject
 384
 385     wxFileDataObject is a specialization of wxDataObject for file names. The
 386     program works with it just as if it were a list of absolute file names, but
 387     internally it uses the same format as Explorer and other compatible
 388     programs under Windows or GNOME/KDE filemanager under Unix which makes it
 389     possible to receive files from them using this class.
 390
 391     @warning Under all non-Windows platforms this class is currently
 392              "input-only", i.e. you can receive the files from another
 393              application, but copying (or dragging) file(s) from a wxWidgets
 394              application is not currently supported. PS: GTK2 should work as
 395              well.
 396
 397     @library{wxcore}
 398     @category{dnd}
 399
 400     @see wxDataObject, wxDataObjectSimple, wxTextDataObject,
 401          wxBitmapDataObject, wxDataObject
 402 */
 403 class wxFileDataObject : public wxDataObjectSimple
 404 {
 405 public:
 406     /**
 407         Constructor.
 408     */
 409     wxFileDataObject();
 410
 411     /**
 412         Adds a file to the file list represented by this data object (Windows
 413         only).
 414     */
 415     void AddFile(const wxString& file);
 416
 417     /**
 418         Returns the array of file names.
 419     */
 420     const wxArrayString& GetFilenames() const;
 421 };
 422
 423
 424
 425 /**
 426     @class wxDataFormat
 427
 428     A wxDataFormat is an encapsulation of a platform-specific format handle
 429     which is used by the system for the clipboard and drag and drop operations.
 430     The applications are usually only interested in, for example, pasting data
 431     from the clipboard only if the data is in a format the program understands
 432     and a data format is something which uniquely identifies this format.
 433
 434     On the system level, a data format is usually just a number (@c CLIPFORMAT
 435     under Windows or @c Atom under X11, for example) and the standard formats
 436     are, indeed, just numbers which can be implicitly converted to wxDataFormat.
 437     The standard formats are:
 438
 439     @beginDefList
 440     @itemdef{wxDF_INVALID,
 441              An invalid format - used as default argument for functions taking
 442              a wxDataFormat argument sometimes.}
 443     @itemdef{wxDF_TEXT,
 444              Text format (wxString).}
 445     @itemdef{wxDF_BITMAP,
 446              A bitmap (wxBitmap).}
 447     @itemdef{wxDF_METAFILE,
 448              A metafile (wxMetafile, Windows only).}
 449     @itemdef{wxDF_FILENAME,
 450              A list of filenames.}
 451     @itemdef{wxDF_HTML,
 452              An HTML string. This is only valid when passed to
 453              wxSetClipboardData when compiled with Visual C++ in non-Unicode
 454              mode.}
 455     @endDefList
 456
 457     As mentioned above, these standard formats may be passed to any function
 458     taking wxDataFormat argument because wxDataFormat has an implicit
 459     conversion from them (or, to be precise from the type
 460     @c wxDataFormat::NativeFormat which is the type used by the underlying
 461     platform for data formats).
 462
 463     Aside the standard formats, the application may also use custom formats
 464     which are identified by their names (strings) and not numeric identifiers.
 465     Although internally custom format must be created (or @e registered) first,
 466     you shouldn't care about it because it is done automatically the first time
 467     the wxDataFormat object corresponding to a given format name is created.
 468     The only implication of this is that you should avoid having global
 469     wxDataFormat objects with non-default constructor because their
 470     constructors are executed before the program has time to perform all
 471     necessary initialisations and so an attempt to do clipboard format
 472     registration at this time will usually lead to a crash!
 473
 474     @library{wxbase}
 475     @category{dnd}
 476
 477     @see @ref overview_dnd, @ref page_samples_dnd, wxDataObject
 478 */
 479 class wxDataFormat
 480 {
 481 public:
 482     /**
 483         Constructs a data format object for one of the standard data formats or
 484         an empty data object (use SetType() or SetId() later in this case).
 485     */
 486     wxDataFormat(wxDataFormatId format = wxDF_INVALID);
 487
 488     /**
 489         Constructs a data format object for a custom format identified by its
 490         name @a format.
 491     */
 492     wxDataFormat(const wxChar format);
 493
 494     /**
 495         Returns the name of a custom format (this function will fail for a
 496         standard format).
 497     */
 498     wxString GetId() const;
 499
 500     /**
 501         Returns the platform-specific number identifying the format.
 502     */
 503     wxDataFormatId GetType() const;
 504
 505     /**
 506         Sets the format to be the custom format identified by the given name.
 507     */
 508     void SetId(const wxChar format);
 509
 510     /**
 511         Sets the format to the given value, which should be one of wxDF_XXX
 512         constants.
 513     */
 514     void SetType(wxDataFormatId type);
 515
 516     /**
 517         Returns @true if the formats are different.
 518     */
 519     bool operator !=(const wxDataFormat& format) const;
 520
 521     /**
 522         Returns @true if the formats are equal.
 523     */
 524     bool operator ==(const wxDataFormat& format) const;
 525 };
 526
 527
 528
 529 /**
 530     @class wxDataObject
 531
 532     A wxDataObject represents data that can be copied to or from the clipboard,
 533     or dragged and dropped. The important thing about wxDataObject is that this
 534     is a 'smart' piece of data unlike 'dumb' data containers such as memory
 535     buffers or files. Being 'smart' here means that the data object itself
 536     should know what data formats it supports and how to render itself in each
 537     of its supported formats.
 538
 539     A supported format, incidentally, is exactly the format in which the data
 540     can be requested from a data object or from which the data object may be
 541     set. In the general case, an object may support different formats on
 542     'input' and 'output', i.e. it may be able to render itself in a given
 543     format but not be created from data on this format or vice versa.
 544     wxDataObject defines an enumeration type which distinguishes between them:
 545
 546     @code
 547     enum Direction
 548     {
 549         Get  = 0x01,    // format is supported by GetDataHere()
 550         Set  = 0x02     // format is supported by SetData()
 551     };
 552     @endcode
 553
 554     See wxDataFormat documentation for more about formats.
 555
 556     Not surprisingly, being 'smart' comes at a price of added complexity. This
 557     is reasonable for the situations when you really need to support multiple
 558     formats, but may be annoying if you only want to do something simple like
 559     cut and paste text.
 560
 561     To provide a solution for both cases, wxWidgets has two predefined classes
 562     which derive from wxDataObject: wxDataObjectSimple and
 563     wxDataObjectComposite. wxDataObjectSimple is the simplest wxDataObject
 564     possible and only holds data in a single format (such as HTML or text) and
 565     wxDataObjectComposite is the simplest way to implement a wxDataObject that
 566     does support multiple formats because it achieves this by simply holding
 567     several wxDataObjectSimple objects.
 568
 569     So, you have several solutions when you need a wxDataObject class (and you
 570     need one as soon as you want to transfer data via the clipboard or drag and
 571     drop):
 572
 573     -# Use one of the built-in classes.
 574         - You may use wxTextDataObject, wxBitmapDataObject or wxFileDataObject
 575           in the simplest cases when you only need to support one format and
 576           your data is either text, bitmap or list of files.
 577     -# Use wxDataObjectSimple
 578         - Deriving from wxDataObjectSimple is the simplest solution for custom
 579           data - you will only support one format and so probably won't be able
 580           to communicate with other programs, but data transfer will work in
 581           your program (or between different copies of it).
 582     -# Use wxDataObjectComposite
 583         - This is a simple but powerful solution which allows you to support
 584           any number of formats (either standard or custom if you combine it
 585           with the previous solution).
 586     -# Use wxDataObject Directly
 587         - This is the solution for maximal flexibility and efficiency, but it
 588           is also the most difficult to implement.
 589
 590     Please note that the easiest way to use drag and drop and the clipboard
 591     with multiple formats is by using wxDataObjectComposite, but it is not the
 592     most efficient one as each wxDataObjectSimple would contain the whole data
 593     in its respective formats. Now imagine that you want to paste 200 pages of
 594     text in your proprietary format, as well as Word, RTF, HTML, Unicode and
 595     plain text to the clipboard and even today's computers are in trouble. For
 596     this case, you will have to derive from wxDataObject directly and make it
 597     enumerate its formats and provide the data in the requested format on
 598     demand.
 599
 600     Note that neither the GTK+ data transfer mechanisms for clipboard and drag
 601     and drop, nor OLE data transfer, copy any data until another application
 602     actually requests the data. This is in contrast to the 'feel' offered to
 603     the user of a program who would normally think that the data resides in the
 604     clipboard after having pressed 'Copy' - in reality it is only declared to
 605     be available.
 606
 607     There are several predefined data object classes derived from
 608     wxDataObjectSimple: wxFileDataObject, wxTextDataObject, wxBitmapDataObject
 609     and wxURLDataObject which can be used without change.
 610
 611     You may also derive your own data object classes from wxCustomDataObject
 612     for user-defined types. The format of user-defined data is given as a
 613     mime-type string literal, such as "application/word" or "image/png". These
 614     strings are used as they are under Unix (so far only GTK+) to identify a
 615     format and are translated into their Windows equivalent under Win32 (using
 616     the OLE IDataObject for data exchange to and from the clipboard and for
 617     drag and drop). Note that the format string translation under Windows is
 618     not yet finished.
 619
 620     Each class derived directly from wxDataObject must override and implement
 621     all of its functions which are pure virtual in the base class. The data
 622     objects which only render their data or only set it (i.e. work in only one
 623     direction), should return 0 from GetFormatCount().
 624
 625     @beginWxPythonOnly
 626     At this time this class is not directly usable from wxPython. Derive a
 627     class from wxPyDataObjectSimple() instead.
 628     @endWxPythonOnly
 629
 630     @beginWxPerlOnly
 631     This class is not currently usable from wxPerl; you may use
 632     Wx::PlDataObjectSimple instead.
 633     @endWxPerlOnly
 634
 635     @library{wxcore}
 636     @category{dnd}
 637
 638     @see @ref overview_dnd, @ref page_samples_dnd, wxFileDataObject,
 639          wxTextDataObject, wxBitmapDataObject, wxCustomDataObject,
 640          wxDropTarget, wxDropSource, wxTextDropTarget, wxFileDropTarget
 641 */
 642 class wxDataObject
 643 {
 644 public:
 645     /**
 646         Constructor.
 647     */
 648     wxDataObject();
 649
 650     /**
 651         Destructor.
 652     */
 653     virtual ~wxDataObject();
 654
 655     /**
 656         Copy all supported formats in the given direction to the array pointed
 657         to by @a formats. There is enough space for GetFormatCount(dir) formats
 658         in it.
 659     */
 660     virtual void GetAllFormats(wxDataFormat* formats,
 661                                  Direction dir = Get) const;
 662
 663     /**
 664         The method will write the data of the format @a format in the buffer
 665         @a buf and return @true on success, @false on failure.
 666     */
 667     virtual bool GetDataHere(const wxDataFormat& format, void* buf) const = 0;
 668
 669     /**
 670         Returns the data size of the given format @a format.
 671     */
 672     virtual size_t GetDataSize(const wxDataFormat& format) const = 0;
 673
 674     /**
 675         Returns the number of available formats for rendering or setting the
 676         data.
 677     */
 678     virtual size_t GetFormatCount(Direction dir = Get) const = 0;
 679
 680     /**
 681         Returns the preferred format for either rendering the data (if @a dir
 682         is @c Get, its default value) or for setting it. Usually this will be
 683         the native format of the wxDataObject.
 684     */
 685     virtual wxDataFormat GetPreferredFormat(Direction dir = Get) const = 0;
 686
 687     /**
 688         Set the data in the format @a format of the length @a len provided in
 689         the buffer @a buf.
 690
 691         @return @true on success, @false on failure.
 692     */
 693     virtual bool SetData(const wxDataFormat& format, size_t len,
 694                          const void* buf);
 695 };
 696