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 bool 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 only).
 413     */
 414     void AddFile(const wxString& file);
 415
 416     /**
 417         Returns the array of file names.
 418     */
 419     const wxArrayString& GetFilenames() const;
 420 };
 421
 422
 423
 424 /**
 425     @class wxDataFormat
 426
 427     A wxDataFormat is an encapsulation of a platform-specific format handle
 428     which is used by the system for the clipboard and drag and drop operations.
 429     The applications are usually only interested in, for example, pasting data
 430     from the clipboard only if the data is in a format the program understands
 431     and a data format is something which uniquely identifies this format.
 432
 433     On the system level, a data format is usually just a number (@c CLIPFORMAT
 434     under Windows or @c Atom under X11, for example) and the standard formats
 435     are, indeed, just numbers which can be implicitly converted to wxDataFormat.
 436     The standard formats are:
 437
 438     @beginDefList
 439     @itemdef{wxDF_INVALID,
 440              An invalid format - used as default argument for functions taking
 441              a wxDataFormat argument sometimes.}
 442     @itemdef{wxDF_TEXT,
 443              Text format (wxString).}
 444     @itemdef{wxDF_BITMAP,
 445              A bitmap (wxBitmap).}
 446     @itemdef{wxDF_METAFILE,
 447              A metafile (wxMetafile, Windows only).}
 448     @itemdef{wxDF_FILENAME,
 449              A list of filenames.}
 450     @itemdef{wxDF_HTML,
 451              An HTML string. This is only valid when passed to
 452              wxSetClipboardData when compiled with Visual C++ in non-Unicode
 453              mode.}
 454     @endDefList
 455
 456     As mentioned above, these standard formats may be passed to any function
 457     taking wxDataFormat argument because wxDataFormat has an implicit
 458     conversion from them (or, to be precise from the type
 459     @c wxDataFormat::NativeFormat which is the type used by the underlying
 460     platform for data formats).
 461
 462     Aside the standard formats, the application may also use custom formats
 463     which are identified by their names (strings) and not numeric identifiers.
 464     Although internally custom format must be created (or @e registered) first,
 465     you shouldn't care about it because it is done automatically the first time
 466     the wxDataFormat object corresponding to a given format name is created.
 467     The only implication of this is that you should avoid having global
 468     wxDataFormat objects with non-default constructor because their
 469     constructors are executed before the program has time to perform all
 470     necessary initialisations and so an attempt to do clipboard format
 471     registration at this time will usually lead to a crash!
 472
 473     @library{wxbase}
 474     @category{dnd}
 475
 476     @see @ref overview_dnd, @ref page_samples_dnd, wxDataObject
 477 */
 478 class wxDataFormat
 479 {
 480 public:
 481     /**
 482         Constructs a data format object for one of the standard data formats or
 483         an empty data object (use SetType() or SetId() later in this case).
 484     */
 485     wxDataFormat(wxDataFormatId format = wxDF_INVALID);
 486
 487     /**
 488         Constructs a data format object for a custom format identified by its
 489         name @a format.
 490     */
 491     wxDataFormat(const wxString& format);
 492
 493     /**
 494         Returns the name of a custom format (this function will fail for a
 495         standard format).
 496     */
 497     wxString GetId() const;
 498
 499     /**
 500         Returns the platform-specific number identifying the format.
 501     */
 502     wxDataFormatId GetType() const;
 503
 504     /**
 505         Sets the format to be the custom format identified by the given name.
 506     */
 507     void SetId(const wxString& format);
 508
 509     /**
 510         Sets the format to the given value, which should be one of wxDF_XXX
 511         constants.
 512     */
 513     void SetType(wxDataFormatId type);
 514
 515     /**
 516         Returns @true if the formats are different.
 517     */
 518     bool operator !=(wxDataFormatId format) const;
 519
 520     /**
 521         Returns @true if the formats are equal.
 522     */
 523     bool operator ==(wxDataFormatId format) const;
 524 };
 525
 526
 527
 528 /**
 529     @class wxDataObject
 530
 531     A wxDataObject represents data that can be copied to or from the clipboard,
 532     or dragged and dropped. The important thing about wxDataObject is that this
 533     is a 'smart' piece of data unlike 'dumb' data containers such as memory
 534     buffers or files. Being 'smart' here means that the data object itself
 535     should know what data formats it supports and how to render itself in each
 536     of its supported formats.
 537
 538     A supported format, incidentally, is exactly the format in which the data
 539     can be requested from a data object or from which the data object may be
 540     set. In the general case, an object may support different formats on
 541     'input' and 'output', i.e. it may be able to render itself in a given
 542     format but not be created from data on this format or vice versa.
 543     wxDataObject defines an enumeration type which distinguishes between them:
 544
 545     @code
 546     enum Direction
 547     {
 548         Get  = 0x01,    // format is supported by GetDataHere()
 549         Set  = 0x02     // format is supported by SetData()
 550     };
 551     @endcode
 552
 553     See wxDataFormat documentation for more about formats.
 554
 555     Not surprisingly, being 'smart' comes at a price of added complexity. This
 556     is reasonable for the situations when you really need to support multiple
 557     formats, but may be annoying if you only want to do something simple like
 558     cut and paste text.
 559
 560     To provide a solution for both cases, wxWidgets has two predefined classes
 561     which derive from wxDataObject: wxDataObjectSimple and
 562     wxDataObjectComposite. wxDataObjectSimple is the simplest wxDataObject
 563     possible and only holds data in a single format (such as HTML or text) and
 564     wxDataObjectComposite is the simplest way to implement a wxDataObject that
 565     does support multiple formats because it achieves this by simply holding
 566     several wxDataObjectSimple objects.
 567
 568     So, you have several solutions when you need a wxDataObject class (and you
 569     need one as soon as you want to transfer data via the clipboard or drag and
 570     drop):
 571
 572     -# Use one of the built-in classes.
 573         - You may use wxTextDataObject, wxBitmapDataObject or wxFileDataObject
 574           in the simplest cases when you only need to support one format and
 575           your data is either text, bitmap or list of files.
 576     -# Use wxDataObjectSimple
 577         - Deriving from wxDataObjectSimple is the simplest solution for custom
 578           data - you will only support one format and so probably won't be able
 579           to communicate with other programs, but data transfer will work in
 580           your program (or between different copies of it).
 581     -# Use wxDataObjectComposite
 582         - This is a simple but powerful solution which allows you to support
 583           any number of formats (either standard or custom if you combine it
 584           with the previous solution).
 585     -# Use wxDataObject Directly
 586         - This is the solution for maximal flexibility and efficiency, but it
 587           is also the most difficult to implement.
 588
 589     Please note that the easiest way to use drag and drop and the clipboard
 590     with multiple formats is by using wxDataObjectComposite, but it is not the
 591     most efficient one as each wxDataObjectSimple would contain the whole data
 592     in its respective formats. Now imagine that you want to paste 200 pages of
 593     text in your proprietary format, as well as Word, RTF, HTML, Unicode and
 594     plain text to the clipboard and even today's computers are in trouble. For
 595     this case, you will have to derive from wxDataObject directly and make it
 596     enumerate its formats and provide the data in the requested format on
 597     demand.
 598
 599     Note that neither the GTK+ data transfer mechanisms for clipboard and drag
 600     and drop, nor OLE data transfer, copy any data until another application
 601     actually requests the data. This is in contrast to the 'feel' offered to
 602     the user of a program who would normally think that the data resides in the
 603     clipboard after having pressed 'Copy' - in reality it is only declared to
 604     be available.
 605
 606     There are several predefined data object classes derived from
 607     wxDataObjectSimple: wxFileDataObject, wxTextDataObject, wxBitmapDataObject
 608     and wxURLDataObject which can be used without change.
 609
 610     You may also derive your own data object classes from wxCustomDataObject
 611     for user-defined types. The format of user-defined data is given as a
 612     mime-type string literal, such as "application/word" or "image/png". These
 613     strings are used as they are under Unix (so far only GTK+) to identify a
 614     format and are translated into their Windows equivalent under Win32 (using
 615     the OLE IDataObject for data exchange to and from the clipboard and for
 616     drag and drop). Note that the format string translation under Windows is
 617     not yet finished.
 618
 619     Each class derived directly from wxDataObject must override and implement
 620     all of its functions which are pure virtual in the base class. The data
 621     objects which only render their data or only set it (i.e. work in only one
 622     direction), should return 0 from GetFormatCount().
 623
 624     @beginWxPythonOnly
 625     At this time this class is not directly usable from wxPython. Derive a
 626     class from wxPyDataObjectSimple() instead.
 627     @endWxPythonOnly
 628
 629     @beginWxPerlOnly
 630     This class is not currently usable from wxPerl; you may use
 631     Wx::PlDataObjectSimple instead.
 632     @endWxPerlOnly
 633
 634     @library{wxcore}
 635     @category{dnd}
 636
 637     @see @ref overview_dnd, @ref page_samples_dnd, wxFileDataObject,
 638          wxTextDataObject, wxBitmapDataObject, wxCustomDataObject,
 639          wxDropTarget, wxDropSource, wxTextDropTarget, wxFileDropTarget
 640 */
 641 class wxDataObject
 642 {
 643 public:
 644     /**
 645         Constructor.
 646     */
 647     wxDataObject();
 648
 649     /**
 650         Destructor.
 651     */
 652     virtual ~wxDataObject();
 653
 654     /**
 655         Copy all supported formats in the given direction to the array pointed
 656         to by @a formats. There is enough space for GetFormatCount(dir) formats
 657         in it.
 658     */
 659     virtual void GetAllFormats(wxDataFormat* formats,
 660                                Direction dir = Get) const = 0;
 661
 662     /**
 663         The method will write the data of the format @a format in the buffer
 664         @a buf and return @true on success, @false on failure.
 665     */
 666     virtual bool GetDataHere(const wxDataFormat& format, void* buf) const = 0;
 667
 668     /**
 669         Returns the data size of the given format @a format.
 670     */
 671     virtual size_t GetDataSize(const wxDataFormat& format) const = 0;
 672
 673     /**
 674         Returns the number of available formats for rendering or setting the
 675         data.
 676     */
 677     virtual size_t GetFormatCount(Direction dir = Get) const = 0;
 678
 679     /**
 680         Returns the preferred format for either rendering the data (if @a dir
 681         is @c Get, its default value) or for setting it. Usually this will be
 682         the native format of the wxDataObject.
 683     */
 684     virtual wxDataFormat GetPreferredFormat(Direction dir = Get) const = 0;
 685
 686     /**
 687         Set the data in the format @a format of the length @a len provided in
 688         the buffer @a buf.
 689
 690         @return @true on success, @false on failure.
 691     */
 692     virtual bool SetData(const wxDataFormat& format, size_t len, const void* buf);
 693 };
 694