interface/wx/config.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        config.h
   3 // Purpose:     interface of wxConfigBase
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows license
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 /**
  10     @class wxConfigBase
  11
  12     wxConfigBase defines the basic interface of all config classes. It can not
  13     be used by itself (it is an abstract base class) and you will always use
  14     one of its derivations: wxFileConfig, wxRegConfig or any other.
  15
  16     However, usually you don't even need to know the precise nature of the
  17     class you're working with but you would just use the wxConfigBase methods.
  18     This allows you to write the same code regardless of whether you're working
  19     with the registry under Win32 or text-based config files under Unix (or
  20     even Windows 3.1 .INI files if you're really unlucky). To make writing the
  21     portable code even easier, wxWidgets provides a typedef wxConfig which is
  22     mapped onto the native wxConfigBase implementation on the given platform:
  23     i.e. wxRegConfig under Win32 and wxFileConfig otherwise.
  24
  25     See @ref overview_config for a description of all features of this class.
  26
  27     It is highly recommended to use static functions Get() and/or Set(), so
  28     please have a look at them.
  29
  30     Related Include Files:
  31
  32     @li @c <wx/config.h>   - Let wxWidgets choose a wxConfig class for your
  33                              platform.
  34     @li @c <wx/confbase.h> - Base config class.
  35     @li @c <wx/fileconf.h> - wxFileConfig class.
  36     @li @c <wx/msw/regconf.h> - wxRegConfig class, see also wxRegKey.
  37
  38
  39     @section configbase_example Example
  40
  41     Here is how you would typically use this class:
  42
  43     @code
  44     // using wxConfig instead of writing wxFileConfig or wxRegConfig enhances
  45     // portability of the code
  46     wxConfig *config = new wxConfig("MyAppName");
  47
  48     wxString str;
  49     if ( config->Read("LastPrompt", &str) ) {
  50         // last prompt was found in the config file/registry and its value is
  51         // now in str
  52         // ...
  53     }
  54     else {
  55         // no last prompt...
  56     }
  57
  58     // another example: using default values and the full path instead of just
  59     // key name: if the key is not found , the value 17 is returned
  60     long value = config->ReadLong("/LastRun/CalculatedValues/MaxValue", 17);
  61
  62     // at the end of the program we would save everything back
  63     config->Write("LastPrompt", str);
  64     config->Write("/LastRun/CalculatedValues/MaxValue", value);
  65
  66     // the changes will be written back automatically
  67     delete config;
  68     @endcode
  69
  70     This basic example, of course, doesn't show all wxConfig features, such as
  71     enumerating, testing for existence and deleting the entries and groups of
  72     entries in the config file, its abilities to automatically store the
  73     default values or expand the environment variables on the fly. However, the
  74     main idea is that using this class is easy and that it should normally do
  75     what you expect it to.
  76
  77     @note In the documentation of this class, the words "config file" also mean
  78           "registry hive" for wxRegConfig and, generally speaking, might mean
  79           any physical storage where a wxConfigBase-derived class stores its
  80           data.
  81
  82
  83     @section configbase_static Static Functions
  84
  85     The static functions provided deal with the "default" config object.
  86     Although its usage is not at all mandatory it may be convenient to use a
  87     global config object instead of creating and deleting the local config
  88     objects each time you need one (especially because creating a wxFileConfig
  89     object might be a time consuming operation). In this case, you may create
  90     this global config object in the very start of the program and Set() it as
  91     the default. Then, from anywhere in your program, you may access it using
  92     the Get() function. This global wxConfig object will be deleted by
  93     wxWidgets automatically if it exists. Note that this implies that if you do
  94     delete this object yourself (usually in wxApp::OnExit()) you must use
  95     Set(@NULL) to prevent wxWidgets from deleting it the second time.
  96
  97     As it happens, you may even further simplify the procedure described above:
  98     you may forget about calling Set(). When Get() is called and there is no
  99     current object, it will create one using Create() function. To disable this
 100     behaviour DontCreateOnDemand() is provided.
 101
 102     @note You should use either Set() or Get() because wxWidgets library itself
 103           would take advantage of it and could save various information in it.
 104           For example wxFontMapper or Unix version of wxFileDialog have the
 105           ability to use wxConfig class.
 106
 107
 108     @section configbase_paths Path Management
 109
 110     As explained in the @ref overview_config "config overview", the config
 111     classes support a file system-like hierarchy of keys (files) and groups
 112     (directories). As in the file system case, to specify a key in the config
 113     class you must use a path to it. Config classes also support the notion of
 114     the current group, which makes it possible to use the relative paths. To
 115     clarify all this, here is an example (it is only for the sake of
 116     demonstration, it doesn't do anything sensible!):
 117
 118     @code
 119     wxConfig *config = new wxConfig("FooBarApp");
 120
 121     // right now the current path is '/'
 122     conf->Write("RootEntry", 1);
 123
 124     // go to some other place: if the group(s) don't exist, they will be created
 125     conf->SetPath("/Group/Subgroup");
 126
 127     // create an entry in subgroup
 128     conf->Write("SubgroupEntry", 3);
 129
 130     // '..' is understood
 131     conf->Write("../GroupEntry", 2);
 132     conf->SetPath("..");
 133
 134     wxASSERT( conf->ReadLong("Subgroup/SubgroupEntry", 0) == 3 );
 135
 136     // use absolute path: it is allowed, too
 137     wxASSERT( conf->ReadLong("/RootEntry", 0) == 1 );
 138     @endcode
 139
 140     It is highly recommended that you restore the path to its old value on
 141     function exit:
 142
 143     @code
 144     void foo(wxConfigBase *config)
 145     {
 146         wxString strOldPath = config->GetPath();
 147
 148         config->SetPath("/Foo/Data");
 149         // ...
 150
 151         config->SetPath(strOldPath);
 152     }
 153     @endcode
 154
 155     Otherwise the assert in the following example will surely fail (we suppose
 156     here that the foo() function is the same as above except that it doesn’t
 157     save and restore the path):
 158
 159     @code
 160     void bar(wxConfigBase *config)
 161     {
 162         config->Write("Test", 17);
 163
 164         foo(config);
 165
 166         // we're reading "/Foo/Data/Test" here! -1 will probably be returned...
 167         wxASSERT( config->ReadLong("Test", -1) == 17 );
 168     }
 169     @endcode
 170
 171     Finally, the path separator in wxConfigBase and derived classes is always
 172     "/", regardless of the platform (i.e. it is not "\\" under Windows).
 173
 174
 175     @section configbase_enumeration Enumeration
 176
 177     The enumeration functions allow you to enumerate all entries and groups in
 178     the config file. All functions here return @false when there are no more
 179     items.
 180
 181     You must pass the same index to GetNext() and GetFirst() (don't modify it).
 182     Please note that it is not the index of the current item (you will have
 183     some great surprises with wxRegConfig if you assume this) and you shouldn't
 184     even look at it: it is just a "cookie" which stores the state of the
 185     enumeration. It can't be stored inside the class because it would prevent
 186     you from running several enumerations simultaneously, that's why you must
 187     pass it explicitly.
 188
 189     Having said all this, enumerating the config entries/groups is very simple:
 190
 191     @code
 192     wxConfigBase *config = ...;
 193     wxArrayString aNames;
 194
 195     // enumeration variables
 196     wxString str;
 197     long dummy;
 198
 199     // first enum all entries
 200     bool bCont = config->GetFirstEntry(str, dummy);
 201     while ( bCont ) {
 202         aNames.Add(str);
 203
 204         bCont = GetConfig()->GetNextEntry(str, dummy);
 205     }
 206
 207     // ... we have all entry names in aNames...
 208
 209     // now all groups...
 210     bCont = GetConfig()->GetFirstGroup(str, dummy);
 211     while ( bCont ) {
 212         aNames.Add(str);
 213
 214         bCont = GetConfig()->GetNextGroup(str, dummy);
 215     }
 216
 217     // ... we have all group (and entry) names in aNames...
 218     @endcode
 219
 220     There are also functions to get the number of entries/subgroups without
 221     actually enumerating them, but you will probably never need them.
 222
 223
 224     @section configbase_keyaccess Key Access
 225
 226     The key access functions are the core of wxConfigBase class: they allow you
 227     to read and write config file data. All Read() functions take a default
 228     value which will be returned if the specified key is not found in the
 229     config file.
 230
 231     Currently, supported types of data are: wxString, @c long, @c double,
 232     @c bool, wxColour and any other types for which the functions
 233     wxToString() and wxFromString() are defined.
 234
 235     Try not to read long values into string variables and vice versa:
 236     although it just might work with wxFileConfig, you will get a system
 237     error with wxRegConfig because in the Windows registry the different
 238     types of entries are indeed used.
 239
 240     Final remark: the @a szKey parameter for all these functions can
 241     contain an arbitrary path (either relative or absolute), not just the
 242     key name.
 243
 244     @beginWxPythonOnly
 245     In place of a single overloaded method name, wxPython implements the
 246     following methods:
 247     - Read(key, default="") - Returns a string.
 248     - ReadInt(key, default=0) - Returns an integer.
 249     - ReadFloat(key, default=0.0) - Returns a floating point number.
 250     - ReadBool(key, default=0) - Returns a boolean.
 251     - Write(key, value) - Writes a string.
 252     - WriteInt(key, value) - Writes an int.
 253     - WriteFloat(key, value) - Writes a floating point number.
 254     @endWxPythonOnly
 255
 256
 257     @library{wxbase}
 258     @category{misc}
 259 */
 260 class wxConfigBase : public wxObject
 261 {
 262 public:
 263     /**
 264         This is the default and only constructor of the wxConfigBase class, and
 265         derived classes.
 266
 267         @param appName
 268             The application name. If this is empty, the class will normally use
 269             wxApp::GetAppName() to set it. The application name is used in the
 270             registry key on Windows, and can be used to deduce the local
 271             filename parameter if that is missing.
 272         @param vendorName
 273             The vendor name. If this is empty, it is assumed that no vendor
 274             name is wanted, if this is optional for the current config class.
 275             The vendor name is appended to the application name for
 276             wxRegConfig.
 277         @param localFilename
 278             Some config classes require a local filename. If this is not
 279             present, but required, the application name will be used instead.
 280         @param globalFilename
 281             Some config classes require a global filename. If this is not
 282             present, but required, the application name will be used instead.
 283         @param style
 284             Can be one of wxCONFIG_USE_LOCAL_FILE and wxCONFIG_USE_GLOBAL_FILE.
 285             The style interpretation depends on the config class and is ignored
 286             by some implementations. For wxFileConfig, these styles determine
 287             whether a local or global config file is created or used: if
 288             wxCONFIG_USE_GLOBAL_FILE is used, then settings are read from the
 289             global config file and if wxCONFIG_USE_LOCAL_FILE is used, settings
 290             are read from and written to local config file (if they are both
 291             set, global file is read first, then local file, overwriting global
 292             settings). If the flag is present but the parameter is empty, the
 293             parameter will be set to a default. If the parameter is present but
 294             the style flag not, the relevant flag will be added to the style.
 295             For wxRegConfig, thie GLOBAL flag refers to HKLM key while LOCAL
 296             one is for the usual HKCU one.
 297             @n For wxFileConfig you can also add wxCONFIG_USE_RELATIVE_PATH by
 298             logically or'ing it to either of the _FILE options to tell
 299             wxFileConfig to use relative instead of absolute paths.
 300             @n On non-VMS Unix systems, the default local configuration file is
 301             "~/.appname". However, this path may be also used as user data
 302             directory (see wxStandardPaths::GetUserDataDir()) if the
 303             application has several data files. In this case
 304             wxCONFIG_USE_SUBDIR flag, which changes the default local
 305             configuration file to "~/.appname/appname" should be used. Notice
 306             that this flag is ignored if localFilename is provided.
 307             wxCONFIG_USE_SUBDIR is new since wxWidgets version 2.8.2.
 308             @n For wxFileConfig, you can also add
 309             wxCONFIG_USE_NO_ESCAPE_CHARACTERS which will turn off character
 310             escaping for the values of entries stored in the config file: for
 311             example a foo key with some backslash characters will be stored as
 312             "foo=C:\mydir" instead of the usual storage of "foo=C:\\mydir".
 313             @n The wxCONFIG_USE_NO_ESCAPE_CHARACTERS style can be helpful if your
 314             config file must be read or written to by a non-wxWidgets program
 315             (which might not understand the escape characters). Note, however,
 316             that if wxCONFIG_USE_NO_ESCAPE_CHARACTERS style is used, it is is
 317             now your application's responsibility to ensure that there is no
 318             newline or other illegal characters in a value, before writing that
 319             value to the file.
 320         @param conv
 321             This parameter is only used by wxFileConfig when compiled in
 322             Unicode mode. It specifies the encoding in which the configuration
 323             file is written.
 324
 325         @remarks By default, environment variable expansion is on and recording
 326                  defaults is off.
 327     */
 328     wxConfigBase(const wxString& appName = wxEmptyString,
 329                  const wxString& vendorName = wxEmptyString,
 330                  const wxString& localFilename = wxEmptyString,
 331                  const wxString& globalFilename = wxEmptyString,
 332                  long style = 0,
 333                  const wxMBConv& conv = wxConvAuto());
 334
 335     /**
 336         Empty but ensures that dtor of all derived classes is virtual.
 337     */
 338     virtual ~wxConfigBase();
 339
 340
 341     /**
 342         @name Path Management
 343
 344         See @ref configbase_paths
 345     */
 346     //@{
 347
 348     /**
 349         Retrieve the current path (always as absolute path).
 350     */
 351     virtual const wxString& GetPath() const = 0;
 352
 353     /**
 354         Set current path: if the first character is '/', it is the absolute
 355         path, otherwise it is a relative path. '..' is supported. If @a strPath
 356         doesn't exist it is created.
 357     */
 358     virtual void SetPath(const wxString& strPath) = 0;
 359
 360     //@}
 361
 362
 363     /**
 364         @name Enumeration
 365
 366         See @ref configbase_enumeration
 367     */
 368     //@{
 369
 370     /**
 371         Gets the first entry.
 372
 373         @beginWxPythonOnly
 374         The wxPython version of this method returns a 3-tuple consisting of the
 375         continue flag, the value string, and the index for the next call.
 376         @endWxPythonOnly
 377     */
 378     virtual bool GetFirstEntry(wxString& str, long& index) const = 0;
 379
 380     /**
 381         Gets the first group.
 382
 383         @beginWxPythonOnly
 384         The wxPython version of this method returns a 3-tuple consisting of the
 385         continue flag, the value string, and the index for the next call.
 386         @endWxPythonOnly
 387     */
 388     virtual bool GetFirstGroup(wxString& str, long& index) const = 0;
 389
 390     /**
 391         Gets the next entry.
 392
 393         @beginWxPythonOnly
 394         The wxPython version of this method returns a 3-tuple consisting of the
 395         continue flag, the value string, and the index for the next call.
 396         @endWxPythonOnly
 397     */
 398     virtual bool GetNextEntry(wxString& str, long& index) const = 0;
 399
 400     /**
 401         Gets the next group.
 402
 403         @beginWxPythonOnly
 404         The wxPython version of this method returns a 3-tuple consisting of the
 405         continue flag, the value string, and the index for the next call.
 406         @endWxPythonOnly
 407     */
 408     virtual bool GetNextGroup(wxString& str, long& index) const = 0;
 409
 410     /**
 411         Get number of entries in the current group.
 412     */
 413     virtual size_t GetNumberOfEntries(bool bRecursive = false) const = 0;
 414
 415     /**
 416         Get number of entries/subgroups in the current group, with or without
 417         its subgroups.
 418     */
 419     virtual size_t GetNumberOfGroups(bool bRecursive = false) const = 0;
 420
 421     //@}
 422
 423
 424     enum EntryType
 425     {
 426         Type_Unknown,
 427         Type_String,
 428         Type_Boolean,
 429         Type_Integer,
 430         Type_Float
 431     };
 432
 433     /**
 434         @name Tests of Existence
 435     */
 436     //@{
 437
 438     /**
 439         @return @true if either a group or an entry with a given name exists.
 440     */
 441     bool Exists(const wxString& strName) const;
 442
 443     /**
 444         Returns the type of the given entry or @e Unknown if the entry doesn't
 445         exist. This function should be used to decide which version of Read()
 446         should be used because some of wxConfig implementations will complain
 447         about type mismatch otherwise: e.g., an attempt to read a string value
 448         from an integer key with wxRegConfig will fail.
 449     */
 450     virtual wxConfigBase::EntryType GetEntryType(const wxString& name) const;
 451
 452     /**
 453         @return @true if the entry by this name exists.
 454     */
 455     virtual bool HasEntry(const wxString& strName) const = 0;
 456
 457     /**
 458         @return @true if the group by this name exists.
 459     */
 460     virtual bool HasGroup(const wxString& strName) const = 0;
 461
 462     //@}
 463
 464
 465     /**
 466         @name Miscellaneous Functions
 467     */
 468     //@{
 469
 470     /**
 471         Returns the application name.
 472     */
 473     wxString GetAppName() const;
 474
 475     /**
 476         Returns the vendor name.
 477     */
 478     wxString GetVendorName() const;
 479
 480     //@}
 481
 482
 483     /**
 484         @name Key Access
 485
 486         See @ref configbase_keyaccess
 487     */
 488     //@{
 489
 490     /**
 491         Permanently writes all changes (otherwise, they're only written from
 492         object's destructor).
 493     */
 494     virtual bool Flush(bool bCurrentOnly = false) = 0;
 495
 496     /**
 497         Read a string from the key, returning @true if the value was read. If
 498         the key was not found, @a str is not changed.
 499     */
 500     bool Read(const wxString& key, wxString* str) const;
 501     /**
 502         Read a string from the key. The default value is returned if the key
 503         was not found.
 504
 505         @return @true if value was really read, @false if the default was used.
 506     */
 507     bool Read(const wxString& key, wxString* str,
 508               const wxString& defaultVal) const;
 509     /**
 510         Another version of Read(), returning the string value directly.
 511     */
 512     const wxString Read(const wxString& key,
 513                         const wxString& defaultVal) const;
 514     /**
 515         Reads a long value, returning @true if the value was found. If the
 516         value was not found, @a l is not changed.
 517     */
 518     bool Read(const wxString& key, long* l) const;
 519     /**
 520         Reads a long value, returning @true if the value was found. If the
 521         value was not found, @a defaultVal is used instead.
 522     */
 523     bool Read(const wxString& key, long* l,
 524               long defaultVal) const;
 525     /**
 526         Reads a double value, returning @true if the value was found. If the
 527         value was not found, @a d is not changed.
 528     */
 529     bool Read(const wxString& key, double* d) const;
 530     /**
 531         Reads a double value, returning @true if the value was found. If the
 532         value was not found, @a defaultVal is used instead.
 533     */
 534     bool Read(const wxString& key, double* d,
 535                      double defaultVal) const;
 536     /**
 537         Reads a bool value, returning @true if the value was found. If the
 538         value was not found, @a b is not changed.
 539     */
 540     bool Read(const wxString& key, bool* b) const;
 541     /**
 542         Reads a bool value, returning @true if the value was found. If the
 543         value was not found, @a defaultVal is used instead.
 544     */
 545     bool Read(const wxString& key, bool* d,
 546               bool defaultVal) const;
 547     /**
 548         Reads a binary block, returning @true if the value was found. If the
 549         value was not found, @a buf is not changed.
 550     */
 551     bool Read(const wxString& key, wxMemoryBuffer* buf) const;
 552     /**
 553         Reads a value of type T, for which function wxFromString() is defined,
 554         returning @true if the value was found. If the value was not found,
 555         @a value is not changed.
 556     */
 557     bool Read(const wxString& key, T* value) const;
 558     /**
 559         Reads a value of type T, for which function wxFromString() is defined,
 560         returning @true if the value was found. If the value was not found,
 561         @a defaultVal is used instead.
 562     */
 563     bool Read(const wxString& key, T* value,
 564               const T& defaultVal) const;
 565
 566     /**
 567         Reads a bool value from the key and returns it. @a defaultVal is
 568         returned if the key is not found.
 569     */
 570     bool ReadBool(const wxString& key, bool defaultVal) const;
 571
 572     /**
 573         Reads a double value from the key and returns it. @a defaultVal is
 574         returned if the key is not found.
 575     */
 576     double ReadDouble(const wxString& key, double defaultVal) const;
 577
 578     /**
 579         Reads a long value from the key and returns it. @a defaultVal is
 580         returned if the key is not found.
 581     */
 582     long ReadLong(const wxString& key, long defaultVal) const;
 583
 584     /**
 585         Reads a value of type T (for which the function wxFromString() must be
 586         defined) from the key and returns it. @a defaultVal is returned if the
 587         key is not found.
 588     */
 589     T ReadObject(const wxString& key, T const& defaultVal) const;
 590
 591     /**
 592         Writes the wxString value to the config file and returns @true on
 593         success.
 594     */
 595     bool Write(const wxString& key, const wxString& value);
 596     /**
 597         Writes the long value to the config file and returns @true on success.
 598     */
 599     bool Write(const wxString& key, long value);
 600     /**
 601         Writes the double value to the config file and returns @true on
 602         success.
 603     */
 604     bool Write(const wxString& key, double value);
 605     /**
 606         Writes the bool value to the config file and returns @true on success.
 607     */
 608     bool Write(const wxString& key, bool value);
 609     /**
 610         Writes the wxMemoryBuffer value to the config file and returns @true on
 611         success.
 612     */
 613     bool Write(const wxString& key, const wxMemoryBuffer& buf);
 614     /**
 615         Writes the specified value to the config file and returns @true on
 616         success. The function wxToString() must be defined for type @e T.
 617     */
 618     bool Write(const wxString& key, T const& buf);
 619
 620     //@}
 621
 622
 623     /**
 624         @name Rename Entries/Groups
 625
 626         These functions allow renaming entries or subgroups of the current
 627         group. They will return @false on error, typically because either the
 628         entry/group with the original name doesn't exist, because the
 629         entry/group with the new name already exists or because the function is
 630         not supported in this wxConfig implementation.
 631     */
 632     //@{
 633
 634     /**
 635         Renames an entry in the current group. The entries names (both the old
 636         and the new one) shouldn't contain backslashes, i.e. only simple names
 637         and not arbitrary paths are accepted by this function.
 638
 639         @return @false if @a oldName doesn't exist or if @a newName already
 640                 exists.
 641     */
 642     virtual bool RenameEntry(const wxString& oldName,
 643                              const wxString& newName) = 0;
 644
 645     /**
 646         Renames a subgroup of the current group. The subgroup names (both the
 647         old and the new one) shouldn't contain backslashes, i.e. only simple
 648         names and not arbitrary paths are accepted by this function.
 649
 650         @return @false if @a oldName doesn't exist or if @a newName already
 651                 exists.
 652     */
 653     virtual bool RenameGroup(const wxString& oldName,
 654                              const wxString& newName) = 0;
 655
 656     //@}
 657
 658
 659     /**
 660         @name Delete Entries/Groups
 661
 662         These functions delete entries and/or groups of entries from the config
 663         file. DeleteAll() is especially useful if you want to erase all traces
 664         of your program presence: for example, when you uninstall it.
 665     */
 666     //@{
 667
 668     /**
 669         Delete the whole underlying object (disk file, registry key, ...).
 670         Primarly for use by uninstallation routine.
 671     */
 672     virtual bool DeleteAll() = 0;
 673
 674     /**
 675         Deletes the specified entry and the group it belongs to if it was the
 676         last key in it and the second parameter is @true.
 677     */
 678     virtual bool DeleteEntry(const wxString& key,
 679                              bool bDeleteGroupIfEmpty = true) = 0;
 680
 681     /**
 682         Delete the group (with all subgroups). If the current path is under the
 683         group being deleted it is changed to its deepest still existing
 684         component. E.g. if the current path is @c "/A/B/C/D" and the group @c C
 685         is deleted, the path becomes @c "/A/B".
 686     */
 687     virtual bool DeleteGroup(const wxString& key) = 0;
 688
 689     //@}
 690
 691
 692     /**
 693         @name Options
 694
 695         Some aspects of wxConfigBase behaviour can be changed during run-time.
 696         The first of them is the expansion of environment variables in the
 697         string values read from the config file: for example, if you have the
 698         following in your config file:
 699
 700         @code
 701         # config file for my program
 702         UserData = $HOME/data
 703
 704         # the following syntax is valud only under Windows
 705         UserData = %windir%\\data.dat
 706         @endcode
 707
 708         The call to Read("UserData") will return something like
 709         @c "/home/zeitlin/data" on linux for example.
 710
 711         Although this feature is very useful, it may be annoying if you read a
 712         value which containts '$' or '%' symbols (% is used for environment
 713         variables expansion under Windows) which are not used for environment
 714         variable expansion. In this situation you may call
 715         SetExpandEnvVars(@false) just before reading this value and
 716         SetExpandEnvVars(@true) just after. Another solution would be to prefix
 717         the offending symbols with a backslash.
 718     */
 719     //@{
 720
 721     /**
 722         Returns @true if we are expanding environment variables in key values.
 723     */
 724     bool IsExpandingEnvVars() const;
 725
 726     /**
 727         Returns @true if we are writing defaults back to the config file.
 728     */
 729     bool IsRecordingDefaults() const;
 730
 731     /**
 732         Determine whether we wish to expand environment variables in key
 733         values.
 734     */
 735     void SetExpandEnvVars(bool bDoIt = true);
 736
 737     /**
 738         Sets whether defaults are recorded to the config file whenever an
 739         attempt to read the value which is not present in it is done.
 740
 741         If on (default is off) all default values for the settings used by the
 742         program are written back to the config file. This allows the user to
 743         see what config options may be changed and is probably useful only for
 744         wxFileConfig.
 745     */
 746     void SetRecordDefaults(bool bDoIt = true);
 747
 748     //@}
 749
 750
 751     /**
 752         Create a new config object: this function will create the "best"
 753         implementation of wxConfig available for the current platform, see
 754         comments near the definition of wxCONFIG_WIN32_NATIVE for details. It
 755         returns the created object and also sets it as the current one.
 756     */
 757     static wxConfigBase* Create();
 758
 759     /**
 760         Calling this function will prevent @e Get() from automatically creating
 761         a new config object if the current one is @NULL. It might be useful to
 762         call it near the program end to prevent "accidental" creation of a new
 763         config object.
 764     */
 765     static void DontCreateOnDemand();
 766
 767     /**
 768         Get the current config object. If there is no current object and
 769         @a CreateOnDemand is @true, this creates one (using Create()) unless
 770         DontCreateOnDemand() was called previously.
 771     */
 772     static wxConfigBase* Get(bool CreateOnDemand = true);
 773
 774     /**
 775         Sets the config object as the current one, returns the pointer to the
 776         previous current object (both the parameter and returned value may be
 777         @NULL).
 778     */
 779     static wxConfigBase* Set(wxConfigBase* pConfig);
 780 };
 781