wxWidgets/interface/mimetype.h

/////////////////////////////////////////////////////////////////////////////
// Name:        mimetype.h
// Purpose:     documentation for wxMimeTypesManager class
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////

/**
    @class wxMimeTypesManager
    @wxheader{mimetype.h}
    
    This class allows the application to retrieve the information about all known
    MIME types from a system-specific location and the filename extensions to the
    MIME types and vice versa. After initialization the functions
    wxMimeTypesManager::GetFileTypeFromMimeType 
    and wxMimeTypesManager::GetFileTypeFromExtension 
    may be called: they will return a wxFileType object which
    may be further queried for file description, icon and other attributes.
    
    @b Windows: MIME type information is stored in the registry and no additional
    initialization is needed.
    
    @b Unix: MIME type information is stored in the files mailcap and mime.types
    (system-wide) and .mailcap and .mime.types in the current user's home directory:
    all of these files are searched for and loaded if found by default. However,
    additional functions 
    wxMimeTypesManager::ReadMailcap and 
    wxMimeTypesManager::ReadMimeTypes are
    provided to load additional files.
    
    If GNOME or KDE desktop environment is installed, then wxMimeTypesManager 
    gathers MIME information from respective files (e.g. .kdelnk files under KDE).
    
    NB: Currently, wxMimeTypesManager is limited to reading MIME type information
    but it will support modifying it as well in future versions.
    
    @library{wxbase}
    @category{misc}
    
    @seealso
    wxFileType
*/
class wxMimeTypesManager 
{
public:
    /**
        Constructor puts the object in the "working" state, no additional initialization
        are needed - but @ref init() ReadXXX may be used to load
        additional mailcap/mime.types files.
    */
    wxMimeTypesManager();

    /**
        Destructor is not virtual, so this class should not be derived from.
    */
    ~wxMimeTypesManager();

    /**
        This function may be used to provide hard-wired fallbacks for the MIME types
        and extensions that might not be present in the system MIME database.
        
        Please see the typetest sample for an example of using it.
    */
    void AddFallbacks(const wxFileTypeInfo * fallbacks);

    /**
        NB: You won't normally need to use more than one wxMimeTypesManager object in a
        program.
        
        @ref ctor() wxMimeTypesManager
        
        @ref dtor() ~wxMimeTypesManager
    */


    /**
        Gather information about the files with given extension and return the
        corresponding wxFileType object or @NULL if the extension
        is unknown.
        
        The @e extension parameter may have, or not, the leading dot, if it has it,
        it is stripped automatically. It must not however be empty.
    */
    wxFileType* GetFileTypeFromExtension(const wxString& extension);

    /**
        Gather information about the files with given MIME type and return the
        corresponding wxFileType object or @NULL if the MIME type
        is unknown.
    */
    wxFileType* GetFileTypeFromMimeType(const wxString& mimeType);

    /**
        All of these functions are static (i.e. don't need a wxMimeTypesManager object
        to call them) and provide some useful operations for string representations of
        MIME types. Their usage is recommended instead of directly working with MIME
        types using wxString functions.
        
        IsOfType()
    */


    /**
        @b Unix: These functions may be used to load additional files (except for the
        default ones which are loaded automatically) containing MIME
        information in either mailcap(5) or mime.types(5) format.
        
        ReadMailcap()
        
        ReadMimeTypes()
        
        AddFallbacks()
    */


    /**
        This function returns @true if either the given @e mimeType is exactly the
        same as @e wildcard or if it has the same category and the subtype of
        @e wildcard is '*'. Note that the '*' wildcard is not allowed in
        @e mimeType itself.
        
        The comparison don by this function is case insensitive so it is not
        necessary to convert the strings to the same case before calling it.
    */
    bool IsOfType(const wxString& mimeType, const wxString& wildcard);

    /**
        These functions are the heart of this class: they allow to find a @ref
        overview_wxfiletype "file type" object
        from either file extension or MIME type.
        If the function is successful, it returns a pointer to the wxFileType object
        which @b must be deleted by the caller, otherwise @NULL will be returned.
        
        GetFileTypeFromMimeType()
        
        GetFileTypeFromExtension()
    */


    /**
        Load additional file containing information about MIME types and associated
        information in mailcap format. See metamail(1) and mailcap(5) for more
        information.
        
        @e fallback parameter may be used to load additional mailcap files without
        overriding the settings found in the standard files: normally, entries from
        files loaded with ReadMailcap will override the entries from files loaded
        previously (and the standard ones are loaded in the very beginning), but this
        will not happen if this parameter is set to @true (default is @false).
        
        The return value is @true if there were no errors in the file or @false
        otherwise.
    */
    bool ReadMailcap(const wxString& filename, bool fallback = @false);

    /**
        Load additional file containing information about MIME types and associated
        information in mime.types file format. See metamail(1) and mailcap(5) for more
        information.
        
        The return value is @true if there were no errors in the file or @false
        otherwise.
    */
    bool ReadMimeTypes(const wxString& filename);
};


/**
    @class wxFileType
    @wxheader{mimetype.h}
    
    This class holds information about a given @e file type. File type is the same
    as
    MIME type under Unix, but under Windows it corresponds more to an extension than
    to MIME type (in fact, several extensions may correspond to a file type). This
    object may be created in several different ways: the program might know the file
    extension and wish to find out the corresponding MIME type or, conversely, it
    might want to find the right extension for the file to which it writes the
    contents of given MIME type. Depending on how it was created some fields may be
    unknown so the return value of all the accessors @b must be checked: @false
    will be returned if the corresponding information couldn't be found.
    
    The objects of this class are never created by the application code but are
    returned by wxMimeTypesManager::GetFileTypeFromMimeType and 
    wxMimeTypesManager::GetFileTypeFromExtension methods.
    But it is your responsibility to delete the returned pointer when you're done
    with it!
    
    A brief reminder about what the MIME types are (see the RFC 1341 for more
    information): basically, it is just a pair category/type (for example,
    "text/plain") where the category is a basic indication of what a file is.
    Examples of categories are "application", "image", "text", "binary", and
    type is a precise definition of the document format: "plain" in the example
    above means just ASCII text without any formatting, while "text/html" is the
    HTML document source.
    
    A MIME type may have one or more associated extensions: "text/plain" will
    typically correspond to the extension ".txt", but may as well be associated with
    ".ini" or ".conf".
    
    @library{wxbase}
    @category{FIXME}
    
    @seealso
    wxMimeTypesManager
*/
class wxFileType 
{
public:
    /**
        The default constructor is private because you should never create objects of
        this type: they are only returned by wxMimeTypesManager methods.
    */
    wxFileType();

    /**
        The destructor of this class is not virtual, so it should not be derived from.
    */
    ~wxFileType();

    /**
        This function is primarily intended for GetOpenCommand and GetPrintCommand
        usage but may be also used by the application directly if, for example, you want
        to use some non-default command to open the file.
        
        The function replaces all occurrences of
        
        
        format specification
        
        
        with
        
        %s
        
        
        the full file name
        
        %t
        
        
        the MIME type
        
        %{param}
        
        
        the value of the parameter @e param
        
        using the MessageParameters object you pass to it.
        
        If there is no '%s' in the command string (and the string is not empty), it is
        assumed that the command reads the data on stdin and so the effect is the same
        as " %s" were appended to the string.
        
        Unlike all other functions of this class, there is no error return for this
        function.
    */
    static wxString ExpandCommand(const wxString& command,
                                  MessageParameters& params);

    /**
        If the function returns @true, the string pointed to by @e desc is filled
        with a brief description for this file type: for example, "text document" for
        the "text/plain" MIME type.
    */
    bool GetDescription(wxString* desc);

    /**
        If the function returns @true, the array @e extensions is filled
        with all extensions associated with this file type: for example, it may
        contain the following two elements for the MIME type "text/html" (notice the
        absence of the leading dot): "html" and "htm".
        
        @b Windows: This function is currently not implemented: there is no
        (efficient) way to retrieve associated extensions from the given MIME type on
        this platform, so it will only return @true if the wxFileType object was
        created
        by wxMimeTypesManager::GetFileTypeFromExtension 
        function in the first place.
    */
    bool GetExtensions(wxArrayString& extensions);

    /**
        If the function returns @true, the @c iconLoc is filled with the
        location of the icon for this MIME type. A wxIcon may be
        created from @e iconLoc later.
        
        @b Windows: The function returns the icon shown by Explorer for the files of
        the specified type.
        
        @b Mac: This function is not implemented and always returns @false.
        
        @b Unix: MIME manager gathers information about icons from GNOME
        and KDE settings and thus GetIcon's success depends on availability
        of these desktop environments.
    */
    bool GetIcon(wxIconLocation * iconLoc);

    /**
        If the function returns @true, the string pointed to by @e mimeType is filled
        with full MIME type specification for this file type: for example, "text/plain".
    */
    bool GetMimeType(wxString* mimeType);

    /**
        Same as GetMimeType() but returns array of MIME
        types. This array will contain only one item in most cases but sometimes,
        notably under Unix with KDE, may contain more MIME types. This happens when
        one file extension is mapped to different MIME types by KDE, mailcap and
        mime.types.
    */
    bool GetMimeType(wxArrayString& mimeTypes);

    //@{
    /**
        With the first version of this method, if the @true is returned, the
        string pointed to by @e command is filled with the command which must be
        executed (see wxExecute) in order to open the file of the
        given type. In this case, the name of the file as well as any other parameters
        is retrieved from MessageParameters() 
        class.
        
        In the second case, only the filename is specified and the command to be used
        to open this kind of file is returned directly. An empty string is returned to
        indicate that an error occurred (typically meaning that there is no standard way
        to open this kind of files).
    */
    bool GetOpenCommand(wxString* command,
                        MessageParameters& params);
        wxString GetOpenCommand(const wxString& filename);
    //@}

    /**
        If the function returns @true, the string pointed to by @e command is filled
        with the command which must be executed (see wxExecute) in
        order to print the file of the given type. The name of the file is
        retrieved from MessageParameters() class.
    */
    bool GetPrintCommand(wxString* command,
                         MessageParameters& params);

    /**
        One of the most common usages of MIME is to encode an e-mail message. The MIME
        type of the encoded message is an example of a @e message parameter. These
        parameters are found in the message headers ("Content-XXX"). At the very least,
        they must specify the MIME type and the version of MIME used, but almost always
        they provide additional information about the message such as the original file
        name or the charset (for the text documents).
        
        These parameters may be useful to the program used to open, edit, view or print
        the message, so, for example, an e-mail client program will have to pass them to
        this program. Because wxFileType itself can not know about these parameters,
        it uses MessageParameters class to query them. The default implementation only
        requires the caller to provide the file name (always used by the program to be
        called - it must know which file to open) and the MIME type and supposes that
        there are no other parameters. If you wish to supply additional parameters, you
        must derive your own class from MessageParameters and override GetParamValue()
        function, for example:
        Now you only need to create an object of this class and pass it to, for example,
        GetOpenCommand() like this:
        @b Windows: As only the file name is used by the program associated with the
        given extension anyhow (but no other message parameters), there is no need to
        ever derive from MessageParameters class for a Windows-only program.
    */
};