wxWidgets/interface/wx/html/htmlpars.h

/////////////////////////////////////////////////////////////////////////////
// Name:        html/htmlpars.h
// Purpose:     interface of wxHtmlTagHandler
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////

/**
    @class wxHtmlTagHandler


    @library{wxhtml}
    @category{html}

    @see Overview(), wxHtmlTag
*/
class wxHtmlTagHandler : public wxObject
{
public:
    /**
        Constructor.
    */
    wxHtmlTagHandler();

    /**
        Returns list of supported tags. The list is in uppercase and tags
        are delimited by ','. Example : @c "I,B,FONT,P"
    */
    virtual wxString GetSupportedTags();

    /**
        This is the core method of each handler. It is called each time
        one of supported tags is detected. @a tag contains all necessary
        info (see wxHtmlTag for details).
        
        @return @true if ParseInner was called, @false otherwise.
    */
    virtual bool HandleTag(const wxHtmlTag& tag);

    /**
        This method calls parser's wxHtmlParser::DoParsing method
        for the string between this tag and the paired ending tag:
        
        In this example, a call to ParseInner (with @a tag pointing to A tag)
        will parse 'Hello, world!'.
    */
    void ParseInner(const wxHtmlTag& tag);

    /**
        Assigns @a parser to this handler. Each @b instance of handler
        is guaranteed to be called only from the parser.
    */
    virtual void SetParser(wxHtmlParser parser);

    /**
        @b wxHtmlParser* m_Parser
        This attribute is used to access parent parser. It is protected so that
        it can't be accessed by user but can be accessed from derived classes.
    */
};



/**
    @class wxHtmlParser

    Classes derived from this handle the @b generic parsing of HTML documents: it
    scans
    the document and divide it into blocks of tags (where one block
    consists of beginning and ending tag and of text between these
    two tags).

    It is independent from wxHtmlWindow and can be used as stand-alone parser
    (Julian Smart's idea of speech-only HTML viewer or wget-like utility -
    see InetGet sample for example).

    It uses system of tag handlers to parse the HTML document. Tag handlers
    are not statically shared by all instances but are created for each
    wxHtmlParser instance. The reason is that the handler may contain
    document-specific temporary data used during parsing (e.g. complicated
    structures like tables).

    Typically the user calls only the wxHtmlParser::Parse method.

    @library{wxhtml}
    @category{html}

    @see @ref overview_cells "Cells Overview", @ref overview_handlers "Tag Handlers
    Overview", wxHtmlTag
*/
class wxHtmlParser
{
public:
    /**
        Constructor.
    */
    wxHtmlParser();

    /**
        This may (and may not) be overwritten in derived class.
        This method is called each time new tag is about to be added.
        @a tag contains information about the tag. (See wxHtmlTag
        for details.)
        Default (wxHtmlParser) behaviour is this:
        First it finds a handler capable of handling this tag and then it calls
        handler's HandleTag method.
    */
    virtual void AddTag(const wxHtmlTag& tag);

    /**
        Adds handler to the internal list ( hash table) of handlers. This
        method should not be called directly by user but rather by derived class'
        constructor.
        This adds the handler to this @b instance of wxHtmlParser, not to
        all objects of this class! (Static front-end to AddTagHandler is provided
        by wxHtmlWinParser).
        All handlers are deleted on object deletion.
    */
    virtual void AddTagHandler(wxHtmlTagHandler handler);

    /**
        Must be overwritten in derived class.
        This method is called by DoParsing()
        each time a part of text is parsed. @a txt is NOT only one word, it is
        substring of input. It is not formatted or preprocessed (so white spaces are
        unmodified).
    */
    virtual void AddWord(const wxString& txt);

    //@{
    /**
        Parses the m_Source from begin_pos to end_pos-1.
        (in noparams version it parses whole m_Source)
    */
    void DoParsing(int begin_pos, int end_pos);
    void DoParsing();
    //@}

    /**
        This must be called after DoParsing().
    */
    virtual void DoneParser();

    /**
        Returns pointer to the file system. Because each tag handler has
        reference to it is parent parser it can easily request the file by
        calling
    */
    wxFileSystem* GetFS() const;

    /**
        Returns product of parsing. Returned value is result of parsing
        of the document. The type of this result depends on internal
        representation in derived parser (but it must be derived from wxObject!).
        See wxHtmlWinParser for details.
    */
    virtual wxObject* GetProduct();

    /**
        Returns pointer to the source being parsed.
    */
    wxString* GetSource();

    /**
        Setups the parser for parsing the @a source string. (Should be overridden
        in derived class)
    */
    virtual void InitParser(const wxString& source);

    /**
        Opens given URL and returns @c wxFSFile object that can be used to read data
        from it. This method may return @NULL in one of two cases: either the URL doesn't
        point to any valid resource or the URL is blocked by overridden implementation
        of @e OpenURL in derived class.
        
        @param type
            Indicates type of the resource. Is one of:
        
        
        
        
        
        
            wxHTML_URL_PAGE
        
        
        
        
            Opening a HTML page.
        
        
        
        
        
            wxHTML_URL_IMAGE
        
        
        
        
            Opening an image.
        
        
        
        
        
            wxHTML_URL_OTHER
        
        
        
        
            Opening a resource that doesn't fall into
            any other category.
        @param url
            URL being opened.
    */
    virtual wxFSFile* OpenURL(wxHtmlURLType type,
                              const wxString& url);

    /**
        Proceeds parsing of the document. This is end-user method. You can simply
        call it when you need to obtain parsed output (which is parser-specific)
        The method does these things:
         calls @ref initparser() InitParser(source)
         calls DoParsing()
         calls GetProduct()
         calls DoneParser()
         returns value returned by GetProduct
        You shouldn't use InitParser, DoParsing, GetProduct or DoneParser directly.
    */
    wxObject* Parse(const wxString& source);

    /**
        Restores parser's state before last call to
        PushTagHandler().
    */
    void PopTagHandler();

    /**
        Forces the handler to handle additional tags
        (not returned by wxHtmlTagHandler::GetSupportedTags).
        The handler should already be added to this parser.
        
        @param handler
            the handler
        @param tags
            List of tags (in same format as GetSupportedTags's return value). The parser
            will redirect these tags to handler (until call to PopTagHandler).
    */
    void PushTagHandler(wxHtmlTagHandler* handler,
                        const wxString& tags);

    /**
        Sets the virtual file system that will be used to request additional
        files. (For example @c IMG tag handler requests wxFSFile with the
        image data.)
    */
    void SetFS(wxFileSystem fs);

    /**
        Call this function to interrupt parsing from a tag handler. No more tags
        will be parsed afterward. This function may only be called from
        Parse() or any function called
        by it (i.e. from tag handlers).
    */
    virtual void StopParsing();
};