ccdcde00d9
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@15178 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
147 lines
4.3 KiB
TeX
147 lines
4.3 KiB
TeX
\subsection{Tag Handlers}\label{handlers}
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The wxHTML library provides architecture of pluggable {\it tag handlers}.
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Tag handler is class that understands particular HTML tag (or tags) and is
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able to interpret it.
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\helpref{wxHtmlWinParser}{wxhtmlwinparser} has static table of {\bf modules}.
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Each module contains one or more tag handlers. Each time a new wxHtmlWinParser
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object is constructed all modules are scanned and handlers are added
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to wxHtmlParser's list of available handlers (note: wxHtmlParser's list
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is non-static).
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\wxheading{How it works}
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Common tag handler's \helpref{HandleTag}{wxhtmltaghandlerhandletag} method
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works in four steps:
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\begin{enumerate}\itemsep=0pt
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\item Save state of parent parser into local variables
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\item Change parser state according to tag's params
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\item Parse text between the tag and paired ending tag (if present)
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\item Restore original parser state
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\end{enumerate}
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See \helpref{wxHtmlWinParser}{wxhtmlwinparser} for methods for modifying
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parser's state. In general you can do things like opening/closing containers,
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changing colors, fonts etc.
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\wxheading{Providing own tag handlers}
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You should create new .cpp file and place following lines into it:
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\begin{verbatim}
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#include <mod_templ.h>
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#include <forcelink.h>
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FORCE_LINK_ME(yourmodulefilenamewithoutcpp)
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\end{verbatim}
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Then you must define handlers and one module.
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\wxheading{Tag handlers}
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The handler is derived from \helpref{wxHtmlWinTagHandler}{wxhtmlwintaghandler}
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(or directly from \helpref{wxHtmlTagHandler}{wxhtmltaghandler})
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You can use set of macros to define the handler (see src/html/m\_*.cpp files
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for details). Handler definition must start with {\bf TAG\_HANDLER\_BEGIN} macro
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and end with {\bf TAG\_HANDLER\_END} macro. I strongly recommend to have a look
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at {\it include/wxhtml/mod\_templ.h} file. Otherwise you won't understand
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the structure of macros. See macros reference:
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{\bf TAG\_HANDLER\_BEGIN}({\it name}, {\it tags})
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Starts handler definition. {\it name} is handler identifier (in fact
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part of class name), {\it tags} is string containing list of tags
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supported by this handler (in uppercase). This macro derives new class from
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wxHtmlWinTagHandler and implements it is
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\helpref{GetSupportedTags}{wxhtmltaghandlergetsupportedtags} method.
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Example: TAG\_HANDLER\_BEGIN(FONTS, "B,I,U,T")
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{\bf TAG\_HANDLER\_VARS}
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This macro starts block of variables definitions. (Variables are identical
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to class attributes.) Example:
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\begin{verbatim}
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TAG_HANDLER_BEGIN(VARS_ONLY, "CRAZYTAG")
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TAG_HANDLER_VARS
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int my_int_var;
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wxString something_else;
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TAG_HANDLER_END(VARS_ONLY)
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\end{verbatim}
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This macro is used only in rare cases.
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{\bf TAG\_HANDLER\_CONSTR}({\it name})
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This macro supplies object constructor. {\it name} is same name as the one
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from TAG\_HANDLER\_BEGIN macro. Body of constructor follow after
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this macro (you must use { and } ). Example:
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\begin{verbatim}
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TAG_HANDLER_BEGIN(VARS2, "CRAZYTAG")
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TAG_HANDLER_VARS
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int my_int_var;
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TAG_HANDLER_CONSTR(vars2)
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{ // !!!!!!
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my_int_var = 666;
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} // !!!!!!
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TAG_HANDLER_END(VARS2)
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\end{verbatim}
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Never used in wxHTML :-)
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{\bf TAG\_HANDLER\_PROC}({\it varib})
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This is very important macro. It defines \helpref{HandleTag}{wxhtmltaghandlerhandletag}
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method. {\it varib} is name of parameter passed to the method, usually
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{\it tag}. Body of method follows after this macro.
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Note than you must use { and } ! Example:
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\begin{verbatim}
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TAG_HANDLER_BEGIN(TITLE, "TITLE")
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TAG_HANDLER_PROC(tag)
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{
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printf("TITLE found...\n");
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}
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TAG_HANDLER_END(TITLE)
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\end{verbatim}
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{\bf TAG\_HANDLER\_END}({\it name})
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Ends definition of tag handler {\it name}.
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\wxheading{Tags Modules}
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You can use set of 3 macros TAGS\_MODULE\_BEGIN, TAGS\_MODULE\_ADD and
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TAGS\_MODULE\_END to inherit new module from
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\helpref{wxHtmlTagsModule}{wxhtmltagsmodule} and to create instance of it.
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See macros reference:
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{\bf TAGS\_MODULE\_BEGIN}({\it modname})
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Begins module definition. {\it modname} is part of class name and must
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be unique.
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{\bf TAGS\_MODULE\_ADD}({\it name})
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Adds the handler to this module. {\it name} is the identifier from
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TAG\_HANDLER\_BEGIN.
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{\bf TAGS\_MODULE\_END}({\it modname})
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Ends the definition of module.
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{\bf Example:}
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\begin{verbatim}
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TAGS_MODULE_BEGIN(Examples)
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TAGS_MODULE_ADD(VARS_ONLY)
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TAGS_MODULE_ADD(VARS2)
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TAGS_MODULE_ADD(TITLE)
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TAGS_MODULE_END(Examples)
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\end{verbatim}
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