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To include the definitions of the module's classes, use the following directive: \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 0 To link against the module, add this line to your \l qmake \c .pro file: \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 1 \note These classes are part of the \l{Open Source Versions of Qt} and \l{Qt Commercial Editions}{Qt Full Framework Edition} for commercial users. \section1 Topics \tableofcontents \section1 Overview The Qt help system includes tools for generating and viewing Qt help files. In addition it provides classes for accessing help contents programatically to be able to integrate online help into Qt applications. The actual help data, meaning the table of contents, index keywords or html documents, is contained in Qt compressed help files. So, one such a help file represents usually one manual or documentation set. Since most products are more comprehensive and consist of a number of tools, one manual is rarely enough. Instead, more manuals which should be accessible at the same time, exist. Ideally, it should also be possible to reference certain points of interest of one manual to another. Therefore, the Qt help system operates on help collection files which include any number of compressed help files. However, having collection files to merge many documentation sets may lead to some problems. For example, one index keyword may be defined in different documentations. So, when only seeing it in the index and activating it, you cannot be sure that the expected documentation will be shown. Therefore, the Qt help system offers the possibiltiy to filter the help contents after certain attributes. This requires however, that the attributes have been assigned to the help contents before the generation of the compressed help file. As already mentioned, the Qt compressed help file contains all data, so there is no need any longer to ship all single html files. Instead, only the compressed help file and optionally the collection file has to be distributed. The collection file is optional since any existing collection file, e.g. from an older release could be used. So, in general, there are four files interacting with the help system, two used for generating Qt help and two meant for distribution: \table \header \o Name \o Extension \o Brief Description \row \o \l {Qt Help Project} \o .qhp \o The input file for the help generator consisting of the table of contents, indices and references to the actual documentation files (*.html); it also defines a unique namespace for the documentation. \row \o Qt Compressed Help \o .qch \o The output file of the help generator. This binary file contains all information specified in the help project file along with all compressed documentation files. \row \o \l {Qt Help Collection Project} \o .qhcp \o The input file for the help collection generator. It contains references to compressed help files which should be included in the collection; it also may contain other information for customizing Qt Assistant. \row \o Qt Help Collection \o .qhc \o The output of the help collection generator. This is the file QHelpEngine operates on. It contains references to any number of compressed help files as well as additional information, such as custom filters. \endtable \section1 Generating Qt Help Building help files for the Qt help system assumes that the html documentation files already exist, i.e. the Qt help system does not offer the possibility to create html files like e.g. Doxygen. Once the html documentents are in place, a \l {Qt Help Project} file has to be created. After specifying all relevant information in this file, it needs to be compiled by calling: \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 2 The file 'doc.qch' contains then all html files in compressed form along with the table of contents and index keywords. To test if the generated file is correct, open Qt Assistant and install the file via the Settings|Documentation page. \target Qt Help Collection Project \section2 Creating a Qt Help Collection The first step is to create a Qt Help Collection Project file. Since a Qt help collection stores primarily references to compressed help files, the project 'mycollection.qhcp' file looks unsurprisingly simple: \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 3 For actually creating the collection file call: \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 4 Instead of running two tools, one for generating the compressed help and one for generating the collection file, it is also possible to just run the qcollectiongenerator tool with a slightly modified project file instructing the generator to create the compressed help first. \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 5 Of course, it is possible to specify more than one file in the 'generate' or 'register' section, so any number of compressed help files can be generated and registered in one go. \section1 Using Qt Help Accessing the help contents can be done in two ways: Using Qt Assistant as documentation browser or using the QHelpEngine API for embedding the help contents directly in an application. \section2 Using Qt Assistant \QA operates on a collection file which can be specified before start up. If no collection file is given, a default one will be created and used. In either case, it is possible to register any Qt compressed help file and access the help contents. When using Assistant as the help browser for an application, it would be desirable that it can be customized to fit better to the application and doesn't look like an independent, standalone help browser. To achieve this, several additional properties can be set in an Qt help collection file, to change e.g. the title or application icon of Qt Assistant. For more information on this topic have a look at the \l{assistant-manual.html} {Qt Assistant manual}. \section2 Using QHelpEngine API Instead of showing the help in an external application like the Qt Assistant, it is also possible to embed the online help in the application. The contents can then be retrieved via the QHelpEngine class and can be displayed in nearly any form. Showing it in a QTextBrowser is probably the most common way, but embedding it in What's This help is also perfectly possible. Retrieving help data from the file engine does not involve a lot of code. The first step is to create an instance of the help engine. Then we ask the engine for the links assigned to the identifier, in this case "MyDialog::ChangeButton". If a link was found, meaning at least one help document exists to this topic, we get the actual help contents by calling fileData() and display the document to the user. \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 6 For further information on how to use the API, have a look at the QHelpEngine class reference. \section1 License Information The QtHelp module uses the CLucene indexing library to provide full-text searching capabilities for Qt Assistant and applications that use the features of QtHelp. Qt Commercial Edition licensees that wish to distribute applications that use these features of the QtHelp module need to be aware of their obligations under the GNU Lesser General Public License (LGPL). Developers using the Open Source Edition can choose to redistribute the module under the appropriate version of the GNU LGPL; version 2.1 for applications and libraries licensed under the GNU GPL version 2, or version 3 for applications and libraries licensed under the GNU GPL version 3. \legalese Copyright (C) 2003-2006 Ben van Klinken and the CLucene Team \BR Changes are Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA \endlegalese */ /*! \page qthelpproject.html \title Qt Help Project A Qt help project collects all data necessary to generate a compressed help file. Along with the actual help data, like the table of contents, index keywords and help documents, it contains some extra information like a namespace to identify the help file. One help project stands for one documentation, e.g. the Qt Assistant manual. \section1 Qt Help Project File Format The file format is XML based. For a better understanding of the format we'll discuss the following example: \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 7 \section2 Namespace To enable the QHelpEngine to retrieve the proper documentation to a given link, every documentation set has to have a unique identifier. A unique identifier makes is also possible for the help collection to keep track of a documentation set without relying on its file name. The Qt help system uses a namespace as identifier which is defined by the mandatory namespace tags. In the example above, the namespace is "mycompany.com.myapplication.1_0". \target Virtual Folders \section2 Virtual Folders Having a namespace for every documentation naturally means that the documentation sets are quite separated. From the help engines point of view this is beneficial, but from the documentors view it is often desirable to cross reference certain topic from one manual to another without having to specify absolute links. To solve this problem, the help system introduced the concept of virtual folders. A virtual folder will become the root directory of all files referenced in a compressed help file. When two documentations share the same virtual folder, they can use relative paths when defining hyperlinks pointing to the other documentation. If a file is contained in both documentations or manuals, the one from the current manual has precedence over the other. \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 8 The above example specifies 'doc' as virtual folder. If another manual, e.g. for a small helper tool for 'My Application' specifies the same folder, it is sufficient to write 'doc.html#section1' to reference the first section in the 'My Application' manual. The virtual folder tag is mandatory and the folder must not contain any '/'. \target Custom Filters \section2 Custom Filters Next in the Qt help project file are the optional definitions of custom filters. A custom filter contains a list of filter attributes which will be used later to display only the documentation which has all those attributes assigned to. So, when setting the current filter in the QHelpEngine to "My Application 1.0" only the documentation which has "myapp" and "1.0" set as filter attributes will be shown. \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 9 It is possible to define any number of custom filters in a help project file. Important to know is, that the filter attributes have not to be specified in the same project file; they can be defined in any other help file. The definition of a filter attributes takes place by specifying them in a filter section. \target Filter Section \section2 Filter Section A filter section contains the actual documentation. One Qt help project file may contain more than one filter sections. Every filter section consists of four parts, the filter attributes section, the table of contents, the keywords and the files list. In theory all parts are optional but not specifying anything there will result in an empty documentation. \section3 Filter Attributes Every filter section should have filter attributes assigned to it, to enable documentation filtering. If no filter attribute is defined, the documentation will only be shown if no filtering occurs, meaning the current custom filter in the QHelpEngine does not contain any filter attributes. \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 10 In this case, the filter attributes 'myapp' and '1.0' are assigned to the filter section, i.e. all contents specified in this section will only be shown if the current custom filter has 'myapp' or '1.0' or both as filter attributes. \section3 Table of contents \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 11 One section tag represents one item in the table of contents. The sections can be nested to any degree, but from a users perspective it shouldn't be more than four or five levels. A section is defined by its title and reference. The reference, like all file references in a Qt help project file are relative to the help project file itself. \section3 Keywords \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 12 The keyword section lists all keywords of this filter section. A keyword consists basically of a name and a file reference. If the attribute 'name' is used then the keyword specified there will appear in the visible index, i.e. it will be accessible through the QHelpIndexModel. If 'id' is used, the keyword does not appear in the index and is only accessible via the linksForIdentifier() function of the QHelpEngineCore. 'name' and 'id' can be specified at the same time. \section3 Files \snippet doc/src/snippets/code/doc_src_qthelp.qdoc 13 Finally, the actual documentation files have to be listed. Make sure that all files neccessary to display the help are mentioned, i.e. stylesheets or similar files need to be there as well. All listed files will be compressed and written to the Qt compressed help file. So, in the end, one single Qt help file contains all documentation files along with the contents and indices. */