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/*!

    \example help/simpletextviewer

    \title Simple Text Viewer Example

    The Simple Text Viewer example shows how to use \QA as a customized

    help viewer for your application.

    This is done in two stages. Firstly, documentation is created and \QA

    is customized; secondly, the functionality to launch and control

    \QA is added to the application.

    \image simpletextviewer-example.png

    The Simple Text Viewer application lets the user select and view

    existing files.

    The application provides its own custom documentation that is

    available from the \gui Help menu in the main window's menu bar

    or by clicking the \gui Help button in the application's find file

    dialog.

    The example consists of four classes:

    \list

        \o \c Assistant provides functionality to launch \QA.

        \o \c MainWindow is the main application window.

        \o \c FindFileDialog allows the user to search for

           files using wildcard matching.

        \o \c TextEdit provides a rich text browser that makes

           sure that images referenced in HTML documents are

           displayed properly.

    \endlist

    Note that we will only comment on the parts of the implementation

    that are relevant to the main issue, that is making Qt Assistant

    act as a customized help viewer for our Simple Text Viewer

    application.

    \section1 Creating Documentation and Customizing \QA

    How to create the actual documentation in the form of HTML pages is

    not in the scope of this example. In general, HTML pages can either

    be written by hand or generated with the help of documentation tools

    like qdoc or Doxygen. For the purposes of this example we assume that

    the HTML files have already been created. So, the only thing that

    remains to be done is to tell \QA how to structure and display the

    help information.

    \section2 Organizing Documentation for \QA

    Plain HTML files only contain text or documentation about specific topics,

    but they usually include no information about how several HTML documents

    relate to each other or in which order they are supposed to be read.

    What is missing is a table of contents along with an index to access

    certain help contents quickly, without having to browse through a lot

    of documents in order to find a piece of information.

    To organize the documentation and make it available for \QA, we have

    to create a Qt help project (.qhp) file. The first and most important

    part of the project file is the definition of the namespace. The namespace

    has to be unique and will be the first part of the page URL in \QA.

    In addition, we have to set a virtual folder which acts as a common

    folder for documentation sets. This means, that two documentation sets

    identified by two different namespaces can cross reference HTML files

    since those files are in one big virtual folder. However, for this

    example, we'll only have one documentation set available, so the

    virtual folder name and functionality are not important.

    \code

    <?xml version="1.0" encoding="UTF-8"?>

    <QtHelpProject version="1.0">

      <namespace>com.trolltech.examples.simpletextviewer</namespace>

      <virtualFolder>doc</virtualFolder>

    \endcode

    The next step is to define the filter section. A filter section

    contains the table of contents, indices and a complete list of

    all documentation files, and can have any number of filter attributes

    assigned to it. A filter attribute is an ordinary string which can

    be freely chosen. Later in \QA, users can then define a custom

    filter referencing those attributes. If the attributes of a filter

    section match the attributes of the custom filter the documentation

    will be shown, otherwise \QA will hide the documentation.

    Again, since we'll only have one documentation set, we do not need

    the filtering functionality of \QA and can therefore skip the

    filter attributes.

    Now, we build up the table of contents. An item in the table is

    defined by the \c section tag which contains the attributes for the

    item title as well as link to the actual page. Section tags can be

    nested infinitely, but for practical reasons it is not recommended

    to nest them deeper than three or four levels. For our example we

    want to use the following outline for the table of contents:

    \list

    \o Simple Text Viewer

      \list

      \o Find File

        \list

        \o File Dialog

        \o Wildcard Matching

        \o Browse

        \endlist

      \o Open File      

      \endlist

    \endlist

    In the help project file, the outline is represented by:

    \code

     <filterSection>

       <toc>

         <section title="Simple Text Viewer" ref="index.html">

           <section title="Find File" ref="./findfile.html">

             <section title="File Dialog" ref="./filedialog.html"></section>

             <section title="Wildcard Matching" ref="./wildcardmatching.html"></section>

             <section title="Browse" ref="./browse.html"></section>

           </section>

           <section title="Open File" ref="./openfile.html"></section>

         </section>

       </toc>

    \endcode

    After the table of contents is defined, we will list all index keywords:      

    \code

        <keywords>

          <keyword name="Display" ref="./index.html"/>

          <keyword name="Rich text" ref="./index.html"/>

          <keyword name="Plain text" ref="./index.html"/>

          <keyword name="Find" ref="./findfile.html"/>

          <keyword name="File menu" ref="./findfile.html"/>

          <keyword name="File name" ref="./filedialog.html"/>

          <keyword name="File dialog" ref="./filedialog.html"/>

          <keyword name="File globbing" ref="./wildcardmatching.html"/>

          <keyword name="Wildcard matching" ref="./wildcardmatching.html"/>

          <keyword name="Wildcard syntax" ref="./wildcardmatching.html"/>

          <keyword name="Browse" ref="./browse.html"/>

          <keyword name="Directory" ref="./browse.html"/>

          <keyword name="Open" ref="./openfile.html"/>

          <keyword name="Select" ref="./openfile.html"/>

        </keywords>

    \endcode

    As the last step, we have to list all files making up the documentation.

    An important point to note here is that all files have to listed, including

    image files, and even stylesheets if they are used.

    \code

        <files>

          <file>browse.html</file>

          <file>filedialog.html</file>

          <file>findfile.html</file>

          <file>index.html</file>

          <file>intro.html</file>

          <file>openfile.html</file>

          <file>wildcardmatching.html</file>

          <file>images/browse.png</file>

          <file>images/*.png</file>

        </files>

      </filterSection>

    </QtHelpProject>

    \endcode

    The help project file is now finished. If you want to see the resulting

    documentation in \QA, you have to generate a Qt compressed help file

    out of it and register it with the default help collection of \QA.

    \code

    qhelpgenerator simpletextviewer.qhp -o simpletextviewer.qch

    assistant -register simpletextviewer.qch

    \endcode

    If you start \QA now, you'll see the Simple Text Viewer documentation

    beside the Qt documentation. This is OK for testing purposes, but

    for the final version we want to only have the Simple Text Viewer

    documentation in \QA.

    \section2 Customizing \QA

    The easiest way to make \QA only display the Simple Text Viewer

    documentation is to create our own help collection file. A collection

    file is stored in a binary format, similar to the compressed help file,

    and generated from a help collection project file (*.qhcp). With

    the help of a collection file, we can customize the appearance and even

    some functionality offered by \QA.

    At first, we change the window title and icon. Instead of showing "\QA"

    it will show "Simple Text Viewer", so it is much clearer for the user

    that the help viewer actually belongs to our application.    

    \code

    <?xml version="1.0" encoding="UTF-8"?>

    <QHelpCollectionProject version="1.0">

    <assistant>

        <title>Simple Text Viewer</title>

        <applicationIcon>images/handbook.png</applicationIcon>        

        <cacheDirectory>Trolltech/SimpleTextViewer</cacheDirectory>

    \endcode

    The \c cacheDirectory tag specifies a subdirectory of the users

    data directory (see the

    \l{Using Qt Assistant as a Custom Help Viewer#Qt Help Collection Files}{Qt Help Collection Files})

    where the cache file for the full text search or the settings file will

    be stored.

    After this, we set the page displayed by \QA when launched for the very

    first time in its new configuration. The URL consists of the namespace

    and virtual folder defined in the Qt help project file, followed by the

    actual page file name.

    \code

        <startPage>qthelp://com.trolltech.examples.simpletextviewer/doc/index.html</startPage>

    \endcode

    Next, we alter the name of the "About" menu item to "About Simple

    Text Viewer". The contents of the \gui{About} dialog are also changed

    by specifying a file where the about text or icon is taken from.

    \code

        <aboutMenuText>

            <text>About Simple Text Viewer</text>

        </aboutMenuText>

        <aboutDialog>

            <file>about.txt</file>

            <icon>images/icon.png</icon>

        </aboutDialog>

    \endcode

    \QA offers the possibility to add or remove documentation via its

    preferences dialog. This functionality is helpful when using \QA

    as the central help viewer for more applications, but in our case

    we want to actually prevent the user from removing the documentation.

    So, we disable the documentation manager.

    Since the address bar is not really relevant in such a small

    documentation set we switch it off as well. By having just one filter

    section, without any filter attributes, we can also disable the filter

    functionality of \QA, which means that the filter page and the filter

    toolbar will not be available.

    \code

        <enableDocumentationManager>false</enableDocumentationManager>

        <enableAddressBar>false</enableAddressBar>

        <enableFilterFunctionality>false</enableFilterFunctionality>

    </assistant>

    \endcode

    For testing purposes, we already generated the compressed help file

    and registered it with \QA's default help collection. With the

    following lines we achieve the same result. The only and important

    difference is that we register the compressed help file, not in

    the default collection, but in our own collection file.

    \code

      <docFiles>

        <generate>

            <file>

                <input>simpletextviewer.qhp</input>

                <output>simpletextviewer.qch</output>

                </file>

            </generate>

        <register>

            <file>simpletextviewer.qch</file>

            </register>

        </docFiles>

    </QHelpCollectionProject>

    \endcode

    As the last step, we have to generate the binary collection file

    out of the help collection project file. This is done by running the

    \c qcollectiongenerator tool.

    \code

    qcollectiongenerator simpletextviewer.qhcp -o simpletextviewer.qhc

    \endcode

    To test all our customizations made to \QA, we add the collection

    file name to the command line:

    \code

    assistant -collectionFile simpletextviewer.qhc

    \endcode

    \section1 Controlling \QA via the Assistant Class

    We will first take a look at how to start and operate \QA from a

    remote application. For that purpose, we create a class called

    \c Assistant.

    This class provides a public function that is used to show pages

    of the documentation, and one private helper function to make sure

    that \QA is up and running.

    Launching \QA is done in the function \c startAssistant() by simply

    creating and starting a QProcess. If the process is already running,

    the function returns immediately. Otherwise, the process has

    to be set up and started.

    \snippet examples/help/simpletextviewer/assistant.cpp 2

    To start the process we need the executable name of \QA as well as the

    command line arguments for running \QA in a customized mode. The

    executable name is a little bit tricky since it depends on the

    platform, but fortunately it is only different on Mac OS X.

    The displayed documentation can be altered using the \c -collectionFile

    command line argument when launching \QA. When started without any options,

    \QA displays a default set of documentation. When Qt is installed,

    the default documentation set in \QA contains the Qt reference

    documentation as well as the tools that come with Qt, such as Qt

    Designer and \c qmake.

    In our example, we replace the default documentation set with our

    custom documentation by passing our application-specific collection

    file to the process's command line options.

    As the last argument, we add \c -enableRemoteControl, which makes \QA

    listen to its \c stdin channel for commands, such as those to display

    a certain page in the documentation.

    Then we start the process and wait until it is actually running. If,

    for some reason \QA cannot be started, \c startAssistant() will return

    false.

    The implementation for \c showDocumentation() is now straightforward.

    Firstly, we ensure that \QA is running, then we send the request to

    display the \a page via the \c stdin channel of the process. It is very

    important here that the command is terminated by the '\\0' character

    followed by an end of line token to flush the channel.

    \snippet examples/help/simpletextviewer/assistant.cpp 1

    Finally, we make sure that \QA is terminated properly in the case that

    the application is shut down. The destructor of QProcess kills the

    process, meaning that the application has no possibility to do things

    like save user settings, which would result in corrupted settings files.

    To avoid this, we ask \QA to terminate in the destructor of the

    \c Assistant class.

    \snippet examples/help/simpletextviewer/assistant.cpp 0

    \section1 MainWindow Class 

    \image simpletextviewer-mainwindow.png

    The \c MainWindow class provides the main application window with

    two menus: the \gui File menu lets the user open and view an

    existing file, while the \gui Help menu provides information about

    the application and about Qt, and lets the user open \QA to

    display the application's documentation.

    To be able to access the help functionality, we initialize the

    \c Assistant object in the \c MainWindow's constructor.

    \snippet examples/help/simpletextviewer/mainwindow.cpp 0

    \dots

    \snippet examples/help/simpletextviewer/mainwindow.cpp 1

    Then we create all the actions for the Simple Text Viewer application.

    Of special interest is the \c assistantAct action accessible

    via the \key{F1} shortcut or the \menu{Help|Help Contents} menu item.

    This action is connected to the \c showDocumentation() slot of

    the \c MainWindow class.

    \snippet examples/help/simpletextviewer/mainwindow.cpp 4

    \dots

    \snippet examples/help/simpletextviewer/mainwindow.cpp 5

    In the \c showDocumentation() slot, we call the \c showDocumentation()

    function of the \c Assistant class with the URL of home page of the

    documentation.

    \snippet examples/help/simpletextviewer/mainwindow.cpp 3

    Finally, we must reimplement the protected QWidget::closeEvent()

    event handler to ensure that the application's \QA instance is

    properly closed before we terminate the application.

    \snippet examples/help/simpletextviewer/mainwindow.cpp 2

    \section1 FindFileDialog Class

    \image simpletextviewer-findfiledialog.png

    The Simple Text Viewer application provides a find file dialog

    allowing the user to search for files using wildcard matching. The

    search is performed within the specified directory, and the user

    is given an option to browse the existing file system to find the

    relevant directory.

    In the constructor we save the references to the \c Assistant

    and \c QTextEdit objects passed as arguments. The \c Assistant

    object will be used in the \c FindFileDialog's \c help() slot,

    as we will see shortly, while the QTextEdit will be used in the

    dialog's \c openFile() slot to display the chosen file.

    \snippet examples/help/simpletextviewer/findfiledialog.cpp 0

    \dots

    \snippet examples/help/simpletextviewer/findfiledialog.cpp 1

    The most relevant member to observe in the \c FindFileDialog

    class is the private \c help() slot. The slot is connected to the

    dialog's \gui Help button, and brings the current \QA instance

    to the foreground with the documentation for the dialog by

    calling \c Assistant's \c showDocumentation() function.

    \snippet examples/help/simpletextviewer/findfiledialog.cpp 2

    \section1 Summary

    In order to make \QA act as a customized help tool for

    your application, you must provide your application with a

    process that controls \QA in addition to a custom help collection

    file including Qt compressed help files.

    The \l{Using Qt Assistant as a Custom Help Viewer} document contains

    more information about the options and settings available to

    applications that use \QA as a custom help viewer.

*/