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 set, for example the qmake Manual.

Qt Help Project File Format

The file format is XML-based. For a better understanding of the format we will discuss the following example:

<?xml version="1.0" encoding="UTF-8"?>
<QtHelpProject version="1.0">
    <namespace>mycompany.com.myapplication.1.0</namespace>
    <virtualFolder>doc</virtualFolder>
    <customFilter name="My Application 1.0">
        <filterAttribute>myapp</filterAttribute>
        <filterAttribute>1.0</filterAttribute>
    </customFilter>
    <filterSection>
        <filterAttribute>myapp</filterAttribute>
        <filterAttribute>1.0</filterAttribute>
        <toc>
            <section title="My Application Manual" ref="index.html">
                <section title="Chapter 1" ref="doc.html#chapter1"/>
                <section title="Chapter 2" ref="doc.html#chapter2"/>
                <section title="Chapter 3" ref="doc.html#chapter3"/>
            </section>
        </toc>
        <keywords>
            <keyword name="foo" id="MyApplication::foo" ref="doc.html#foo"/>
            <keyword name="bar" ref="doc.html#bar"/>
            <keyword id="MyApplication::foobar" ref="doc.html#foobar"/>
        </keywords>
        <files>
            <file>classic.css</file>
            <file>*.html</file>
        </files>
    </filterSection>
</QtHelpProject>

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 also makes it 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".

Virtual Folders

Having a namespace for every documentation set naturally means that the documentation sets are quite separated. From the help engine's point of view, this is beneficial. However, from the writer's view it is often desirable to cross reference certain topics 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 documentation sets share the same virtual folder, they can use relative paths when defining hyperlinks pointing to each other. If a file is contained in both documentation sets, the one from the current set has precedence over the other.

...
<virtualFolder>doc</virtualFolder>
...

The above example specifies doc as virtual folder. If another manual specifies the same folder, for example for a small helper tool My Application, 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 name must not contain any slashes (/).

Filter Section

A filter section contains the actual documentation. A Qt help project file may contain more than one filter section. Every filter section consists of 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 set.

Table of Contents

...
<toc>
    <section title="My Application Manual" ref="index.html">
        <section title="Chapter 1" ref="doc.html#chapter1"/>
        <section title="Chapter 2" ref="doc.html#chapter2"/>
        <section title="Chapter 3" ref="doc.html#chapter3"/>
    </section>
</toc>
...

One section tag represents one item in the table of contents. The sections can be nested to any degree, but from a user's perspective it should not 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, are relative to the help project file itself.

Keywords

...
<keywords>
   <keyword name="foo" id="MyApplication::foo" ref="doc.html#foo"/>
   <keyword name="bar" ref="doc.html#bar"/>
   <keyword id="MyApplication::foobar" ref="doc.html#foobar"/>
</keywords>
...

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, the keyword specified there will appear in the visible index. That is, it will be accessible through the QHelpIndexModel class. If id is used, the keyword does not appear in the index and is only accessible via QHelpEngineCore::documentsForIdentifier(). name and id can be specified at the same time.

Files

...
<files>
    <file>classic.css</file>
    <file>*.html</file>
</files>
...

Finally, the actual documentation files have to be listed. Make sure that all files necessary to display the help are mentioned. That is, stylesheets or similar files need to be listed as well. The files, like all file references in a Qt help project, are relative to the help project file itself. As the example shows, files (but not directories) can also be specified as patterns using wildcards. 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.