1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
|
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the Technology Preview License Agreement accompanying
** this package.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights. These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
**
**
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\group helpsystem
\title Help System
\ingroup groups
\brief Classes used to provide online-help for applications.
\keyword help system
These classes provide for all forms of online-help in your application,
with three levels of detail:
\list 1
\o Tool Tips and Status Bar message - flyweight help, extremely brief,
entirely integrated in the user interface, requiring little
or no user interaction to invoke.
\o What's This? - lightweight, but can be
a three-paragraph explanation.
\o Online Help - can encompass any amount of information,
but is typically slower to call up, somewhat separated
from the user's work, and often users feel that using online
help is a digression from their real task.
\endlist
*/
/*!
\page qthelp-framework.html
\title The Qt Help Framework
\brief Integrating Documentation in Applications
\ingroup frameworks-technologies
\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.
*/
/*!
\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 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.
\note The referenced files must be inside the same directory (or within a
subdirectory) as the help project file. An absolute file path is not supported
either.
\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. 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. \note The referenced files must be inside the same directory
(or within a subdirectory) as the help project file. An absolute file path
is not supported either.
*/
|