diff options
author | Topi Reinio <topi.reinio@digia.com> | 2014-10-15 13:50:27 +0200 |
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committer | Topi Reiniƶ <topi.reinio@digia.com> | 2014-10-17 14:57:13 +0200 |
commit | cf8f369f8575dcb9ca4d5116f3afc7cff4a080af (patch) | |
tree | a685f393b50786a892fcd3ad638b4c01e9002894 /examples/corelib/threads/doc/src/queuedcustomtype.qdoc | |
parent | 45485d9eb47d3129b8a74c2e9d854c07673161cd (diff) |
Move Qt Core examples under a common subdirectory
Qt Core examples were scattered into several subdirectories under
qtbase/examples. This caused an issue with the example manifest
file generated by QDoc; it expects to find all examples under a
common directory in order to produde correct paths to the example
.pro files. Qt Creator will not find the examples without a valid
manifest file.
This change moves the examples and edits the documentation files
accordingly.
Task-number: QTBUG-41963
Change-Id: I51d86782e0ba21c5c9bae5f15401ec774abe5cf8
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Diffstat (limited to 'examples/corelib/threads/doc/src/queuedcustomtype.qdoc')
-rw-r--r-- | examples/corelib/threads/doc/src/queuedcustomtype.qdoc | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/examples/corelib/threads/doc/src/queuedcustomtype.qdoc b/examples/corelib/threads/doc/src/queuedcustomtype.qdoc new file mode 100644 index 0000000000..cca68b4513 --- /dev/null +++ b/examples/corelib/threads/doc/src/queuedcustomtype.qdoc @@ -0,0 +1,166 @@ +/**************************************************************************** +** +** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies). +** Contact: http://www.qt-project.org/legal +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:FDL$ +** Commercial License Usage +** Licensees holding valid commercial Qt licenses may use this file in +** accordance with the commercial license agreement provided with the +** Software or, alternatively, in accordance with the terms contained in +** a written agreement between you and Digia. For licensing terms and +** conditions see http://qt.digia.com/licensing. For further information +** use the contact form at http://qt.digia.com/contact-us. +** +** GNU Free Documentation License Usage +** Alternatively, this file may be used under the terms of the GNU Free +** Documentation License version 1.3 as published by the Free Software +** Foundation and appearing in the file included in the packaging of +** this file. Please review the following information to ensure +** the GNU Free Documentation License version 1.3 requirements +** will be met: http://www.gnu.org/copyleft/fdl.html. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! + \example threads/queuedcustomtype + \title Queued Custom Type Example + \brief Demonstrates multi-thread programming using Qt + \ingroup qtconcurrent-mtexamples + + \brief The Queued Custom Type example shows how to send custom types between + threads with queued signals and slots. + + \image queuedcustomtype-example.png + + Contents: + + \tableofcontents + + \section1 Overview + + In the \l{Custom Type Example}, we showed how to integrate custom types with + the meta-object system, enabling them to be stored in QVariant objects, written + out in debugging information and used in signal-slot communication. + + In this example, we create a new value class, \c Block, and register it + with the meta-object system to enable us to send instances of it between + threads using queued signals and slots. + + \section1 The Block Class + + The \c Block class is similar to the \c Message class described in the + \l{Custom Type Example}. It provides the default constructor, copy + constructor and destructor in the public section of the class that the + meta-object system requires. It describes a colored rectangle. + + \snippet threads/queuedcustomtype/block.h custom type definition and meta-type declaration + + We will still need to register it with the meta-object system at + run-time by calling the qRegisterMetaType() template function before + we make any signal-slot connections that use this type. + Even though we do not intend to use the type with QVariant in this example, + it is good practice to also declare the new type with Q_DECLARE_METATYPE(). + + The implementation of the \c Block class is trivial, so we avoid quoting + it here. + + \section1 The Window Class + + We define a simple \c Window class with a public slot that accepts a + \c Block object. The rest of the class is concerned with managing the + user interface and handling images. + + \snippet threads/queuedcustomtype/window.h Window class definition + + The \c Window class also contains a worker thread, provided by a + \c RenderThread object. This will emit signals to send \c Block objects + to the window's \c addBlock(Block) slot. + + The parts of the \c Window class that are most relevant are the constructor + and the \c addBlock(Block) slot. + + The constructor creates a thread for rendering images, sets up a user + interface containing a label and two push buttons that are connected to + slots in the same class. + + \snippet threads/queuedcustomtype/window.cpp Window constructor start + \snippet threads/queuedcustomtype/window.cpp set up widgets and connections + \snippet threads/queuedcustomtype/window.cpp connecting signal with custom type + + In the last of these connections, we connect a signal in the + \c RenderThread object to the \c addBlock(Block) slot in the window. + + \dots + \snippet threads/queuedcustomtype/window.cpp Window constructor finish + + The rest of the constructor simply sets up the layout of the window. + + The \c addBlock(Block) slot receives blocks from the rendering thread via + the signal-slot connection set up in the constructor: + + \snippet threads/queuedcustomtype/window.cpp Adding blocks to the display + + We simply paint these onto the label as they arrive. + + \section1 The RenderThread Class + + The \c RenderThread class processes an image, creating \c Block objects + and using the \c sendBlock(Block) signal to send them to other components + in the example. + + \snippet threads/queuedcustomtype/renderthread.h RenderThread class definition + + The constructor and destructor are not quoted here. These take care of + setting up the thread's internal state and cleaning up when it is destroyed. + + Processing is started with the \c processImage() function, which calls the + \c RenderThread class's reimplementation of the QThread::run() function: + + \snippet threads/queuedcustomtype/renderthread.cpp processing the image (start) + + Ignoring the details of the way the image is processed, we see that the + signal containing a block is emitted in the usual way: + + \dots + \snippet threads/queuedcustomtype/renderthread.cpp processing the image (finish) + + Each signal that is emitted will be queued and delivered later to the + window's \c addBlock(Block) slot. + + \section1 Registering the Type + + In the example's \c{main()} function, we perform the registration of the + \c Block class as a custom type with the meta-object system by calling the + qRegisterMetaType() template function: + + \snippet threads/queuedcustomtype/main.cpp main function + + This call is placed here to ensure that the type is registered before any + signal-slot connections are made that use it. + + The rest of the \c{main()} function is concerned with setting a seed for + the pseudo-random number generator, creating and showing the window, and + setting a default image. See the source code for the implementation of the + \c createImage() function. + + \section1 Further Reading + + This example showed how a custom type can be registered with the + meta-object system so that it can be used with signal-slot connections + between threads. For ordinary communication involving direct signals and + slots, it is enough to simply declare the type in the way described in the + \l{Custom Type Example}. + + In practice, both the Q_DECLARE_METATYPE() macro and the qRegisterMetaType() + template function can be used to register custom types, but + qRegisterMetaType() is only required if you need to perform signal-slot + communication or need to create and destroy objects of the custom type + at run-time. + + More information on using custom types with Qt can be found in the + \l{Creating Custom Qt Types} document. +*/ |