summaryrefslogtreecommitdiffstats
path: root/doc/src/porting/qt4-styles.qdoc
diff options
context:
space:
mode:
authorJason Barron <jbarron@trolltech.com>2009-08-18 06:34:18 (GMT)
committerJason Barron <jbarron@trolltech.com>2009-08-18 06:34:18 (GMT)
commitfd6740b6ade6e7f8e51a9cc558b723e7fae15ccf (patch)
treeaa2ba4ce64d047d73c29ab0616e8a89d352c3abd /doc/src/porting/qt4-styles.qdoc
parentd24029e3d4639f1300e7a68858936911df969f69 (diff)
parent572e165dcb8cc8fcdfaa4ab9bdab050f6a6cc173 (diff)
downloadQt-fd6740b6ade6e7f8e51a9cc558b723e7fae15ccf.zip
Qt-fd6740b6ade6e7f8e51a9cc558b723e7fae15ccf.tar.gz
Qt-fd6740b6ade6e7f8e51a9cc558b723e7fae15ccf.tar.bz2
Merge commit 'qt/master'
Conflicts: doc/src/examples.qdoc doc/src/plugins-howto.qdoc doc/src/topics.qdoc examples/phonon/musicplayer/mainwindow.cpp src/3rdparty/freetype/src/base/ftobjs.c src/corelib/global/qglobal.h src/corelib/tools/qalgorithms.h src/corelib/tools/qshareddata.cpp src/corelib/tools/qsharedpointer.cpp src/corelib/tools/tools.pri src/corelib/xml/qxmlstream.h src/gui/painting/painting.pri src/gui/widgets/qdatetimeedit.cpp tests/auto/qdesktopservices/qdesktopservices.pro tests/auto/qgraphicsitem/tst_qgraphicsitem.cpp tests/auto/qtextcodec/test/test.pro
Diffstat (limited to 'doc/src/porting/qt4-styles.qdoc')
-rw-r--r--doc/src/porting/qt4-styles.qdoc157
1 files changed, 157 insertions, 0 deletions
diff --git a/doc/src/porting/qt4-styles.qdoc b/doc/src/porting/qt4-styles.qdoc
new file mode 100644
index 0000000..4134962
--- /dev/null
+++ b/doc/src/porting/qt4-styles.qdoc
@@ -0,0 +1,157 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** 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 either Technology Preview License Agreement or the
+** Beta Release License Agreement.
+**
+** 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 1.0, included in the file LGPL_EXCEPTION.txt in this
+** package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+** If you are unsure which license is appropriate for your use, please
+** contact the sales department at http://qt.nokia.com/contact.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+ \page qt4-styles.html
+ \title The Qt 4 Style API
+
+ \contentspage {What's New in Qt 4}{Home}
+ \previouspage The Network Module in Qt 4
+ \nextpage Thread Support in Qt 4
+
+ Qt's style API is responsible for performing the widget drawing
+ for built-in widgets. The Qt 4 style API has been revised to make
+ it possible for a style to draw widgets without calling any
+ functions on the widget.
+
+ Because Qt 4 is split across multiple libraries, Qt needed this
+ update to be able to draw widgets from other libraries than
+ QtGui. For application developers, this has other benefits, such
+ as more managable parameter lists and the possibility of drawing
+ any graphical element without having a widget of a specific
+ type.
+
+ \section1 General Overview
+
+ The QStyle class is an abstract base class that encapsulates
+ the look and feel of a GUI. Qt's built-in widgets use it to
+ perform nearly all of their drawing, ensuring that they look
+ exactly like the equivalent native widgets.
+
+ Most draw functions now take four arguments:
+
+ \list
+ \o an enum value specifying which graphical element to draw
+ \o a QStyleOption specifying how and where to render that element
+ \o a QPainter that should be used to draw the element
+ \o a QWidget on which the drawing is performed (optional)
+ \endlist
+
+ The style gets all the information it needs to render the
+ graphical element from QStyleOption. The widget is passed as the
+ last argument in case the style needs it to perform special
+ effects (such as animated default buttons on Mac OS X), but it
+ isn't mandatory. In fact, QStyle can be used to draw on any
+ paint device, not just widgets, by setting the QPainter properly.
+
+ Thanks to QStyleOption, it is now possible to make QStyle draw
+ widgets without linking in any code for the widget. This is how
+ Qt's built-in styles can draw Qt 3 widgets such as
+ Q3ListView without necessarily linking against the Qt3Support
+ library. Another significant benefit of the new approach is that
+ it's now possible to use \l{QStyle}'s draw functions on other
+ widgets than the built-in widgets; for example, you can draw a
+ combobox on any widget, not just on a QComboBox.
+
+ QStyleOption has various subclasses for the various types of
+ graphical elements that can be drawn, and it's possible to create
+ custom subclasses. For example, the QStyle::PE_FrameFocusRect
+ element expects a QStyleOptionFocusRect argument. This is
+ documented for each enum value.
+
+ When reimplementing QStyle functions that take a
+ QStyleOption parameter, you often need to cast the
+ QStyleOption to a subclass (e.g., QStyleOptionFocusRect). For
+ safety, you can use qstyleoption_cast() to ensure that the
+ pointer type is correct. If the object isn't of the right type,
+ qstyleoption_cast() returns 0. For example:
+
+ \snippet doc/src/snippets/code/doc_src_qt4-styles.qdoc 0
+
+ For performance reasons, there are few member functions and the
+ access to the variables is direct. This "low-level" feel makes
+ the structures use straightforward and emphasizes that these are
+ simply parameters used by the style functions. In addition, the
+ caller of a QStyle function usually creates QStyleOption
+ objects on the stack. This combined with Qt's extensive use of
+ \l{implicit sharing} for types such as QString, QPalette, and
+ QColor ensures that no memory allocation needlessly takes place.
+ (Dynamic memory allocation can be an expensive operation,
+ especially when drawing very often in a short time.)
+
+ \section1 Example Code
+
+ The following code snippet illustrates how to use QStyle to
+ draw the focus rectangle from a custom widget's paintEvent():
+
+ \snippet doc/src/snippets/code/doc_src_qt4-styles.qdoc 1
+
+ The next example shows how to derive from an existing style to
+ customize the look of a graphical element:
+
+ \snippet doc/src/snippets/customstyle/customstyle.h 0
+ \codeline
+ \snippet doc/src/snippets/customstyle/customstyle.cpp 2
+ \snippet doc/src/snippets/customstyle/customstyle.cpp 3
+ \snippet doc/src/snippets/customstyle/customstyle.cpp 4
+
+ See also the \l{Styles Example} for a more detailed description of
+ how custom styles can be created.
+
+ \section1 Comparison with Qt 3
+
+ The QStyle class has a similar API in Qt 4 as in Qt 3, with
+ more or less the same functions. What has changed is the
+ signature of the functions and the role played by QStyleOption.
+ For example, here's the signature of the QStyle::drawControl()
+ function in Qt 3:
+
+ \snippet doc/src/snippets/code/doc_src_qt4-styles.qdoc 2
+
+ Here's the signature of the same function in Qt 4:
+
+ \snippet doc/src/snippets/code/doc_src_qt4-styles.qdoc 3
+
+ In Qt 3, some of the information required to draw a graphical
+ element was stored in a QStyleOption parameter, while the rest
+ was deduced by querying the widget. In Qt 4, everything is stored
+ in the QStyleOption parameter.
+*/