summaryrefslogtreecommitdiff
path: root/doc/src/platforms/x11overlays.qdoc
diff options
context:
space:
mode:
authorJason Barron <jbarron@trolltech.com>2009-08-18 08:34:18 +0200
committerJason Barron <jbarron@trolltech.com>2009-08-18 08:34:18 +0200
commitfd6740b6ade6e7f8e51a9cc558b723e7fae15ccf (patch)
treeaa2ba4ce64d047d73c29ab0616e8a89d352c3abd /doc/src/platforms/x11overlays.qdoc
parentd24029e3d4639f1300e7a68858936911df969f69 (diff)
parent572e165dcb8cc8fcdfaa4ab9bdab050f6a6cc173 (diff)
downloadqt4-tools-fd6740b6ade6e7f8e51a9cc558b723e7fae15ccf.tar.gz
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/platforms/x11overlays.qdoc')
-rw-r--r--doc/src/platforms/x11overlays.qdoc98
1 files changed, 98 insertions, 0 deletions
diff --git a/doc/src/platforms/x11overlays.qdoc b/doc/src/platforms/x11overlays.qdoc
new file mode 100644
index 0000000000..7d7a77639e
--- /dev/null
+++ b/doc/src/platforms/x11overlays.qdoc
@@ -0,0 +1,98 @@
+/****************************************************************************
+**
+** 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 x11overlays.html
+ \title How to Use X11 Overlays with Qt
+
+ X11 overlays are a powerful mechanism for drawing
+ annotations etc., on top of an image without destroying it, thus saving
+ a great deal of image rendering time. For more information, see the highly
+ recommended book \e{OpenGL Programming for the X Window System} (Mark
+ Kilgard, Addison Wesley Developers Press 1996).
+
+ \warning The Qt OpenGL Extension includes direct support for the
+ use of OpenGL overlays. For many uses of overlays, this makes the
+ technique described below redundant. The following is a discussion
+ on how to use non-QGL widgets in overlay planes.
+
+ In the typical case, X11 overlays can easily be used together with the
+ current version of Qt and the Qt OpenGL Extension. The following
+ requirements apply:
+
+ \list 1
+ \i Your X server and graphics card/hardware must support overlays.
+ For many X servers, overlay support can be turned on with
+ a configuration option; consult your X server installation
+ documentation.
+
+ \i Your X server must (be configured to) use an overlay visual as the
+ default visual. Most modern X servers do this, since this has the
+ added advantage that pop-up menus, overlapping windows etc., will
+ \e not affect underlying images in the main plane, thereby
+ avoiding expensive redraws.
+
+ \i The best (deepest) visual for OpenGL rendering is in the main
+ plane. This is the normal case. Typically, X servers that support
+ overlays provide a 24-bit \c TrueColor visual in the main plane,
+ and an 8-bit \c PseudoColor (default) visual in the overlay plane.
+ \endlist
+
+ Assuming that the requirements mentioned above are met, a
+ QGLWidget will default to using the main plane visual, while all
+ other widgets will use the overlay visual. Thus, we can place a
+ normal widget on top of the QGLWidget, and do drawing on it,
+ without affecting the image in the OpenGL window. In other words,
+ we can use all the drawing capabilities of QPainter to draw
+ annotations, rubberbands, etc. For the typical use of overlays,
+ this is much easier than using OpenGL for rendering annotations.
+
+ An overlay plane has a specific color called the transparent
+ color. Pixels drawn in this color will not be visible; instead
+ the underlying OpenGL image will show through.
+
+ To use this technique, you must not use the
+ QApplication::ManyColor or QApplication::TrueColor color
+ specification for QApplication, because this will force the
+ normal Qt widgets to use a \c TrueColor visual, which will
+ typically be in the main plane, not in the overlay plane as
+ desired.
+*/