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Improve QOpenGLWidget docs regarding fb preservation

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QOpenGLWindow already has some notes regarding this. It must be
mentioned in QOpenGLWidget too.

Change-Id: I0af90c9410a1c44cb9dd9ce58aa0371a58c57f65
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>
This commit is contained in:
Laszlo Agocs 2014-09-08 10:10:07 +02:00
parent df5db1dfb2
commit 935186d76e
1 changed files with 17 additions and 1 deletions
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18
src/widgets/kernel/qopenglwidget.cpp
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@ -228,6 +228,22 @@ QT_BEGIN_NAMESPACE
regarding stacking orders for example. QOpenGLWidget avoids this by not
creating a separate native window.
Due to being backed by a framebuffer object, the behavior of QOpenGLWidget is
very similar to QOpenGLWindow with the update behavior set to \c
PartialUpdateBlit or \c PartialUpdateBlend. This means that the contents are
preserved between paintGL() calls so that incremental rendering is
possible. With QGLWidget (and naturally QOpenGLWindow with the default update
behavior) this is usually not the case because swapping the buffers leaves the
back buffer with undefined contents.
\note Most applications do not need incremental rendering because they will
render everything in the view on every paint call. In this case it is
important to call glClear() as early as possible in paintGL(). This helps
mobile GPUs that use a tile-based architecture to recognize that the tile
buffer does not need to be reloaded with the framebuffer's previous
contents. Omitting the clear call can lead to significant performance drops on
such systems.
\section1 Multisampling
To enable multisampling, set the number of requested samples on the
@ -372,7 +388,7 @@ QT_BEGIN_NAMESPACE
\e{OpenGL is a trademark of Silicon Graphics, Inc. in the United States and other
countries.}
\sa QOpenGLFunctions
\sa QOpenGLFunctions, QOpenGLWindow
*/
/*!