diff options
| -rw-r--r-- | examples/opengl/doc/src/hellogl.qdoc | 22 | ||||
| -rw-r--r-- | examples/opengl/hellogl/glwidget.cpp | 6 |
2 files changed, 21 insertions, 7 deletions
diff --git a/examples/opengl/doc/src/hellogl.qdoc b/examples/opengl/doc/src/hellogl.qdoc index b4aef0ae02..9740c91408 100644 --- a/examples/opengl/doc/src/hellogl.qdoc +++ b/examples/opengl/doc/src/hellogl.qdoc @@ -109,10 +109,24 @@ \snippet hellogl/glwidget.cpp 5 - In the above slot, the \c xRot variable is updated only if the new angle - is different to the old one, the \c xRotationChanged() signal is emitted to - allow other components to be updated, and the widget's - \l{QGLWidget::updateGL()}{updateGL()} handler function is called. + In the above slot, the \c xRot variable is updated only if the new angle is + different to the old one, the \c xRotationChanged() signal is emitted to + allow other components to be updated, and an update is scheduled. + + Note that the widget's \l{QGLWidget::updateGL()}{updateGL()} function is not + called directly from here. Triggering rendering and buffer swaps directly + from the input event handlers is not desirable. Such events may, depending + on the platform, occur at a high frequency, and calling a potentially + blocking function like \l{QOpenGLContext::swapBuffers()}{swapBuffers} may + lead to unexpected results due to the main thread not being able to process + the input events at a proper rate. + + Instead, update() is used. This will eventually lead to a paint event, which + will in turn invoke paintGL(). Multiple calls to update() in a row will make + no difference while the event is still pending. This way the UI will perform + equally well with blocking swaps, that is, a a + \l{QGLFormat::swapInterval()}{swap interval} of 1, and non-vsynced + configurations. The \c setYRotation() and \c setZRotation() slots perform the same task for rotations measured by the \c yRot and \c zRot variables. diff --git a/examples/opengl/hellogl/glwidget.cpp b/examples/opengl/hellogl/glwidget.cpp index 29879fa804..3a9faaca5f 100644 --- a/examples/opengl/hellogl/glwidget.cpp +++ b/examples/opengl/hellogl/glwidget.cpp @@ -100,7 +100,7 @@ void GLWidget::setXRotation(int angle) if (angle != xRot) { xRot = angle; emit xRotationChanged(angle); - updateGL(); + update(); } } //! [5] @@ -111,7 +111,7 @@ void GLWidget::setYRotation(int angle) if (angle != yRot) { yRot = angle; emit yRotationChanged(angle); - updateGL(); + update(); } } @@ -121,7 +121,7 @@ void GLWidget::setZRotation(int angle) if (angle != zRot) { zRot = angle; emit zRotationChanged(angle); - updateGL(); + update(); } } |