Qt-jambi-interest Archive, August 2007
Handling a QObject from another thread
Message 1 in thread
Hi,
i'm trying to handle a QGLWidget from another thread to use it in the 3d
engine Xith3D.
The QtJambi canvas i've implemented for Xith is almost working. It works
in runmode "RUN_IN_SEPARATE_THREAD_AND_WAIT",
that's mean you have to generate a new frame yourself with the Xith
command nextFrame().
If anyone is interested, you can find the sources of this canvas
implementation here : http://xith.org/forum/index.php/topic,482.0.html
The problem i meet is that the QGLWidget is not refreshed when i want to
generate new frames fastly,
for example in a loop for displaying a 3D animation.
To handle the qGLWidget from another thread, i use
QApplication.invokeLater(Runnable).
But the problem with this method is that the runnable is called only when
the application is idle (doing nothing).
So, is there another fast way to update the QGLWidget from another thread ?
Something like QApplication.invokeNow(runnable) would be great !
Or a fonction similar to the SWT fonction syncExec(Runnable).
Here is an extract of my canvas for Xith3D :
public class CanvasPeerImplQtJambi extends CanvasPeerImplBase
{
...
//this class/method updates the qGLWidget
public class RenderRunnable extends QObject implements Runnable
{
// public Signal1<QGLWidget> qGLSignal = new Signal1<QGLWidget>();
QGLWidget qGL;
// not used
public void setQGL(QGLWidget _qGLWidget)
{
this.qGL = _qGLWidget;
}
public void run()
{
System.out.println("frame " + frameId);
if (!destroyed)
{
isRendering = true;
EnvironmentCapabilities capabilities =
EnvironmentCapabilities.getInstance();
qGL = qGLWidget; // this QGLWidget is created in the main
thread
qGL.makeCurrent();
context.makeCurrent();
gl = context.getGL();
if (swapIntervalChanged)
{
swapIntervalChanged = false;
if (capabilities.isVSyncSwitchingAllowed( OPENGL_LAYER
))
{
gl.setSwapInterval( getSwapInterval() );
}
}
display();
qGL.swapBuffers();
qGL.updateGL();
qGL.update();
context.release();
isRendering = false;
}
}
}
...
//this method is called from the Xith loop in another thread
private final void doRender() {
...
//renderRunnable is instantied in the constuctor
QApplication.invokeLater(renderRunnable);
}
}
Message 2 in thread
Hi, Ludovic.
Ludovic Marcé wrote:
>
>
> Something like QApplication.invokeNow(runnable) would be great !
> Or a fonction similar to the SWT fonction syncExec(Runnable).
>
A method for synchronous invocation of functions on the gui thread is
indeed planned for Qt Jambi 4.4.0_01 (the next feature release.) I'm
also attaching a quick implementation of such functionality to this mail
that you might be able to use in the meantime.
Use the static invokeAndWait() method, and make sure an event loop is
running in the gui thread. Then the method will not return until the
runnable has actually finished executing.
-- Eskil
import com.trolltech.qt.core.QCoreApplication;
import com.trolltech.qt.core.QCoreApplication;
import com.trolltech.qt.core.QEvent;
import com.trolltech.qt.core.QObject;
import com.trolltech.qt.gui.QApplication;
public class SynchronousInvokable extends QObject {
static QEvent.Type SYNCHRONOUS_INVOKABLE_EVENT = QEvent.Type.resolve(QEvent.Type.User.value() + 1);
private Runnable runnable;
private SynchronousInvokable(Runnable runnable) {
disableGarbageCollection();
if(QCoreApplication.instance().nativeId() != 0) {
moveToThread(QCoreApplication.instance().thread());
this.runnable = runnable;
}
if (runnable == null || Thread.currentThread().equals(QApplication.instance().thread())) {
runnable.run();
invoked = true;
}
}
private Boolean invoked = false;
private synchronized void waitForInvoked() {
while (!invoked) {
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
invoked = false;
}
public static void invokeAndWait(Runnable runnable) {
SynchronousInvokable invokable = new SynchronousInvokable(runnable);
QCoreApplication.postEvent(invokable, new QEvent(SYNCHRONOUS_INVOKABLE_EVENT));
invokable.waitForInvoked();
invokable.disposeLater();
}
@Override
public final boolean event(com.trolltech.qt.core.QEvent e) {
if (e.type() == SYNCHRONOUS_INVOKABLE_EVENT && runnable != null) {
runnable.run();
synchronized (this) {
invoked = true;
notifyAll();
}
return true;
}
return super.event(e);
}
}
Message 3 in thread
On Fri, 24 Aug 2007 10:21:34 +0200, Eskil Abrahamsen Blomfeldt
<eblomfel@xxxxxxxxxxxxx> wrote:
> Hi, Ludovic.
>
> Ludovic Marcé wrote:
>>
>>
>> Something like QApplication.invokeNow(runnable) would be great !
>> Or a fonction similar to the SWT fonction syncExec(Runnable).
>>
>
> A method for synchronous invocation of functions on the gui thread is
> indeed planned for Qt Jambi 4.4.0_01 (the next feature release.) I'm
> also attaching a quick implementation of such functionality to this mail
> that you might be able to use in the meantime.
>
> Use the static invokeAndWait() method, and make sure an event loop is
> running in the gui thread. Then the method will not return until the
> runnable has actually finished executing.
>
> -- Eskil
Thanks you !
But I don't know how to add an event loop in the gui thread.
Is it something like that :
QEventLoop eventLoop = new QEventLoop();
QApplication.invokeLater( new Runnable() {
public void run() {
System.out.println("eventLoop");
eventLoop.exec();
}
} );
Message 4 in thread
Hi, Ludovic.
Ludovic Marcé wrote:
> Thanks you !
>
> But I don't know how to add an event loop in the gui thread.
>
> Is it something like that :
>
> QEventLoop eventLoop = new QEventLoop();
> QApplication.invokeLater( new Runnable() {
> public void run() {
> System.out.println("eventLoop");
> eventLoop.exec();
> }
> } );
>
By gui thread, I mean the main thread where your call to
QApplication.initialize() is located. This is the only thread that is
allowed to access GUI resources. The invokeLater() method cannot be used
to start an event loop in this thread, as it depends on the event loop
already running. Usually you use QApplication.exec() to start a
synchronous event loop in the gui thread, as follows:
public static void main(String args[]) {
QApplication.initialize(args);
// Set up stuff (start other threads etc.)
QApplication.exec(); // <-- This call runs an event loop and does
not return until the application quits
}
You can also use QCoreApplication.processEvents() if you want more
control over the event processing in the application.
See:
http://doc.trolltech.com/qtjambi-4.3.1_01/com/trolltech/qt/gui/QApplication.html#exec()
http://doc.trolltech.com/qtjambi-4.3.1_01/com/trolltech/qt/core/QCoreApplication.html#processEvents()
-- Eskil
