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Merge pull request #36624 from rldhont/backport-35158-release-3_10

[Backport release-3_10] Fix issues when content cache is used in blocking mode
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rldhont committed Jun 10, 2020
2 parents 7f04b8e + c184270 commit b235a80d8936c61b32011ddc56388324d4411761
Showing with 17 additions and 6 deletions.
  1. +17 −6 src/core/qgsabstractcontentcache.h
@@ -402,7 +402,12 @@ class CORE_EXPORT QgsAbstractContentCache : public QgsAbstractContentCacheBase
if ( ok )
{
// read the content data
mRemoteContentCache.insert( path, new QByteArray( reply->readAll() ) );
const QByteArray ba = reply->readAll();

// because of the fragility listed below in waitForTaskFinished, this slot may get called twice. In that case
// the second time will have an empty reply (we've already read it all...)
if ( !ba.isEmpty() )
mRemoteContentCache.insert( path, new QByteArray( ba ) );
}
QMetaObject::invokeMethod( const_cast< QgsAbstractContentCacheBase * >( qobject_cast< const QgsAbstractContentCacheBase * >( this ) ), "onRemoteContentFetched", Qt::QueuedConnection, Q_ARG( QString, path ), Q_ARG( bool, true ) );
} );
@@ -447,7 +452,7 @@ class CORE_EXPORT QgsAbstractContentCache : public QgsAbstractContentCacheBase
}

/**
* Blocks the current thread until the \a task finishes or an arbitrary setting maximum wait to 5 seconds
* Blocks the current thread until the \a task finishes (or user's preset network timeout expires)
*
* \warning this method must NEVER be used from GUI based applications (like the main QGIS application)
* or crashes will result. Only for use in external scripts or QGIS server.
@@ -459,22 +464,28 @@ class CORE_EXPORT QgsAbstractContentCache : public QgsAbstractContentCacheBase
bool waitForTaskFinished( QgsNetworkContentFetcherTask *task ) const
{
// First step, waiting for task running
if ( task->status() != QgsTask::Running )
bool waitForTaskBegun = ( task->status() != QgsTask::Running
&& task->status() != QgsTask::Complete
&& task->status() != QgsTask::Terminated );
if ( waitForTaskBegun )
{
QEventLoop loop;
connect( task, &QgsNetworkContentFetcherTask::begun, &loop, &QEventLoop::quit );
if ( task->status() != QgsTask::Running )
if ( waitForTaskBegun )
loop.exec();
}

// Second step, wait 5 seconds for task finished
if ( task->waitForFinished( 5000 ) )
// Second step, wait for task finished
// Wait up to timeout seconds for task finished
if ( task->waitForFinished( QgsNetworkAccessManager::timeout() ) )
{
// The wait did not time out
// Third step, check status as complete
if ( task->status() == QgsTask::Complete )
{
// Fourth step, force the signal fetched to be sure reply has been checked

// ARGH this is BAD BAD BAD. The connection will get called twice as a result!!!
task->fetched();
return true;
}

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