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Improve QgsVectorLayer::countSymbolFeatures() responsiveness.

The method can display a progress dialog when it takes a long time to
complete.
- Attach this dialog to the QGIS main window.
- Use the interruption checker mechanism of iterators so that the
  to-be-committed improved WFS feature iterator can use it
- Call QCoreApplication::processEvents() for better UI responsiveness.
  • Loading branch information
rouault committed Apr 5, 2016
1 parent 114c108 commit e792576d022e4e1535345fe52f325446ba314fae
Showing with 84 additions and 8 deletions.
  1. +84 −8 src/core/qgsvectorlayer.cpp
@@ -697,6 +697,44 @@ long QgsVectorLayer::featureCount( QgsSymbolV2* symbol )
return mSymbolFeatureCountMap.value( symbol );
}

/** Used by QgsVectorLayer::countSymbolFeatures() to provide an interruption checker
* @note not available in Python bindings
*/
class QgsVectorLayerInterruptionCheckerDuringCountSymbolFeatures: public QgsInterruptionChecker
{
public:

/** Constructor */
QgsVectorLayerInterruptionCheckerDuringCountSymbolFeatures( QProgressDialog* dialog )
: mDialog( dialog )
{
}

virtual bool mustStop() const
{
if ( mDialog->isVisible() )
{
// So that we get a chance of hitting the Abort button
#ifdef Q_OS_LINUX
// For some reason on Windows hasPendingEvents() always return true,
// but one iteration is actually enough on Windows to get good interactivity
// whereas on Linux we must allow for far more iterations.
// For safety limit the number of iterations
int nIters = 0;
while ( QCoreApplication::hasPendingEvents() && ++nIters < 100 )
#endif
{
QCoreApplication::processEvents();
}
return mDialog->wasCanceled();
}
return false;
}

private:
QProgressDialog* mDialog;
};

bool QgsVectorLayer::countSymbolFeatures( bool showProgress )
{
if ( mSymbolFeatureCounted )
@@ -729,12 +767,34 @@ bool QgsVectorLayer::countSymbolFeatures( bool showProgress )
}

long nFeatures = featureCount();
QProgressDialog progressDialog( tr( "Updating feature count for layer %1" ).arg( name() ), tr( "Abort" ), 0, nFeatures );

QWidget* mainWindow = nullptr;
Q_FOREACH ( QWidget* widget, qApp->topLevelWidgets() )
{
if ( widget->objectName() == "QgisApp" )
{
mainWindow = widget;
break;
}
}

QProgressDialog progressDialog( tr( "Updating feature count for layer %1" ).arg( name() ), tr( "Abort" ), 0, nFeatures, mainWindow );
progressDialog.setWindowTitle( tr( "QGIS" ) );
progressDialog.setWindowModality( Qt::WindowModal );
if ( showProgress )
{
// Properly initialize to 0 as recommended in doc so that the evaluation
// of the total time properly works
progressDialog.setValue( 0 );
}
int featuresCounted = 0;

QgsFeatureIterator fit = getFeatures( QgsFeatureRequest().setFlags( QgsFeatureRequest::NoGeometry ) );
QgsVectorLayerInterruptionCheckerDuringCountSymbolFeatures interruptionCheck( &progressDialog );
if ( showProgress )
{
fit.setInterruptionChecker( &interruptionCheck );
}

// Renderer (rule based) may depend on context scale, with scale is ignored if 0
QgsRenderContext renderContext;
@@ -746,6 +806,8 @@ bool QgsVectorLayer::countSymbolFeatures( bool showProgress )
mRendererV2->startRender( renderContext, fields() );

QgsFeature f;
QTime time;
time.start();
while ( fit.nextFeature( f ) )
{
renderContext.expressionContext().setFeature( f );
@@ -758,19 +820,33 @@ bool QgsVectorLayer::countSymbolFeatures( bool showProgress )

if ( showProgress )
{
if ( featuresCounted % 50 == 0 )
// Refresh progress every 50 features or second
if (( featuresCounted % 50 == 0 ) || time.elapsed() > 1000 )
{
time.restart();
if ( featuresCounted > nFeatures ) //sometimes the feature count is not correct
{
progressDialog.setMaximum( 0 );
}
progressDialog.setValue( featuresCounted );
if ( progressDialog.wasCanceled() )
{
mSymbolFeatureCountMap.clear();
mRendererV2->stopRender( renderContext );
return false;
}
}
// So that we get a chance of hitting the Abort button
#ifdef Q_OS_LINUX
// For some reason on Windows hasPendingEvents() always return true,
// but one iteration is actually enough on Windows to get good interactivity
// whereas on Linux we must allow for far more iterations.
// For safety limit the number of iterations
int nIters = 0;
while ( QCoreApplication::hasPendingEvents() && ++nIters < 100 )
#endif
{
QCoreApplication::processEvents();
}
if ( progressDialog.wasCanceled() )
{
mSymbolFeatureCountMap.clear();
mRendererV2->stopRender( renderContext );
return false;
}
}
}

1 comment on commit e792576

@nirvn

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@nirvn nirvn commented on e792576 Feb 6, 2017

@rouault , I think this led to the regression described here: http://hub.qgis.org/issues/16149

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