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nyalldawsonnyalldawson
committedOct 19, 2016
Avoid creating multiple render contexts when calculating legend
node size Partial fix for qgis slowdown when using layer with large number of legend nodes
·
ltr-3_40final-3_0_0
1 parent cf60049 commit c9251c5

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6 files changed

+66
-12
lines changed

6 files changed

+66
-12
lines changed
 

‎python/core/layertree/qgslayertreemodel.sip

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -166,7 +166,7 @@ class QgsLayerTreeModel : QAbstractItemModel
166166
//! Get hints about map view - to be used in legend nodes. Arguments that are not null will receive values.
167167
//! If there are no valid map view data (from previous call to setLegendMapViewData()), returned values are zeros.
168168
//! @note added in 2.6
169-
void legendMapViewData( double *mapUnitsPerPixel /Out/, int *dpi /Out/, double *scale /Out/ );
169+
void legendMapViewData( double *mapUnitsPerPixel /Out/, int *dpi /Out/, double *scale /Out/ ) const;
170170

171171
//! Get map of map layer style overrides (key: layer ID, value: style name) where a different style should be used instead of the current one
172172
//! @note added in 2.10

‎python/core/layertree/qgslayertreemodellegendnode.sip

Lines changed: 15 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -141,10 +141,23 @@ class QgsSymbolLegendNode : QgsLayerTreeModelLegendNode
141141
//! @note added in 2.10
142142
QSize iconSize() const;
143143

144-
//! Get the minimum icon size to prevent cropping
145-
//! @note added in 2.10
144+
/**
145+
* Calculates the minimum icon size to prevent cropping. When evaluating
146+
* the size for multiple icons it is more efficient to create a single
147+
* render context in advance and use the variant which accepts a QgsRenderContext
148+
* argument.
149+
* @note added in 2.10
150+
*/
146151
QSize minimumIconSize() const;
147152

153+
/**
154+
* Calculates the minimum icon size to prevent cropping. When evaluating
155+
* the size for multiple icons it is more efficient to create a single
156+
* render context in advance and call this method instead of minimumIconSize().
157+
* @note added in QGIS 2.18
158+
*/
159+
QSize minimumIconSize( QgsRenderContext &context ) const;
160+
148161
/** Returns the symbol used by the legend node.
149162
* @see setSymbol()
150163
* @note added in QGIS 2.14

‎src/core/layertree/qgslayertreemodel.cpp

Lines changed: 20 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -663,7 +663,7 @@ void QgsLayerTreeModel::setLegendMapViewData( double mapUnitsPerPixel, int dpi,
663663
refreshScaleBasedLayers();
664664
}
665665

666-
void QgsLayerTreeModel::legendMapViewData( double* mapUnitsPerPixel, int* dpi, double* scale )
666+
void QgsLayerTreeModel::legendMapViewData( double* mapUnitsPerPixel, int* dpi, double* scale ) const
667667
{
668668
if ( mapUnitsPerPixel ) *mapUnitsPerPixel = mLegendMapViewMupp;
669669
if ( dpi ) *dpi = mLegendMapViewDpi;
@@ -1269,6 +1269,22 @@ void QgsLayerTreeModel::tryBuildLegendTree( LayerLegendData& data )
12691269
}
12701270
}
12711271

1272+
QgsRenderContext* QgsLayerTreeModel::createTemporaryRenderContext() const
1273+
{
1274+
double scale = 0.0;
1275+
double mupp = 0.0;
1276+
int dpi = 0;
1277+
legendMapViewData( &mupp, &dpi, &scale );
1278+
bool validData = !qgsDoubleNear( mupp, 0.0 ) && dpi != 0 && !qgsDoubleNear( scale, 0.0 );
1279+
1280+
// setup temporary render context
1281+
QScopedPointer<QgsRenderContext> context( new QgsRenderContext );
1282+
context->setScaleFactor( dpi / 25.4 );
1283+
context->setRendererScale( scale );
1284+
context->setMapToPixel( QgsMapToPixel( mupp ) );
1285+
return validData ? context.take() : nullptr;
1286+
}
1287+
12721288

12731289
QgsLayerTreeModelLegendNode* QgsLayerTreeModel::index2legendNode( const QModelIndex& index )
12741290
{
@@ -1470,6 +1486,8 @@ void QgsLayerTreeModel::invalidateLegendMapBasedData()
14701486
// we do that here because for symbols with size defined in map units
14711487
// the symbol sizes changes depends on the zoom level
14721488

1489+
QScopedPointer<QgsRenderContext> context( createTemporaryRenderContext() );
1490+
14731491
Q_FOREACH ( const LayerLegendData& data, mLegend )
14741492
{
14751493
QList<QgsSymbolLegendNode*> symbolNodes;
@@ -1479,7 +1497,7 @@ void QgsLayerTreeModel::invalidateLegendMapBasedData()
14791497
QgsSymbolLegendNode* n = dynamic_cast<QgsSymbolLegendNode*>( legendNode );
14801498
if ( n )
14811499
{
1482-
const QSize sz( n->minimumIconSize() );
1500+
const QSize sz( n->minimumIconSize( *context ) );
14831501
const QString parentKey( n->data( QgsLayerTreeModelLegendNode::ParentRuleKeyRole ).toString() );
14841502
widthMax[parentKey] = qMax( sz.width(), widthMax.contains( parentKey ) ? widthMax[parentKey] : 0 );
14851503
n->setIconSize( sz );

‎src/core/layertree/qgslayertreemodel.h

Lines changed: 7 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -31,6 +31,7 @@ class QgsMapHitTest;
3131
class QgsMapLayer;
3232
class QgsMapSettings;
3333
class QgsExpression;
34+
class QgsRenderContext;
3435

3536
/** \ingroup core
3637
* The QgsLayerTreeModel class is model implementation for Qt item views framework.
@@ -191,7 +192,7 @@ class CORE_EXPORT QgsLayerTreeModel : public QAbstractItemModel
191192
//! Get hints about map view - to be used in legend nodes. Arguments that are not null will receive values.
192193
//! If there are no valid map view data (from previous call to setLegendMapViewData()), returned values are zeros.
193194
//! @note added in 2.6
194-
void legendMapViewData( double *mapUnitsPerPixel, int *dpi, double *scale );
195+
void legendMapViewData( double *mapUnitsPerPixel, int *dpi, double *scale ) const;
195196

196197
//! Get map of map layer style overrides (key: layer ID, value: style name) where a different style should be used instead of the current one
197198
//! @note added in 2.10
@@ -328,6 +329,11 @@ class CORE_EXPORT QgsLayerTreeModel : public QAbstractItemModel
328329
int mLegendMapViewDpi;
329330
double mLegendMapViewScale;
330331
QTimer mDeferLegendInvalidationTimer;
332+
333+
private:
334+
335+
//! Returns a temporary render context
336+
QgsRenderContext* createTemporaryRenderContext() const;
331337
};
332338

333339
Q_DECLARE_OPERATORS_FOR_FLAGS( QgsLayerTreeModel::Flags )

‎src/core/layertree/qgslayertreemodellegendnode.cpp

Lines changed: 8 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -157,23 +157,27 @@ Qt::ItemFlags QgsSymbolLegendNode::flags() const
157157

158158

159159
QSize QgsSymbolLegendNode::minimumIconSize() const
160+
{
161+
QScopedPointer<QgsRenderContext> context( createTemporaryRenderContext() );
162+
return minimumIconSize( *context );
163+
}
164+
165+
QSize QgsSymbolLegendNode::minimumIconSize( QgsRenderContext& context ) const
160166
{
161167
QSize minSz( 16, 16 );
162168
if ( mItem.symbol() && mItem.symbol()->type() == QgsSymbol::Marker )
163169
{
164-
QScopedPointer<QgsRenderContext> context( createTemporaryRenderContext() );
165170
minSz = QgsImageOperation::nonTransparentImageRect(
166171
QgsSymbolLayerUtils::symbolPreviewPixmap( mItem.symbol(), QSize( 512, 512 ),
167-
context.data() ).toImage(),
172+
&context ).toImage(),
168173
minSz,
169174
true ).size();
170175
}
171176
else if ( mItem.symbol() && mItem.symbol()->type() == QgsSymbol::Line )
172177
{
173-
QScopedPointer<QgsRenderContext> context( createTemporaryRenderContext() );
174178
minSz = QgsImageOperation::nonTransparentImageRect(
175179
QgsSymbolLayerUtils::symbolPreviewPixmap( mItem.symbol(), QSize( minSz.width(), 512 ),
176-
context.data() ).toImage(),
180+
&context ).toImage(),
177181
minSz,
178182
true ).size();
179183
}

‎src/core/layertree/qgslayertreemodellegendnode.h

Lines changed: 15 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -171,10 +171,23 @@ class CORE_EXPORT QgsSymbolLegendNode : public QgsLayerTreeModelLegendNode
171171
//! @note added in 2.10
172172
QSize iconSize() const { return mIconSize; }
173173

174-
//! Get the minimum icon size to prevent cropping
175-
//! @note added in 2.10
174+
/**
175+
* Calculates the minimum icon size to prevent cropping. When evaluating
176+
* the size for multiple icons it is more efficient to create a single
177+
* render context in advance and use the variant which accepts a QgsRenderContext
178+
* argument.
179+
* @note added in 2.10
180+
*/
176181
QSize minimumIconSize() const;
177182

183+
/**
184+
* Calculates the minimum icon size to prevent cropping. When evaluating
185+
* the size for multiple icons it is more efficient to create a single
186+
* render context in advance and call this method instead of minimumIconSize().
187+
* @note added in QGIS 2.18
188+
*/
189+
QSize minimumIconSize( QgsRenderContext &context ) const;
190+
178191
/** Returns the symbol used by the legend node.
179192
* @see setSymbol()
180193
* @note added in QGIS 2.14

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