[composer] Fix initial size of legend is wrong if symbol size in

map units is used (fix #11921)

On behalf of Faunalia, sponsored by ENEL

src/core/composer/qgscomposerlegend.cpp

@@ -42,11 +42,10 @@ QgsComposerLegend::QgsComposerLegend( QgsComposition* composition )
     , mFilterOutAtlas( false )
     , mFilterAskedForUpdate( false )
     , mInAtlas( false )
+    , mInitialMapScaleCalculated( false )
 {
   mLegendModel2 = new QgsLegendModelV2( QgsProject::instance()->layerTreeRoot() );
 
-  adjustBoxSize();
-
   connect( &mLegendModel, SIGNAL( layersChanged() ), this, SLOT( synchronizeWithModel() ) );
 
   connect( &composition->atlasComposition(), SIGNAL( renderEnded() ), this, SLOT( onAtlasEnded() ) );
@@ -115,12 +114,7 @@ void QgsComposerLegend::paint( QPainter* painter, const QStyleOptionGraphicsItem
     ms.setOutputDpi( dpi );
     mSettings.setMapScale( ms.scale() );
   }
-
-  drawBackground( painter );
-  painter->save();
-  //antialiasing on
-  painter->setRenderHint( QPainter::Antialiasing, true );
-  painter->setPen( QPen( QColor( 0, 0, 0 ) ) );
+  mInitialMapScaleCalculated = true;
 
   QgsLegendRenderer legendRenderer( mLegendModel2, mSettings );
   legendRenderer.setLegendSize( rect().size() );
@@ -140,6 +134,12 @@ void QgsComposerLegend::paint( QPainter* painter, const QStyleOptionGraphicsItem
     setSceneRect( evalItemRect( targetRect, true ) );
   }
 
+  drawBackground( painter );
+  painter->save();
+  //antialiasing on
+  painter->setRenderHint( QPainter::Antialiasing, true );
+  painter->setPen( QPen( QColor( 0, 0, 0 ) ) );
+
   legendRenderer.drawLegend( painter );
 
   painter->restore();
@@ -170,6 +170,15 @@ QSizeF QgsComposerLegend::paintAndDetermineSize( QPainter* painter )
 
 void QgsComposerLegend::adjustBoxSize()
 {
+  if ( !mInitialMapScaleCalculated )
+  {
+    // this is messy - but until we have painted the item we have no knowledge of the current DPI
+    // and so cannot correctly calculate the map scale. This results in incorrect size calculations
+    // for marker symbols with size in map units, causing the legends to initially expand to huge
+    // sizes if we attempt to calculate the box size first.
+    return;
+  }
+
   QgsLegendRenderer legendRenderer( mLegendModel2, mSettings );
   QSizeF size = legendRenderer.minimumSize();
   QgsDebugMsg( QString( "width = %1 height = %2" ).arg( size.width() ).arg( size.height() ) );

src/core/composer/qgscomposerlegend.h

@@ -293,6 +293,9 @@ class CORE_EXPORT QgsComposerLegend : public QgsComposerItem
     void doUpdateFilterByMap();
 
     bool mInAtlas;
+
+    //! Will be false until the associated map scale and DPI have been calculated
+    bool mInitialMapScaleCalculated;
 };
 
 #endif

tests/src/python/CMakeLists.txt

@@ -25,6 +25,7 @@ ADD_PYTHON_TEST(PyQgsColorSchemeRegistry test_qgscolorschemeregistry.py)
 ADD_PYTHON_TEST(PyQgsComposerEffects test_qgscomposereffects.py)
 ADD_PYTHON_TEST(PyQgsComposerHtml test_qgscomposerhtml.py)
 ADD_PYTHON_TEST(PyQgsComposerLabel test_qgscomposerlabel.py)
+ADD_PYTHON_TEST(PyQgsComposerLegend test_qgscomposerlegend.py)
 ADD_PYTHON_TEST(PyQgsComposerMap test_qgscomposermap.py)
 ADD_PYTHON_TEST(PyQgsComposerMapGrid test_qgscomposermapgrid.py)
 ADD_PYTHON_TEST(PyQgsComposerPicture test_qgscomposerpicture.py)

tests/src/python/test_qgscomposerlegend.py

@@ -0,0 +1,82 @@
+# -*- coding: utf-8 -*-
+"""QGIS Unit tests for QgsComposerLegend.
+
+.. note:: This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+"""
+__author__ = '(C) 2016 by Nyall Dawson'
+__date__ = '13/07/2016'
+__copyright__ = 'Copyright 2016, The QGIS Project'
+# This will get replaced with a git SHA1 when you do a git archive
+__revision__ = '$Format:%H$'
+
+from qgis.PyQt.QtCore import QRectF
+from qgis.PyQt.QtGui import QColor
+
+from qgis.core import (QgsComposerLegend,
+                       QgsComposerMap,
+                       QgsComposition,
+                       QgsMapSettings,
+                       QgsVectorLayer,
+                       QgsMapLayerRegistry,
+                       QgsMarkerSymbolV2,
+                       QgsSingleSymbolRendererV2
+                       )
+from qgis.testing import (start_app,
+                          unittest
+                          )
+from utilities import unitTestDataPath
+from qgscompositionchecker import QgsCompositionChecker
+import os
+
+start_app()
+TEST_DATA_DIR = unitTestDataPath()
+
+
+class TestQgsComposerLegend(unittest.TestCase):
+
+    def __init__(self, methodName):
+        """Run once on class initialization."""
+        unittest.TestCase.__init__(self, methodName)
+        point_path = os.path.join(TEST_DATA_DIR, 'points.shp')
+        self.point_layer = QgsVectorLayer(point_path, 'points', 'ogr')
+        QgsMapLayerRegistry.instance().addMapLayers([self.point_layer])
+
+    def testInitialSizeSymbolMapUnits(self):
+        """Test initial size of legend with a symbol size in map units"""
+
+        marker_symbol = QgsMarkerSymbolV2.createSimple({'color': '#ff0000', 'outline_style': 'no', 'size': '5', 'size_unit': 'MapUnit'})
+
+        self.point_layer.setRendererV2(QgsSingleSymbolRendererV2(marker_symbol))
+
+        s = QgsMapSettings()
+        s.setLayers([self.point_layer.id()])
+        s.setCrsTransformEnabled(False)
+        composition = QgsComposition(s)
+        composition.setPaperSize(297, 210)
+
+        composer_map = QgsComposerMap(composition, 20, 20, 80, 80)
+        composer_map.setFrameEnabled(True)
+        composition.addComposerMap(composer_map)
+        composer_map.setNewExtent(self.point_layer.extent())
+
+        legend = QgsComposerLegend(composition)
+        legend.setSceneRect(QRectF(120, 20, 80, 80))
+        legend.setFrameEnabled(True)
+        legend.setFrameOutlineWidth(2)
+        legend.setBackgroundColor(QColor(200, 200, 200))
+        legend.setTitle('')
+        composition.addComposerLegend(legend)
+        legend.setComposerMap(composer_map)
+
+        checker = QgsCompositionChecker(
+            'composer_legend_mapunits', composition)
+        checker.setControlPathPrefix("composer_legend")
+        result, message = checker.testComposition()
+        self.assertTrue(result, message)
+
+
+if __name__ == '__main__':
+    unittest.main()