[composer] Correctly draw overview frame when map item CRS differs

src/core/composer/qgscomposermapoverview.cpp

@@ -23,6 +23,7 @@
 #include "qgsmapsettings.h"
 #include "qgspainting.h"
 #include "qgscomposerutils.h"
+#include "qgscsexception.h"
 
 #include <QPainter>
 
@@ -82,6 +83,25 @@ void QgsComposerMapOverview::draw( QPainter *painter )
 
   //get polygon for other overview frame map's extent (use visibleExtentPolygon as it accounts for map rotation)
   QPolygonF otherExtent = overviewFrameMap->visibleExtentPolygon();
+  if ( overviewFrameMap->crs() !=
+       mComposerMap->crs() )
+  {
+    QgsGeometry g = QgsGeometry::fromQPolygonF( otherExtent );
+
+    // reproject extent
+    QgsCoordinateTransform ct( overviewFrameMap->crs(),
+                               mComposerMap->crs() );
+    g = g.densifyByCount( 20 );
+    try
+    {
+      g.transform( ct );
+    }
+    catch ( QgsCsException & )
+    {
+    }
+
+    otherExtent = g.asQPolygonF();
+  }
 
   //get current map's extent as a QPolygonF
   QPolygonF thisExtent = mComposerMap->visibleExtentPolygon();

tests/src/core/testqgscomposermapoverview.cpp

@@ -50,6 +50,7 @@ class TestQgsComposerMapOverview : public QObject
     void overviewMapBlending(); //test if blend modes with overview map frame works
     void overviewMapInvert(); //test if invert of overview map frame works
     void overviewMapCenter(); //test if centering of overview map frame works
+    void overviewReprojected(); //test that overview frame is reprojected
 
   private:
     QgsComposition *mComposition = nullptr;
@@ -217,5 +218,27 @@ void TestQgsComposerMapOverview::overviewMapCenter()
   QVERIFY( testResult );
 }
 
+void TestQgsComposerMapOverview::overviewReprojected()
+{
+  QgsComposerMap *overviewMap = new QgsComposerMap( mComposition, 20, 130, 70, 70 );
+  overviewMap->setFrameEnabled( true );
+  //overviewMap->setLayers( QList<QgsMapLayer *>() << mRasterLayer );
+  mComposition->addComposerMap( overviewMap );
+
+  mComposerMap->setCrs( QgsCoordinateReferenceSystem::fromEpsgId( 4326 ) );
+  overviewMap->setCrs( QgsCoordinateReferenceSystem::fromEpsgId( 54030 ) );
+
+  mComposerMap->setNewExtent( QgsRectangle( 93, -64.245, 120.6, -45 ) );
+  overviewMap->setNewExtent( QgsRectangle( 4712502, -7620278, 10872777, -2531356 ) );
+  overviewMap->overview()->setFrameMap( mComposerMap->id() );
+
+  QgsCompositionChecker checker( QStringLiteral( "composermap_overview_reprojected" ), mComposition );
+  checker.setControlPathPrefix( QStringLiteral( "composer_mapoverview" ) );
+
+  bool testResult = checker.testComposition( mReport, 0, 0 );
+  mComposition->removeComposerItem( overviewMap );
+  QVERIFY( testResult );
+}
+
 QGSTEST_MAIN( TestQgsComposerMapOverview )
 #include "testqgscomposermapoverview.moc"