[layouts] Add API allowing drawing map overviews under map layers

or under map labels

python/core/auto_generated/layout/qgslayoutitemmapitem.sip.in

@@ -243,9 +243,13 @@ map item after restoration from XML.
 .. seealso:: :py:func:`readXml`
 %End
 
-    void drawItems( QPainter *painter );
+    void drawItems( QPainter *painter, bool ignoreStacking = true );
 %Docstring
 Draws the items from the stack on a specified ``painter``.
+
+If ``ignoreStacking`` is true, then all items will be drawn, regardless
+of their actual stacking position settings. If it is false, only items
+which are set to stack above the map item will be drawn.
 %End
 
     bool containsAdvancedEffects() const;

src/core/layout/qgslayoutitemmap.cpp

@@ -854,7 +854,7 @@ void QgsLayoutItemMap::paint( QPainter *painter, const QStyleOptionGraphicsItem
 
     if ( shouldDrawPart( OverviewMapExtent ) )
     {
-      mOverviewStack->drawItems( painter );
+      mOverviewStack->drawItems( painter, false );
     }
     if ( shouldDrawPart( Grid ) )
     {
@@ -922,7 +922,7 @@ void QgsLayoutItemMap::paint( QPainter *painter, const QStyleOptionGraphicsItem
 
       if ( shouldDrawPart( OverviewMapExtent ) )
       {
-        mOverviewStack->drawItems( &p );
+        mOverviewStack->drawItems( &p, false );
       }
       if ( shouldDrawPart( Grid ) )
       {
@@ -960,7 +960,7 @@ void QgsLayoutItemMap::paint( QPainter *painter, const QStyleOptionGraphicsItem
 
       if ( shouldDrawPart( OverviewMapExtent ) )
       {
-        mOverviewStack->drawItems( painter );
+        mOverviewStack->drawItems( painter, false );
       }
       if ( shouldDrawPart( Grid ) )
       {
@@ -1006,7 +1006,13 @@ void QgsLayoutItemMap::drawMap( QPainter *painter, const QgsRectangle &extent, Q
   }
 
   // render
-  QgsMapRendererCustomPainterJob job( mapSettings( extent, size, dpi, true ), painter );
+  QgsMapSettings ms( mapSettings( extent, size, dpi, true ) );
+  if ( shouldDrawPart( OverviewMapExtent ) )
+  {
+    ms.setLayers( mOverviewStack->modifyMapLayerList( ms.layers() ) );
+  }
+
+  QgsMapRendererCustomPainterJob job( ms, painter );
   // Render the map in this thread. This is done because of problems
   // with printing to printer on Windows (printing to PDF is fine though).
   // Raster images were not displayed - see #10599
@@ -1084,6 +1090,12 @@ void QgsLayoutItemMap::recreateCachedImageInBackground()
   mCacheInvalidated = false;
   mPainter.reset( new QPainter( mCacheRenderingImage.get() ) );
   QgsMapSettings settings( mapSettings( ext, QSizeF( w, h ), mCacheRenderingImage->logicalDpiX(), true ) );
+
+  if ( shouldDrawPart( OverviewMapExtent ) )
+  {
+    settings.setLayers( mOverviewStack->modifyMapLayerList( settings.layers() ) );
+  }
+
   mPainterJob.reset( new QgsMapRendererCustomPainterJob( settings, mPainter.get() ) );
   connect( mPainterJob.get(), &QgsMapRendererCustomPainterJob::finished, this, &QgsLayoutItemMap::painterJobFinished );
   mPainterJob->start();

src/core/layout/qgslayoutitemmapitem.cpp

@@ -239,7 +239,7 @@ void QgsLayoutItemMapItemStack::finalizeRestoreFromXml()
   }
 }
 
-void QgsLayoutItemMapItemStack::drawItems( QPainter *painter )
+void QgsLayoutItemMapItemStack::drawItems( QPainter *painter, bool ignoreStacking )
 {
   if ( !painter )
   {
@@ -248,7 +248,21 @@ void QgsLayoutItemMapItemStack::drawItems( QPainter *painter )
 
   for ( QgsLayoutItemMapItem *item : qgis::as_const( mItems ) )
   {
-    item->draw( painter );
+    switch ( item->stackingPosition() )
+    {
+      case QgsLayoutItemMapItem::StackBelowMap:
+      case QgsLayoutItemMapItem::StackAboveMapLayer:
+      case QgsLayoutItemMapItem::StackBelowMapLayer:
+      case QgsLayoutItemMapItem::StackBelowMapLabels:
+        if ( !ignoreStacking )
+          break;
+
+        FALLTHROUGH
+      case QgsLayoutItemMapItem::StackAboveMapLabels:
+        item->draw( painter );
+        break;
+
+    }
   }
 }
 

src/core/layout/qgslayoutitemmapitem.h

@@ -250,8 +250,12 @@ class CORE_EXPORT QgsLayoutItemMapItemStack
 
     /**
      * Draws the items from the stack on a specified \a painter.
+     *
+     * If \a ignoreStacking is true, then all items will be drawn, regardless
+     * of their actual stacking position settings. If it is false, only items
+     * which are set to stack above the map item will be drawn.
      */
-    void drawItems( QPainter *painter );
+    void drawItems( QPainter *painter, bool ignoreStacking = true );
 
     /**
      * Returns whether any items within the stack contain advanced effects,

src/core/layout/qgslayoutitemmapoverview.cpp

@@ -230,7 +230,7 @@ void QgsLayoutItemMapOverview::setLinkedMap( QgsLayoutItemMap *map )
   mFrameMap = map;
   //connect to new map signals
   connectSignals();
-  mMap->update();
+  mMap->invalidateCache();
 }
 
 QgsLayoutItemMap *QgsLayoutItemMapOverview::linkedMap()
@@ -358,13 +358,10 @@ void QgsLayoutItemMapOverview::overviewExtentChanged()
                               center.x() - extent.width() / 2 + extent.width(),
                               center.y() - extent.height() / 2 + extent.height() );
     mMap->setExtent( movedExtent );
-
-    //must invalidate cache so that map gets redrawn
-    mMap->invalidateCache();
   }
 
   //repaint map so that overview gets updated
-  mMap->update();
+  mMap->invalidateCache();
 }
 
 

tests/src/python/test_qgslayoutmapoverview.py

@@ -289,6 +289,47 @@ class TestQgsLayoutMap(unittest.TestCase, LayoutItemTestCase):
         self.assertEqual(overviewMap.overviews().modifyMapLayerList([self.raster_layer, self.vector_layer]),
                          [overviewMap.overviews().overview(1).asMapLayer(), self.raster_layer, self.vector_layer, overviewMap.overview().asMapLayer()])
 
+    def testOverviewStacking(self):
+        l = QgsLayout(QgsProject.instance())
+        l.initializeDefaults()
+        map = QgsLayoutItemMap(l)
+        map.attemptSetSceneRect(QRectF(20, 20, 200, 100))
+        map.setFrameEnabled(True)
+        map.setLayers([self.raster_layer])
+        l.addLayoutItem(map)
+
+        overviewMap = QgsLayoutItemMap(l)
+        overviewMap.attemptSetSceneRect(QRectF(20, 130, 70, 70))
+        l.addLayoutItem(overviewMap)
+        overviewMap.setFrameEnabled(True)
+        overviewMap.setLayers([self.raster_layer])
+        # zoom in
+        myRectangle = QgsRectangle(96, -152, 160, -120)
+        map.setExtent(myRectangle)
+        myRectangle2 = QgsRectangle(-20, -276, 276, 20)
+        overviewMap.setExtent(myRectangle2)
+        overviewMap.overview().setLinkedMap(map)
+        overviewMap.overview().setInverted(True)
+        overviewMap.overview().setStackingPosition(QgsLayoutItemMapItem.StackBelowMapLayer)
+        overviewMap.overview().setStackingLayer(self.raster_layer)
+
+        checker = QgsLayoutChecker('composermap_overview_belowmap', l)
+        checker.setColorTolerance(6)
+        checker.setControlPathPrefix("composer_mapoverview")
+        myTestResult, myMessage = checker.testLayout()
+        self.report += checker.report()
+        self.assertTrue(myTestResult, myMessage)
+
+        overviewMap.overview().setStackingPosition(QgsLayoutItemMapItem.StackAboveMapLayer)
+        overviewMap.overview().setStackingLayer(self.raster_layer)
+
+        checker = QgsLayoutChecker('composermap_overview_abovemap', l)
+        checker.setColorTolerance(6)
+        checker.setControlPathPrefix("composer_mapoverview")
+        myTestResult, myMessage = checker.testLayout()
+        self.report += checker.report()
+        self.assertTrue(myTestResult, myMessage)
+
 
 if __name__ == '__main__':
     unittest.main()