Correctly handle reading/writing multiple canvas to project

Author: nyalldawson

src/gui/qgsmapcanvas.cpp

@@ -1857,6 +1857,21 @@ void QgsMapCanvas::readProject( const QDomDocument &doc )
   {
     QDomNode node = nodes.item( 0 );
 
+    // Search the specific MapCanvas node using the name
+    if ( nodes.count() > 1 )
+    {
+      for ( int i = 0; i < nodes.size(); ++i )
+      {
+        QDomElement elementNode = nodes.at( i ).toElement();
+
+        if ( elementNode.hasAttribute( "name" ) && elementNode.attribute( "name" ) == objectName() )
+        {
+          node = nodes.at( i );
+          break;
+        }
+      }
+    }
+
     QgsMapSettings tmpSettings;
     tmpSettings.readXml( node );
     setDestinationCrs( tmpSettings.destinationCrs() );
@@ -1886,6 +1901,7 @@ void QgsMapCanvas::writeProject( QDomDocument &doc )
   QDomNode qgisNode = nl.item( 0 );  // there should only be one, so zeroth element ok
 
   QDomElement mapcanvasNode = doc.createElement( QStringLiteral( "mapcanvas" ) );
+  mapcanvasNode.setAttribute( "name", objectName() );
   qgisNode.appendChild( mapcanvasNode );
 
   mSettings.writeXml( mapcanvasNode, doc );

tests/src/python/test_qgsmapcanvas.py

@@ -14,7 +14,8 @@
 
 import qgis  # NOQA
 
-from qgis.core import (QgsCoordinateReferenceSystem,
+from qgis.core import (QgsMapSettings,
+                       QgsCoordinateReferenceSystem,
                        QgsRectangle,
                        QgsVectorLayer,
                        QgsFeature,
@@ -23,10 +24,13 @@
                        QgsFillSymbol,
                        QgsSingleSymbolRenderer,
                        QgsMapThemeCollection,
-                       QgsProject)
+                       QgsProject,
+                       QgsApplication)
 from qgis.gui import (QgsMapCanvas)
 
-from qgis.PyQt.QtCore import QDir
+from qgis.PyQt.QtCore import (Qt,
+                              QDir)
+from qgis.PyQt.QtXml import (QDomDocument, QDomElement)
 import time
 from qgis.testing import start_app, unittest
 
@@ -337,6 +341,35 @@ def canvasImageCheck(self, name, reference_image, canvas):
         print((self.report))
         return result
 
+    def testSaveMultipleCanvasesToProject(self):
+        # test saving/restoring canvas state to project with multiple canvases
+        c1 = QgsMapCanvas()
+        c1.setObjectName('c1')
+        c1.setDestinationCrs(QgsCoordinateReferenceSystem('EPSG:3111'))
+        c1.setRotation(45)
+        c2 = QgsMapCanvas()
+        c2.setObjectName('c2')
+        c2.setDestinationCrs(QgsCoordinateReferenceSystem('EPSG:4326'))
+        c2.setRotation(65)
+
+        doc = QDomDocument("testdoc")
+        elem = doc.createElement("qgis")
+        doc.appendChild(elem)
+        c1.writeProject(doc)
+        c2.writeProject(doc)
+
+        c3 = QgsMapCanvas()
+        c3.setObjectName('c1')
+        c4 = QgsMapCanvas()
+        c4.setObjectName('c2')
+        c3.readProject(doc)
+        c4.readProject(doc)
+
+        self.assertEqual(c3.mapSettings().destinationCrs().authid(), 'EPSG:3111')
+        self.assertEqual(c3.rotation(), 45)
+        self.assertEqual(c4.mapSettings().destinationCrs().authid(), 'EPSG:4326')
+        self.assertEqual(c4.rotation(), 65)
+
 
 if __name__ == '__main__':
     unittest.main()