src/core/composer/qgscomposermap.cpp

@@ -49,18 +49,8 @@ QgsComposerMap::QgsComposerMap( QgsComposition *composition, int x, int y, int w
   mOverviewFrameMapSymbol = 0;
   createDefaultOverviewFrameSymbol();
 
-  //mId = mComposition->composerMapItems().size();
-  int maxId = -1;
-  QList<const QgsComposerMap*> mapList = mComposition->composerMapItems();
-  QList<const QgsComposerMap*>::const_iterator mapIt = mapList.constBegin();
-  for ( ; mapIt != mapList.constEnd(); ++mapIt )
-  {
-    if (( *mapIt )->id() > maxId )
-    {
-      maxId = ( *mapIt )->id();
-    }
-  }
-  mId = maxId + 1;
+  mId = 0;
+  assignFreeId();
 
   mMapRenderer = mComposition->mapRenderer();
   mPreviewMode = QgsComposerMap::Rectangle;
@@ -1957,3 +1947,29 @@ void QgsComposerMap::createDefaultOverviewFrameSymbol()
   mOverviewFrameMapSymbol = QgsFillSymbolV2::createSimple( properties );
   mOverviewFrameMapSymbol->setAlpha( 0.3 );
 }
+
+void QgsComposerMap::assignFreeId()
+{
+  if ( !mComposition )
+  {
+    return;
+  }
+
+  const QgsComposerMap* existingMap = mComposition->getComposerMapById( mId );
+  if ( !existingMap )
+  {
+    return; //keep mId as it is still available
+  }
+
+  int maxId = -1;
+  QList<const QgsComposerMap*> mapList = mComposition->composerMapItems();
+  QList<const QgsComposerMap*>::const_iterator mapIt = mapList.constBegin();
+  for ( ; mapIt != mapList.constEnd(); ++mapIt )
+  {
+    if (( *mapIt )->id() > maxId )
+    {
+      maxId = ( *mapIt )->id();
+    }
+  }
+  mId = maxId + 1;
+}

src/core/composer/qgscomposermap.h

@@ -300,6 +300,10 @@ class CORE_EXPORT QgsComposerMap : public QgsComposerItem
     void setOverviewFrameMapSymbol( QgsFillSymbolV2* symbol );
     QgsFillSymbolV2* overviewFrameMapSymbol() { return mOverviewFrameMapSymbol; }
 
+    /**Sets mId to a number not yet used in the composition. mId is kept if it is not in use.
+        Usually, this function is called before adding the composer map to the composition*/
+    void assignFreeId();
+
   signals:
     void extentChanged();
 

src/core/composer/qgscomposition.cpp

@@ -309,6 +309,7 @@ void QgsComposition::addItemsFromXML( const QDomElement& elem, const QDomDocumen
     QDomElement currentComposerMapElem = composerMapList.at( i ).toElement();
     QgsComposerMap* newMap = new QgsComposerMap( this );
     newMap->readXML( currentComposerMapElem, doc );
+    newMap->assignFreeId();
 
     if ( mapsToRestore )
     {

tests/src/core/testqgscomposermap.cpp

@@ -37,6 +37,7 @@ class TestQgsComposerMap: public QObject
     void render(); //test if rendering of the composition with composr map is correct
     void grid(); //test if grid and grid annotation works
     void overviewMap(); //test if overview map frame works
+    void uniqueId(); //test if map id is adapted when doing copy paste
 
   private:
     QgsComposition* mComposition;
@@ -131,5 +132,32 @@ void TestQgsComposerMap::overviewMap()
   QVERIFY( testResult );
 }
 
+void TestQgsComposerMap::uniqueId()
+{
+  QDomDocument doc;
+  QDomElement documentElement = doc.createElement( "ComposerItemClipboard" );
+  mComposerMap->writeXML( documentElement, doc );
+  mComposition->addItemsFromXML( documentElement, doc, 0, false );
+
+  //test if both composer maps have different ids
+  const QgsComposerMap* newMap = 0;
+  QList<const QgsComposerMap*> mapList = mComposition->composerMapItems();
+  QList<const QgsComposerMap*>::const_iterator mapIt = mapList.constBegin();
+  for ( ; mapIt != mapList.constEnd(); ++mapIt )
+  {
+    if ( *mapIt != mComposerMap )
+    {
+      newMap = *mapIt;
+      break;
+    }
+  }
+  int oldId = mComposerMap->id();
+  int newId = newMap->id();
+
+  mComposition->removeComposerItem( const_cast<QgsComposerMap*>( newMap ) );
+
+  QVERIFY( oldId != newId );
+}
+
 QTEST_MAIN( TestQgsComposerMap )
 #include "moc_testqgscomposermap.cxx"