Add QgsVectorLayer::canCommitChanges

m-kuhn · m-kuhn · commit a56deacf546a · 2018-09-26T16:17:24.000+02:00
to control if changes can be saved or not. This signal is emitted before a layer is being saved and if a connected slot marks the canCommit variable as False, the layer will not be saved
diff --git a/python/core/auto_generated/qgsvectorlayer.sip.in b/python/core/auto_generated/qgsvectorlayer.sip.in
@@ -2352,6 +2352,16 @@ Is emitted, when editing on this layer has started
     void editingStopped();
 %Docstring
 Is emitted, when edited changes successfully have been written to the data provider
+%End
+
+    void canCommitChanges( bool &canCommit );
+%Docstring
+Emitted when a layer wants to commit changes to the data provider.
+Can be used to prevent the layer from being saved by setting ``canCommit`` to false.
+
+It is the developers responsibility to inform the user about this in a suitable manner.
+
+.. versionadded:: 3.4
 %End
 
     void beforeCommitChanges();
diff --git a/src/core/qgsvectorlayer.cpp b/src/core/qgsvectorlayer.cpp
@@ -2924,6 +2924,13 @@ bool QgsVectorLayer::commitChanges()
     return false;
   }
 
+  bool canCommit = true;
+
+  emit canCommitChanges( canCommit );
+
+  if ( !canCommit )
+    return false;
+
   emit beforeCommitChanges();
 
   bool success = mEditBuffer->commitChanges( mCommitErrors );
diff --git a/src/core/qgsvectorlayer.h b/src/core/qgsvectorlayer.h
@@ -2114,6 +2114,16 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
     //! Is emitted, when edited changes successfully have been written to the data provider
     void editingStopped();
 
+    /**
+     * Emitted when a layer wants to commit changes to the data provider.
+     * Can be used to prevent the layer from being saved by setting \a canCommit to false.
+     *
+     * It is the developers responsibility to inform the user about this in a suitable manner.
+     *
+     * \since QGIS 3.4
+     */
+    void canCommitChanges( bool &canCommit );
+
     //! Is emitted, before changes are committed to the data provider
     void beforeCommitChanges();
 
