Add QgsMapLayer::flagsChanged() signal

Author: wonder-sk

python/core/auto_generated/qgsmaplayer.sip.in

@@ -1378,6 +1378,17 @@ Emitted when the layer's metadata is changed.
 .. seealso:: :py:func:`metadata`
 
 .. versionadded:: 3.0
+%End
+
+    void flagsChanged();
+%Docstring
+Emitted when layer's flags have been modified.
+
+.. seealso:: :py:func:`setFlags`
+
+.. seealso:: :py:func:`flags`
+
+.. versionadded:: 3.4
 %End
 
   protected:

src/core/qgsmaplayer.cpp

@@ -151,7 +151,11 @@ QgsMapLayer::LayerFlags QgsMapLayer::flags() const
 
 void QgsMapLayer::setFlags( QgsMapLayer::LayerFlags flags )
 {
+  if ( flags == mFlags )
+    return;
+
   mFlags = flags;
+  emit flagsChanged();
 }
 
 QString QgsMapLayer::id() const

src/core/qgsmaplayer.h

@@ -1200,6 +1200,14 @@ class CORE_EXPORT QgsMapLayer : public QObject
      */
     void metadataChanged();
 
+    /**
+     * Emitted when layer's flags have been modified.
+     * \see setFlags()
+     * \see flags()
+     * \since QGIS 3.4
+     */
+    void flagsChanged();
+
   private slots:
 
     void onNotifiedTriggerRepaint( const QString &message );