allow to save/read enum/flags as map layer properties (#44329)

python/core/auto_generated/qgsmaplayer.sip.in

@@ -696,6 +696,8 @@ Read all custom properties from layer. Properties are stored in a map and saved
 .. versionadded:: 3.14
 %End
 
+
+
     void removeCustomProperty( const QString &key );
 %Docstring
 Remove a custom property from layer. Properties are stored in a map and saved in project file.

src/core/qgsmaplayer.h

@@ -40,6 +40,7 @@
 #include "qgsreadwritecontext.h"
 #include "qgsdataprovider.h"
 #include "qgis.h"
+#include "qgslogger.h"
 
 class QgsAbstract3DRenderer;
 class QgsDataProvider;
@@ -675,6 +676,165 @@ class CORE_EXPORT QgsMapLayer : public QObject
      */
     const QgsObjectCustomProperties &customProperties() const;
 
+#ifndef SIP_RUN
+
+    /**
+     * Returns the property value for a property based on an enum.
+     * This forces the output to be a valid and existing entry of the enum.
+     * Hence if the property value is incorrect, the given default value is returned.
+     * This tries first with property as a string (as the enum) and then as an integer value.
+     * \note The enum needs to be declared with Q_ENUM, and flags with Q_FLAG (not Q_FLAGS).
+     * \see setCustomEnumProperty
+     * \see customFlagProperty
+     * \since QGIS 3.22
+     */
+    template <class T>
+    T customEnumProperty( const QString &key, const T &defaultValue )
+    {
+      QMetaEnum metaEnum = QMetaEnum::fromType<T>();
+      Q_ASSERT( metaEnum.isValid() );
+      if ( !metaEnum.isValid() )
+      {
+        QgsDebugMsg( QStringLiteral( "Invalid metaenum. Enum probably misses Q_ENUM or Q_FLAG declaration." ) );
+      }
+
+      T v;
+      bool ok = false;
+
+      if ( metaEnum.isValid() )
+      {
+        // read as string
+        QByteArray ba = customProperty( key, metaEnum.valueToKey( static_cast<int>( defaultValue ) ) ).toString().toUtf8();
+        const char *vs = ba.data();
+        v = static_cast<T>( metaEnum.keyToValue( vs, &ok ) );
+        if ( ok )
+          return v;
+      }
+
+      // if failed, try to read as int (old behavior)
+      // this code shall be removed later
+      // then the method could be marked as const
+      v = static_cast<T>( customProperty( key, static_cast<int>( defaultValue ) ).toInt( &ok ) );
+      if ( metaEnum.isValid() )
+      {
+        if ( !ok || !metaEnum.valueToKey( static_cast<int>( v ) ) )
+        {
+          v = defaultValue;
+        }
+        else
+        {
+          // found property as an integer
+          // convert the property to the new form (string)
+          setCustomEnumProperty( key, v );
+        }
+      }
+
+      return v;
+    }
+
+    /**
+     * Set the value of a property based on an enum.
+     * The property will be saved as string.
+     * \note The enum needs to be declared with Q_ENUM, and flags with Q_FLAG (not Q_FLAGS).
+     * \see customEnumProperty
+     * \see setCustomFlagProperty
+     * \since QGIS 3.22
+     */
+    template <class T>
+    void setCustomEnumProperty( const QString &key, const T &value )
+    {
+      QMetaEnum metaEnum = QMetaEnum::fromType<T>();
+      Q_ASSERT( metaEnum.isValid() );
+      if ( metaEnum.isValid() )
+      {
+        setCustomProperty( key, metaEnum.valueToKey( static_cast<int>( value ) ) );
+      }
+      else
+      {
+        QgsDebugMsg( QStringLiteral( "Invalid metaenum. Enum probably misses Q_ENUM or Q_FLAG declaration." ) );
+      }
+    }
+
+    /**
+     * Returns the property value for a property based on a flag.
+     * This forces the output to be a valid and existing entry of the flag.
+     * Hence if the property value is incorrect, the given default value is returned.
+     * This tries first with property as a string (using a byte array) and then as an integer value.
+     * \note The flag needs to be declared with Q_FLAG (not Q_FLAGS).
+     * \note for Python bindings, a custom implementation is achieved in Python directly.
+     * \see setCustomFlagProperty
+     * \see customEnumProperty
+     * \since QGIS 3.22
+     */
+    template <class T>
+    T customFlagProperty( const QString &key, const T &defaultValue )
+    {
+      QMetaEnum metaEnum = QMetaEnum::fromType<T>();
+      Q_ASSERT( metaEnum.isValid() );
+      if ( !metaEnum.isValid() )
+      {
+        QgsDebugMsg( QStringLiteral( "Invalid metaenum. Enum probably misses Q_ENUM or Q_FLAG declaration." ) );
+      }
+
+      T v = defaultValue;
+      bool ok = false;
+
+      if ( metaEnum.isValid() )
+      {
+        // read as string
+        QByteArray ba = customProperty( key, metaEnum.valueToKeys( defaultValue ) ).toString().toUtf8();
+        const char *vs = ba.data();
+        v = static_cast<T>( metaEnum.keysToValue( vs, &ok ) );
+      }
+      if ( !ok )
+      {
+        // if failed, try to read as int (old behavior)
+        // this code shall be removed later
+        // then the method could be marked as const
+        v = T( customProperty( key, static_cast<int>( defaultValue ) ).toInt( &ok ) );
+        if ( metaEnum.isValid() )
+        {
+          if ( !ok || metaEnum.valueToKeys( static_cast<int>( v ) ).isEmpty() )
+          {
+            v = defaultValue;
+          }
+          else
+          {
+            // found property as an integer
+            // convert the property to the new form (string)
+            setCustomFlagProperty( key, v );
+          }
+        }
+      }
+
+      return v;
+    }
+
+    /**
+     * Set the value of a property based on a flag.
+     * The property will be saved as string.
+     * \note The flag needs to be declared with Q_FLAG (not Q_FLAGS).
+     * \see customFlagProperty
+     * \see customEnumProperty
+     * \since QGIS 3.22
+     */
+    template <class T>
+    void setCustomFlagProperty( const QString &key, const T &value )
+    {
+      QMetaEnum metaEnum = QMetaEnum::fromType<T>();
+      Q_ASSERT( metaEnum.isValid() );
+      if ( metaEnum.isValid() )
+      {
+        setCustomProperty( key, metaEnum.valueToKeys( value ) );
+      }
+      else
+      {
+        QgsDebugMsg( QStringLiteral( "Invalid metaenum. Enum probably misses Q_ENUM or Q_FLAG declaration." ) );
+      }
+    }
+#endif
+
+
     /**
      * Remove a custom property from layer. Properties are stored in a map and saved in project file.
      * \see setCustomProperty()

tests/src/core/testqgsmaplayer.cpp

@@ -28,6 +28,7 @@
 #include <qgsproviderregistry.h>
 #include "qgsvectorlayerref.h"
 #include "qgsmaplayerlistutils.h"
+#include "qgsmaplayerproxymodel.h"
 
 /**
  * \ingroup UnitTests
@@ -64,6 +65,8 @@ class TestQgsMapLayer : public QObject
 
     void notify();
 
+    void customEnumFlagProperties();
+
   private:
     QgsVectorLayer *mpLayer = nullptr;
 };
@@ -387,5 +390,59 @@ void TestQgsMapLayer::notify()
   QCOMPARE( spyDataChanged.count(), 2 );
 }
 
+void TestQgsMapLayer::customEnumFlagProperties()
+{
+  std::unique_ptr<QgsVectorLayer> ml = std::make_unique<QgsVectorLayer>( QStringLiteral( "Point" ), QStringLiteral( "name" ), QStringLiteral( "memory" ) );
+
+  // assign to inexisting property
+  ml->setCustomProperty( QStringLiteral( "my_property_for_units" ), -1 );
+  ml->setCustomProperty( QStringLiteral( "my_property_for_units_as_string" ), QStringLiteral( "myString" ) );
+  // just to be sure it really doesn't exist
+  QVERIFY( static_cast<int>( QgsUnitTypes::LayoutMeters ) != -1 );
+
+  // standard method returns invalid property
+  int v1 = ml->customProperty( QStringLiteral( "my_property_for_units" ), QgsUnitTypes::LayoutMeters ).toInt();
+  QCOMPARE( v1, -1 );
+
+  // enum method returns default property if current property is incorrect
+  QgsUnitTypes::LayoutUnit v2 = ml->customEnumProperty( QStringLiteral( "my_property_for_units" ), QgsUnitTypes::LayoutMeters );
+  QCOMPARE( v2, QgsUnitTypes::LayoutMeters );
+  QgsUnitTypes::LayoutUnit v2s = ml->customEnumProperty( QStringLiteral( "my_property_for_units_as_string" ), QgsUnitTypes::LayoutMeters );
+  QCOMPARE( v2s, QgsUnitTypes::LayoutMeters );
+
+  // test a different property than default
+  ml->setCustomEnumProperty( QStringLiteral( "my_property_for_units" ), QgsUnitTypes::LayoutCentimeters );
+  QgsUnitTypes::LayoutUnit v3 = ml->customEnumProperty( QStringLiteral( "my_property_for_units" ), QgsUnitTypes::LayoutMeters );
+  QCOMPARE( v3, QgsUnitTypes::LayoutCentimeters );
+  ml->setCustomEnumProperty( QStringLiteral( "my_property_for_units" ), QgsUnitTypes::LayoutCentimeters );
+  // auto conversion of old ml (int to str)
+  QCOMPARE( ml->customProperty( "my_property_for_units" ).toString(), QStringLiteral( "LayoutCentimeters" ) );
+  QgsUnitTypes::LayoutUnit v3s = ml->customEnumProperty( QStringLiteral( "my_property_for_units" ), QgsUnitTypes::LayoutMeters );
+  QCOMPARE( v3s, QgsUnitTypes::LayoutCentimeters );
+  QString v3ss = ml->customProperty( QStringLiteral( "my_property_for_units" ), QStringLiteral( "myDummyValue" ) ).toString();
+  QCOMPARE( v3ss, QStringLiteral( "LayoutCentimeters" ) );
+
+  // Flags
+  QgsMapLayerProxyModel::Filters pointAndLine = QgsMapLayerProxyModel::Filters( QgsMapLayerProxyModel::PointLayer | QgsMapLayerProxyModel::LineLayer );
+  QgsMapLayerProxyModel::Filters pointAndPolygon = QgsMapLayerProxyModel::Filters( QgsMapLayerProxyModel::PointLayer | QgsMapLayerProxyModel::PolygonLayer );
+  ml->setCustomProperty( QStringLiteral( "my_property_for_a_flag" ), 1e8 ); // invalid
+  // this should be switched to customFlagProperty (see https://stackoverflow.com/questions/68485843/how-to-test-if-a-value-is-valid-for-a-qflags)
+  QgsMapLayerProxyModel::Filters v4 = ml->customEnumProperty( QStringLiteral( "my_property_for_a_flag" ), pointAndLine );
+  QCOMPARE( v4, pointAndLine );
+
+  ml->setCustomProperty( QStringLiteral( "my_property_for_a_flag" ), static_cast<int>( pointAndPolygon ) );
+  QgsMapLayerProxyModel::Filters v5 = ml->customFlagProperty( QStringLiteral( "my_property_for_a_flag" ), pointAndLine );
+  QCOMPARE( v5, pointAndPolygon );
+  // auto conversion of old property (int to str)
+  QCOMPARE( ml->customProperty( "my_property_for_a_flag" ).toString(), QStringLiteral( "PointLayer|PolygonLayer" ) );
+
+  ml->setCustomFlagProperty( QStringLiteral( "my_property_for_a_flag_as_string" ), pointAndPolygon );
+  QgsMapLayerProxyModel::Filters v5s = ml->customFlagProperty( QStringLiteral( "my_property_for_a_flag_as_string" ), pointAndLine );
+  QCOMPARE( v5s, pointAndPolygon );
+  QString v5ss = ml->customProperty( QStringLiteral( "my_property_for_a_flag_as_string" ), QStringLiteral( "myDummyString" ) ).toString();
+  QCOMPARE( v5ss, QStringLiteral( "PointLayer|PolygonLayer" ) );
+}
+
+
 QGSTEST_MAIN( TestQgsMapLayer )
 #include "testqgsmaplayer.moc"