Add support for adding custom properties to providers

python/core/qgsdataprovider.sip

@@ -33,6 +33,19 @@ class QgsDataProvider : QObject
       Net
     };
 
+    /**
+     * Properties are used to pass custom configuration options into data providers.
+     * This enum defines a list of custom properties which can be used on different
+     * providers. It depends on the provider, which properties are supported.
+     * In addition to these default properties, providers can add their custom properties
+     * starting from CustomData.
+     */
+    enum ProviderProperty
+    {
+      EvaluateDefaultValues,       //!< Evaluate default values on provider side when calling QgsVectorDataProvider::defaultValue( int index ) rather than on commit.
+      CustomData   = 3000          //!< Custom properties for 3rd party providers or very provider-specific properties which are not expected to be of interest for other providers can be added starting from this value up.
+    };
+
     QgsDataProvider( const QString & uri = "" );
 
     /**
@@ -264,6 +277,38 @@ class QgsDataProvider : QObject
      */
     virtual bool leaveUpdateMode();
 
+    /**
+     * Allows setting arbitrary properties on the provider.
+     * It depends on the provider which properties are supported.
+     *
+     * @note added in 2.16
+     */
+    void setProviderProperty( ProviderProperty property, const QVariant& value );
+
+    /**
+     * Allows setting arbitrary properties on the provider.
+     * It depends on the provider which properties are supported.
+     *
+     * @note added in 2.16
+     */
+    // void setProviderProperty( int property, const QVariant& value );
+
+    /**
+     * Get the current value of a certain provider property.
+     * It depends on the provider which properties are supported.
+     *
+     * @note added in 2.16
+     */
+    QVariant providerProperty( ProviderProperty property, const QVariant& defaultValue = QVariant() ) const;
+
+    /**
+     * Get the current value of a certain provider property.
+     * It depends on the provider which properties are supported.
+     *
+     * @note added in 2.16
+     */
+    // QVariant providerProperty( int property , const QVariant& defaultValue ) const;
+
   signals:
 
     /**

src/core/CMakeLists.txt

@@ -102,6 +102,7 @@ SET(QGIS_CORE_SRCS
   qgsdataitemprovider.cpp
   qgsdataitemproviderregistry.cpp
   qgsdatasourceuri.cpp
+  qgsdataprovider.cpp
   qgsdatetimestatisticalsummary.cpp
   qgsdatumtransformstore.cpp
   qgsdbfilterproxymodel.cpp

src/core/qgsdataprovider.cpp

@@ -0,0 +1,38 @@
+/***************************************************************************
+    qgsdataprovider.cpp - DataProvider Interface
+     --------------------------------------
+    Date                 : May 2016
+    Copyright            : (C) 2016 by Matthias Kuhn
+    email                : matthias@opengis.ch
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsdataprovider.h"
+
+
+void QgsDataProvider::setProviderProperty( QgsDataProvider::ProviderProperty property, const QVariant& value )
+{
+  mProviderProperties.insert( property, value );
+}
+
+void QgsDataProvider::setProviderProperty( int property, const QVariant& value )
+{
+  mProviderProperties.insert( property, value );
+}
+
+QVariant QgsDataProvider::providerProperty( QgsDataProvider::ProviderProperty property, const QVariant& defaultValue ) const
+{
+  return mProviderProperties.value( property, defaultValue );
+}
+
+QVariant QgsDataProvider::providerProperty( int property, const QVariant& defaultValue = QVariant() ) const
+{
+  return mProviderProperties.value( property, defaultValue );
+}
+

src/core/qgsdataprovider.h

@@ -61,6 +61,19 @@ class CORE_EXPORT QgsDataProvider : public QObject
       Net                 = 1 << 3  // Internet source
     };
 
+    /**
+     * Properties are used to pass custom configuration options into data providers.
+     * This enum defines a list of custom properties which can be used on different
+     * providers. It depends on the provider, which properties are supported.
+     * In addition to these default properties, providers can add their custom properties
+     * starting from CustomData.
+     */
+    enum ProviderProperty
+    {
+      EvaluateDefaultValues,       //!< Evaluate default values on provider side when calling QgsVectorDataProvider::defaultValue( int index ) rather than on commit.
+      CustomData   = 3000          //!< Custom properties for 3rd party providers or very provider-specific properties which are not expected to be of interest for other providers can be added starting from this value up.
+    };
+
     QgsDataProvider( QString const & uri = "" )
         : mDataSourceURI( uri )
     {}
@@ -352,6 +365,38 @@ class CORE_EXPORT QgsDataProvider : public QObject
      */
     virtual bool leaveUpdateMode() { return true; }
 
+    /**
+     * Allows setting arbitrary properties on the provider.
+     * It depends on the provider which properties are supported.
+     *
+     * @note added in 2.16
+     */
+    void setProviderProperty( ProviderProperty property, const QVariant& value );
+
+    /**
+     * Allows setting arbitrary properties on the provider.
+     * It depends on the provider which properties are supported.
+     *
+     * @note added in 2.16
+     */
+    void setProviderProperty( int property, const QVariant& value );
+
+    /**
+     * Get the current value of a certain provider property.
+     * It depends on the provider which properties are supported.
+     *
+     * @note added in 2.16
+     */
+    QVariant providerProperty( ProviderProperty property, const QVariant& defaultValue = QVariant() ) const;
+
+    /**
+     * Get the current value of a certain provider property.
+     * It depends on the provider which properties are supported.
+     *
+     * @note added in 2.16
+     */
+    QVariant providerProperty( int property , const QVariant& defaultValue ) const;
+
   signals:
 
     /**
@@ -398,6 +443,8 @@ class CORE_EXPORT QgsDataProvider : public QObject
      * This could be a file, database, or server address.
      */
     QString mDataSourceURI;
+
+    QMap< int, QVariant > mProviderProperties;
 };
 
 

src/core/qgsvectordataprovider.h

@@ -168,6 +168,7 @@ class CORE_EXPORT QgsVectorDataProvider : public QgsDataProvider
      * @return map of fields
      * @see QgsFields
      */
+    // TODO QGIS 3: return by value
     virtual const QgsFields &fields() const = 0;
 
     /**