add classification methods registry

src/core/qgsapplication.cpp

@@ -41,6 +41,7 @@
 #include "qgssymbollayerutils.h"
 #include "callouts/qgscalloutsregistry.h"
 #include "qgspluginlayerregistry.h"
+#include "qgsclassificationmethodregistry.h"
 #include "qgsmessagelog.h"
 #include "qgsannotationregistry.h"
 #include "qgssettings.h"
@@ -1920,6 +1921,11 @@ QgsPluginLayerRegistry *QgsApplication::pluginLayerRegistry()
   return members()->mPluginLayerRegistry;
 }
 
+QgsClassificationMethodRegistry *QgsApplication::classificationMethodRegistry()
+{
+  return members()->mClassificationMethodRegistry;
+}
+
 QgsMessageLog *QgsApplication::messageLog()
 {
   return members()->mMessageLog;
@@ -1983,6 +1989,7 @@ QgsApplication::ApplicationMembers::ApplicationMembers()
   mProjectStorageRegistry = new QgsProjectStorageRegistry();
   mNetworkContentFetcherRegistry = new QgsNetworkContentFetcherRegistry();
   mValidityCheckRegistry = new QgsValidityCheckRegistry();
+  mClassificationMethodRegistry = new QgsClassificationMethodRegistry();
 }
 
 QgsApplication::ApplicationMembers::~ApplicationMembers()
@@ -2010,6 +2017,7 @@ QgsApplication::ApplicationMembers::~ApplicationMembers()
   delete mSymbolLayerRegistry;
   delete mTaskManager;
   delete mNetworkContentFetcherRegistry;
+  delete mClassificationMethodRegistry;
 }
 
 QgsApplication::ApplicationMembers *QgsApplication::members()

src/core/qgsapplication.h

@@ -40,6 +40,7 @@ class QgsRasterRendererRegistry;
 class QgsGpsConnectionRegistry;
 class QgsDataItemProviderRegistry;
 class QgsPluginLayerRegistry;
+class QgsClassificationMethodRegistry;
 class QgsMessageLog;
 class QgsProcessingRegistry;
 class QgsAnnotationRegistry;
@@ -637,6 +638,13 @@ class CORE_EXPORT QgsApplication : public QApplication
      */
     static QgsPluginLayerRegistry *pluginLayerRegistry() SIP_KEEPREFERENCE;
 
+    /**
+     * Returns the application's classification methods registry, used in graduated renderer
+     * \since QGIS 3.10
+     */
+    static QgsClassificationMethodRegistry *classificationMethodRegistry() SIP_KEEPREFERENCE;
+
+
     /**
      * Returns the application's message log.
      * \since QGIS 3.0
@@ -869,6 +877,7 @@ class CORE_EXPORT QgsApplication : public QApplication
       QgsMessageLog *mMessageLog = nullptr;
       QgsPaintEffectRegistry *mPaintEffectRegistry = nullptr;
       QgsPluginLayerRegistry *mPluginLayerRegistry = nullptr;
+      QgsClassificationMethodRegistry *mClassificationMethodRegistry = nullptr;
       QgsProcessingRegistry *mProcessingRegistry = nullptr;
       QgsProjectStorageRegistry *mProjectStorageRegistry = nullptr;
       QgsPageSizeRegistry *mPageSizeRegistry = nullptr;

src/core/symbology/classification/qgsclassificationmethodregistry.cpp

@@ -0,0 +1,54 @@
+/***************************************************************************
+    qgsclassificationmethodregistry.h
+    ---------------------
+    begin                : September 2019
+    copyright            : (C) 2019 by Denis Rouzaud
+    email                : denis@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 "qgsclassificationmethodregistry.h"
+
+// classification methods
+#include "qgsclassificationcustom.h"
+#include "qgsclassificationequalinterval.h"
+#include "qgsclassificationquantile.h"
+#include "qgsclassificationjenks.h"
+#include "qgsclassificationstandarddeviation.h"
+#include "qgsclassificationprettybreaks.h"
+
+QgsClassificationMethodRegistry::QgsClassificationMethodRegistry()
+{
+  addMethod( new QgsClassificationEqualInterval() );
+  addMethod( new QgsClassificationQuantile() );
+  addMethod( new QgsClassificationJenks() );
+  addMethod( new QgsClassificationStandardDeviation() );
+  addMethod( new QgsClassificationPrettyBreaks() );
+}
+
+void QgsClassificationMethodRegistry::addMethod( QgsClassificationMethod *method )
+{
+  mMethods.insert( method->id(), method );
+}
+
+QgsClassificationMethod *QgsClassificationMethodRegistry::method( const QString &id )
+{
+  QgsClassificationMethod *method = mMethods.value( id, new QgsClassificationCustom() );
+  return method->clone();
+}
+
+QMap<QString, QString> QgsClassificationMethodRegistry::methodNames() const
+{
+  QMap<QString, QString> methods;
+  for ( const QgsClassificationMethod *method : qgis::as_const( mMethods ) )
+    methods.insert( method->id(), method->name() );
+  return methods;
+}
+

src/core/symbology/classification/qgsclassificationmethodregistry.h

@@ -0,0 +1,55 @@
+/***************************************************************************
+    qgsclassificationmethodregistry.h
+    ---------------------
+    begin                : September 2019
+    copyright            : (C) 2019 by Denis Rouzaud
+    email                : denis@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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+
+#ifndef QGSCLASSIFICATIONMETHODREGISTRY_H
+#define QGSCLASSIFICATIONMETHODREGISTRY_H
+
+#include <QMap>
+
+#include "qgis_core.h"
+#include "qgis_sip.h"
+
+class QgsClassificationMethod;
+
+/**
+ * \ingroup gui
+ * This class manages all known classification methods
+ *
+ * QgsClassificationMethodRegistry is not usually directly created, but rather accessed through
+ * QgsApplication::classificationMethodRegistry().
+ *
+ * \since QGIS 3.10
+ */
+class CORE_EXPORT QgsClassificationMethodRegistry
+{
+  public:
+    QgsClassificationMethodRegistry();
+
+    //! Adds a method to the registry
+    void addMethod( QgsClassificationMethod *method SIP_TRANSFER );
+
+    //! Return a new instance of the method for the given id
+    QgsClassificationMethod *method( const QString &id );
+
+    //! Returns a map <id, name> of all registered methods
+    QMap<QString, QString> methodNames() const;
+
+  private:
+
+    QMap<QString, QgsClassificationMethod *> mMethods;
+};
+
+#endif // QGSCLASSIFICATIONMETHODREGISTRY_H