Add a QgsDataItemGuiProvider interface and registry for providers

These providers will be used to control how the browser data items
behave within GUI, and to allow separation of GUI related
properties of browser items from the core code.

A new registry QgsDataItemGuiProviderRegistry has been created
(modeled off QgsDataItemProviderRegistry), with an application
wide instance available from QgsGui::instance()->dataItemGuiProviderRegistry()

python/core/auto_generated/qgsdataitemproviderregistry.sip.in

@@ -34,17 +34,19 @@ QgsDataItemProviderRegistry is not usually directly created, but rather accessed
 
     QList<QgsDataItemProvider *> providers() const;
 %Docstring
-Gets list of available providers
+Returns the list of available providers.
 %End
 
     void addProvider( QgsDataItemProvider *provider /Transfer/ );
 %Docstring
-Add a provider implementation. Takes ownership of the object.
+Adds a ``provider`` implementation to the registry. Ownership of the provider
+is transferred to the registry.
 %End
 
     void removeProvider( QgsDataItemProvider *provider );
 %Docstring
-Remove provider implementation from the list (provider object is deleted)
+Removes a ``provider`` implementation from the registry.
+The provider object is automatically deleted.
 %End
 
   private:

python/gui/auto_generated/qgsdataitemguiprovider.sip.in

@@ -0,0 +1,44 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/gui/qgsdataitemguiprovider.h                                     *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+class QgsDataItemGuiProvider
+{
+%Docstring
+
+Abstract base class for providers which affect how QgsDataItem items behave
+within the application GUI.
+
+Providers must be registered via QgsDataItemGuiProviderRegistry.
+
+.. versionadded:: 3.6
+%End
+
+%TypeHeaderCode
+#include "qgsdataitemguiprovider.h"
+%End
+  public:
+
+    virtual ~QgsDataItemGuiProvider();
+
+    virtual QString name() = 0;
+%Docstring
+Returns the provider's name.
+%End
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/gui/qgsdataitemguiprovider.h                                     *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/gui/auto_generated/qgsdataitemguiproviderregistry.sip.in

@@ -0,0 +1,61 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/gui/qgsdataitemguiproviderregistry.h                             *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+class QgsDataItemGuiProviderRegistry
+{
+%Docstring
+This class keeps a list of data item GUI providers that may affect how QgsDataItems
+behave within the application GUI.
+
+QgsDataItemGuiProviderRegistry is not usually directly created, but rather accessed through
+QgsGui.instance()->dataItemGuiProviderRegistry().
+
+.. versionadded:: 3.6
+%End
+
+%TypeHeaderCode
+#include "qgsdataitemguiproviderregistry.h"
+%End
+  public:
+
+    QgsDataItemGuiProviderRegistry();
+
+    ~QgsDataItemGuiProviderRegistry();
+
+
+    QList<QgsDataItemGuiProvider *> providers() const;
+%Docstring
+Returns the list of available providers.
+%End
+
+    void addProvider( QgsDataItemGuiProvider *provider /Transfer/ );
+%Docstring
+Adds a ``provider`` implementation to the registry. Ownership of the provider
+is transferred to the registry.
+%End
+
+    void removeProvider( QgsDataItemGuiProvider *provider );
+%Docstring
+Removes a ``provider`` implementation from the registry.
+The provider object is automatically deleted.
+%End
+
+  private:
+    QgsDataItemGuiProviderRegistry( const QgsDataItemGuiProviderRegistry &rh );
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/gui/qgsdataitemguiproviderregistry.h                             *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/gui/auto_generated/qgsgui.sip.in

@@ -74,6 +74,14 @@ Returns the global processing gui registry, used for registering the GUI behavio
 Returns the global processing recent algorithm log, used for tracking recently used processing algorithms.
 
 .. versionadded:: 3.4
+%End
+
+    static QgsDataItemGuiProviderRegistry *dataItemGuiProviderRegistry();
+%Docstring
+Returns the global data item GUI provider registry, used for tracking providers which affect the browser
+GUI.
+
+.. versionadded:: 3.6
 %End
 
     static void enableAutoGeometryRestore( QWidget *widget, const QString &key = QString() );

python/gui/gui_auto.sip

@@ -1,5 +1,7 @@
 // Include auto-generated SIP files
 %Include auto_generated/qgsattributeforminterface.sip
+%Include auto_generated/qgsdataitemguiprovider.sip
+%Include auto_generated/qgsdataitemguiproviderregistry.sip
 %Include auto_generated/qgsdetaileditemdata.sip
 %Include auto_generated/qgsexpressionbuilderdialog.sip
 %Include auto_generated/qgsgeometryrubberband.sip

src/core/qgsdataitemproviderregistry.h

@@ -46,13 +46,21 @@ class CORE_EXPORT QgsDataItemProviderRegistry
     //! QgsDataItemProviderRegistry cannot be copied.
     QgsDataItemProviderRegistry &operator=( const QgsDataItemProviderRegistry &rh ) = delete;
 
-    //! Gets list of available providers
+    /**
+     * Returns the list of available providers.
+     */
     QList<QgsDataItemProvider *> providers() const { return mProviders; }
 
-    //! Add a provider implementation. Takes ownership of the object.
+    /**
+     * Adds a \a provider implementation to the registry. Ownership of the provider
+     * is transferred to the registry.
+     */
     void addProvider( QgsDataItemProvider *provider SIP_TRANSFER );
 
-    //! Remove provider implementation from the list (provider object is deleted)
+    /**
+     * Removes a \a provider implementation from the registry.
+     * The provider object is automatically deleted.
+     */
     void removeProvider( QgsDataItemProvider *provider );
 
   private:
@@ -60,7 +68,7 @@ class CORE_EXPORT QgsDataItemProviderRegistry
     QgsDataItemProviderRegistry( const QgsDataItemProviderRegistry &rh );
 #endif
 
-    //! available providers. this class owns the pointers
+    //! Available providers, owned by this class
     QList<QgsDataItemProvider *> mProviders;
 
 };

src/gui/CMakeLists.txt

@@ -243,6 +243,8 @@ SET(QGIS_GUI_SRCS
   qgscredentialdialog.cpp
   qgscustomdrophandler.cpp
   qgscurveeditorwidget.cpp
+  qgsdataitemguiprovider.cpp
+  qgsdataitemguiproviderregistry.cpp
   qgsdatumtransformdialog.cpp
   qgsdatasourceselectdialog.cpp
   qgsdetaileditemdata.cpp
@@ -767,6 +769,8 @@ ENDIF(MSVC)
 SET(QGIS_GUI_HDRS
   qgsattributeforminterface.h
   qgsattributeformlegacyinterface.h
+  qgsdataitemguiprovider.h
+  qgsdataitemguiproviderregistry.h
   qgsdetaileditemdata.h
   qgsexpressionbuilderdialog.h
   qgsgeometryrubberband.h

src/gui/qgsdataitemguiprovider.cpp

@@ -0,0 +1,18 @@
+/***************************************************************************
+  qgsdataitemguiprovider.cpp
+  --------------------------------------
+  Date                 : October 2018
+  Copyright            : (C) 2018 by Nyall Dawson
+  Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   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 "qgsdataitemguiprovider.h"
+
+// no implementation currently

src/gui/qgsdataitemguiprovider.h

@@ -0,0 +1,47 @@
+/***************************************************************************
+  qgsdataitemguiprovider.h
+  --------------------------------------
+  Date                 : October 2018
+  Copyright            : (C) 2018 by Nyall Dawson
+  Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   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 QGSDATAITEMGUIPROVIDER_H
+#define QGSDATAITEMGUIPROVIDER_H
+
+#include "qgis_gui.h"
+
+class QString;
+
+/**
+ * \class QgsDataItemGuiProvider
+ * \ingroup gui
+ *
+ * Abstract base class for providers which affect how QgsDataItem items behave
+ * within the application GUI.
+ *
+ * Providers must be registered via QgsDataItemGuiProviderRegistry.
+ *
+ * \since QGIS 3.6
+ */
+class GUI_EXPORT QgsDataItemGuiProvider
+{
+  public:
+
+    virtual ~QgsDataItemGuiProvider() = default;
+
+    /**
+     * Returns the provider's name.
+     */
+    virtual QString name() = 0;
+
+};
+
+#endif // QGSDATAITEMGUIPROVIDER_H

src/gui/qgsdataitemguiproviderregistry.cpp

@@ -0,0 +1,38 @@
+/***************************************************************************
+  qgsdataitemguiproviderregistry.cpp
+  --------------------------------------
+  Date                 : October 2018
+  Copyright            : (C) 2018 by Nyall Dawson
+  Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   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 "qgsdataitemguiproviderregistry.h"
+#include "qgsdataitemguiprovider.h"
+
+QgsDataItemGuiProviderRegistry::QgsDataItemGuiProviderRegistry()
+{
+}
+
+QgsDataItemGuiProviderRegistry::~QgsDataItemGuiProviderRegistry()
+{
+  qDeleteAll( mProviders );
+}
+
+void QgsDataItemGuiProviderRegistry::addProvider( QgsDataItemGuiProvider *provider )
+{
+  mProviders.append( provider );
+}
+
+void QgsDataItemGuiProviderRegistry::removeProvider( QgsDataItemGuiProvider *provider )
+{
+  int index = mProviders.indexOf( provider );
+  if ( index >= 0 )
+    delete mProviders.takeAt( index );
+}

src/gui/qgsdataitemguiproviderregistry.h

@@ -0,0 +1,76 @@
+/***************************************************************************
+  qgsdataitemguiproviderregistry.h
+  --------------------------------------
+  Date                 : October 2018
+  Copyright            : (C) 2018 by Nyall Dawson
+  Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   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 QGSDATAITEMGUIPROVIDERREGISTRY_H
+#define QGSDATAITEMGUIPROVIDERREGISTRY_H
+
+#include "qgis_gui.h"
+#include "qgis_sip.h"
+#include <QList>
+
+class QgsDataItemGuiProvider;
+
+/**
+ * \class QgsDataItemGuiProviderRegistry
+ * \ingroup gui
+ * This class keeps a list of data item GUI providers that may affect how QgsDataItems
+ * behave within the application GUI.
+ *
+ * QgsDataItemGuiProviderRegistry is not usually directly created, but rather accessed through
+ * QgsGui::instance()->dataItemGuiProviderRegistry().
+ *
+ * \since QGIS 3.6
+ */
+class GUI_EXPORT QgsDataItemGuiProviderRegistry
+{
+  public:
+
+    QgsDataItemGuiProviderRegistry();
+
+    ~QgsDataItemGuiProviderRegistry();
+
+    //! QgsDataItemGuiProviderRegistry cannot be copied.
+    QgsDataItemGuiProviderRegistry( const QgsDataItemGuiProviderRegistry &rh ) = delete;
+    //! QgsDataItemGuiProviderRegistry cannot be copied.
+    QgsDataItemGuiProviderRegistry &operator=( const QgsDataItemGuiProviderRegistry &rh ) = delete;
+
+    /**
+     * Returns the list of available providers.
+     */
+    QList<QgsDataItemGuiProvider *> providers() const { return mProviders; }
+
+    /**
+     * Adds a \a provider implementation to the registry. Ownership of the provider
+     * is transferred to the registry.
+     */
+    void addProvider( QgsDataItemGuiProvider *provider SIP_TRANSFER );
+
+    /**
+     * Removes a \a provider implementation from the registry.
+     * The provider object is automatically deleted.
+     */
+    void removeProvider( QgsDataItemGuiProvider *provider );
+
+  private:
+#ifdef SIP_RUN
+    QgsDataItemGuiProviderRegistry( const QgsDataItemGuiProviderRegistry &rh );
+#endif
+
+    //! Available providers, owned by this class
+    QList<QgsDataItemGuiProvider *> mProviders;
+
+};
+
+#endif // QGSDATAITEMGUIPROVIDERREGISTRY_H

src/gui/qgsgui.cpp

@@ -43,6 +43,7 @@
 #include "qgsprocessingrecentalgorithmlog.h"
 #include "qgswindowmanagerinterface.h"
 #include "qgssettings.h"
+#include "qgsdataitemguiproviderregistry.h"
 
 QgsGui *QgsGui::instance()
 {
@@ -95,6 +96,11 @@ QgsProcessingRecentAlgorithmLog *QgsGui::processingRecentAlgorithmLog()
   return instance()->mProcessingRecentAlgorithmLog;
 }
 
+QgsDataItemGuiProviderRegistry *QgsGui::dataItemGuiProviderRegistry()
+{
+  return instance()->mDataItemGuiProviderRegistry;
+}
+
 void QgsGui::enableAutoGeometryRestore( QWidget *widget, const QString &key )
 {
   if ( widget->objectName().isEmpty() )
@@ -130,6 +136,7 @@ QgsGui::HigFlags QgsGui::higFlags()
 QgsGui::~QgsGui()
 {
   delete mProcessingGuiRegistry;
+  delete mDataItemGuiProviderRegistry;
   delete mProcessingRecentAlgorithmLog;
   delete mLayoutItemGuiRegistry;
   delete mLayerTreeEmbeddedWidgetRegistry;
@@ -168,4 +175,5 @@ QgsGui::QgsGui()
   mWidgetStateHelper = new QgsWidgetStateHelper();
   mProcessingRecentAlgorithmLog = new QgsProcessingRecentAlgorithmLog();
   mProcessingGuiRegistry = new QgsProcessingGuiRegistry();
+  mDataItemGuiProviderRegistry = new QgsDataItemGuiProviderRegistry();
 }

src/gui/qgsgui.h

@@ -34,6 +34,7 @@ class QgsWidgetStateHelper;
 class QgsProcessingGuiRegistry;
 class QgsProcessingRecentAlgorithmLog;
 class QgsWindowManagerInterface;
+class QgsDataItemGuiProviderRegistry;
 
 /**
  * \ingroup gui
@@ -105,6 +106,13 @@ class GUI_EXPORT QgsGui
      */
     static QgsProcessingRecentAlgorithmLog *processingRecentAlgorithmLog();
 
+    /**
+     * Returns the global data item GUI provider registry, used for tracking providers which affect the browser
+     * GUI.
+     * \since QGIS 3.6
+     */
+    static QgsDataItemGuiProviderRegistry *dataItemGuiProviderRegistry();
+
     /**
      * Register the widget to allow its position to be automatically saved and restored when open and closed.
      * Use this to avoid needing to call saveGeometry() and restoreGeometry() on your widget.
@@ -158,6 +166,7 @@ class GUI_EXPORT QgsGui
     QgsLayoutItemGuiRegistry *mLayoutItemGuiRegistry = nullptr;
     QgsProcessingGuiRegistry *mProcessingGuiRegistry = nullptr;
     QgsProcessingRecentAlgorithmLog *mProcessingRecentAlgorithmLog = nullptr;
+    QgsDataItemGuiProviderRegistry *mDataItemGuiProviderRegistry = nullptr;
     std::unique_ptr< QgsWindowManagerInterface > mWindowManager;
 
 #ifdef SIP_RUN

tests/src/python/CMakeLists.txt

@@ -34,6 +34,7 @@ ADD_PYTHON_TEST(PyQgsCoordinateTransformContext test_qgscoordinatetransformconte
 ADD_PYTHON_TEST(PyQgsDefaultValue test_qgsdefaultvalue.py)
 ADD_PYTHON_TEST(PyQgsXmlUtils test_qgsxmlutils.py)
 ADD_PYTHON_TEST(PyQgsCoordinateTransform test_qgscoordinatetransform.py)
+ADD_PYTHON_TEST(PyQgsDataItemGuiProviderRegistry test_qgsdataitemguiproviderregistry.py)
 ADD_PYTHON_TEST(PyQgsDataItemProviderRegistry test_qgsdataitemproviderregistry.py)
 ADD_PYTHON_TEST(PyQgsDateTimeEdit test_qgsdatetimeedit.py)
 ADD_PYTHON_TEST(PyQgsDateTimeStatisticalSummary test_qgsdatetimestatisticalsummary.py)

tests/src/python/test_qgsdataitemguiproviderregistry.py

@@ -0,0 +1,70 @@
+# -*- coding: utf-8 -*-
+"""QGIS Unit tests for QgsDataItemGuiProviderRegistry
+
+.. note:: 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.
+"""
+__author__ = 'Nyall Dawson'
+__date__ = '27/10/2018'
+__copyright__ = 'Copyright 2018, The QGIS Project'
+# This will get replaced with a git SHA1 when you do a git archive
+__revision__ = '$Format:%H$'
+
+import qgis  # NOQA
+
+from qgis.gui import (QgsGui,
+                      QgsDataItemGuiProvider,
+                      QgsDataItemGuiProviderRegistry)
+from qgis.testing import start_app, unittest
+
+app = start_app()
+
+
+class TestProvider(QgsDataItemGuiProvider):
+
+    def __init__(self, name):
+        super().__init__()
+        self._name = name
+
+    def name(self):
+        return self._name
+
+
+class TestQgsDataItemGuiProviderRegistry(unittest.TestCase):
+
+    def testAppRegistry(self):
+        # ensure there is an application instance
+        self.assertIsNotNone(QgsGui.dataItemGuiProviderRegistry())
+
+    def testRegistry(self):
+        registry = QgsDataItemGuiProviderRegistry()
+        initial_providers = registry.providers()
+
+        # add a new provider
+        p1 = TestProvider('p1')
+        registry.addProvider(p1)
+        self.assertIn(p1, registry.providers())
+
+        p2 = TestProvider('p2')
+        registry.addProvider(p2)
+        self.assertIn(p1, registry.providers())
+        self.assertIn(p2, registry.providers())
+
+        registry.removeProvider(None)
+        p3 = TestProvider('p3')
+        # not in registry yet
+        registry.removeProvider(p3)
+
+        registry.removeProvider(p1)
+        self.assertNotIn('p1', [p.name() for p in registry.providers()])
+        self.assertIn(p2, registry.providers())
+
+        registry.removeProvider(p2)
+        self.assertNotIn('p2', [p.name() for p in registry.providers()])
+        self.assertEqual(registry.providers(), initial_providers)
+
+
+if __name__ == '__main__':
+    unittest.main()

tests/src/python/test_qgsdataitemproviderregistry.py

@@ -73,7 +73,7 @@ class TestQgsDataItemProviderRegistry(unittest.TestCase):
         registry.removeProvider(p2)
         self.assertNotIn('p2', [p.name() for p in registry.providers()])
         self.assertEqual(registry.providers(), initial_providers)
-        
+
 
 if __name__ == '__main__':
     unittest.main()