QgsSourceSelectProviderRegistry delayed initialization

Due to QgsGui being initialized after data provider.
qgis · Sep 4, 2017 · 1816087 · 1816087
1 parent 42bd913
commit 1816087
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Showing 3 changed files with 65 additions and 33 deletions.
diff --git a/python/gui/qgssourceselectproviderregistry.sip b/python/gui/qgssourceselectproviderregistry.sip
@@ -17,6 +17,12 @@ class QgsSourceSelectProviderRegistry
  QgsSourceSelectProviderRegistry is not usually directly created, but rather accessed through
  QgsGui.sourceSelectProviderRegistry().
 
+.. note::
+
+   This class access to QgsProviderRegistry instance to initialize, but QgsProviderRegistry is
+ typically initialized after QgsGui is constructed, for this reason a delayed initialization has been
+ implemented in the class.
+
 .. versionadded:: 3.0
 %End
 
@@ -29,7 +35,7 @@ class QgsSourceSelectProviderRegistry
     ~QgsSourceSelectProviderRegistry();
 
 
-    QList< QgsSourceSelectProvider *> providers() const;
+    QList< QgsSourceSelectProvider *> providers();
 %Docstring
 Get list of available providers
  :rtype: list of QgsSourceSelectProvider
@@ -45,13 +51,13 @@ Add a provider implementation. Takes ownership of the object.
 Remove provider implementation from the list (provider object is deleted)
 %End
 
-    QgsSourceSelectProvider *providerByName( const QString &name ) const;
+    QgsSourceSelectProvider *providerByName( const QString &name );
 %Docstring
 Return a provider by name or None if not found
  :rtype: QgsSourceSelectProvider
 %End
 
-    QList<QgsSourceSelectProvider *> providersByKey( const QString &providerKey ) const;
+    QList<QgsSourceSelectProvider *> providersByKey( const QString &providerKey );
 %Docstring
 Return a (possibly empty) list of providers by data provider's key
  :rtype: list of QgsSourceSelectProvider

diff --git a/src/gui/qgssourceselectproviderregistry.cpp b/src/gui/qgssourceselectproviderregistry.cpp
@@ -24,33 +24,20 @@ typedef QList<QgsSourceSelectProvider *> *sourceSelectProviders_t();
 
 QgsSourceSelectProviderRegistry::QgsSourceSelectProviderRegistry()
 {
-  QStringList providersList = QgsProviderRegistry::instance()->providerList();
-
-  Q_FOREACH ( const QString &key, providersList )
-  {
-    std::unique_ptr< QLibrary > library( QgsProviderRegistry::instance()->createProviderLibrary( key ) );
-    if ( !library )
-      continue;
-
-    sourceSelectProviders_t *sourceSelectProvidersFn = reinterpret_cast< sourceSelectProviders_t * >( cast_to_fptr( library->resolve( "sourceSelectProviders" ) ) );
-    if ( sourceSelectProvidersFn )
-    {
-      QList<QgsSourceSelectProvider *> *providerList = sourceSelectProvidersFn();
-      // the function is a factory - we keep ownership of the returned providers
-      for ( auto provider : qgsAsConst( *providerList ) )
-      {
-        addProvider( provider );
-      }
-      delete providerList;
-    }
-  }
+  // Initialization is delayed
 }
 
 QgsSourceSelectProviderRegistry::~QgsSourceSelectProviderRegistry()
 {
   qDeleteAll( mProviders );
 }
 
+QList<QgsSourceSelectProvider *> QgsSourceSelectProviderRegistry::providers()
+{
+  init();
+  return mProviders;
+}
+
 void QgsSourceSelectProviderRegistry::addProvider( QgsSourceSelectProvider *provider )
 {
   mProviders.append( provider );
@@ -67,9 +54,10 @@ void QgsSourceSelectProviderRegistry::removeProvider( QgsSourceSelectProvider *p
     delete mProviders.takeAt( index );
 }
 
-QgsSourceSelectProvider *QgsSourceSelectProviderRegistry::providerByName( const QString &name ) const
+QgsSourceSelectProvider *QgsSourceSelectProviderRegistry::providerByName( const QString &name )
 {
-  for ( const auto provider : qgsAsConst( mProviders ) )
+  const QList<QgsSourceSelectProvider *> providerList = providers();
+  for ( const auto provider :  providerList )
   {
     if ( provider->name() == name )
     {
@@ -79,15 +67,45 @@ QgsSourceSelectProvider *QgsSourceSelectProviderRegistry::providerByName( const
   return nullptr;
 }
 
-QList<QgsSourceSelectProvider *> QgsSourceSelectProviderRegistry::providersByKey( const QString &providerKey ) const
+QList<QgsSourceSelectProvider *> QgsSourceSelectProviderRegistry::providersByKey( const QString &providerKey )
 {
-  QList<QgsSourceSelectProvider *> providerList;
-  for ( const auto provider : qgsAsConst( mProviders ) )
+  QList<QgsSourceSelectProvider *> result;
+  const QList<QgsSourceSelectProvider *> providerList = providers();
+  for ( const auto provider : providerList )
   {
     if ( provider->providerKey() == providerKey )
     {
-      providerList << provider;
+      result << provider;
+    }
+  }
+  return result;
+}
+
+void QgsSourceSelectProviderRegistry::init()
+{
+  if ( mInitialized )
+  {
+    return;
+  }
+  QStringList providersList = QgsProviderRegistry::instance()->providerList();
+  Q_FOREACH ( const QString &key, providersList )
+  {
+    std::unique_ptr< QLibrary > library( QgsProviderRegistry::instance()->createProviderLibrary( key ) );
+    if ( !library )
+      continue;
+
+    sourceSelectProviders_t *sourceSelectProvidersFn = reinterpret_cast< sourceSelectProviders_t * >( cast_to_fptr( library->resolve( "sourceSelectProviders" ) ) );
+    if ( sourceSelectProvidersFn )
+    {
+      QList<QgsSourceSelectProvider *> *providerList = sourceSelectProvidersFn();
+      // the function is a factory - we keep ownership of the returned providers
+      for ( auto provider : qgsAsConst( *providerList ) )
+      {
+        addProvider( provider );
+      }
+      delete providerList;
     }
   }
-  return providerList;
+  mInitialized = true;
 }
+
diff --git a/src/gui/qgssourceselectproviderregistry.h b/src/gui/qgssourceselectproviderregistry.h
@@ -28,6 +28,10 @@ class QgsSourceSelectProvider;
  * QgsSourceSelectProviderRegistry is not usually directly created, but rather accessed through
  * QgsGui::sourceSelectProviderRegistry().
  *
+ * \note This class access to QgsProviderRegistry instance to initialize, but QgsProviderRegistry is
+ * typically initialized after QgsGui is constructed, for this reason a delayed initialization has been
+ * implemented in the class.
+ *
  * \since QGIS 3.0
  */
 class GUI_EXPORT QgsSourceSelectProviderRegistry
@@ -43,7 +47,7 @@ class GUI_EXPORT QgsSourceSelectProviderRegistry
     QgsSourceSelectProviderRegistry &operator=( const QgsSourceSelectProviderRegistry &rh ) = delete;
 
     //! Get list of available providers
-    QList< QgsSourceSelectProvider *> providers() const { return mProviders; }
+    QList< QgsSourceSelectProvider *> providers();
 
     //! Add a provider implementation. Takes ownership of the object.
     void addProvider( QgsSourceSelectProvider *provider SIP_TRANSFER );
@@ -52,13 +56,17 @@ class GUI_EXPORT QgsSourceSelectProviderRegistry
     void removeProvider( QgsSourceSelectProvider *provider );
 
     //! Return a provider by name or nullptr if not found
-    QgsSourceSelectProvider *providerByName( const QString &name ) const;
+    QgsSourceSelectProvider *providerByName( const QString &name );
 
     //! Return a (possibly empty) list of providers by data provider's key
-    QList<QgsSourceSelectProvider *> providersByKey( const QString &providerKey ) const;
+    QList<QgsSourceSelectProvider *> providersByKey( const QString &providerKey );
 
 
   private:
+    //! Populate the providers list, this needs to happen after the data provider
+    //! registry has been initialized.
+    void init();
+    bool mInitialized = false;
 #ifdef SIP_RUN
     QgsSourceSelectProviderRegistry( const QgsSourceSelectProviderRegistry &rh );
 #endif