Add a new QgsCoordinateReferenceSystemRegistry singleton attached

to QgsApplication In the long term all methods for retrieving available CRS details should be moved here (instead of being scattered all over the place, as they are now). But for now the logic for saving and updating user CRS definitions has been moved here only. The initial motivation is to create a central place where objects can connect to in order to listen for when a user makes changes to their custom projections. Refs #40704
qgis · Jan 27, 2021 · 1499250 · 1499250
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diff --git a/python/core/auto_generated/qgsapplication.sip.in b/python/core/auto_generated/qgsapplication.sip.in
@@ -694,6 +694,14 @@ Returns the application's data item provider registry, which keeps a list of dat
 providers that may add items to the browser tree.
 
 .. versionadded:: 3.0
+%End
+
+    static QgsCoordinateReferenceSystemRegistry *coordinateReferenceSystemRegistry() /KeepReference/;
+%Docstring
+Returns the application's coordinate reference system (CRS) registry, which handles
+known CRS definitions (including user-defined CRSes).
+
+.. versionadded:: 3.18
 %End
 
     static QgsSvgCache *svgCache();

diff --git a/python/core/auto_generated/qgscoordinatereferencesystem.sip.in b/python/core/auto_generated/qgscoordinatereferencesystem.sip.in
@@ -840,7 +840,7 @@ Update proj.4 parameters in our database from proj.4
 
     long saveAsUserCrs( const QString &name, Format nativeFormat = FormatWkt );
 %Docstring
-Saves the CRS as a custom ("USER") CRS.
+Saves the CRS as a new custom ("USER") CRS.
 
 Returns the new CRS :py:func:`~QgsCoordinateReferenceSystem.srsid`, or -1 if the CRS could not be saved.
 
@@ -851,6 +851,10 @@ definition. FormatWkt is recommended as it is a lossless format.
 
    Not all CRS definitions can be represented as a Proj string, so
    take care when using the FormatProj option.
+
+.. note::
+
+   Since QGIS 3.18, internally this calls :py:func:`QgsCoordinateReferenceSystemRegistry.addUserCrs()`.
 %End
 
     QString geographicCrsAuthId() const;

diff --git a/python/core/auto_generated/qgscoordinatereferencesystemregistry.sip.in b/python/core/auto_generated/qgscoordinatereferencesystemregistry.sip.in
@@ -0,0 +1,116 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgscoordinatereferencesystemregistry.h                      *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+class QgsCoordinateReferenceSystemRegistry : QObject
+{
+%Docstring
+A registry for known coordinate reference system (CRS) definitions, including
+any user-defined CRSes.
+
+QgsCoordinateReferenceSystemRegistry is not usually directly created, but rather accessed through
+:py:func:`QgsApplication.coordinateReferenceSystemRegistry()`.
+
+.. versionadded:: 3.18
+%End
+
+%TypeHeaderCode
+#include "qgscoordinatereferencesystemregistry.h"
+%End
+  public:
+
+    explicit QgsCoordinateReferenceSystemRegistry( QObject *parent = 0 );
+%Docstring
+Constructor for QgsCoordinateReferenceSystemRegistry, with the specified ``parent`` object.
+%End
+
+    long addUserCrs( const QgsCoordinateReferenceSystem &crs, const QString &name, QgsCoordinateReferenceSystem::Format nativeFormat = QgsCoordinateReferenceSystem::FormatWkt );
+%Docstring
+Adds a new ``crs`` definition as a custom ("USER") CRS.
+
+Returns the new CRS :py:func:`~QgsCoordinateReferenceSystemRegistry.srsid`, or -1 if the CRS could not be saved.
+
+The ``nativeFormat`` argument specifies the format to use when saving the CRS
+definition. FormatWkt is recommended as it is a lossless format.
+
+.. warning::
+
+   Not all CRS definitions can be represented as a Proj string, so
+   take care when using the FormatProj option.
+
+.. seealso:: :py:func:`updateUserCrs`
+
+.. seealso:: :py:func:`userCrsAdded`
+%End
+
+    bool updateUserCrs( long id, const QgsCoordinateReferenceSystem &crs, const QString &name, QgsCoordinateReferenceSystem::Format nativeFormat = QgsCoordinateReferenceSystem::FormatWkt );
+%Docstring
+Updates the definition of the existing user CRS with matching ``id``.
+
+The ``crs`` argument specifies a CRS with the desired new definition.
+
+Returns ``False`` if the new CRS definition could not be saved.
+
+The ``nativeFormat`` argument specifies the format to use when saving the CRS
+definition. FormatWkt is recommended as it is a lossless format.
+
+.. warning::
+
+   Not all CRS definitions can be represented as a Proj string, so
+   take care when using the FormatProj option.
+
+.. seealso:: :py:func:`addUserCrs`
+
+.. seealso:: :py:func:`userCrsChanged`
+%End
+
+  signals:
+
+    void userCrsChanged( const QString &id );
+%Docstring
+Emitted whenever an existing user CRS definition is changed.
+
+The ``id`` argument specifies the ID of the user CRS which has been changed.
+
+Objects which store QgsCoordinateReferenceSystem members should connect to this signal
+and update any stored CRS definitions to ensure that they always use the current
+definition of any user defined CRSes.
+
+.. seealso:: :py:func:`crsDefinitionsChanged`
+
+.. seealso:: :py:func:`userCrsAdded`
+%End
+
+    void userCrsAdded( const QString &id );
+%Docstring
+Emitted whenever a new user CRS definition is added.
+
+The ``id`` argument specifies the ID of the user CRS which has been changed.
+
+.. seealso:: :py:func:`userCrsChanged`
+
+.. seealso:: :py:func:`crsDefinitionsChanged`
+%End
+
+    void crsDefinitionsChanged();
+%Docstring
+Emitted whenever an operation has caused any of the known CRS definitions (including
+user-defined CRS) to change.
+%End
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgscoordinatereferencesystemregistry.h                      *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
diff --git a/python/core/core_auto.sip b/python/core/core_auto.sip
@@ -31,6 +31,7 @@
 %Include auto_generated/qgsconnectionregistry.sip
 %Include auto_generated/qgscoordinateformatter.sip
 %Include auto_generated/qgscoordinatereferencesystem.sip
+%Include auto_generated/qgscoordinatereferencesystemregistry.sip
 %Include auto_generated/qgscoordinatetransform.sip
 %Include auto_generated/qgscoordinatetransformcontext.sip
 %Include auto_generated/qgscredentials.sip

diff --git a/src/app/qgscustomprojectiondialog.cpp b/src/app/qgscustomprojectiondialog.cpp
@@ -27,6 +27,7 @@
 #include "qgssettings.h"
 #include "qgssqliteutils.h"
 #include "qgsgui.h"
+#include "qgscoordinatereferencesystemregistry.h"
 
 //qt includes
 #include <QFileInfo>
@@ -259,45 +260,20 @@ bool QgsCustomProjectionDialog::saveCrs( QgsCoordinateReferenceSystem crs, const
   QString ellipsoidAcronym = crs.ellipsoidAcronym();
   if ( newEntry )
   {
-    returnId = crs.saveAsUserCrs( name, format );
+    returnId = QgsApplication::coordinateReferenceSystemRegistry()->addUserCrs( crs, name, format );
     if ( returnId == -1 )
       return false;
     else
       id = QString::number( returnId );
   }
   else
   {
-    sql = "update tbl_srs set description="
-          + QgsSqliteUtils::quotedString( name )
-          + ",projection_acronym=" + ( !projectionAcronym.isEmpty() ? QgsSqliteUtils::quotedString( projectionAcronym ) : QStringLiteral( "''" ) )
-          + ",ellipsoid_acronym=" + ( !ellipsoidAcronym.isEmpty() ? QgsSqliteUtils::quotedString( ellipsoidAcronym ) : QStringLiteral( "''" ) )
-          + ",parameters=" + ( !crs.toProj().isEmpty() ? QgsSqliteUtils::quotedString( crs.toProj() ) : QStringLiteral( "''" ) )
-          + ",is_geo=0" // <--shamelessly hard coded for now
-          + ",wkt=" + ( format == QgsCoordinateReferenceSystem::FormatWkt ? QgsSqliteUtils::quotedString( crs.toWkt( QgsCoordinateReferenceSystem::WKT_PREFERRED, false ) ) : QStringLiteral( "''" ) )
-          + " where srs_id=" + QgsSqliteUtils::quotedString( id )
-          ;
-    QgsDebugMsgLevel( sql, 4 );
-    sqlite3_database_unique_ptr database;
-    //check if the db is available
-    int result = database.open( QgsApplication::qgisUserDatabaseFilePath() );
-    if ( result != SQLITE_OK )
+    if ( !QgsApplication::coordinateReferenceSystemRegistry()->updateUserCrs( id.toLong(), crs, name ) )
     {
-      QgsDebugMsg( QStringLiteral( "Can't open database: %1 \n please notify  QGIS developers of this error \n %2 (file name) " ).arg( database.errorMessage(),
-                   QgsApplication::qgisUserDatabaseFilePath() ) );
-      // XXX This will likely never happen since on open, sqlite creates the
-      //     database if it does not exist.
-      Q_ASSERT( result == SQLITE_OK );
-    }
-    sqlite3_statement_unique_ptr preparedStatement = database.prepare( sql, result );
-    if ( result != SQLITE_OK || preparedStatement.step() != SQLITE_DONE )
-    {
-      QgsDebugMsg( QStringLiteral( "failed to write to database in custom projection dialog: %1 [%2]" ).arg( sql, database.errorMessage() ) );
-    }
-
-    preparedStatement.reset();
-    if ( result != SQLITE_OK )
       return false;
+    }
   }
+
   mExistingCRSwkt[id] = format == QgsCoordinateReferenceSystem::FormatWkt ? crs.toWkt( QgsCoordinateReferenceSystem::WKT_PREFERRED, false ) : QString();
   mExistingCRSproj[id] = format == QgsCoordinateReferenceSystem::FormatProj ? crs.toProj() : QString();
   mExistingCRSnames[id] = name;
@@ -313,7 +289,6 @@ bool QgsCustomProjectionDialog::saveCrs( QgsCoordinateReferenceSystem crs, const
   return true;
 }
 
-
 void QgsCustomProjectionDialog::pbnAdd_clicked()
 {
   QString name = tr( "new CRS" );

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
@@ -283,6 +283,7 @@ set(QGIS_CORE_SRCS
   qgsconnectionregistry.cpp
   qgscoordinateformatter.cpp
   qgscoordinatereferencesystem.cpp
+  qgscoordinatereferencesystemregistry.cpp
   qgscoordinatetransform.cpp
   qgscoordinatetransform_p.cpp
   qgscoordinatetransformcontext.cpp
@@ -867,6 +868,7 @@ set(QGIS_CORE_HDRS
   qgsconnectionregistry.h
   qgscoordinateformatter.h
   qgscoordinatereferencesystem.h
+  qgscoordinatereferencesystemregistry.h
   qgscoordinatetransform.h
   qgscoordinatetransformcontext.h
   qgscoordinateutils.h

diff --git a/src/core/qgsapplication.cpp b/src/core/qgsapplication.cpp
@@ -43,6 +43,7 @@
 #include "qgsrasterrendererregistry.h"
 #include "qgsrendererregistry.h"
 #include "qgspointcloudrendererregistry.h"
+#include "qgscoordinatereferencesystemregistry.h"
 #include "qgssymbollayerregistry.h"
 #include "qgssymbollayerutils.h"
 #include "qgscalloutsregistry.h"
@@ -2212,6 +2213,11 @@ QgsDataItemProviderRegistry *QgsApplication::dataItemProviderRegistry()
   }
 }
 
+QgsCoordinateReferenceSystemRegistry *QgsApplication::coordinateReferenceSystemRegistry()
+{
+  return members()->mCrsRegistry;
+}
+
 QgsSvgCache *QgsApplication::svgCache()
 {
   return members()->mSvgCache;
@@ -2355,6 +2361,11 @@ QgsApplication::ApplicationMembers::ApplicationMembers()
   mMessageLog = new QgsMessageLog();
   QgsRuntimeProfiler *profiler = QgsRuntimeProfiler::threadLocalInstance();
 
+  {
+    profiler->start( tr( "Setup coordinate reference system registry" ) );
+    mCrsRegistry = new QgsCoordinateReferenceSystemRegistry();
+    profiler->end();
+  }
   {
     profiler->start( tr( "Create connection registry" ) );
     mConnectionRegistry = new QgsConnectionRegistry();
@@ -2546,6 +2557,7 @@ QgsApplication::ApplicationMembers::~ApplicationMembers()
   delete mBookmarkManager;
   delete mConnectionRegistry;
   delete mLocalizedDataPathRegistry;
+  delete mCrsRegistry;
 }
 
 QgsApplication::ApplicationMembers *QgsApplication::members()

diff --git a/src/core/qgsapplication.h b/src/core/qgsapplication.h
@@ -65,6 +65,7 @@ class QgsScaleBarRendererRegistry;
 class Qgs3DSymbolRegistry;
 class QgsPointCloudRendererRegistry;
 class QgsTileDownloadManager;
+class QgsCoordinateReferenceSystemRegistry;
 
 /**
  * \ingroup core
@@ -654,6 +655,14 @@ class CORE_EXPORT QgsApplication : public QApplication
      */
     static QgsDataItemProviderRegistry *dataItemProviderRegistry() SIP_KEEPREFERENCE;
 
+    /**
+     * Returns the application's coordinate reference system (CRS) registry, which handles
+     * known CRS definitions (including user-defined CRSes).
+     *
+     * \since QGIS 3.18
+     */
+    static QgsCoordinateReferenceSystemRegistry *coordinateReferenceSystemRegistry() SIP_KEEPREFERENCE;
+
     /**
      * Returns the application's SVG cache, used for caching SVG images and handling parameter replacement
      * within SVG files.
@@ -985,6 +994,7 @@ class CORE_EXPORT QgsApplication : public QApplication
 
     struct ApplicationMembers
     {
+      QgsCoordinateReferenceSystemRegistry *mCrsRegistry = nullptr;
       Qgs3DRendererRegistry *m3DRendererRegistry = nullptr;
       Qgs3DSymbolRegistry *m3DSymbolRegistry = nullptr;
       QgsActionScopeRegistry *mActionScopeRegistry = nullptr;