Move retrieval of lists of known ellipsoids to QgsEllipsoidUtils

Author: nyalldawson

python/core/qgsellipsoidutils.sip

@@ -53,13 +53,45 @@ Associated coordinate reference system
 %End
     };
 
+    struct EllipsoidDefinition
+    {
+      QString acronym;
+%Docstring
+Acronym for ellipsoid
+%End
+      QString description;
+%Docstring
+Description of ellipsoid
+%End
+      QgsEllipsoidUtils::EllipsoidParameters parameters;
+%Docstring
+Ellipsoid parameters
+%End
+    };
+
     static EllipsoidParameters ellipsoidParameters( const QString &ellipsoid );
 %Docstring
  Returns the parameters for the specified ``ellipsoid``.
  Results are cached to allow for fast retrieval of parameters.
  :rtype: EllipsoidParameters
 %End
 
+    static QList< QgsEllipsoidUtils::EllipsoidDefinition > definitions();
+%Docstring
+ Returns a list of the definitions for all known ellipsoids from the
+ internal ellipsoid database.
+ \see acronyms()
+ :rtype: list of QgsEllipsoidUtils.EllipsoidDefinition
+%End
+
+    static QStringList acronyms();
+%Docstring
+ Returns a list of all known ellipsoid acronyms from the internal
+ ellipsoid database.
+ \see definitions()
+ :rtype: list of str
+%End
+
 };
 
 

src/app/qgsprojectproperties.cpp

@@ -1805,10 +1805,6 @@ void QgsProjectProperties::populateEllipsoidList()
   //
   // Populate the ellipsoid list
   //
-  sqlite3      *myDatabase = nullptr;
-  const char   *myTail = nullptr;
-  sqlite3_stmt *myPreparedStatement = nullptr;
-  int           myResult;
   EllipsoidDefs myItem;
 
   myItem.acronym = GEO_NONE;
@@ -1823,58 +1819,17 @@ void QgsProjectProperties::populateEllipsoidList()
   myItem.semiMinor = 6370997.0;
   mEllipsoidList.append( myItem );
 
-  //check the db is available
-  myResult = sqlite3_open_v2( QgsApplication::srsDatabaseFilePath().toUtf8().data(), &myDatabase, SQLITE_OPEN_READONLY, nullptr );
-  if ( myResult )
+  Q_FOREACH ( const QgsEllipsoidUtils::EllipsoidDefinition &def, QgsEllipsoidUtils::definitions() )
   {
-    QgsDebugMsg( QString( "Can't open database: %1" ).arg( sqlite3_errmsg( myDatabase ) ) );
-    // XXX This will likely never happen since on open, sqlite creates the
-    //     database if it does not exist.
-    Q_ASSERT( myResult == 0 );
+    myItem.acronym = def.acronym;
+    myItem.description = def.description;
+    // Fall-back values
+    myItem.semiMajor = 0.0;
+    myItem.semiMinor = 0.0;
+    myItem.semiMajor = def.parameters.semiMajor;
+    myItem.semiMinor = def.parameters.semiMinor;
+    mEllipsoidList.append( myItem );
   }
-
-  // Set up the query to retrieve the projection information needed to populate the ELLIPSOID list
-  QString mySql = QStringLiteral( "select acronym, name, radius, parameter2 from tbl_ellipsoid order by name" );
-  myResult = sqlite3_prepare( myDatabase, mySql.toUtf8(), mySql.toUtf8().length(), &myPreparedStatement, &myTail );
-  // XXX Need to free memory from the error msg if one is set
-  if ( myResult == SQLITE_OK )
-  {
-    while ( sqlite3_step( myPreparedStatement ) == SQLITE_ROW )
-    {
-      QString para1, para2;
-      myItem.acronym = ( const char * )sqlite3_column_text( myPreparedStatement, 0 );
-      myItem.description = ( const char * )sqlite3_column_text( myPreparedStatement, 1 );
-
-      // Copied from QgsDistanecArea. Should perhaps be moved there somehow?
-      // No error checking, this values are for show only, never used in calculations.
-
-      // Fall-back values
-      myItem.semiMajor = 0.0;
-      myItem.semiMinor = 0.0;
-      // Crash if no column?
-      para1 = ( const char * )sqlite3_column_text( myPreparedStatement, 2 );
-      para2 = ( const char * )sqlite3_column_text( myPreparedStatement, 3 );
-      myItem.semiMajor = para1.midRef( 2 ).toDouble();
-      if ( para2.left( 2 ) == QLatin1String( "b=" ) )
-      {
-        myItem.semiMinor = para2.midRef( 2 ).toDouble();
-      }
-      else if ( para2.left( 3 ) == QLatin1String( "rf=" ) )
-      {
-        double invFlattening = para2.midRef( 3 ).toDouble();
-        if ( invFlattening != 0.0 )
-        {
-          myItem.semiMinor = myItem.semiMajor - ( myItem.semiMajor / invFlattening );
-        }
-      }
-      mEllipsoidList.append( myItem );
-    }
-  }
-
-  // close the sqlite3 statement
-  sqlite3_finalize( myPreparedStatement );
-  sqlite3_close( myDatabase );
-
   // Add all items to selector
 
   Q_FOREACH ( const EllipsoidDefs &i, mEllipsoidList )

src/core/qgsellipsoidutils.cpp

@@ -21,7 +21,8 @@
 
 QReadWriteLock QgsEllipsoidUtils::sEllipsoidCacheLock;
 QHash< QString, QgsEllipsoidUtils::EllipsoidParameters > QgsEllipsoidUtils::sEllipsoidCache;
-
+QReadWriteLock QgsEllipsoidUtils::sDefinitionCacheLock;
+QList< QgsEllipsoidUtils::EllipsoidDefinition > QgsEllipsoidUtils::sDefinitionCache;
 
 QgsEllipsoidUtils::EllipsoidParameters QgsEllipsoidUtils::ellipsoidParameters( const QString &ellipsoid )
 {
@@ -177,3 +178,71 @@ QgsEllipsoidUtils::EllipsoidParameters QgsEllipsoidUtils::ellipsoidParameters( c
   sEllipsoidCacheLock.unlock();
   return params;
 }
+
+QList<QgsEllipsoidUtils::EllipsoidDefinition> QgsEllipsoidUtils::definitions()
+{
+  sDefinitionCacheLock.lockForRead();
+  if ( !sDefinitionCache.isEmpty() )
+  {
+    QList<QgsEllipsoidUtils::EllipsoidDefinition> defs = sDefinitionCache;
+    sDefinitionCacheLock.unlock();
+    return defs;
+  }
+  sDefinitionCacheLock.unlock();
+
+  sDefinitionCacheLock.lockForWrite();
+  sqlite3 *database = nullptr;
+  const char *tail = nullptr;
+  sqlite3_stmt *preparedStatement = nullptr;
+  int result;
+
+  QList<QgsEllipsoidUtils::EllipsoidDefinition> defs;
+
+  //check the db is available
+  result = sqlite3_open_v2( QgsApplication::srsDatabaseFilePath().toUtf8().data(), &database, SQLITE_OPEN_READONLY, nullptr );
+  if ( result )
+  {
+    QgsDebugMsg( QString( "Can't open database: %1" ).arg( sqlite3_errmsg( database ) ) );
+    // XXX This will likely never happen since on open, sqlite creates the
+    //     database if it does not exist.
+    Q_ASSERT( result == 0 );
+  }
+
+  // Set up the query to retrieve the projection information needed to populate the ELLIPSOID list
+  QString sql = QStringLiteral( "select acronym, name from tbl_ellipsoid order by name" );
+  result = sqlite3_prepare( database, sql.toUtf8(), sql.toUtf8().length(), &preparedStatement, &tail );
+  // XXX Need to free memory from the error msg if one is set
+  if ( result == SQLITE_OK )
+  {
+    while ( sqlite3_step( preparedStatement ) == SQLITE_ROW )
+    {
+      EllipsoidDefinition def;
+      def.acronym = ( const char * )sqlite3_column_text( preparedStatement, 0 );
+      def.description = ( const char * )sqlite3_column_text( preparedStatement, 1 );
+
+      // use ellipsoidParameters so that result is cached
+      def.parameters = ellipsoidParameters( def.acronym );
+
+      defs << def;
+    }
+  }
+
+  // close the sqlite3 statement
+  sqlite3_finalize( preparedStatement );
+  sqlite3_close( database );
+
+  sDefinitionCache = defs;
+  sDefinitionCacheLock.unlock();
+
+  return defs;
+}
+
+QStringList QgsEllipsoidUtils::acronyms()
+{
+  QStringList result;
+  Q_FOREACH ( const QgsEllipsoidUtils::EllipsoidDefinition &def, definitions() )
+  {
+    result << def.acronym;
+  }
+  return result;
+}

src/core/qgsellipsoidutils.h

@@ -19,6 +19,7 @@
 #include "qgis_core.h"
 #include "qgis.h"
 #include "qgscoordinatereferencesystem.h"
+#include <QStringList>
 
 /**
  * \class QgsEllipsoidUtils
@@ -32,7 +33,7 @@ class CORE_EXPORT QgsEllipsoidUtils
   public:
 
     /**
-     * Contains parameter definitions for an ellipsoid.
+     * Contains parameters for an ellipsoid.
      * \since QGIS 3.0
      */
     struct EllipsoidParameters
@@ -55,17 +56,47 @@ class CORE_EXPORT QgsEllipsoidUtils
       QgsCoordinateReferenceSystem crs;
     };
 
+    /**
+     * Contains definition of an ellipsoid.
+     * \since QGIS 3.0
+     */
+    struct EllipsoidDefinition
+    {
+      //! Acronym for ellipsoid
+      QString acronym;
+      //! Description of ellipsoid
+      QString description;
+      //! Ellipsoid parameters
+      QgsEllipsoidUtils::EllipsoidParameters parameters;
+    };
+
     /**
      * Returns the parameters for the specified \a ellipsoid.
      * Results are cached to allow for fast retrieval of parameters.
      */
     static EllipsoidParameters ellipsoidParameters( const QString &ellipsoid );
 
+    /**
+     * Returns a list of the definitions for all known ellipsoids from the
+     * internal ellipsoid database.
+     * \see acronyms()
+     */
+    static QList< QgsEllipsoidUtils::EllipsoidDefinition > definitions();
+
+    /**
+     * Returns a list of all known ellipsoid acronyms from the internal
+     * ellipsoid database.
+     * \see definitions()
+     */
+    static QStringList acronyms();
+
   private:
 
     // ellipsoid cache
     static QReadWriteLock sEllipsoidCacheLock;
     static QHash< QString, EllipsoidParameters > sEllipsoidCache;
+    static QReadWriteLock sDefinitionCacheLock;
+    static QList< QgsEllipsoidUtils::EllipsoidDefinition > sDefinitionCache;
 
 };
 

tests/src/python/test_qgsellipsoidutils.py

@@ -29,6 +29,15 @@ def testParams(self):
 
         # run each test twice, so that ellipsoid is fetched from cache on the second time
 
+        for i in range(2):
+            params = QgsEllipsoidUtils.ellipsoidParameters("WGS84")
+            self.assertTrue(params.valid)
+            self.assertEqual(params.semiMajor, 6378137.0)
+            self.assertAlmostEqual(params.semiMinor, 6356752.314245179, 5)
+            self.assertAlmostEqual(params.inverseFlattening, 298.257223563, 5)
+            self.assertFalse(params.useCustomParameters)
+            self.assertEqual(params.crs.authid(), 'EPSG:4030')
+
         for i in range(2):
             params = QgsEllipsoidUtils.ellipsoidParameters("Ganymede2000")
             self.assertTrue(params.valid)
@@ -53,6 +62,23 @@ def testParams(self):
             params = QgsEllipsoidUtils.ellipsoidParameters("Babies first ellipsoid!")
             self.assertFalse(params.valid)
 
+    def testAcronyms(self):
+        self.assertTrue('WGS84' in QgsEllipsoidUtils.acronyms())
+        self.assertTrue('Ganymede2000' in QgsEllipsoidUtils.acronyms())
+
+    def testDefinitions(self):
+        defs = QgsEllipsoidUtils.definitions()
+
+        gany_defs = [d for d in defs if d.acronym == 'Ganymede2000'][0]
+        self.assertEqual(gany_defs.acronym, 'Ganymede2000')
+        self.assertEqual(gany_defs.description, 'Ganymede2000')
+        self.assertTrue(gany_defs.parameters.valid)
+        self.assertEqual(gany_defs.parameters.semiMajor, 2632400.0)
+        self.assertEqual(gany_defs.parameters.semiMinor, 2632350.0)
+        self.assertEqual(gany_defs.parameters.inverseFlattening, 52648.0)
+        self.assertFalse(gany_defs.parameters.useCustomParameters)
+        self.assertEqual(gany_defs.parameters.crs.authid(), '')
+
 
 if __name__ == '__main__':
     unittest.main()