Add helper method to determine whether a proj string uses angular units

nyalldawson · nyalldawson · commit 353060dc3631 · 2019-04-05T11:33:08.000+10:00
diff --git a/src/app/qgscustomprojectiondialog.cpp b/src/app/qgscustomprojectiondialog.cpp
@@ -538,16 +538,23 @@ void QgsCustomProjectionDialog::pbnCalculate_clicked()
   {
     QString tmp;
 
-    int precision = 7;
+    int precision = 4;
+    bool isLatLong = false;
 
-#if PROJ_VERSION_MAJOR<6
-    if ( pj_is_latlong( proj ) )
+#if PROJ_VERSION_MAJOR>= 6
+    isLatLong = QgsProjUtils::usesAngularUnit( projDef );
+#else
+    isLatLong = pj_is_latlong( proj );
+    if ( isLatLong )
     {
       northing *= RAD_TO_DEG;
       easting *= RAD_TO_DEG;
-      precision = 7;
     }
 #endif
+    if ( isLatLong )
+    {
+      precision = 7;
+    }
 
     tmp = QLocale().toString( northing, 'f', precision );
     projectedX->setText( tmp );
diff --git a/src/core/qgscoordinatetransform_p.cpp b/src/core/qgscoordinatetransform_p.cpp
@@ -267,7 +267,7 @@ ProjData QgsCoordinateTransformPrivate::threadLocalProjData()
   locker.changeMode( QgsReadWriteLocker::Write );
 
 #if PROJ_VERSION_MAJOR>=6
-  ProjData res = proj_create_crs_to_crs( context, mSourceProjString.toUtf8(), mDestProjString.toUtf8(), nullptr );
+  ProjData res = proj_create_crs_to_crs( context, mSourceProjString.toUtf8().constData(), mDestProjString.toUtf8().constData(), nullptr );
   mProjProjections.insert( reinterpret_cast< uintptr_t>( context ), res );
 #else
 #ifdef USE_THREAD_LOCAL
diff --git a/src/core/qgsprojutils.cpp b/src/core/qgsprojutils.cpp
@@ -15,6 +15,7 @@
  *                                                                         *
  ***************************************************************************/
 #include "qgsprojutils.h"
+#include <QString>
 
 #if PROJ_VERSION_MAJOR>=6
 #include <proj.h>
@@ -71,4 +72,44 @@ void QgsProjUtils::ProjPJDeleter::operator()( PJ *object )
 {
   proj_destroy( object );
 }
+
+bool QgsProjUtils::usesAngularUnit( const QString &projDef )
+{
+  const QString crsDef = QStringLiteral( "%1 +type=crs" ).arg( projDef );
+  PJ_CONTEXT *context = QgsProjContext::get();
+  QgsProjUtils::proj_pj_unique_ptr projSingleOperation( proj_create( context, crsDef.toUtf8().constData() ) );
+  if ( !projSingleOperation )
+    return false;
+
+  QgsProjUtils::proj_pj_unique_ptr coordinateSystem( proj_crs_get_coordinate_system( context, projSingleOperation.get() ) );
+  if ( !coordinateSystem )
+    return false;
+
+  const int axisCount = proj_cs_get_axis_count( context, coordinateSystem.get() );
+  if ( axisCount > 0 )
+  {
+    const char *outUnitAuthName = nullptr;
+    const char *outUnitAuthCode = nullptr;
+    // Read only first axis
+    proj_cs_get_axis_info( context, coordinateSystem.get(), 0,
+                           nullptr,
+                           nullptr,
+                           nullptr,
+                           nullptr,
+                           nullptr,
+                           &outUnitAuthName,
+                           &outUnitAuthCode );
+
+    if ( outUnitAuthName && outUnitAuthCode )
+    {
+      const char *unitCategory = nullptr;
+      if ( proj_uom_get_info_from_database( context, outUnitAuthName, outUnitAuthCode, nullptr, nullptr, &unitCategory ) )
+      {
+        return QString( unitCategory ).compare( QLatin1String( "angular" ), Qt::CaseInsensitive ) == 0;
+      }
+    }
+  }
+  return false;
+}
+
 #endif
diff --git a/src/core/qgsprojutils.h b/src/core/qgsprojutils.h
@@ -73,6 +73,14 @@ class CORE_EXPORT QgsProjUtils
      */
     using proj_pj_unique_ptr = std::unique_ptr< PJ, ProjPJDeleter >;
 
+    /**
+     * Returns true if the given proj coordinate system uses angular units. \a projDef must be
+     * a proj string defining a CRS object.
+     */
+    static bool usesAngularUnit( const QString &projDef );
+
+
+
 #endif
 #endif
 };
diff --git a/tests/src/core/testqgsprojutils.cpp b/tests/src/core/testqgsprojutils.cpp
@@ -29,6 +29,7 @@ class TestQgsProjUtils: public QObject
     void initTestCase();
     void cleanupTestCase();
     void threadSafeContext();
+    void usesAngularUnits();
 
 };
 
@@ -67,5 +68,14 @@ void TestQgsProjUtils::threadSafeContext()
   QtConcurrent::blockingMap( list, ProjContextWrapper() );
 }
 
+void TestQgsProjUtils::usesAngularUnits()
+{
+  QVERIFY( !QgsProjUtils::usesAngularUnit( QString() ) );
+  QVERIFY( !QgsProjUtils::usesAngularUnit( QString( "" ) ) );
+  QVERIFY( !QgsProjUtils::usesAngularUnit( QStringLiteral( "x" ) ) );
+  QVERIFY( QgsProjUtils::usesAngularUnit( QStringLiteral( "+proj=longlat +ellps=WGS60 +no_defs" ) ) );
+  QVERIFY( !QgsProjUtils::usesAngularUnit( QStringLiteral( "+proj=tmerc +lat_0=0 +lon_0=147 +k_0=0.9996 +x_0=500000 +y_0=10000000 +ellps=GRS80 +units=m +no_defs" ) ) );
+}
+
 QGSTEST_MAIN( TestQgsProjUtils )
 #include "testqgsprojutils.moc"
