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Use a custom proj error handler to collect descriptive coordinate

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operation creation errors, and report these back to users

Because these errors contain useful information for users to debug,
e.g. "Source and target ellipsoid do not belong to the same celestial
body"
This commit is contained in:
Nyall Dawson 2019-06-11 11:48:03 +10:00
parent d35197f317
commit 46f364a431
1 changed files with 41 additions and 1 deletions
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42
src/core/qgscoordinatetransform_p.cpp
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@ -268,6 +268,26 @@ void QgsCoordinateTransformPrivate::calculateTransforms( const QgsCoordinateTran
#endif
}
#if PROJ_VERSION_MAJOR>=6
static void proj_collecting_logger( void *user_data, int /*level*/, const char *message )
{
QStringList *dest = reinterpret_cast< QStringList * >( user_data );
dest->append( QString( message ) );
}
static void proj_logger( void *, int level, const char *message )
{
if ( level == PJ_LOG_ERROR )
{
QgsDebugMsg( QString( message ) );
}
else if ( level == PJ_LOG_DEBUG )
{
QgsDebugMsgLevel( QString( message ), 3 );
}
}
#endif
ProjData QgsCoordinateTransformPrivate::threadLocalProjData()
{
QgsReadWriteLocker locker( mProjLock, QgsReadWriteLocker::Read );
@ -303,6 +323,10 @@ ProjData QgsCoordinateTransformPrivate::threadLocalProjData()
locker.changeMode( QgsReadWriteLocker::Write );
#if PROJ_VERSION_MAJOR>=6
// use a temporary proj error collector
QStringList projErrors;
proj_log_func( context, &projErrors, proj_collecting_logger );
QgsProjUtils::proj_pj_unique_ptr transform;
if ( !mProjCoordinateOperation.isEmpty() )
{
@ -333,7 +357,10 @@ ProjData QgsCoordinateTransformPrivate::threadLocalProjData()
if ( !transform ) // fallback on default proj pathway
{
if ( !mSourceCRS.projObject() || ! mDestCRS.projObject() )
{
proj_log_func( context, nullptr, nullptr );
return nullptr;
}
PJ_OPERATION_FACTORY_CONTEXT *operationContext = proj_create_operation_factory_context( context, nullptr );
@ -481,10 +508,20 @@ ProjData QgsCoordinateTransformPrivate::threadLocalProjData()
{
nonAvailableError = QString( proj_errno_string( errNo ) );
}
else
else if ( !projErrors.empty() )
{
nonAvailableError = projErrors.constLast();
}
if ( nonAvailableError.isEmpty() )
{
nonAvailableError = QObject::tr( "No coordinate operations are available between these two reference systems" );
}
else
{
// strip proj prefixes from error string, so that it's nicer for users
nonAvailableError = nonAvailableError.remove( QStringLiteral( "internal_proj_create_operations: " ) );
}
}
if ( !nonAvailableError.isEmpty() )
@ -502,6 +539,9 @@ ProjData QgsCoordinateTransformPrivate::threadLocalProjData()
}
}
// reset logger to terminal output
proj_log_func( context, nullptr, proj_logger );
if ( !transform )
{
// ouch!