[Backport release-3_40] Fix CRS exception when fallback operation occurs, fix invalid CRS transform for status bar display

src/app/qgsstatusbarcoordinateswidget.cpp

@@ -374,6 +374,7 @@ void QgsStatusBarCoordinatesWidget::refreshMapCanvas()
 void QgsStatusBarCoordinatesWidget::showMouseCoordinates( const QgsPointXY &p )
 {
   mLastCoordinate = p;
+  mLastCoordinateCrs = mMapCanvas->mapSettings().destinationCrs();
   updateCoordinateDisplay();
 }
 
@@ -431,7 +432,7 @@ void QgsStatusBarCoordinatesWidget::updateCoordinateDisplay()
   if ( mLastCoordinate.isEmpty() )
     mLineEdit->clear();
   else
-    mLineEdit->setText( QgsCoordinateUtils::formatCoordinateForProject( QgsProject::instance(), mLastCoordinate, mMapCanvas->mapSettings().destinationCrs(), static_cast<int>( mMousePrecisionDecimalPlaces ) ) );
+    mLineEdit->setText( QgsCoordinateUtils::formatCoordinateForProject( QgsProject::instance(), mLastCoordinate, mLastCoordinateCrs, static_cast<int>( mMousePrecisionDecimalPlaces ) ) );
 
   ensureCoordinatesVisible();
 }

src/app/qgsstatusbarcoordinateswidget.h

@@ -28,6 +28,7 @@ class QgsMapCanvas;
 
 #include "qgis_app.h"
 #include "qgspointxy.h"
+#include "qgscoordinatereferencesystem.h"
 
 #include <QWidget>
 #include <QElapsedTimer>
@@ -87,6 +88,7 @@ class APP_EXPORT QgsStatusBarCoordinatesWidget : public QWidget
     unsigned int mMousePrecisionDecimalPlaces;
 
     QgsPointXY mLastCoordinate;
+    QgsCoordinateReferenceSystem mLastCoordinateCrs;
 
     bool mIsFirstSizeChange = true;
     QElapsedTimer mLastSizeChangeTimer;

src/core/proj/qgscoordinatetransform.cpp

@@ -840,10 +840,13 @@ void QgsCoordinateTransform::transformCoords( int numPoints, double *x, double *
     {
       projResult = 0;
       proj_errno_reset( transform );
+      memcpy( x, xprev.data(), sizeof( double ) * numPoints );
+      memcpy( y, yprev.data(), sizeof( double ) * numPoints );
+      memcpy( z, zprev.data(), sizeof( double ) * numPoints );
       proj_trans_generic( transform, direction == Qgis::TransformDirection::Forward ? PJ_FWD : PJ_INV,
-                          xprev.data(), sizeof( double ), numPoints,
-                          yprev.data(), sizeof( double ), numPoints,
-                          zprev.data(), sizeof( double ), numPoints,
+                          x, sizeof( double ), numPoints,
+                          y, sizeof( double ), numPoints,
+                          z, sizeof( double ), numPoints,
                           useTime ? t.data() : nullptr, sizeof( double ), useTime ? numPoints : 0 );
       // Try to - approximately - emulate the behavior of pj_transform()...
       // In the case of a single point transform, and a transformation error occurs,
@@ -859,14 +862,11 @@ void QgsCoordinateTransform::transformCoords( int numPoints, double *x, double *
         // hmm - something very odd here. We can't trust proj_errno( transform ), as that's giving us incorrect error numbers
         // (such as "failed to load datum shift file", which is definitely incorrect for a default proj created operation!)
         // so we resort to testing values ourselves...
-        errorOccurredDuringFallbackOperation = std::isinf( xprev[0] ) || std::isinf( yprev[0] ) || std::isinf( zprev[0] );
+        errorOccurredDuringFallbackOperation = std::isinf( x[0] ) || std::isinf( y[0] ) || std::isinf( z[0] );
       }
 
       if ( !errorOccurredDuringFallbackOperation )
       {
-        memcpy( x, xprev.data(), sizeof( double ) * numPoints );
-        memcpy( y, yprev.data(), sizeof( double ) * numPoints );
-        memcpy( z, zprev.data(), sizeof( double ) * numPoints );
         mFallbackOperationOccurred = true;
       }