[Backport branch-8-0] Refresh cached reprojector when changing map pr…

…ojection between drawMap() calls (fixes #6896) (#6899)

mapdraw.c

@@ -1770,16 +1770,12 @@ int pointLayerDrawShape(mapObj *map, imageObj *image, layerObj *layer, shapeObj
 
   if (layer->project && layer->transform == MS_TRUE)
   {
-      if( layer->reprojectorLayerToMap == NULL )
+      reprojectionObj* reprojector = msLayerGetReprojectorToMap(layer, map);
+      if( reprojector == NULL )
       {
-          layer->reprojectorLayerToMap = msProjectCreateReprojector(
-              &layer->projection, &map->projection);
-        if( layer->reprojectorLayerToMap == NULL )
-        {
-            return MS_FAILURE;
-        }
+        return MS_FAILURE;
       }
-      msProjectShapeEx(layer->reprojectorLayerToMap, shape);
+      msProjectShapeEx(reprojector, shape);
   }
 
   // Only take into account map rotation if the label and style angles are
@@ -2098,16 +2094,12 @@ int msDrawShape(mapObj *map, layerObj *layer, shapeObj *shape, imageObj *image,
 
   if (layer->project && layer->transform == MS_TRUE)
   {
-      if( layer->reprojectorLayerToMap == NULL )
+      reprojectionObj* reprojector = msLayerGetReprojectorToMap(layer, map);
+      if( reprojector == NULL )
       {
-          layer->reprojectorLayerToMap = msProjectCreateReprojector(
-              &layer->projection, &map->projection);
-        if( layer->reprojectorLayerToMap == NULL )
-        {
-            return MS_FAILURE;
-        }
+        return MS_FAILURE;
       }
-      msProjectShapeEx(layer->reprojectorLayerToMap, shape);
+      msProjectShapeEx(reprojector, shape);
   }
 
   /* check if we'll need the unclipped shape */

maplayer.c

@@ -1915,6 +1915,25 @@ void msLayerEnablePaging(layerObj *layer, int value)
   layer->vtable->LayerEnablePaging(layer, value);
 }
 
+/** Returns a cached reprojector from the layer projection to the map projection */
+reprojectionObj* msLayerGetReprojectorToMap(layerObj* layer, mapObj* map)
+{
+  if( layer->reprojectorLayerToMap != NULL &&
+      !msProjectIsReprojectorStillValid(layer->reprojectorLayerToMap) )
+  {
+    msProjectDestroyReprojector(layer->reprojectorLayerToMap);
+    layer->reprojectorLayerToMap = NULL;
+  }
+
+  if( layer->reprojectorLayerToMap == NULL )
+  {
+    layer->reprojectorLayerToMap = msProjectCreateReprojector(
+      &layer->projection, &map->projection);
+  }
+  return layer->reprojectorLayerToMap;
+}
+
+
 int LayerDefaultGetExtent(layerObj *layer, rectObj *extent)
 {
   (void)layer;

mapogcsos.c

@@ -362,14 +362,10 @@ void  msSOSAddGeometryNode(xmlNsPtr psNsGml, xmlNsPtr psNsMs, xmlNodePtr psParen
 
   if (psParent && psShape) {
     if (msProjectionsDiffer(&map->projection, &lp->projection) == MS_TRUE) {
-      if( lp->reprojectorLayerToMap == NULL )
+      reprojectionObj* reprojector = msLayerGetReprojectorToMap(lp, map);
+      if( reprojector )
       {
-        lp->reprojectorLayerToMap = msProjectCreateReprojector(
-            &lp->projection, &map->projection);
-      }
-      if( lp->reprojectorLayerToMap )
-      {
-        msProjectShapeEx(lp->reprojectorLayerToMap, psShape);
+        msProjectShapeEx(reprojector, psShape);
       }
       msOWSGetEPSGProj(&(map->projection), &(lp->metadata), "SO", MS_TRUE, &pszEpsg_buf);
       pszEpsg = pszEpsg_buf;
@@ -780,14 +776,10 @@ void msSOSAddMemberNode(xmlNsPtr psNsGml, xmlNsPtr psNsOm, xmlNsPtr psNsSwe, xml
 
     if(msProjectionsDiffer(&(lp->projection), &(map->projection)))
     {
-      if( lp->reprojectorLayerToMap == NULL )
-      {
-        lp->reprojectorLayerToMap = msProjectCreateReprojector(
-            &lp->projection, &map->projection);
-      }
-      if( lp->reprojectorLayerToMap )
+      reprojectionObj* reprojector = msLayerGetReprojectorToMap(lp, map);
+      if( reprojector )
       {
-        msProjectShapeEx(lp->reprojectorLayerToMap, &sShape);
+        msProjectShapeEx(reprojector, &sShape);
       }
     }
 

mapogroutput.cpp

@@ -1136,13 +1136,9 @@ int msOGRWriteFromQuery( mapObj *map, outputFormatObj *format, int sendheaders )
       }
 
       if( layer->project && resultshape.type != MS_SHAPE_NULL) {
-        if( layer->reprojectorLayerToMap == NULL )
-        {
-            layer->reprojectorLayerToMap = msProjectCreateReprojector(
-                &layer->projection, &layer->map->projection);
-        }
-        if( layer->reprojectorLayerToMap )
-            status = msProjectShapeEx(layer->reprojectorLayerToMap, &resultshape);
+        reprojectionObj* reprojector = msLayerGetReprojectorToMap(layer, layer->map);
+        if( reprojector )
+            status = msProjectShapeEx(reprojector, &resultshape);
         else
             status = MS_FAILURE;
       }

mapproject.c

@@ -414,11 +414,19 @@ void msProjectionContextUnref(projectionContext* ctx)
 /*                        msProjectCreateReprojector()                  */
 /************************************************************************/
 
+/* The pointed objects need to remain valid during the lifetime of the
+ * reprojector, as only their pointer is stored.
+ *
+ * If the *content* of in and/or out is changed, then the reprojector is
+ * no longer valid. This can be detected with msProjectIsReprojectorStillValid()
+ */
 reprojectionObj* msProjectCreateReprojector(projectionObj* in, projectionObj* out)
 {
     reprojectionObj* obj = (reprojectionObj*)msSmallCalloc(1, sizeof(reprojectionObj));
     obj->in = in;
     obj->out = out;
+    obj->generation_number_in = in ? in->generation_number : 0;
+    obj->generation_number_out = out ? out->generation_number : 0;
     obj->lineCuttingCase = LINE_CUTTING_UNKNOWN;
 
     /* -------------------------------------------------------------------- */
@@ -551,6 +559,8 @@ reprojectionObj* msProjectCreateReprojector(projectionObj* in, projectionObj* ou
     obj = (reprojectionObj*)msSmallCalloc(1, sizeof(reprojectionObj));
     obj->in = in;
     obj->out = out;
+    obj->generation_number_in = in ? in->generation_number : 0;
+    obj->generation_number_out = out ? out->generation_number : 0;
     obj->lineCuttingCase = LINE_CUTTING_UNKNOWN;
 
     /* -------------------------------------------------------------------- */
@@ -626,6 +636,7 @@ int msInitProjection(projectionObj *p)
 #elif PJ_VERSION >= 480
   p->proj_ctx = NULL;
 #endif
+  p->generation_number = 0;
   return(0);
 }
 
@@ -654,6 +665,7 @@ void msFreeProjection(projectionObj *p)
   msFreeCharArray(p->args, p->numargs);
   p->args = NULL;
   p->numargs = 0;
+  p->generation_number ++;
 }
 
 void msFreeProjectionExceptContext(projectionObj *p)
@@ -845,6 +857,8 @@ int msProcessProjection(projectionObj *p)
 {
   assert( p->proj == NULL );
 
+  p->generation_number ++;
+
   if( strcasecmp(p->args[0],"GEOGRAPHIC") == 0 ) {
     msSetError(MS_PROJERR,
                "PROJECTION 'GEOGRAPHIC' no longer supported.\n"
@@ -1367,6 +1381,19 @@ static msLineCuttingCase msProjectGetLineCuttingCase(reprojectionObj* reprojecto
 }
 #endif
 
+/************************************************************************/
+/*                msProjectIsReprojectorStillValid()                    */
+/************************************************************************/
+
+int msProjectIsReprojectorStillValid(reprojectionObj* reprojector)
+{
+    if( reprojector->in && reprojector->in->generation_number != reprojector->generation_number_in )
+        return MS_FALSE;
+    if( reprojector->out && reprojector->out->generation_number != reprojector->generation_number_out )
+        return MS_FALSE;
+    return MS_TRUE;
+}
+
 /************************************************************************/
 /*                         msProjectShapeLine()                         */
 /*                                                                      */

mapproject.h

@@ -89,7 +89,8 @@ but are not directly exposed by the mapscript module
     %immutable;
 #endif
     int numargs; ///< Actual number of projection args
-    int automatic; ///< Projection object was to fetched from the layer
+    short automatic; ///< Projection object was to fetched from the layer
+    unsigned short generation_number; ///< To be incremented when the content of the object change, so that reprojector can be invalidated
 #ifdef SWIG
     %mutable;
 #endif
@@ -116,12 +117,15 @@ but are not directly exposed by the mapscript module
     int no_op;
 #endif
 #endif
+    unsigned short generation_number_in;
+    unsigned short generation_number_out;
   } reprojectionObj;
 
 #ifndef SWIG
 
   MS_DLL_EXPORT reprojectionObj* msProjectCreateReprojector(projectionObj* in, projectionObj* out);
   MS_DLL_EXPORT void msProjectDestroyReprojector(reprojectionObj* reprojector);
+  MS_DLL_EXPORT int msProjectIsReprojectorStillValid(reprojectionObj* reprojector);
 
   MS_DLL_EXPORT projectionContext* msProjectionContextGetFromPool(void);
   MS_DLL_EXPORT void msProjectionContextReleaseToPool(projectionContext* ctx);

mapserver.h

@@ -2618,6 +2618,8 @@ extern "C" {
   int msOGRLayerGetShape(layerObj *layer, shapeObj *shape, resultObj *record);
   int msOGRLayerGetExtent(layerObj *layer, rectObj *extent);
 
+  reprojectionObj MS_DLL_EXPORT* msLayerGetReprojectorToMap(layerObj* layer, mapObj* map);
+
   MS_DLL_EXPORT int msOGRGeometryToShape(OGRGeometryH hGeometry, shapeObj *shape,
                                          OGRwkbGeometryType type);
 

maptemplate.c

@@ -1619,14 +1619,10 @@ static int processShplabelTag(layerObj *layer, char **line, shapeObj *origshape)
         if(layer->transform == MS_TRUE) {
           if(layer->project && msProjectionsDiffer(&(layer->projection), &(layer->map->projection)))
           {
-            if( layer->reprojectorLayerToMap == NULL )
+            reprojectionObj* reprojector = msLayerGetReprojectorToMap(layer, layer->map);
+            if( reprojector )
             {
-                layer->reprojectorLayerToMap = msProjectCreateReprojector(
-                    &layer->projection, &layer->map->projection);
-            }
-            if( layer->reprojectorLayerToMap )
-            {
-                msProjectShapeEx(layer->reprojectorLayerToMap, shape);
+                msProjectShapeEx(reprojector, shape);
             }
           }
 
@@ -1640,14 +1636,10 @@ static int processShplabelTag(layerObj *layer, char **line, shapeObj *origshape)
       if(layer->transform == MS_TRUE) {
         if(layer->project && msProjectionsDiffer(&(layer->projection), &(layer->map->projection)))
         {
-            if( layer->reprojectorLayerToMap == NULL )
+            reprojectionObj* reprojector = msLayerGetReprojectorToMap(layer, layer->map);
+            if( reprojector )
             {
-                layer->reprojectorLayerToMap = msProjectCreateReprojector(
-                    &layer->projection, &layer->map->projection);
-            }
-            if( layer->reprojectorLayerToMap )
-            {
-                msProjectShapeEx(layer->reprojectorLayerToMap, shape);
+                msProjectShapeEx(reprojector, shape);
             }
         }
 
@@ -1680,14 +1672,10 @@ static int processShplabelTag(layerObj *layer, char **line, shapeObj *origshape)
       if(layer->transform == MS_TRUE) {
         if(layer->project && msProjectionsDiffer(&(layer->projection), &(layer->map->projection)))
         {
-            if( layer->reprojectorLayerToMap == NULL )
-            {
-                layer->reprojectorLayerToMap = msProjectCreateReprojector(
-                    &layer->projection, &layer->map->projection);
-            }
-            if( layer->reprojectorLayerToMap )
+            reprojectionObj* reprojector = msLayerGetReprojectorToMap(layer, layer->map);
+            if( reprojector )
             {
-                msProjectShapeEx(layer->reprojectorLayerToMap, shape);
+                msProjectShapeEx(reprojector, shape);
             }
         }
 
@@ -1778,14 +1766,10 @@ static int processShplabelTag(layerObj *layer, char **line, shapeObj *origshape)
       /* if necessary, project the shape to match the map */
       if(msProjectionsDiffer(&(layer->projection), &(layer->map->projection)))
       {
-        if( layer->reprojectorLayerToMap == NULL )
-        {
-            layer->reprojectorLayerToMap = msProjectCreateReprojector(
-                &layer->projection, &layer->map->projection);
-        }
-        if( layer->reprojectorLayerToMap )
+        reprojectionObj* reprojector = msLayerGetReprojectorToMap(layer, layer->map);
+        if( reprojector )
         {
-            msProjectShapeEx(layer->reprojectorLayerToMap, &tShape);
+            msProjectShapeEx(reprojector, &tShape);
         }
       }
 
@@ -2155,14 +2139,10 @@ static int processShpxyTag(layerObj *layer, char **line, shapeObj *shape)
       /* if necessary, project the shape to match the map */
       if(msProjectionsDiffer(&(layer->projection), &(layer->map->projection)))
       {
-        if( layer->reprojectorLayerToMap == NULL )
-        {
-            layer->reprojectorLayerToMap = msProjectCreateReprojector(
-                &layer->projection, &layer->map->projection);
-        }
-        if( layer->reprojectorLayerToMap )
+        reprojectionObj* reprojector = msLayerGetReprojectorToMap(layer, layer->map);
+        if( reprojector )
         {
-            msProjectShapeEx(layer->reprojectorLayerToMap, &tShape);
+            msProjectShapeEx(reprojector, &tShape);
         }
       }
 

msautotest/mspython/test_bug_check.py

@@ -232,3 +232,52 @@ def test_reprojection_from_lonlat_wrap_0():
     set_x = [point11.x, point12.x, point21.x, point22.x]
     set_x.sort()
     assert set_x == pytest.approx([-180, -179, 178, 180], abs=1e-2)
+
+
+###############################################################################
+# Check that we can draw a map several times by changing the map projection
+
+def test_bug_6896():
+
+    try:
+        os.mkdir(get_relpath_to_this('result'))
+    except:
+        pass
+
+    def load_map():
+        # Generate a reference image
+        map = mapscript.mapObj(get_relpath_to_this('../misc/ogr_direct.map'))
+        layer = map.getLayer(0)
+        layer.setProjection('+proj=utm +zone=11 +datum=WGS84')
+        return map
+
+    def draw_another_projection(map):
+        # Draw map with one reprojection.
+        map.setProjection('+proj=utm +zone=12 +datum=WGS84')
+        map.setExtent(-10675, 4781937, -7127, 4784428 )
+        map.draw()
+
+    def draw_wgs84(map):
+        # Draw map with WGS 84 projection
+        map.setProjection('+proj=latlong +datum=WGS84')
+        map.setExtent(-117.25,43.02,-117.21,43.05)
+        img = map.draw()
+        return img
+
+    map = load_map()
+    img = draw_wgs84(map)
+    ref_filename = get_relpath_to_this('result/bug6896_ref.png')
+    img.save(ref_filename)
+
+    # Reload map
+    map = load_map()
+    draw_another_projection(map)
+    img = draw_wgs84(map)
+    test_filename = get_relpath_to_this('result/bug6896.png')
+    img.save(test_filename)
+
+    assert open(ref_filename, 'rb').read() == \
+           open(test_filename, 'rb').read()
+
+    os.unlink(ref_filename)
+    os.unlink(test_filename)