non-square pixels not working correctly

[brianp@…]

I am attempting to include the MapServer as a c library into a seperate C++
program I am using.  I am explicitly setting the extent to the exact lat/lon
values I want for the images.  The extent is shifting from
EXTENT -113.981498074503 50.7247102624229 -113.961752952407 50.7319757375771
to 
EXTENT -113.981498074503 50.7226042699327 -113.961752952407 50.7340817300673

it doesn't matter if I call msSetConfigOption(map, "MS_NONSQUARE", "YES"); the
extent changes by the same ammount.  If I do set the option for non-square
pixels, the resulting image is blank (white which is the background color).

Please see the various attactments.

[brianp@…]

Map file

[brianp@…]

Sample source

[brianp@…]

Results with square pixels

[brianp@…]

Results with nonsquare pixels

[brianp@…]

Trying to provide as much info as possible.  Here is my configure command:
./configure --prefix=/usr/local --with-freetype --with-zlib --without-png --with
-jpeg --without-xpm --with-libiconv --with-gd --without-pdf --without-eppl --wit
h-proj --with-threads --without-sde --without-mpatrol --without-geos --with-ogr=
/usr/local/bin/gdal-config --with-gdal=/usr/local/bin/gdal-config --with-tiff --
without-postgis --without-mygis --without-oraclespatial --without-ming --without
-wms --without-wfs --without-wcs --without-wmsclient --without-wfsclient --witho
ut-curl-config --without-fastcgi --with-httpd=/usr/local/apache_1.3.29/bin/httpd
 --without-php

Here is my Mapserver compile flags after configure:
gcc -c -O2 -fPIC -Wall   -DIGNORE_MISSING_DATA  -DHAVE_VSNPRINTF -DNEED_STRLCAT
  -DUSE_PROJ    -DUSE_TIFF  -DUSE_GD_PNG -DUSE_GD_JPEG -DUSE_GD_WBMP -DUSE_GD_FT
-DGD_HAS_GETBITMAPFONTS    -DUSE_OGR -DUSE_GDAL  -DUSE_ICONV       -DUSE_THREAD
-DUSE_ZLIB -I/usr/include        -I/usr/local/include          mapthread.c -o
mapthread.o
ar rc libmap.a maptemplate.o mapbits.o maphash.o mapshape.o mapxbase.o
mapparser.o maplexer.o maptree.o mapsearch.o mapstring.o mapsymbol.o mapfile.o
maplegend.o maputil.o mapscale.o mapquery.o maplabel.o maperror.o mapprimitive.o
mapproject.o mapraster.o mapsde.o mapogr.o mappostgis.o mapmygis.o maplayer.o
mapresample.o mapwms.o mapwmslayer.o maporaclespatial.o mapgml.o mapprojhack.o
mapthread.o mapdraw.o mapgd.o mapoutput.o mapgdal.o mapswf.o mapimagemap.o
mapows.o mapwfs.o mapwfslayer.o mapcontext.o maphttp.o mapdrawgdal.o mappdf.o
mapjoin.o mapgraticule.o mapcopy.o mapogcfilter.o mapogcsld.o maptime.o mapwcs.o
mapcpl.o cgiutil.o maprasterquery.o mapobject.o mapgeos.o classobject.o
layerobject.o mapio.o mappool.o mapsvg.o mapregex.o mappluginlayer.o
ranlib libmap.a
gcc -O2 -fPIC -Wall   -DIGNORE_MISSING_DATA  -DHAVE_VSNPRINTF -DNEED_STRLCAT  
-DUSE_PROJ    -DUSE_TIFF  -DUSE_GD_PNG -DUSE_GD_JPEG -DUSE_GD_WBMP -DUSE_GD_FT
-DGD_HAS_GETBITMAPFONTS    -DUSE_OGR -DUSE_GDAL  -DUSE_ICONV       -DUSE_THREAD
-DUSE_ZLIB -I/usr/include        -I/usr/local/include          shp2img.o  -L.
-lmap -lgd -L/usr/lib -lgd -ljpeg -lfreetype -lpng -lz    -ltiff -ljpeg
-lfreetype -lpng -lz   -lproj -ljpeg  -L/usr/local/lib -lgdal        -lpthread
-L -lc  -lz -lm -lstdc++  -o shp2img

I have copied all the -D flags to the makefile I use to compile the attached
sample source program.

[sdlime]

I thought Frank was taking this one...

Steve

[fwarmerdam]

By way of demonstrating simplication, the problem can also be demonstrated
with the command:

 shp2img -m test.map -o out.tif

and the file:

   MAP
       CONFIG "MS_NONSQUARE" "YES" 
       NAME HELLO
       EXTENT 0 50 400 300
       SIZE 400 300
       IMAGECOLOR 200 255 255

       IMAGETYPE gtiff

       LAYER
           STATUS DEFAULT
           TYPE LINE
           FEATURE
               POINTS
                   50 50 350 50 350 250 50 250 50 50 
               END
           END
           CLASS
               COLOR 255 0 0
           END
       END
   END

Setting a valid projection on the map and layer fixes the problem.

So the problem is that contrary to my understanding, the NONSQUARE stuff
still only works if there is a valid projection available.  I shall dig
into it from that view point.

[fwarmerdam]

The solution seems to be to default layer->project to MS_TRUE when
the map is initialized.  I have committed this change in 4.9.

The workaround in 4.8 is to set a projection on the layer and map. 
Iterating through the layers manually and setting layer->project to 
MS_TRUE in advance would also work.

I ran my test suite afterwards and it seemed ok.  The first pass
through drawing the map will reset map->project to MS_FALSE if 
msProjectionDiffer() is false. 

I don't feel comfortable with backporting this change back into 4.8.2. 
It seems like the sort of thing that could cause unexpected problems.