<!DOCTYPE html><html><head><title></title><style type="text/css">p.MsoNormal,p.MsoNoSpacing{margin:0}</style></head><body><div>Hi,<br></div><div><br></div><div>I implemented a simple addition to MapScript to retrieve the gmlItemObj for a layer item (field) and added to the pull request. <br></div><div>This currently works for the Python bindings but is throwing an error for C# I'll look into. <br></div><div><br></div><div>To use gmlItemObj I had to include mapows.h in mapscript.i. When I initially did this there were 28 errors similar to below:<br></div><div><br></div><div>mapscriptPYTHON_wrap.obj : error LNK2019: unresolved external symbol msWMSDispatch referenced in function _wrap_msWMSDispatch<br></div><div><br></div><div>The relevant commit is at: <a href="https://github.com/mapserver/mapserver/pull/5765/commits/0260296eecfb8b9bad979fc20ba5f9034ca37ffb">https://github.com/mapserver/mapserver/pull/5765/commits/0260296eecfb8b9bad979fc20ba5f9034ca37ffb</a> (Ill see what happened to the whitespace in this commit and revert with just the relevant changes). <br></div><div><br></div><div>I simply added the macro MS_DLL_EXPORT to export all these functions and was able to build and test the MapScript bindings. <br></div><div>All the other header files included in SWIG have #ifndef SWIG guards everywhere. Is anyone able to explain to me the purpose of these and provide examples of where these should be added to mapows.h?<br></div><div><br></div><div>Seth<br></div><div><br></div><div id="sig62266145"><div class="signature">--<br></div><div class="signature">web:http://geographika.co.uk<br></div><div class="signature">twitter: @geographika<br></div></div><div><br></div><div><br></div><div>On Sat, Mar 16, 2019, at 11:58 AM, Lime, Steve D (MNIT) wrote:<br></div><blockquote type="cite" id="fastmail-quoted"><div>I wish we could make it less GMLish and more generic. For example, it feels odd in MVT code to be relying on what feels like format-specific metadata. The various service specs can use a generic “ows” or service specific metadata namespaces. Could do the same
for output... “out” as the generic namespace with “gml”, “mvt”, “ogr”, “kml” as specific namespaces.<br></div><div> <br></div><div> gmlItemObj and gmlItemListObj could also be renamed more generically and the latter could become iteminfo as part of a layer. A cast function for type conversations would also be helpful for more standard use.<br></div><div> <br></div><div> Just thinking out loud - I know that’s way more than you want to get into,<br></div><div> <br></div><div> —Steve<br></div><div> <br></div><div> <hr style="display:inline-block;width:98%;"> <br></div><div dir="ltr" id="fastmail-quoted-divRplyFwdMsg"><div><span style="font-family:Calibri, sans-serif" class="font"><span style="color:#000000" class="colour"><b>From:</b> mapserver-dev <mapserver-dev-bounces@lists.osgeo.org> on behalf of Seth G <sethg@geographika.co.uk><br> <b>Sent:</b> Friday, March 15, 2019 6:58:41 PM<br> <b>To:</b> mapserver-dev@lists.osgeo.org<br> <b>Subject:</b> Re: [mapserver-dev] Questions on MapServer architecture and attribute conversions</span></span> </div><div> <br></div></div><div class="fastmail-quoted-BodyFragment"><span style="font-size:13px" class="size"><span style="font-size:11pt" class="size"><div class="fastmail-quoted-PlainText"><div>Hi Steve, Even,<br></div><div> <br></div><div> Thanks for your replies. Thinking back I think I've run into the issue of strings being used for int fields from a database, and CLASS expressions. <br></div><div> <br></div><div> I may make an attempt at the following based on both of your comments:<br></div><div> <br></div><div> - add gmlItemObj (and also gmlItemListObj) as classes to MapScript<br></div><div> - allow msGMLGetItems to be called on a layerObj to populate this list<br></div><div> - allow this list to be associated/passed to a method on a shapeObj, and use the GML types to set the output attribute types<br></div><div> - if there are no field definitions supplied then attribute names will simply be indexes, and all values strings<br></div><div> <br></div><div> Seth<br></div><div> --<br></div><div> web:http://geographika.co.uk<br></div><div> twitter: @geographika<br></div><div> <br></div><div> On Thu, Mar 14, 2019, at 10:14 PM, Lime, Steve D (MNIT) wrote:<br></div><div> > Couple of questions here...<br></div><div> > <br></div><div> > On your pull request. I don't think there's a need for a RFC given the <br></div><div> > scope of the change. it's not breaking anything and seems like a nice <br></div><div> > addition - I certainly defer to your expertise as the Python MapScript <br></div><div> > maintainer. I guess it's never a bad idea to alert the -dev list and <br></div><div> > take your email as that notice - so +1 from me.<br></div><div> > <br></div><div> > On your assumptions, both are correct. <br></div><div> > <br></div><div> > On item types, it's funny this hasn't come up more over the years. Type <br></div><div> > conversions seem to happen either for output using the metadata <br></div><div> > referenced or in the expression handling based on context. You're <br></div><div> > correct the that MapScript, most of the time you'd get the column/item <br></div><div> > names from layer but not always since you can work with shapefiles <br></div><div> > directly and independently of a layerObj or mapObj.<br></div><div> > <br></div><div> > Each layer has an attribute has something called iteminfo and it holds <br></div><div> > the index value associated with corresponding value in the items array. <br></div><div> > So you'd look up the item someone wanted for labeling purposes (or <br></div><div> > whatever) and would know what value to grab from a shapes values array. <br></div><div> > Those item index values are stored all over the place (e.g. labelitem <br></div><div> > and labelitemindex). I think with a scheme like Even describes <br></div><div> > items/iteminto could be replaced by one property (items) that would <br></div><div> > equate to an array of field definitions and then specific things like a <br></div><div> > labelitem becomes a struct consisting of a string and a pointer to one <br></div><div> > of the items. For some reason I thought Dan made a run at that at one <br></div><div> > point but I might be mistaken.<br></div><div> > <br></div><div> > -----Original Message-----<br></div><div> > From: mapserver-dev [<a href="mailto:mapserver-dev-bounces@lists.osgeo.org">mailto:mapserver-dev-bounces@lists.osgeo.org</a>] On <br></div><div> > Behalf Of Even Rouault<br></div><div> > Sent: Thursday, March 14, 2019 11:39 AM<br></div><div> > To: mapserver-dev@lists.osgeo.org<br></div><div> > Subject: Re: [mapserver-dev] Questions on MapServer architecture and <br></div><div> > attribute conversions<br></div><div> > <br></div><div> > Seth,<br></div><div> > <br></div><div> > > <br></div><div> > > I've created a pull request to add a __geo_interface__ to the Python<br></div><div> > > MapScript PointObj, LineObj, and ShapeObjs. This allows Python scripts to<br></div><div> > > easily share MapScript objects with other Python geospatial libraries such<br></div><div> > > as Shapely, QGIS, and ArcPy. It also completes a nice cycle as Sean Gillies<br></div><div> > > was a core developer of the MapScript Python bindings and created<br></div><div> > > __geo_interface__. This only affects the Python MapScript bindings - do I<br></div><div> > > need to create a RFC or ask for a vote to merge this for a 7.4 release?<br></div><div> > > <br></div><div> > > I also have a few questions on the internal architecture of MapServer<br></div><div> > > classes. Could other devs confirm (or correct) the following assumptions?<br></div><div> > > <br></div><div> > > - the shapeObj has no link back to a layerObj - they are completely<br></div><div> > > independent with no way to get a reference to a layer from a shape - all<br></div><div> > > shapeObj attribute values are stored internally as strings<br></div><div> > <br></div><div> > Yes that's my understanding too.<br></div><div> > <br></div><div> > > <br></div><div> > > To get attribute names for a shapeObj I had to get retrieve them from the<br></div><div> > > relevant layerObj and store these in a new property on the shapeObj in<br></div><div> > > Python MapScript. I can then output something like the following:<br></div><div> > > <br></div><div> > > "properties": {<br></div><div> > > "guid": "954BADBF-2891-48ED-A132-AED39C60E4C9",<br></div><div> > > "featureid": "203529",<br></div><div> > > "classid": "12"<br></div><div> > > }<br></div><div> > > <br></div><div> > > It would be nice to be able to convert the property values to their relevant<br></div><div> > > types e.g. integers and floats. Looking through the MapServer source they<br></div><div> > > seem to only be converted to types using METADATA blocks and<br></div><div> > > "gml_FIELD_NAME_type" "datatype" and in certain cases e.g. in<br></div><div> > > mapogroutput.c Are these conversions all handled differently for different<br></div><div> > > data inputs? Is there an easy way to reuse these conversions in MapScript?<br></div><div> > <br></div><div> > Yes this lack of proper typing on layer attributes is a bit inconvenient and <br></div><div> > causes lot of adhoc coding in various areas of the code base: ogroutput, OGC <br></div><div> > filtering, WFS, GML output, MVT output, etc.<br></div><div> > The fundamental issue is that layerObj::items is just an array of field names.<br></div><div> > <br></div><div> > For brainstorming... A potential solution could take inspiration from what is <br></div><div> > done in GDAL where:<br></div><div> > OGRLayer (~ equivalent of layerObj) -> contains a OGRFeatureDefn<br></div><div> > OGRFeature (~ equivalent of shapeObj) -> points to a OGRFeatureDefn, and has <br></div><div> > an array of field values<br></div><div> > <br></div><div> > A OGRFeatureDefn contains (among other things) an array of OGRFieldDefn<br></div><div> > A OGRFieldDefn is a set of attribute: field name, field type, etc...<br></div><div> > <br></div><div> > Or if not doing a majorhaul, have indeed a pointer from shapeObj back to <br></div><div> > layerObj (which interesting lifetime consideration, but I'm not sure MapScript <br></div><div> > really shines on maintaining object ownership), and use information returned <br></div><div> > by msGMLGetItems().<br></div><div> > <br></div><div> > <br></div><div> > Even<br></div><div> > <br></div><div> > <br></div><div> > -- <br></div><div> > Spatialys - Geospatial professional services<br></div><div> > <a href="https://gcc01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.spatialys.com&data=02%7C01%7Csteve.lime%40state.mn.us%7C8af807e4be164b6cb28608d6a9a229ad%7Ceb14b04624c445198f26b89c2159828c%7C0%7C0%7C636882911288492978&sdata=gq%2FwxERwIC7hIsUULQuBdz5NuWGPSjEEejynXTrU%2BWc%3D&reserved=0"> https://gcc01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.spatialys.com&data=02%7C01%7Csteve.lime%40state.mn.us%7C8af807e4be164b6cb28608d6a9a229ad%7Ceb14b04624c445198f26b89c2159828c%7C0%7C0%7C636882911288492978&sdata=gq%2FwxERwIC7hIsUULQuBdz5NuWGPSjEEejynXTrU%2BWc%3D&reserved=0</a><br></div><div> > _______________________________________________<br></div><div> > mapserver-dev mailing list<br></div><div> > mapserver-dev@lists.osgeo.org<br></div><div> > <a href="https://gcc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.osgeo.org%2Fmailman%2Flistinfo%2Fmapserver-dev&data=02%7C01%7Csteve.lime%40state.mn.us%7C8af807e4be164b6cb28608d6a9a229ad%7Ceb14b04624c445198f26b89c2159828c%7C0%7C0%7C636882911288492978&sdata=K6js4DgRQJ4giCNpYqJ3oROAb7HQg3W6xHJaAbXgUxI%3D&reserved=0"> https://gcc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.osgeo.org%2Fmailman%2Flistinfo%2Fmapserver-dev&data=02%7C01%7Csteve.lime%40state.mn.us%7C8af807e4be164b6cb28608d6a9a229ad%7Ceb14b04624c445198f26b89c2159828c%7C0%7C0%7C636882911288492978&sdata=K6js4DgRQJ4giCNpYqJ3oROAb7HQg3W6xHJaAbXgUxI%3D&reserved=0</a><br></div><div> > _______________________________________________<br></div><div> > mapserver-dev mailing list<br></div><div> > mapserver-dev@lists.osgeo.org<br></div><div> > <a href="https://gcc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.osgeo.org%2Fmailman%2Flistinfo%2Fmapserver-dev&data=02%7C01%7Csteve.lime%40state.mn.us%7C8af807e4be164b6cb28608d6a9a229ad%7Ceb14b04624c445198f26b89c2159828c%7C0%7C1%7C636882911288502991&sdata=48CiR%2B8XMq030GchIzqmpAdse4sgV1b9Fvjk8Jzt%2Fq8%3D&reserved=0"> https://gcc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.osgeo.org%2Fmailman%2Flistinfo%2Fmapserver-dev&data=02%7C01%7Csteve.lime%40state.mn.us%7C8af807e4be164b6cb28608d6a9a229ad%7Ceb14b04624c445198f26b89c2159828c%7C0%7C1%7C636882911288502991&sdata=48CiR%2B8XMq030GchIzqmpAdse4sgV1b9Fvjk8Jzt%2Fq8%3D&reserved=0</a><br></div><div> _______________________________________________<br></div><div> mapserver-dev mailing list<br></div><div> mapserver-dev@lists.osgeo.org<br></div><div> <a href="https://gcc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.osgeo.org%2Fmailman%2Flistinfo%2Fmapserver-dev&data=02%7C01%7Csteve.lime%40state.mn.us%7C8af807e4be164b6cb28608d6a9a229ad%7Ceb14b04624c445198f26b89c2159828c%7C0%7C1%7C636882911288502991&sdata=48CiR%2B8XMq030GchIzqmpAdse4sgV1b9Fvjk8Jzt%2Fq8%3D&reserved=0">https://gcc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.osgeo.org%2Fmailman%2Flistinfo%2Fmapserver-dev&data=02%7C01%7Csteve.lime%40state.mn.us%7C8af807e4be164b6cb28608d6a9a229ad%7Ceb14b04624c445198f26b89c2159828c%7C0%7C1%7C636882911288502991&sdata=48CiR%2B8XMq030GchIzqmpAdse4sgV1b9Fvjk8Jzt%2Fq8%3D&reserved=0</a><br></div></div></span></span></div></blockquote><div><br></div></body></html>