[MapServer-users] mapserver 8 - CGI map_object substitutions broken?

Steve Lime sdlime at gmail.com
Thu Oct 6 12:49:32 PDT 2022

Hi Tim: I was wondering if I'd see any messages on that topic. Short story
is that the functionality was removed in MS8. I never liked the
all-or-nothing aspect of it and was working on a method to control which
objects would be allowed to be updated. The solutions I came up with were
convoluted and were going to add a lot of complexity to the codebase for
little value. That functionality is poorly documented and by itself overly
complicates the code. So after a note to mapserver-users trying to judge
how much it was used - with limited replies - it was decided to remove it.
I'm dealing with my own upgrade issues as a result, but it's worth it in
the end IMHO.

If necessary, it's better to revisit with another method - ideally
something along the lines of runsubs. The challenge is specifying when to
apply them and how to validate values. Strings are easy, but numeric/color
values aren't so we'd need to do something like add runtime bindings
(similar to attribute bindings) so you'd write SIZE %mysize% instead. One
advantage being you could reuse the variable across layers.

So, what are the options right now? It sort of depends on your needs. Do
you need to only support a couple of sizes for a class or do you truly need
*any* size? Options include:

   - multiple mapfiles - probably using includes to limit redundancy
   - class groups
   - if you're using a db backend I think attribute bindings could work
   paired with runsubs

DATA "shape FROM (select *, %textsize% AS textsize FROM ...)


    "textsize_default" "13"

    "textsize" "^8|10|12|14$"




    SIZE [textsize] # I think attribute binding works here



   - MapScript - load the mapfile, do the changes you need, render the map

Happy to discuss further and perhaps other folks have ideas.


On Thu, Oct 6, 2022 at 12:47 PM Tim Kempisty via MapServer-users <
mapserver-users at lists.osgeo.org> wrote:

> Good afternoon, all.
> I am migrating a project from MS7 to the new Mapserver 8.0.0, and I've
> stumbled upon evidence that map_object notation support for CGI variable
> substitution may be broken.
> Here's the relevant doc for CGI Controls:
> https://mapserver.org/cgi/controls.html
> Scoll down to the heading:  "Changing map file parameters via a form or a
> URL"
> We have been using the map_object notation method to set custom image
> sizes and font sizes.
> Excuse the messy query string.  The important parts are  "&map_size" and
> "&map.layer[...]"
> /var/www/cgi-bin/mapserv.cgi -nh
> "QUERY_STRING=mode=map&map=/usr/local/mapfiles/kempisty/nbm_view/foo.map&layer=genNoDec&model=blend&ver=v4.0&sector=conus&element=maxt&issuancetime=2022-10-06T14:00&validtime=2022-10-08T06:00&mapext=-3270279.3477121103%20-163255.0404466032%202666810.2533767014%203144901.0582670807&map_size=1215+677&map.layer[genNoDec].class[0].label[0]=SIZE+8"
> > /var/www/html/kempisty/foo7.png
> MS7 gives a map size 1215x677 with labels rendered in 8 point font, as
> expected.  The same command, using mapserver 8 instead of 7, gives an
> image size 2345x1597 (map size as defined in the mapfile) with labels
> rendered in 13 point font (also as defined in the mapfile).
> Using MS8... if I send &mapsize=1215+677 instead of &map_size=1215+677 ...
> I will get the image at the correct size.  So the predefined CGI control
> variables still work.  It suggests to me, it is only the map_object
> notation method that is broken.  Has that been disabled in MS8, or is it
> now subject to a new configuration requirement that I'm not aware of?
> Relevant string isolated for reference:
> &map_size=1215+677&map.layer[genNoDec].class[0].label[0]=SIZE+8"
> I'm open to other methods of changing font size on the fly.  We did it
> this way because %var% runtime substitutions aren't supported for CLASS:
> -Tim Kempisty
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> MapServer-users at lists.osgeo.org
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