[rttopo-dev] Tolerance 0 support in master branch

[a.furieri at lqt.it]

On Tue, 6 Sep 2016 11:48:30 +0200, Sandro Santilli wrote:
> I've changed the semantic of tolerance parameter value 0
> from "automatic" to "zero", and added support for value -1
> to mean "automatic".
>
> This basically adds support for really specifying 0 as
> the tolerance value, which would result in no snapping
> ever occurring.
>
> With this change, I tried the spatialite testsuite (check_topology2d)
> and got a failure:
>
>  rtt_AddIsoNode failed TopoGeo_AddLineString() #1 error:
> rtt_AddIsoNode failed
>
> The failure isn't there if I revert the librttopo change.
>
> Alessandro: could you help reducing the testcase to figure out
> what's going on ? Spatialite is the only existing testsuite
> for librttopo...
>

Hi strk,

introducing sudden changes affecting the very basic interpretation
of some API argument never is a good policy and could easily
cause unexpected troubles.

now we have two different implementations of rttopo (depending on
version) returning incompatible results from a call with identical
arguments, and this will easily cause some trouble to the testsuite
that is expecting a consistent behavior from the library API
independently from the specific version being currently linked.

if possible it would be a better choice always leaving an already
existing API unaffected by any subsequent radical change, then adding
a new API with a different name implementing the new behavior as e.g.
rtt_AddIsoNode2() or rtt_AddIsoNodeEx()

this will greatly help to ensure a robust cross-version compatibility
and will prevent many unexpected failures; and will obviously
facilitate maintaining a testsuite safely supporting more than a
single specific version of RTTOPO.

bye Sandro