Re: [Lib2geom-devel] Mandatory path stitching

[Krzysztof K. <twe...@gm...>]

How about flipping the default, i.e. normally exceptions are raised
just before stitching would occur, but you can disable them?

This is similar to the previous behaviour, but would raise errors in
sloppy code at the point where invalid values are inserted into the
path, not when someone later tries to use the broken path.

Regards, Krzysztof

2015-03-29 12:38 GMT+02:00 Johan Engelen <jbc...@sw...>:
> Stitching, i.e. adding segments, is not a good solution to floating point
> rounding problems. IIRC, most of 2geom explicitly sets end-points to the
> same value, solving rounding problems. You have to push 2geom pretty hard to
> have it generate non-continuous paths. When adding little segments to paths
> that generate discontinuities for some operations, I think the problem only
> escalates.
> (Side point: from what I remember, many of the non-continuity exceptions
> arise because of user code pushing NaN points to the path. That's not going
> be solved by stitching.)
>
> In any case, I am simply giving my input having used 2geom a lot in
> Inkscape, but I don't expect to be writing code with/for it in the near
> future.
> I don't see why stitching should be implied default behavior. Stitching is
> useful, but isn't it really just a hack? My course of action would be to
> remove the default Stitching value for all functions that take a Stitching
> argument.
>
> - Johan
>
>
>
> On 29-3-2015 0:25, Nathan Hurst wrote:
>>
>> It's not sloppy code, it's inescapable floating point rounding.
>>
>> njh
>>
>> On Sat, Mar 28, 2015 at 10:29:07PM +0100, Johan Engelen wrote:
>>>
>>> I understood what you wrote.
>>> I argued that the default of allowing sloppy code is probably not a good
>>> default.
>>>
>>> - Johan
>>>
>>>
>>> On 28-3-2015 17:24, Krzysztof Kosiński wrote:
>>>>
>>>> A non-contiguous path is practically always an error, so it makes
>>>> sense to either prevent it or report it as early as possible. Now the
>>>> default behavior is to add those extra segments, which allows sloppily
>>>> written code to function as expected, but you can call
>>>> setStitchExceptions() to enable the throwing of exceptions whenever a
>>>> stitch segment would be appended.
>>>>
>>>> Regards, Krzysztof
>>>>
>>>> 2015-03-28 13:09 GMT+01:00 Johan Engelen <jbc...@sw...>:
>>>>>
>>>>> On 27-3-2015 20:48, Krzysztof Kosiński wrote:
>>>>>>
>>>>>> Every method that modifies a Path has an optional argument called
>>>>>> "stitching" that determines whether additional segments are added to
>>>>>> make the path continuous. By default, stitching is not used. If there
>>>>>> are any discontinuities, calling some of Path will cause an exception
>>>>>> to be thrown, which in most cases means a crash.
>>>>>>
>>>>>> I want to make stitching mandatory. Since in some cases you want to be
>>>>>> sure that no stitching happens in your code, there will be an extra
>>>>>> boolean member variable. When set to true, it will throw an exception
>>>>>> whenever you try to insert a discontinuity into the path.
>>>>>>
>>>>>> Is everyone OK with this idea?
>>>>>
>>>>> I am not so sure about this.
>>>>> It may not be very helpful if 2geom automatically fixes "user errors",
>>>>> leading to unexpected results. If you change the default behavior (from
>>>>> not stitching to stitching), user code will suddenly behave different
>>>>> perhaps without the user knowing (e.g. no compiler error).
>>>>> How about making the _choice_ for stitching behavior mandatory?
>>>>>
>>>>> -Johan
>>>>>
>>>>>
>>>>>
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>