[QGIS-Developer] [Qgis-user] segments_to_lines & @geometry_part_num in QGIS 2.99 & 3.0

[Nyall Dawson]

On 13 May 2018 at 01:59, Anita Graser <anitagraser at gmx.at> wrote:
> Hi,
>
> I'd like to raise this on the dev list since it seems to be a bug. Ticket:
> https://issues.qgis.org/issues/18384
>
> Here is the basic issue as Michel observed it:
>
> On Tue, Mar 6, 2018 at 2:47 PM, Michel Stuyts <michel.stuyts at edegem.be>
> wrote:
>>
>> When creating a style for a polygon layer I noticed a difference between
>> QGIS 2.99 (Windows standalone installer) and QGIS 3.0 (OSGeo4W) when I use
>> segments_to_lines & @geometry_part_num.
>>   *   I created a polygon layer and added some polygons.
>>   *   Then I started editing the layer style:
>>      *   I added a Geometry generator as symbol layer to create a
>> Linestring type that contains  segments_to_lines($geometry)
>>      *   Then I changed the line type of the result to a "Marker line"
>>      *   Then I changed the Symbol layer type of this "Marker line" to
>> "Font marker"
>>      *   Then I changed the "Data defined override" of the content of this
>> font marker to @geometry_part_num
>>      *   Then I changed the font size of the font marker
>> The results are different in QGIS 2.99 and 3.0 (see images below). Is this
>> a bug in 3.0 or is it an intentional change? The result in QGIS 2.18 is the
>> same as in 2.99. The result in QGIS 3.1 is the same as in 3.0.
>
>
> I've actually been able to reproduce 2.18 results in 3.x but only if
> @geometry_part_num was used in a different context besides the marker line
> as well.
>
> Here's a screencast of what I think is pretty odd behavior:
> https://www.dropbox.com/s/cvyqeecpq0uis1j/QGIS%20Geometry%20Generator%20geometry_part_num.mp4?dl=0
>
> Took me a couple of hours to find out why @geometry_part_num behaved
> seemingly randomly.
>
> Was this a purposeful change?

Nope, just a bug. I know what the issue is here, I'll fix when I get a chance.

Nyall

>
> Regards,
> Anita
>
>
>
>
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