[QGIS-Developer] QGIS Server 2.x: issue with @map_scale variable vs. $scale

[Andreas Neumann]

Hi Nyall,

Thanks for explaining this. Makes sense and glad that it will be fixed 
in QGIS 3.

So my follow-up question is: can I rely on $scale to work in future 
version of QGIS or will it be deprecated?

Andreas

On 05.07.2017 00:52, Nyall Dawson wrote:
> On 4 July 2017 at 01:46, Neumann, Andreas <a.neumann at carto.net> wrote:
>> Hi,
>>
>> In a QGIS project that should be published with QGIS Server, I used the
>> @map_scale variable to define the font size with an expression, depending on
>> the map scale. It works fine on QGIS Desktop, but on QGIS server GetMap
>> requests it fails - the font-size (defined in map units) is constant and
>> doesn't react to my scale dependent rule. The interesting thing, is, that
>> the same rule works fine in GetPrint requests.
>>
>> If I change my rule to use $scale instead of @map_scale, my label rule works
>> fine.
>>
>> Could it be that the @map_scale variable doesn't work in QGIS server GetMap
>> requests?
> Exactly - it's a consequence of QGIS 2.x server using the really old
> map renderer, which means it doesn't have access to any variables
> relating to the current map scale/extent/etc. This is also why 2.5d
> renderer is quite broken on server under 2.x.
>
> The good news is that it's all fixed with 3.0.
>
> Nyall
>
>
>
>> Here is my expression:
>>
>> CASE
>>     WHEN @map_scale <= 251 THEN 1
>>     WHEN @map_scale > 251 AND @map_scale <= 501 THEN 2
>>     WHEN @map_scale > 501 AND @map_scale <= 1001 THEN 3
>>     WHEN @map_scale > 1001 AND @map_scale <= 2001 THEN 4
>>     WHEN @map_scale > 2001 AND @map_scale <= 3001 THEN 6
>>     WHEN @map_scale > 3001 AND @map_scale <= 4001 THEN 7
>>     WHEN @map_scale > 4001  THEN 8
>> END
>>
>> Thanks for your ideas.
>>
>> Andreas
>>
>>
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