[QGIS-Developer] $scale vs @map_scale - QGIS v2 vs v3

Andreas Neumann a.neumann at carto.net
Mon Jan 21 22:56:30 PST 2019

Hi Nyall, 

Thanks. It is not about myself - I can live with it - but I fear many
others who migrate might run into the same issue. 

Ideally the old code could still work through the alias, but the $scale
wouldn't be listed anymore in the expression editor - so it wouldn't be
advertised anymore. Is this the idea? 

Anyway - thanks a lot for adding this alias! 

I found projects in our organization where $scale was used >500 times
within the project - used in lots of CASE WHEN END statements for
defining stroke-widths and font-sizes depending on scale ranges in
various layer configuration. 


On 2019-01-21 23:53, Nyall Dawson wrote:

> On Mon, 21 Jan 2019 at 22:52, Andreas Neumann <a.neumann at carto.net> wrote: 
>> Hi,
>> When migrating our version 2 to version 3 projects, most of our symbology needs revision, because our data-defined properties used a lot the "$scale" variable.
>> What is the exact reason that $scale fails in version 3 and had been replaced by @map_scale?
>> Is there really no upgrade path for this? We have many, many projects, and almost all of them need to be upgraded in version 3 to use "@map_scale" instead of "$scale".
> There is a technical reason behind this, but there's also no technical
> reason we couldn't make $scale silently "alias" to @map_scale. My
> original thinking was that I wanted to strip out some of these older
> expression formats, and 3.0 was a good opportunity to do this. But I'm
> happy to reverse this decision.
> PR incoming.
> Nyall
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