[Qgis-developer] Rendering context in rules

[Andreas Neumann]

Hi,

I wonder if we could introduce a "rendering context" for usage in
symbology and labeling with expressions. This would be similar to the
CSS media queries where you could have different styling for printing
and on-screen display.

A render context could be:

* Main map canvas
* regular printing
* atlas printing
* WMS server

Usage scenario:

you want to have different rules or different symbology and labels
depending on the rendering context. E.g. you want to use a different
styling for atlas serial printing than for the general display in the
main map canvas.

With such a rendering context we could have rules like follows:

CASE WHEN rendering_context = 'atlas serial printing' THEN ....
WHEN rendering_context = 'main map canvas' THEN ....
END CASE

Is such a "rendering context" feasible to implement/introduce?

On could go even further and also introduce the screen width/height in a
rule and have different symbology for small screens compared to large
screens ...

Thank you for your thoughts on this very rough proposal.

Andreas