[Qgis-developer] Multiple labeling layers ?

[Hugo Mercier]

Hi all,

We have a request to refine the way layers can be cached and especially
regarding the handling of labels.

The goal is to be able to optimize what is redrawn during the rendering
when features of only some of the vector layers are moving (a script
somewhere makes them move), and the other vector layers stay the same
(same data, same extent)

I would like to allow labels to be manipulated in a new kind of
"labeling" layers, which could be organised as any other layer in the
legend : on top / above other layers, with blending modes, etc.

The (advanced) user could then choose whether or not to use caching on
some labeling layers (assuming there is a way to cache labels). Of
course, it means labels from a layer could conflict with labels from
another layer, but this may be a tradeoff the user is ready to accept.

By default, the current labeling mechanism will take place: every labels
in the same "layer" on top of every other layers.

I think it could allow new interesting use cases, like when one wants to
use the "inverted polygon" renderer to mask features and want to display
labels only on visible parts.

Are there other interests or on the contrary reluctances for this new
feature ?