[QGIS-Developer] Processing 3.0: Possible change to the "polygon from layer extent" algorithm

Nyall Dawson nyall.dawson at gmail.com
Fri Jun 23 20:56:45 PDT 2017

Hi all,

As you may be aware, I've been working on rebuilding the backend of
Processing in c++ and refining how it operates.

As part of this I'd like to clear up the list of existing algorithms
and also refine how they behave. This list of "QGIS" algorithms has
grown organically during the 2.x cycle, and there's now numerous
oddities in the selection of available algorithms and their options.

I'll raise discussion about each change I want to make separately so
that each can be discussed on its own merits.

First up, the "polygon from layer extent" algorithm. I'd like to:

1. drop the option "calculate extent for each feature separately.".
It's not obvious (based on the name of the algorithm) that this option
is present in the algorithm, and accordingly very unlikely that users
will discover it here. It's also redundant - there's a dedicated
"bounding boxes" algorithm which does this in a much more efficient
manner. I think we can safely drop this option and leave this
algorithm as a single function "create a feature for the layer's
extent" only algorithm.

2. rename the algorithm to "Layer extent" or "layer bounds". It's
simpler, and easier to understand what it does. Plus, the algorithm
doesn't really create just a polygon, it creates a new layer with a
feature with the layer's bounding box.



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