This implied a lot of other core changes, which also pushed me into
improving some of the edit actions and PDB calls to be multi-layer aware
in the same time.
Note that it is still work-in-progress, but I just had to commit
something in an acceptable intermediate state otherwise I was just going
crazy.
In particular now the various transform tools are multi-layer aware and
work simultaneously on all selected layers (and the linked layers if any
of the selected layers is linked too). Both preview and final transform
processing works.
In the limitations, preview doesn't work well (only one layer in the
preview) when there is a selection (though the actual transform works).
Also I am left to wonder how we should process this case of canvas
selection+transform on multi-layers. Indeed currently I am just creating
a floating selection (like we used to for the selection+transform case)
containing a transform result of the composited version of all selected
layers. This is a possible expected result, but another could be to get
several transformed layers (without composition). But then should the
"Floating Selection" concept allow for multiple Floating Selections?
Sooo many questions left to answer.
When several layers are selected, select their render, similar to how
"edit-copy-visible" would have copied an image with only these layers
made visible.
Also apply the same logics to PDB function gimp_edit_copy() which can
now be used on several drawables at once.
Add new PDB group "drawable_edit" which has all procedures from the
"edit" group which are not cut/copy/paste.
The new group's procedures don't have opacity, paint_mode
etc. arguments but take them from the context instead. Unlike the old
gimp-edit-fill, gimp-drawable-edit-fill now uses the context's opacity
and paint_mode.
The new gimp-drawable-edit-gradient-fill procedure uses even more
context properties which are also newly added with this commit
(gradient_color_space, gradient_repeat_mode, gradient_reverse).
And some cleanup in context.pdb.
This is still WIP, nothing in the edit group is depcreated yet.
This property is currently only used for gimp_edit_blend() to control
how are computed distances. In the future, it could be used for more
functions making use of "gegl:distance-transform" operation, or even for
other algorithms, if relevant.
This new property obviously comes with 2 new PDB calls:
gimp_context_get_distance_metric() & gimp_context_set_distance_metric()
It never belonged inside "tools". Also rename its "pdb" subdirectory
to "groups". This had to happen before 2.10 so cherry-picking between
branches doesn't become a nightmare in the future.
