... closing one of them crashes GIMP
GimpSymmetry keeps a strong reference to the drawable passed to
gimp_symmetry_set_origin() until the next call to set_origin(), or
until it's destroyed. This can unnecessarily extend the lifetime
of the drawable. In particular, it can extend the lifetime of a
floating selection past the destruction of the image mask, during
image destruction, which results in a NULL mask pointer in
gimp_layer_invalidate_boundary(), called when detaching the
floating selection as part of its destructor.
Add gimp_symmetry_clear_origin(), which clears the origin set using
gimp_symmetry_set_origin(), dropping the reference to the drawable,
and call it in gimp_paint_core_paint() after painting. This avoids
extending the lifetime of the drawable, and fixes the bug.
... edges for MyPaint brush.
Adding the concept of "stateful" symmetry when a tool needs to make sure
of corresponding stroke numbers and orders while painting (i.e. stroke N
at time T+1 is the continuation of stroke N at time T). This is the case
for the MyPaint brushes and the ink tool.
Care for future changes of symmetries, by adding a version property. For
now, all symmetries are at version 0, and no real check is done. If any
symmetry bumps its settings in the future, it will have to override also
update_version() to change settings properly if necessary, according to
any new behavior.
Remove GimpSymmetry::get_settings() and instead tag the properties that
should have a GUI with the GIMP_SYMMETRY_PARAM_GUI flag. Also use plain
g_object_class_install_property() because that allows for separate nick
and blurb. Finally, use gimp_prop_gui_new() to generate the GUI,
You can now set any paint tool to mirror painting relatively
horizontal/vertical axis or a central point (any combination of these 3
symmetries).
This has been implemented as a new multi-stroke core, where every stroke
is actually handled as a multi-stroke (default of size 1).
This is also the first usage of custom guides for symmetry guiding.
Current version has to be activated in the playground.
