2000-02-26 Garry R. Osgood <gosgood@idt.net>
* app/commands.c
* app/gimpimage.c
* app/layer.c
* app/layer.h
* app/resize.c
* app/resize.h

Aliasing artifacts that changed relative positions
of layers under scaling, giving rise to #5271, are
minimized by a new layer.c function,
layer_scale_by_factors(). Closes #5271. See
http://idt.net/~gosgood/gimp-patch/patch07.html for
further detail. See also usage documentation for
layer_scale() and layer_scale_by_factors() in
layer.c.

Provided logic for the Scale Image dialog box to
pre-check an image's layers for the possibility that
a particular scaling, s: 0 < s < 1, reduces a layer
dimension to zero. Should this case prevail, a
boolean dialog box warns the user of the
possibility. The user may (1) Cancel, returning
focus to Scale Image and the possibility of
corrective adjustment, or (2) OK the scaling. The
layers that will vanish upon the new scaling are
culled from the GimpImage::layers list first.