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app: reduce time complexity of layer-group translation

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When translating a layer group, avoid separately updating the
original area of the child layers before translating them (as per
the fix to issue #3484), as this results in quadratic time
complexity w.r.t. to the maximal subgroup nesting level.  Instead,
simply defer the updating of the group's offset until *after*
translating the child layers, so that their original area isn't
clipped by the parent, while their new area is still properly
updated even if the parent's size changes (see comment in code).

(cherry picked from commit ebb3ec4925)
This commit is contained in:
Ell 2019-07-23 10:46:55 +03:00
parent f5e6812131
commit 07bf8c025c
1 changed files with 18 additions and 18 deletions
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36
app/core/gimpgrouplayer.c
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@ -789,15 +789,25 @@ gimp_group_layer_translate (GimpLayer *layer,
/* redirect stack updates to the drawable, rather than to the projection */
private->direct_update++;
/* if this is a nested group layer, we need to update the child-layers'
* original area *before* updating the group's offset. once we update the
* group's offset, our parent's size will also be updated, and the
* subsequent area-updates of the child layers during translation will be
* clipped to the updated parent bounds, potentially failing to update their
* original area. see issue #3484.
/* translate the child layers *before* updating the group's offset, so that,
* if this is a nested group, the parent's bounds still reflect the original
* layer positions. This prevents the original area of the child layers,
* which is updated as part of their translation, from being clipped to the
* post-translation parent bounds (see issue #3484). The new area of the
* child layers, which is likewise updated as part of translation, *may* get
* clipped to the old parent bounds, but the corresponding region will be
* updated anyway when the parent is resized, once we update the group's
* offset.
*/
if (gimp_viewable_get_depth (GIMP_VIEWABLE (group)) > 0)
gimp_drawable_update_all (GIMP_DRAWABLE (group));
for (list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (private->children));
list;
list = g_list_next (list))
{
GimpItem *child = list->data;
/* don't push an undo here because undo will call us again */
gimp_item_translate (child, offset_x, offset_y, FALSE);
}
gimp_item_get_offset (GIMP_ITEM (group), &x, &y);
@ -817,16 +827,6 @@ gimp_group_layer_translate (GimpLayer *layer,
/* update the group layer offset */
gimp_item_set_offset (GIMP_ITEM (group), x, y);
for (list = gimp_item_stack_get_item_iter (GIMP_ITEM_STACK (private->children));
list;
list = g_list_next (list))
{
GimpItem *child = list->data;
/* don't push an undo here because undo will call us again */
gimp_item_translate (child, offset_x, offset_y, FALSE);
}
/* redirect stack updates back to the projection */
private->direct_update--;