• Ell's avatar
    Bug 795410 - Deleting a layer group and then undoing the deletion ... · 37742a9f
    Ell authored
    ... raises a CRITICAL
    
    gimp_item_{start,end}_move() currently serves two different
    purposes:  It is used by GimpLayer to suspend/resume mask resizing
    of the layer's ancestors; this is necessary whenever an operation
    on a layer might affect the size of its ancestors.  It is also used
    by GimpGroupLayer to suspend/resume its own mask resizing; this, on
    the other hand, is only necessary before applying one of the
    transformation functions to the group, so that mask modification is
    handled by GimpLayer.  In other words, the effects of
    gimp_item_{start,end}_move() on group layers are only necessary in
    a subset of the cases in which these functions are used.
    
    While in itself this isn't a problem, it does cause issues when
    removing a group layer:  gimp_image_remove_layer() calls
    gimp_item_start_move() before removing the layer, and
    gimp_item_end_move() afterwards.  While the former function is
    called while the layer is still attached to the image, the latter
    function is called after the layer is no longer attached.  Since
    GimpGroupLayer pushes an undo step in response to these calls, only
    the call to start_move() results in an undo step, while the call to
    end_move() doesn't, resulting in an unbalanced
    GIMP_UNDO_GROUP_LAYER_START_MOVE undo step on the stack.  This
    causes problems when undoing the operation.
    
    Add gimp_item_{start,end}_transform() functions, and corresponding
    GimpItem::{start,end}_transform() virtual functions, which are more
    specialized versions of gimp_item_{start,end}_move(), which should
    be used instead of the former before/after transforming an item; in
    other cases, such as when removing ot reordering an item,
    gimp_item_{start,end}_move() should still be used.  The default
    implementation of GimpItem::{start,end}_transform() calls
    gimp_item_{start,end}_move(), respectively, so subclasses that
    override these functions don't have to do that themselves.
    
    In GimpGroupLayer, override GimpItem::{start,end}_transform(),
    instead of GimpItem::{start,end}_move(), for the same purpose of
    suspending mask resize.  This avoids these functions from being
    called when removing a layer group, fixing the bug.
    37742a9f
gimpimage-undo-push.c 40.3 KB