gschem: undo locked items

[Sergey Alyoshin]

1. Add some items in gschem: components, lines, circles..
2. Lock all this items
3. Delete all this locked items
4. Undo; locked items color will be gray (lock-color), but they are no longer
locked (can be selected by click). Only components remain locked, but not they
attributes.

Tested in gschem
A. Version: 1.6.1.20100214
B. Git: 7c7ad003a34b750a8408b1a6ac2b0bc7dcdb4166

[Sergey Alyoshin (alyoshin-s)]

Similar problem if you copy&paste locked items. Pasted locked items color
will be gray, but they are no locked.

[Vladimir Zhbanov (vzhbanov)]

This is the bug of the current sym/sch file format and the way
undo works.

The file format supports locking only for components, so when you
save and reopen your schematic the locking information of other
items will be lost anyway, even if gschem would keep it somehow
after undo.

As of now, gschem undoes things just by rereading auto-saved
schematic files. Therefore the bug will keep until the whole undo
system is refactored. And again, this wouldn't solve the above
mentioned issue with closing and opening of the schematic.

[Vladimir Zhbanov (vzhbanov)]

See also related bug #698790.