1) Don't factor in pin names when computing symbol body boundingbox.
2) Grid-snap only in the axis corresponding to the layout side.
3) We only need interline spacing *between* lines, not for each line.
4) Also cleans up the unit checking logic as the unit can't be more
than 0 unless it's a multi-unit symbol.
Fixes https://gitlab.com/kicad/code/kicad/issues/7907
This fix required sorting all of the LIB_PART draw items to ensure
accurate comparison between the symbols stored in the schematic and the
original library symbols. This has a noticeable impact on symbol library
load performance. It may also cause significant changes the next time
the library is saved due to changes in the draw item sorting. Hashing
may be a better solution here but this addressed the immediate problem.
A skeleton method SCH_SCREEN::SwapSymbolLinks() was added because there
is most likely an issue with orphaned symbols in the schematic library
symbol cache during undo/redo operations. More testing is required to
verify this.
Fixes https://gitlab.com/kicad/code/kicad/-/issues/7263
Jeff Young
Dominik Wernberger
Wayne Stambaugh