fixbbox

Repairs the FIXED_BBOX property of magic cells so it matches the cell’s true geometric bounding box.

make fixbbox                    # dry run, from work/
make fixbbox BBOPT=--apply      # write

fixbbox <lib_mag_dir> [exclude_cell] [--apply]

A stale or oversized FIXED_BBOX makes magic report the wrong cell extent, and the cell then overhangs its parent or its tile. It also breaks the placement helpers in magic/cic.tcl, which step by exactly that property.

How it gets the right answer

Magic computes the bounding box, not the script: select top cell; box values handles magscale, hierarchy and arrays correctly, and no reimplementation of that would stay correct for long.

The awkward part is getting the value back out without letting magic rewrite the file. Magic is run on the real file so child cells resolve, it writes the property and saves, the new value is read back in the file’s own units, and then the original bytes are restored. Only the string FIXED_BBOX line of the original is patched. A full magic re-serialization would otherwise upgrade the file format, renaming layers and regenerating the checkpaint layer, which turns a one line fix into an unreviewable diff.

The property is added under << properties >> if the cell has none, and a properties section is created before << end >> if that is missing too.

Safety

Dry run by default; --apply is required to write.
exclude_cell, normally the top tile, keeps its fixed tile size.
Symlinked .mag files are always skipped: they point at shared library sources outside the IP and must not be modified.

Output is one line per cell, in colour: ok, would fix, fixed, symlink, skipped or could not compute bbox.