How can I create a font metrically-equivalent to a commercial TrueType font in a legal way? I don't need actual glyphs, just blank rectangles that will preserve the document layout.
What properties are important?
Advance width, left side bearing, line spacing, kerning, something else?
Caladea and Carlito are metric-compatible with Cambria and Calibri.
How they were created with the same metrics without violating the font license? My understanding is that you are not allowed to look at the font file, e.g. OS/2 table.