The specification of how NRGA is computed is based on fontSize as a percentage of root container height, squared. The sum of NRGA for all the glyphs in the glyph cache (previously buffer) must not exceed NGBS, which is 1.
The phrase "as a percentage of Root Container Region height" is confusing. Taking it literally, a single glyph whose font size is, say, 6% of the root container region height would generate NRGA of 6 * 6 = 36, which immediately exceeds NGBS.
I think what is intended here is "as a decimal fraction of Root Container Region height", so that this hypothetical glyph's NRGA = 0.06 * 0.06 = 0.0036.
The specification of how NRGA is computed is based on fontSize as a percentage of root container height, squared. The sum of NRGA for all the glyphs in the glyph cache (previously buffer) must not exceed NGBS, which is 1.
The phrase "as a percentage of Root Container Region height" is confusing. Taking it literally, a single glyph whose font size is, say, 6% of the root container region height would generate NRGA of 6 * 6 = 36, which immediately exceeds NGBS.
I think what is intended here is "as a decimal fraction of Root Container Region height", so that this hypothetical glyph's NRGA = 0.06 * 0.06 = 0.0036.