Measures the advance of text shown at fontSize: the sum of its glyph widths, and of the font's kerning between neighbouring glyphs when kerning.
public double MeasureWidth(ReadOnlySpan<char> text, double fontSize, bool kerning)
The text.
The font size (Tf's size operand).
Whether to add the font's kerning, as ShowText(ReadOnlySpan<Char>, Boolean) with kerning shows it.
ISO 32000-2 §9.2.4 and §9.4.4 (with Tc = Tw = 0 and Th = 1); the kerning is the font's own (for a Standard 14 font, the AFM KPX pairs).