pango:glyph-string-extents-range (glyphs start end font ink logical)

glyphs -- a pango:glyph-string instance
start -- an integer for the start index in bytes
end -- an integer for the end index in bytes
font -- a pango:font instance
ink -- a pango:rectangle instance used to store the extents of the glyph string as drawn or nil to indicate that the result is not needed
logical -- a pango:rectangle instance used to store the logical extents of the glyph string or nil to indicate that the result is not needed

Computes the extents of a sub-portion of a glyph string. The extents are relative to the start of the glyph string range, the origin of their coordinate system is at the start of the range, not at the start of the entire glyph string.