x/image/font: the term 'dot' in the comments is confusing

In the comments of the x/image/font package, the term 'dot' is used as the origin position of rendering. I thought the 'dot' indicated the position of the glyph of the period . (e.g. the center of the period glyph would be (0, 0)), but actually this was not with most fonts. Apparently, the dot indicates the origin position in this figure: https://developer.apple.com/library/archive/documentation/TextFonts/Conceptual/CocoaTextArchitecture/Art/glyphterms_2x.png Is the 'dot' a usual term for typography? If not, I hope the comments would be updated to clarify the things.

/CC @nigeltao