Getting individual glyph positions for cursor rendering

[HalfVoxel]

Suppose I want to make an editable text field. This requires displaying a cursor in the text. However I cannot figure out how to get the position (baseline of the row would probably also be required) of a given glyph at a particular index in a section. I see that it is possible to get the bounding box a complete section, but I individual glyphs seem harder.