2. The method of claim 1 , further comprising: prior to said receiving, sending a request to a server computer for the font subset, wherein the request includes a glyph identification bitmap that identifies the consecutive sequence of the one or more glyphs already in the extensible data structure, wherein the font subset is received from the server computer in response to the request; and receiving from the server computer an updated version of the glyph identification bitmap that indicates each glyph contained in the received requested font subset.
2. The method of claim 1 , further comprising: prior to said receiving, sending a request to a server computer for the font subset, wherein the request includes a glyph identification bitmap that identifies the consecutive sequence of the one or more glyphs already in the extensible data structure, wherein the font subset is received from the server computer in response to the request; and receiving from the server computer an updated version of the glyph identification bitmap that indicates each glyph contained in the received requested font subset. 3. The method of claim 2 , wherein the request specifies Unicode values for the requested font subset.