I was wondering if these cheap digital photo displays could
render text, cost effectively, and I realised that I don't really
know how text is rendered on an LCD display.

I'm guessing, working from the display backwards:-

- How often is a non-changing display refreshed,
  and this would be done by a chip that's dedicated to the LCD,
  updating all the pixels of the display?

 - So that's 4 * 48* 600 bits for a 16 colour VGA display ?

- What are typical resolutions for these 4 to 6 inch photo-displays?

- the line of text  would be encoded char-by-char to H-lines of
    pixels, where H is the pixel-height of the char-font ?
 Obviously the whole line of chars must be built before it's sent.

- and then shifted into the 'dedicated LCD driver' ?

- is it fed in 8-bits wide or what ?

- what knd of signal do video DVD players output: analogue
   composite, or what ?

- So you get:  [char-line] -> [pixel-block] -> [display-driver]  

Can someone point me to a good online tutor ?

== TIA