Here is quick and dirty fragment of code that adds mouse cursor:
memory.Blit(0, 0, w, h, context, l, t)
# start of inserted code
# end of inserted code
It draws 'x' letter instead of actual cursor image.
However, because of the delay (around 1 second) it's inconvenient to use it for pointing and clicking items if you only look at the reader screen. I'm thinking about adding a mouse cursor in the HTML page and quicker updates of its position, independent of screen image updates (new positions could be retrieved with AJAX requests).