I made this as an early Arduino project, and it was only with lots of patient help from the big5 on the forum that I got it going. ( thanks guys )
I could compress the text to repeat 10 or more times across the screen without losing definition.
I stored each lines info ( or several lines repeated to make the blocks ) during the horizontal flyback and first part of the trace, into 2 parallel in / serial out registers, which I read out to make the video signals to add to the video.
Obviously it was all syncd to the H and V pulses on the vga lead.
I chuckle when I think of how I got this going ( no arrays, or anything clever ) and look at my code ............
Check the picture of the leopard watching the mouse steal his meat !