I used to be a graphics card/chip architect for macs in the early/mid 90s - our chips were the fastest, but some programs were resistant because they did stupid stuff: pagemaker invalidated the font cache every time it went thru its main loop, quark with ATM did an n*2 thing every time it wrote text etc etc. We had special hardware to accelerate text drawing and it did nothing because the software pissed it away. We considered creating a plugin that fixed all these things, it would have been hard to maintain, in the end we travelled around to the people who made these apps and talked them through their problems
To be fair excel would erase places white that it wanted to write up to 9 times before it drew any black pixels, we made that very fast! we didn't tell them :-)
At the time 24-bit framebuffers were so slow that before we built graphics acceleration hardware people would switch back to 8-bit to get stuff done, making 24-bit/true colour your daily driver was a big step forward.
This is a horrible and yet not unexpected insight into the internals of Excel
I remember when 24 bit color was exotic and aspirational and you had to settle for 16.
What would have been the purpose of stupid code like that?
Was it a workaround for things that didn’t fully complete on one iteration, so the devs kept hammering away at it until it worked?
Does that make you the first in a long tradition of GPU developers going to blockbuster app devs to say "hey, you should be doing this instead?"
PS – I am looking through the NuBus cards that I have... did you work for SuperMac or RasterOps?