Today I had a chance to fix a few bugs with the hardware thumbnail generation, and actually test it out by writing a small program that does a raster split, with the thumbnail being draw in 256-colour mode in the bottom corner of the screen every frame, as you can see below:
There are still a few glitches, but is is working pretty nicely. In particular, you can see that it is being drawn in real-time, because the thumbnail contains an image of the thumbnail that contains an image of the thumbnail :)
Things you can't see, is that the thumbnail is a bit different every frame, I think because the counter that decides which raster to look at isn't reset at the start of each frame. This causes some weird things to happen. Also, the thumbnail just contains the value of chosen pixels. I am considering changing this so that it shows the average of the pixels in the sample area of the raster line, but at the same time, the current scheme works fairly well.
This is a nice milestone for a few reasons.
First, the hardware thumbnail generator is clearly working to some reasonable degree.
Second, full-colour text mode is working fairly well as well, such that I could write this program.
And finally, I have actually written a programme that does something (slightly) useful, using C65GS special features, and it works :)
Next stop is to fix the counter problem, and see if I am then happy enough with it, and if so, to move on to some of the other interesting things in my queue, like enhanced sprites.