feat: Add FreeInkDisplay functions to work with absolute grayscale luts

[theZiz]

This is needed for using the absolute factory lut of the SS1677 on X4 without device specific information in crosspoint reader.

Summary

First of all I changed the naming from "factory" to "absolute", because it is very X4 specific that we got those lut from the original firmware. In fact the whole point is using a direct rendering approach instead of BW + 2 differential steps. So the naming "absolute".

The method supportsAbsoluteGrayscale is needed to make sure to use this functionality only on einks having absolute lut defined, which is right now only the ssd1677 afaik. Right now I am checking whether the device is an X4 in crosspoint reader and this is not correct as newer X4 might have a different controller.

FreeInkDisplay::displayAbsoluteGrayBuffer is basically a copy of FreeInkDisplay::displayGrayBuffer but with calling _driver->displayGrayAbsolute in the end.

[itsthisjustin]

Ha I just fixed this too and opened the same PR. Compare implementations for me? crosspoint-reader/crosspoint-reader#3046

[theZiz]

Ha, but I was faster 😂

However, I don't see your PR in the freeSDK-space. 🤔

In the crosspoint-reader-space your fix does more or less the same, but

• keeps calling it factory mode instead of absolute and
• doesn't handle the other corner cases I found.

So imho my implementation does a bit more of the needed extra mile. :)

[theZiz]

Tbh I don't see where your change is in the freesdk-space. Don't we work wir PRs here? 🤔

[itsthisjustin]

Tbh I don't see where your change is in the freesdk-space. Don't we work wir PRs here? 🤔

For critical paths I commit directly a lot of times. Feel free to shore up two prs for each repo and we can get them merged together

[theZiz]

Okay, I will update my PR based on your changes. :)

[theZiz]

@itsthisjustin I updated my PR.

I renamed your function and removed the mentioning of the SSD1677 as the functionality itself is display controller independent. If something figures out an absolute lut for the different display controllers (e.g. by extracting them from original firmwares), they could also benefit from this approach and it would work directly in Crosspoint Reader. :)

I also kept the displayAbsoluteGrayBuffer` "shortcut" so that the lut stays in the driver. Again: Another implementation could use it's own absolute lut here.

[theZiz]

Thanks for the 👍, any more to do for merging this, @itsthisjustin ? 🙂