Feature/pixel range list

[ben-xo]

Background

version of FastLED which allows you to render a linked list of pixel ranges, which can be backed by different segments from the same LED buffer.

Builds on work in my previous PRs (FastLED#2)

Probably needs bit more work to work on other pixel controllers than the Clockless Trinket, but I can't test those.

There are 3 example sketches, I've attached videos for two of them.

"Scrolling Comet" demo:

A rotating "comet" (a white pixel followed by a trail) is rotated around an entire strip just by manipulating the length of the ranges surrounding the comet. This is PixelRangeScrollingComet.ino.

Of note, is that, even though the strip is 60 pixels long (so would be >180 bytes of CRGB just for the pixels), the entire sketch only needs 158 bytes of RAM because there are only 17 LEDs in RAM (16 for the comet and 1 for "space" i.e. black, a single pixel with skip=0 which is rendered where the comet is not.) The comet is rendered once, and on each frame 3 ranges are manipulated: start, middle and end. When the comet is fully within the strip, start and end are varying lengths of 1px black, and the comet is rendered as is. When the comet overlaps the end of the strip, start and end are parts of the comet, with middle being black for STRIP_LENGTH - COMET_LENGTH pixels.

148664128-7a14449e-df8b-4757-8850-91bbad09e159.mp4

[ben-xo]

Here's another example. It loops a white dot along the strip, but the six ranges of LEDs which are rendered to the strip are randomly changed and potentially reversed every 2.5 seconds. As you can see, the same sub-range of pixels is often rendered more than once on the same frame.

PixelRangeRandomiser.ino:

127929727-221d150d-17b6-4e31-8a5b-a2d7ec4d71ff.1.mov