Virtual effect classes

[TripleWhy]

Ignore some of the changes of this PR...

What I am trying to figure out with this PR is if you'd be interested in on overhaul of how effects work. I created a virtual base Effect class, and implemented 2 effects as implementations of that:

wled00/effects/Effect.h
wled00/effects/StaticEffect.h
wled00/effects/PaletteEffect.h

Note that this effect class does not handle a segment as a whole like current effects do, but instead handles one pixel at a time. See how this is called in wled00/FX_fcn.cpp WS2812FX::service().

Advantages of this approach:

• not every effect needs to understand the inner workings of how segments work
• when using sparse setups, such as matrices where not all pixels map to physical LEDs, this could potentially safe some work. (Or at least implementing this kind of saving would require one change to service rather than requiring changing of all effects.)
• theoretically, this design should work will with potential future sparse 3D setups (where instead of implementing dense LED cubes, you throw a bunch of LEDs into space, then map their 3D positions)
• things like the 2D expansion that is currently used in the palette effect only could/would have to be implemented globally for all effects rather than once per effect
• EDIT: Another potential advantage might be that this design would allow effects being layered on top of each other without losing information due to brightness being applied immediately (however I don't think this would work for effects that use color values from previous frames)

Disadvantages:

• theoretically one virtual function call per pixel. (A good compiler should be able to resolve the virtual function once per service() call instead of per pixel iteration, but c++ provides no way of enforcing that.)
• currently, this code relies on c++17 and therefore only compiles on esp 8266

Outlook: currently, I only implemented fading transitions (untested). Theoretically, it would be possible to use an extended version of this Effect class to handle transitions, so that there would only have to be one code base for effects and transitions.

What do you think? Are you interested in this kind of work? Should I invest some time into advancing it?

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[DedeHai]

I like the base idea of only calculating pixels that actually exist, as you say, big advantage for mapped setups.

• how does this impact code size and execution speed for normal setups?
• how would you apply blurring which relies on neighbouring pixels?

[TripleWhy]

I didn't produce a clean version that only contains the effect changes, so it's a bit hard to say. But the FPS are indeed a bit lower than on main, which is what I would expect because of the virtual functions and no loops that can be optimized as a whole per effect. I believe it opens up more room for other optimizations though.

Test: 16x16 dense 2D matrix, palette effect.

This PR:
38 FPS
RAM: [====== ] 56.7% (used 46464 bytes from 81920 bytes)
Flash: [======= ] 73.7% (used 770055 bytes from 1044464 bytes)

Main 2d6ad41:
47 FPS
RAM: [====== ] 57.3% (used 46964 bytes from 81920 bytes)
Flash: [======== ] 84.2% (used 879751 bytes from 1044464 bytes)

Blurring:
What is blurring, how is it currently implemented? Where can I look at the code to see some?

If it is just part of some effects, I guess it would continue working the way it did before? If it requires reading the current state of the pixels, that is already part of this PR: The effect function has x, y, and current color as inputs and outputs one new color.

[DedeHai]

that is a significant drop in FPS, unless this can be optimized, its a no-go.

look at void Segment::blur2D() for example. there are other functions to manipulate pixels in that file as well that need to work.

[blazoncek]

Thanks.
This is a hefty change I'm afraid nobody would want to undertake (to reimplement all existing effects if that is the goal).

Regarding "segment workings awareness": I've had a lengthy discussion of pros and cons of the approach PixelBlaze has taken in the past (and why I chose not to go that way with WLED). Some things are easy to implement the way PixelBlaze does it, some are nearly impossible. So the best would be to extend segment API to allow both approaches. My 1st attempt was to create a setPixelColor() that takes relative coordinate (range 0-1, but it can also be -1-1) which would then require appropriate mapping to map certain coordinate into actual pixel drawing. This would also allow sparse set-ups. I tried but in the end abandoned the attempt as it would require writing a new effect that would use it.
The issue (I see) is how would you mix regular/legacy and new/coordinate-agnostic effects or. to put it the other way around how would you mix mappings?

If you are unaware of PixelBlaze, please Google it. It has some nice approaches (including sparse set-ups) but is unfortunately a closed source project.