Reduce segment copies

[TripleWhy]

Use move instead of copy where possible, avoid complexity/memory usage of full copies in other locations.

(Currently, this version would compile with deleted Segment copy functions.)

From the json/differs commit:

Move segment json-specific segment diffing to json.cpp

• Avoid calling Segment copy constructor and destructor. This is fine as long as we only read primitive values.
• Only diff stuff we are actually interested in.
• Only diff stuff if it has an effect.

Note that the json copy code is effectively very similar to before, because the copy constructor also does a memcpy, plus additional work.

About applyValuesToSelectedSegs:
This could be simplified a lot, if we were to alter the behavior such that all selected segments would be modified unconditionally. Which would also address this function comment:

// problem: if the first selected segment already has the value to be set, other selected segments are not updated

Summary by CodeRabbit

• Refactor

  • Streamlined LED segment update and management logic for more efficient operations and smoother effect transitions.
  • Improved logic for handling segment comparisons and updates, enhancing performance and readability.
  • Refactored segment handling to utilize in-place construction, optimizing performance during segment management.

• New Features

  • Replaced segment appending method with a more efficient in-place construction approach.

[coderabbitai[bot]]

Walkthrough

The pull request renames the appendSegment method to emplaceSegment in the WS2812FX class to reflect emplacement semantics. It refactors segment initialization logic in resetSegments, simplifies segment difference checking by removing boolean flags and bitmask comparisons in JSON deserialization, and updates segment creation calls accordingly. The LED module's segment property updates are streamlined, and UDP segment addition uses the new emplacement method.

Changes

File(s)	Change Summary
wled00/FX.h	Renamed WS2812FX::appendSegment to emplaceSegment without changing parameters or logic.
wled00/FX_fcn.cpp	Modified WS2812FX::resetSegments to replace a conditional emplace_back call with explicit if-else calls based on isMatrix for clearer segment initialization.
wled00/json.cpp	Removed three boolean fields from SegmentCopy. Changed differs to return a boolean instead of bitmask, simplifying difference detection. Updated deserializeSegment signature and replaced appendSegment with emplaceSegment. Removed detailed difference tracking logic.
wled00/led.cpp	Refactored applyValuesToSelectedSegs() to precompute colors once and update all selected segments unconditionally, simplifying logic and state change tracking.
wled00/udp.cpp	Replaced strip.appendSegment() with strip.emplaceSegment() in parseNotifyPacket when adding new segments, maintaining existing control flow.

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Reviewing files that changed from the base of the PR and between 4d2ac3a780e24eca7c5511098e3549cdcaf97273 and 46bee5ad7bdeab03100d2068fe4afc15cf60ebf8.

📒 Files selected for processing (5)

• wled00/FX.h (1 hunks)
• wled00/FX_fcn.cpp (1 hunks)
• wled00/json.cpp (5 hunks)
• wled00/led.cpp (1 hunks)
• wled00/udp.cpp (1 hunks)

✅ Files skipped from review due to trivial changes (2)

• wled00/udp.cpp
• wled00/FX_fcn.cpp

🚧 Files skipped from review as they are similar to previous changes (3)

• wled00/led.cpp
• wled00/FX.h
• wled00/json.cpp

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[TripleWhy]

Updated applyValuesToSelectedSegs to the suggested logic.

Removed all copy and diff code from json code, based on this assumption: https://github.com/wled/WLED/pull/4580#issuecomment-2692654622

[blazoncek]

based on this assumption: #4580 (comment)

This is actually a bug in the setOption() code. If the on state didn't change so shouldn't stateChanged. setOption() is used to force transition for changes of on (or power) state. In the past it was used to set other bitfields which are now accessible directly (but such change does not invoke startTransition()).

So, IMO, differs() should stay. However, there is no need to copy entire segment as currently implemented since only segment attributes are compared.

[TripleWhy]

I can remove the commit that removes the differs function from this PR.

However, there is no need to copy entire segment as currently implemented since only segment attributes are compared.

I'm not sure what you are saying here. Are you favoring the version I had in this PR or the version from the other PR?

[blazoncek]

I am just trying to clarify. I did like the solution in https://github.com/wled/WLED/pull/4578/commits/90a49c5a072c668a8c855beb765e029d79821e34

These: stateChanged and stateUpdated() or (God forbid) colorUpdated() are all helpers to (mostly) keep legacy code happy. If you are curious, I don't like any of them.

[TripleWhy]

Removed 4d2ac3a780e24eca7c5511098e3549cdcaf97273, this should be what you want

[DedeHai]

is this PR still relevant with the new layering code?

[blazoncek]

I do not think it is as layer blending did reduce segment copies in a similar way as this PR.

[TripleWhy]

Merged main into this PR, and if you look at the diff now, there isn't really much left of the actual reduction, just some general adjustments

[DedeHai]

I glanced over it, to me it looks like no change at all apart from som re-factoring which is kind of arbitrary / personal style.

[TripleWhy]

All of these changes are clearly improvements, but yes, most of them are minor, and don't affect the number of segment copies

[github-actions[bot]]

Hey! This pull request has been open for quite some time without any new comments now. It will be closed automatically in a week if no further activity occurs. Thank you for contributing to WLED! ❤️