PR #5192 (8b6a5718) causes effects to flicker on slider changes in 0.15.4

[david-hogberg]

What happened?

setGeometry() changed fill(BLACK) from conditional to unconditional:

// before 
if (stop && (spc > 0 || m12 != map1D2D)) fill(BLACK);

// after (#5192)
if (stop) fill(BLACK);

deserializeSegment() calls setGeometry() on every JSON update, including slider changes (speed, intensity, custom1-3) where geometry is unchanged. This wipes the pixel buffer to black every time a slider moves. Effects that accumulate or blend with previous frame data (blendPixelColor, addPixelColor, getPixelColor) read black for one frame, producing a visible flicker.

The original condition correctly limited the clear to cases where LED positions actually shift (non-zero spacing or mapping mode change).

Suggested fix maybe something like this:

bool geometryChanged = !boundsUnchanged || m12 != map1D2D || (grp && (grouping != grp || spacing != spc));
if (stop && geometryChanged) fill(BLACK);

To Reproduce Bug

Adjust slider values on any effect using e.g. blendPixelColor, addPixelColor, getPixelColor.

Expected Behavior

No flickering

Install Method

Self-Compiled

What version of WLED?

WLED 0.15.4

Which microcontroller/board are you seeing the problem on?

ESP32-S3

Relevant log/trace output

Anything else?

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[david-hogberg]

(apologize if this has been adressed already...)

[DedeHai]

while the mentioned PR fixes a different bug, it adds the one mentioned here. There were deeper issues being fixed in #5474
Can you please check if that fixes this?