LED corruption when switching from multi-segment preset to single-segment Solid preset with spacing

[skykingjwc]

What happened?

When switching from a preset that uses multiple segments to a preset that uses a single segment with non-zero spacing and the Solid effect, the LEDs become corrupted.

The corruption is visible both on the physical LEDs and in the Peek preview in the WLED UI. The issue only occurs when transitioning from a multi-segment preset. If the previously active preset also uses a single segment, the corruption does not occur.

To Reproduce Bug

• Upload and apply the attached WLED configuration and preset JSON files
• Activate the preset Christmas Stripe (multi-segment) — renders normally
• Switch to the preset Classy White (single segment, spacing > 0, Solid effect) — corruption appears
• Switch to Christmas Twinkle (single segment) — renders normally
• Switch back to Classy White — corruption no longer appears

Expected Behavior

The Classy White preset should render correctly with the configured spacing, regardless of which preset was previously active.

Install Method

Self-Compiled

What version of WLED?

WLED 0.15.0 - 0.15.3

Which microcontroller/board are you seeing the problem on?

ESP32

Relevant log/trace output

Anything else?

Christmas Stripe, Classy White, and Christmas Twinkle are custom presets included in the uploaded preset configuration file.

The issue appears to require all of the following to trigger the bug:

• Switching from a multi-segment preset to a single-segment preset
• Target preset uses Solid effect and non-zero spacing
• Removing any of these conditions prevents the issue.

The corruption appears as if the Solid preset is being partially overlaid on top of the previously active preset, while the previous preset’s effect becomes effectively paused. In this state, the new preset does not fully clear or reinitialize the LED buffer.

In this example, where the Solid preset uses a spacing value of 5, every 5th LED takes on the color and properties of the Solid preset. However, the LEDs between those spaced pixels continue to display the last frame of the previous preset’s effect, resulting in a mixed and frozen output rather than a clean transition.

Because the corruption is visible in both the physical LEDs and the Peek preview, this appears to be a segment state or buffer reset issue, not a hardware or LED timing problem.

I have experienced this issue since WLED 15.0. I waited for a few point versions to come out, hoping an update would fix the issue. When the issue persisted, I decided to file a bug report.

Used the [WLED_0.15.3_ESP32_Ethernet.bin] binary to flash the ESP32.
https://github.com/wled/WLED/releases/download/v0.15.3/WLED_0.15.3_ESP32_Ethernet.bin

Confi and preset files for testing
wled_cfg_WLED-HOUSE.json
wled_presets_WLED-HOUSE.json

Code of Conduct

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

[skykingjwc]

Workaround:
I was able to work around the issue by adding an initial masking segment that covers the entire LED range. This segment is configured with the Solid effect, zero spacing, and a black color, and is assigned as segment 0.

A second segment (segment 1) is then created with the desired Solid effect and non-zero spacing.

Because segments are rendered in numerical order, the full-length black segment appears to fully clear or reset the LED buffer before the spaced Solid segment is applied, preventing the corruption from occurring.

While this workaround is effective, it seems like the software should reset the LED buffer or the segment state should be fully reset automatically when switching presets, making this manual reset segment unnecessary.

[softhack007]

possibly fixed by this PR

• set unused segments to black #5192

[DedeHai]

@skykingjwc as mentioned, we discussed this and I added a fix in #5192. In 0.16 (nightly) this is completely overhauled as well. So either try nightly build or try the bins from that 0.15 fix.

[skykingjwc]

You're absolutely right. I must have forgotten about that. My apologies. I will give the nightly build a try and report back. It will probably be next week though because I'm on a business trip away from home at the moment.