Color Equalizer: color-inaccuracy with crosshair

Is there an existing issue for this?

• I checked and did not find my issue in the already reported ones

Describe the bug

When setting an offset for the node placement the vertical line generated by the new interactive crosshair is off.

Steps to reproduce

Open Color equalizer
Use the picker to dial in one of the nodes exactly onto a color
disable the picker
hover over the same spot you picked on
Observe the vertical line being off

Adjustments are seemingly put in at the right colour though.

The effect seems to be of different magnitude for different colours.

Expected behavior

darktable should behave

Logfile | Screenshot | Screencast

https://github.com/user-attachments/assets/0da9a542-041e-417f-992b-e1ffe951ffb4

(zoomed in for privacy reason, with this pink colour the effect seemed to be largest)

Commit

No response

Where did you obtain darktable from?

self compiled

darktable version

5.7+758

What OS are you using?

Linux

What is the version of your OS?

bazzite 44

Describe your system

No response

Are you using OpenCL GPU in darktable?

Yes

If yes, what is the GPU card and driver?

RTX2060m

Please provide additional context if applicable. You can attach files too, but might need to rename to .txt or .zip

@Christian-Bouhon

Start by reproducing the issue in Color equalizer using the picker and interactive crosshair on Linux, following the listed steps and comparing the picked node with the hover position. Trace the crosshair's vertical line and node-placement offset, then verify that the line aligns with the selected color across different colors.