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[BUG]: `scattergl` text is hidden behind selected markers

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
48/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
javascript

Research direction

Start with the linked CodePen reproduction and compare the scattergl behavior with the equivalent scatter trace. Trace scattergl text rendering around the vendor line using ctx2.getImageData mentioned in the report, and review issue #7285 for context. Done means selected text is visible like unselected text, with the reported canvas warning addressed or its scope clarified.

Written by the indexing model from the issue text.

Description

bug
Description

scattergl text is hidden behind selected markers

The equivalent scatter trace renders the text correctly.

Reproducible example:

https://codepen.io/Lexachoc/pen/dPvRydx

    mode: "markers+text",
    texttemplate: "x=%{x}",
    selectedpoints: [0],
    selected: {
      textfont: { color: "red" }
    },
    unselected: {
      textfont: {color: 'white'}
    },
Image

For unselect.textfont, both works, only select.textfont is broken for scattergl:

Image
Note

To confirm, uncomment

textposition: 'top-center',
Image

Additional warning observed

When using:

 mode: "markers+text",

or

 mode: "text",

scattergl will throw this warning:

Canvas2D: Multiple readback operations using getImageData are faster with the willReadFrequently attribute set to true. See: https://html.spec.whatwg.org/multipage/canvas.html#concept-canvas-will-read-frequently

caused by this line: var bottomPx = firstTop(ctx2.getImageData(0, 0, l2, l2)); from the vendor package.

Reported before in https://github.com/plotly/plotly.js/issues/7285

Dominant language
JavaScript
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