Get click coordinate after a click with touch device

[josephernest]

Let's say we have the select tool active on a heatmap. Live demo here, see the JS console.

We successfully get the coordinates:

• when drag-and-drop: plotly_selected event => we have the coordinates in event.selections
• when click: plotly_click event => we have the coordinates in event.points

When using a touchscreen, we also successfully get the coordinates when drag-and-drop: the plotly_selected event is fired and we have the coordinates in event.selections. But when clicking (=tap), we only get:

• plotly_selected undefined, and no coordinate.

Question: I know that Plotly.js touch support is limited for now, but is there a way to get plotly_click event when we do a tap on a heatmap (with select tool), and have the coordinates in event.points?

PS: Even if I used an event listener with touch events (such as touchstart, touchend), I wouldn't get the coordinates in Plotly plot coordinate system.

@lvlte Maybe you have an idea? (I know you have experience in these topics!)

[josephernest]

With touch (see here simulated with Dev Console), we only get coordinates when drag-and-drop, but not when single click/tap:

2023-09-12-0947-52.mp4

Is there a workaround for this?

With mouse, we get coordinates in both cases (drag-and-drop, and single pixel click):

2023-09-12-0925-12.mp4

[lvlte]

Hi @josephernest, I did some tests and realized that with dragmode: "zoom" (default), plotly_click events are properly fired on touchscreen devices, whereas with dragmode: "select" they are not, even though the click is detected. This helped me find the involved code and I think I have found a fix, but I have to do some tests to be sure it won't break anything.

[josephernest]

Thanks @lvlte, that's great! Feel free to send me the lines involved, I can try if it fixes it by just manually patching it. Thanks again!

[lvlte]

@josephernest see the unique commit in the linked PR.

[archmoj]

Fixed by #6724.