1679643 - Triple click to highlight paragraph sometimes doesn't de-highlight previous paragraph

Status: NEW

(Core :: DOM: Selection, defect)

Description

[Jack]

Steps to reproduce

• Navigate to https://github.com/servo/servo/blob/master/docs/HACKING_QUICKSTART.md
• Triple click on the first paragraph in the README ("This guide...") to highlight that whole paragraph
• Move cursor upwards to select previous header ("Hacking Servo...")
• Return cursor to first paragraph of README

Actual Behavior

• Previous header remains highlighted

Expected Behavior

• Previous header is un-highlighted

Extra info

Firefox version is 84.0b5 (64-bit)
This seems to happen only when the previous element is an <h> tag and its first child is an <svg> tag.

Comment 1

[Alice0775 White]

Attachment: reduced.html

Regression window:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=e951f4ad123aa87d1d392c286db14cabb41a8560&tochange=e37eeb019cf8739366d6438d75e3630952d0c412

Comment 2

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

I cannot reproduce this on the latest Nightly though...

TYLin: Could you take a look?

Comment 3

[Alice0775 White]

I can still reproduce this on Nightly85.0a1 20201129212213.
Screen capture: https://youtu.be/uGqAg5Ozr90

STR:
mousedown on <p>tag->mouseup->mousedown->mouseup->mousedown->mouseover to <h1>tag -> mouseover to <p>tag ->mouseup

Comment 4

[Ting-Yu Lin [:TYLin] (PDT, UTC-7)]

Thanks Alice0775. The key to reproduce this bug is: don't lift the finger on the third click, and move the mouse immediately up to <h1> and then down to <p>.

There is an investigation in bug 1674763 to remove the code I added in bug 1286882. Remove these lines making svg unselectable can fix this bug, so any proposed solution there may help to solve this bug, too.

Comment 5

[Ting-Yu Lin [:TYLin] (PDT, UTC-7)]

I can still reproduce this bug using the reduced testcase and the STR in comment 4.