Multi-selection: faulty click-and-drag text selection at edges and across blocks

[eidolonnight]

Description

Click-and-drag selection at the edges of paragraph blocks and across blocks of varying types results in unexpected highlighting and selections.

As demonstrated in the attached video, when using click-and-drag selection, the highlighted selection in the editor may not represent the actual selection that will be copied/pasted. The typical highlight applies to entire blocks while the actual selection may be null, a subset of text, or some combination of nearby blocks.

Similarly, the editor may report "X blocks copied" while the blocks were in fact not copied.

This seems to be a long-standing bug. I had assumed for some time that this was a personal issue, plugin conflict, or browser extension incompatibility, but having taken the time to test in isolation, the issue remains. I've observed this since at least WordPress 6.1.

Shift-click selection does not appear to result in the same behavior.

Step-by-step reproduction instructions

1. Create a new post or page
2. Insert various paragraph blocks inter-mingled with other blocks
3. Starting mid-paragraph, click and drag to the bottom edge of the block and into the next block
4. Observe highlighted area
5. Copy using keyboard shortcut
6. Paste to verify clipboard contents

Screenshots, screen recording, code snippet

gutenberg-click-and-drag-selection-issue.mp4

Environment info

Replicated using:

• Mac OS 13.4.1
• WordPress 6.3
• Chrome Version 114.0.5735.248 (Official Build) (arm64)
  • Safari 16.5.2 exhibits slightly different but still unexpected behavior

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[annezazu]

@ellatrix I know you've looked into this and it seems to be intentional for now with some consideration to changing the behavior for multi-select. Curious for your thoughts.

[annezazu]

Noting another version of this same issue with a pattern:

multiselect.mov

This is using WP 6.6.1 and GB 19.0.

[ellatrix]

Hi @eidolonnight!

This PR should fix the first issue you raised: #64928.

The issue with copying a paragraph + list block, I can't reproduce at the moment. I'd recommend creating a separate issue for that.

Yes, selecting from a paragraph into a list block will trigger full selection. This is a know limitation for now, until I have time to work on selection across different root blocks (the paragraph and list items don't share the same root, the list items are inside a list). I'm not sure if we have a tracking issue for that, so feel free to create one for that also.

[ellatrix]

Please submit any remaining issues separately, thank you for the reports!