Preserve formatting when deleting content.

[arkflpc]

🚀 Summary

Preserve formatting when deleting content.

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📌 Related issues

• Closes Formatting, for example font color, is lost when all content is removed / Preserve font styles / Change default font #10517
• Closes Fonts are being reset to the default on new lines and new bullet points. When we type a text and backspace to the start of the line. #19777

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💡 Additional information

Optional: Notes on decisions, edge cases, or anything helpful for reviewers.

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• Is the changelog entry intentionally omitted?
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Note

Medium Risk
Touches core deleteContent() behavior and selection attribute handling, which can affect typing/formatting outcomes across many editor scenarios. The change is narrowly scoped and covered by new regression tests, but it alters a widely used editing primitive.

Overview
deleteContent() now preserves document selection attributes (e.g. bold/italic) when a deletion leaves the live selection in a newly-emptied parent block, so subsequent typing keeps the pre-delete formatting.

It avoids restoring attributes when the parent was already empty (e.g. when deleting via a synthetic selection elsewhere) and keeps the existing behavior of clearing attributes when the entire content is replaced with a fresh paragraph. Tests were updated/added to cover these formatting preservation and non-restoration cases.

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[Witoso]

Could we describe in the PR description the behavior that was introduced with some before/after videos? The ticket that this closes is very complex, and I wonder what feature this touches. Also, I wonder if this would close #19777.

[Reinmar]

I tested it a bit manually to get a feeling where it gets us:

Scenario 1

<p><i>foo</i></p>
<p><i>[bar]</i></p>
<p><i>bom</i></p>

And do either:

• type "x"
• or backspace + type "x"

On this branch: <i>x</i> (style preserved) in both cases

On master:

• type "x" -> style was preserved
• backspace + type "x" -> style was not preserved

Scenario 2 (all content selected)

<p><i>[foo</i></p>
<p><i>bar</i></p>
<p><i>bom]</i></p>

And do either:

• type "x"
• or backspace + type "x"

No changes to the behavior. Both master and this branch:

• type "x" -> style preserved
• backspace + type "x" -> style not preserved

That's something I wanted to maintain. You can easily clean content by ctrl+a and backspace.

Scenario 3 (all content selected but only one paragraph present)

This is an edge case of scenario 2. What if you have just one paragraph and you styled it.

It works like Scenario 1 after changes. I think it's ok and even reasonable because in such case the user would most likely be much more focused on this single paragraph. So, less likely to want to "clear all content".

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Summing up

So, from my brief tests, I like the change.

It fixes the second scenario from #10517 (comment).

[Witoso]

For reviewer/QA, please check if it solves #19777. I created the Closes link in the description.

[pszczesniak]

Implementation looks solid, no issues found 👍

⚠️ One thing missing: changelog entry.

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[pszczesniak]

👍 from my side.