Fix datagrid performance on attached to tree

[IZIDIA]

see #16139

What does the pull request do?

Improves DataGrid display performance when attached to a visual tree

What is the current behavior?

When connected to a visual tree, the table is completely updated, namely, rows and columns are updated. A complete update takes a long time.

What is the updated/expected behavior with this PR?

When you connect a table to a data tree, only the rows are updated. Which allows you to increase productivity. This solution also saves the following solution #12009

How was the solution implemented (if it's not obvious)?

I took measurements using a stopwatch. I replaced false with true. I reproduced the situation from #12009 and found no errors.

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/avalonia-docs with user documentation

Breaking changes

Obsoletions / Deprecations

Fixed issues

Fixes #16139 #15218

[avaloniaui-bot]

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1 out of 2 committers have signed the CLA.

• @maxkatz6
• @IZIDIA

[IZIDIA]

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Please read the following Contributor License Agreement (CLA). If you agree with the CLA, please reply with the following:

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[IZIDIA]

This doesn't solve the problem completely. The next problem remains. #15218.

Maybe we shouldn't use InitializeElements?

[IZIDIA]

I tested updating the rows again. And I discovered that InitializeElements(true /*recycleRows*/); does not reset the scroll position. This solution will actually solve 2 problems at once. Display performance while docked to tree and scroll position

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0049512-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[grokys]

Hard to review this because there are no unit tests for DataGrid and no-one quite knows how it works. However seems to work for me and the change is simple so lets YOLO.

[avaloniaui-bot]

You can test this PR using the following package version. 11.2.999-cibuild0049865-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]