Add diff-view for source translation in sbs-editor

[david-venhoff]

Short description

This pr adds functionality to render the diff of the source translation since the last update of the target translation in the side-by-side page editor.

Proposed changes

• Render the diff of the source translation in sbs-view
• Add a button to toggle between the normal view and the diff view
• Remove disabled tinymce editor instance in source translation for better consistency

Resolved issues

Fixes: #1449, Fixes: #1573

[codeclimate]

Code Climate has analyzed commit d085d41 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 77.7% (50% is the threshold).

This pull request will bring the total coverage in the repository to 74.1% (0.0% change).

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[timobrembeck]

Thanks a lot! 👍
This nearly works as expected, I would just adapt the look of the source translation to the target translation to make it easier to compare both sides (so a fixed size even for very short or very long pages would be good and add a bit of margin so they are horizontally aligned). If possible, the disabled tinymce area would solve this because it already looks like the right side without any adaptions, but if this doesn't work well with the html diff, we could try to at least make it somehow similar.

[timobrembeck]

Amazing, really cool that the styling works in the tinymce area! 👍
Now I just have a small idea for the button's appearance.

[timobrembeck]

Awesome, thanks a lot for your changes! 👍

Almost looks perfect, but sorry, another thought just crossed my mind: When the diff is viewed in the source editor, and then the source content is copied into the target editor, the complete diff including the red/green formatting is copied, which is probably not what was intended. Do you think we could always copy the new source content, no matter whether the diff is currently shown or not?

[david-venhoff]

Oh, somehow missed that...
Should be fixed now!

[timobrembeck]

Thanks a lot! 🙏

I'm sorry about my iterative review loop, but I have just found another problem 😿

Could you inject the old_translation_content template context in both the GET and POST view? At the moment, the diff only works correctly when requesting the form with GET, but after e.g. a submission without changes, the diff does not work correctly...

[david-venhoff]

I have update the pr and the issues with minor edits should be resolved now.

[timobrembeck]

Thank you! 👍 💯