feat: [FC-0070] add events and style for rendering Split xblock in chromeless template

[ihor-romaniuk]

Description

This feature introduces functionalities to improve XBlock interactions within iframes:

• Add styles that adopt default styles for Split Test which renders chromless template via iframe in MFE Authoring.
• When the isIframeEmbed option is enabled, the XBlock sends a postMessage to the parent window. When sending such a message, the standard link transition is cancelled and the transition is carried out in MFE Authoring.

split_test.mov

Related Pull Requests

• feat: [FC-0070] rendering split test content in unit page frontend-app-authoring#1492 - rendering split test in unit page

Testing instructions

• Create a new course.
• Create several units.
• Open the course unit page.
• Add a Content Experiment xBlock to the unit.
• Click the “View” button on the Content Experiment xBlock.

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[PKulkoRaccoonGang]

[question]: We don't use rems in this file. Should we be consistent or do we want to use rems everywhere?

[ihor-romaniuk]

Replaced with $baseline, thanks

[PKulkoRaccoonGang]

[question]: You use $baseline for indentation, should we do this wherever possible?

[ihor-romaniuk]

Replaced

[bradenmacdonald]

Why are there so many changes in this PR related to the "Add New Component" UI? I thought that the MFE is providing that, and I don't like the idea of continuing to use the legacy UI for that. In fact (please correct me if I'm wrong), this seems to be doing something even worse - duplicating the new MFE "Add New Component" UI in the code of the old legacy UI.

[ihor-romaniuk]

Why are there so many changes in this PR related to the "Add New Component" UI? I thought that the MFE is providing that, and I don't like the idea of continuing to use the legacy UI for that. In fact (please correct me if I'm wrong), this seems to be doing something even worse - duplicating the new MFE "Add New Component" UI in the code of the old legacy UI.

I appreciate you pointing out this issue. It’s an important topic, and I share the concern about avoiding duplication and improving the long-term approach to rendering xBlocks.

This pull request includes many style adjustments to align the “Add New Component” block with the MFE styles. Since the Split_test xBlocks renders this block within an internal container, it was decided to visually adapt it within this scope of work, as a complete refactor would take significantly more time.

I fully agree that rendering an iframe within the MFE is not an ideal solution. However, this approach was chosen because the previous implementation had performance issues on the page. Unfortunately, we do not yet have a unified approach or a common mechanism for rendering xBlocks. Once we establish a standardized way to display xBlocks in React, we will be able to completely eliminate the use of iframes.

[bradenmacdonald]

This pull request includes many style adjustments to align the “Add New Component” block with the MFE styles. Since the Split_test xBlocks renders this block within an internal container, it was decided to visually adapt it within this scope of work, as a complete refactor would take significantly more time.

I see. I would have preferred that we don't spend time adapting the look of the legacy UI, but it's not my decision.