Refactor float usage within admin styles. Fix #8126

[thibaudcolas]

Part of our work to support RTL languages – fixes #8126.

Browser support

Now that browser support is good enough for logical float values, we can switch to using them. Browser support started being good enough in October 2023 with Chrome 118. The latest Chrome version is currently 120 so we’re already above our "last 2" browser support target for Chrome.

According to the Chrome roadmap, by the time Wagtail 6.0 ships in February, Chrome 121 will have been out for two weeks, so we will support the "last 4" versions of Chrome (121, 120, 119, 118).

Testing this

There isn’t much testing to do at all – it’s a very mechanical replacement of values from physical to logical, and the browser does the rest. There are 134 occurrences of float across the project, so they can all be checked in the code.

Please check the following:

• Do the tests still pass?[^1]
• Does the code comply with the style guide?
• [ ] For Python changes: Have you added tests to cover the new/fixed behaviour?
• For front-end changes: Did you test on all of Wagtail’s supported environments?[^2]
  • Please list the exact browser and operating system versions you tested: Chrome 120 macOS 14, Safari 17 macOS 14
  • Please list which assistive technologies [^3] you tested: None
• [ ] For new features: Has the documentation been updated accordingly?

[squash-labs]

Manage this branch in Squash

Test this branch here: https://thibaudcolas8126-logical-float-ruqek.squash.io