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Opened 4 years ago

Last modified 2 years ago

#34391 closed defect (bug)

Harden panel/section UI code by removing contents from being logically nested (read: goodbye margin-top hacks) — at Initial Version

Reported by: westonruter Owned by:
Milestone: 4.7 Priority: normal
Severity: normal Version: 4.0
Component: Customize Keywords: early has-patch
Focuses: ui, accessibility, javascript Cc:

Description

The UI concept of sliding panels were introduced to Customizer in 4.0 with the introduction of the “Panel”, a grouping of sections (see #27406). In 4.2 the panel UI paradigm was extended to Sections (groups of controls), which were originally represented as accordions in the Customizer UI (see #31336).

To accomplish the sliding panel UI paradigm in the Customizer while retaining the existing nested DOM structure in a large multidimensional unordered list (panels containing sections containing controls), there have been a lot of headaches trying to get the panels positioned properly with hacks using margin-top, and maintaining this when panels/sections change their active state. (Eliminating the recalculation of the margin-top will also improve DOM performance.) Several bugs have ensued, including:

  • #33567: Panel margin-top glitches when widget areas added
  • #34344: Expanded section margin-top glitches when other section is deactivated
  • #33220: Customizer: layout issues with autofocus'd sections on small screens

It seems clear that another approach is needed to reduce the complexity and improve the robustness of the Customizer UI.

I'd like to propose that the root “panel” of the Customizer (the links to the panels and panel-less sections) is logically independent in the DOM from the panels and sections it links to, and likewise for the links to sections within a panel to be disconnected in the DOM from the container elements for the sections they link to. By keeping these separate, we won't have to do any more margin-top hacks: the panel/section to be shown simply needs to be positioned to the top of the Customizer pane. This will mean accessibility hacks which set the root of the Customizer to visibility:hidden but a nested child element to visibility:visible won't be needed anymore (see #33258). To maintain the accessibility benefit that comes “for free“ with the current nested hierarchical unordered list, we can implement aria-owns to relate the panel/section links with the panel/section containers they link to.

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