Skip to content

clarify minimum-scale expansion for ICB vs. layout viewport #19

@skobes-chromium

Description

@skobes-chromium

The ICB explainer currently suggests that the ICB matches the size of the layout viewport, modulo UA UI shrinkage. That's not really correct, at least for mobile Chrome it is easy to reproduce a layout viewport much larger than the ICB:

https://output.jsbin.com/meyexut/quiet

Screenshot 2022-08-23 4 49 59 PM

A clearer statement would be:

  • The ICB is sized to match the visual viewport at pinch-zoom scale == 1.0
  • The layout viewport is sized to match the visual viewport at the minimum pinch-zoom scale

The minimum pinch-zoom scale is influenced by two things:

  • the minimum-scale parameter in the meta viewport tag
  • the extent of content overflow (zooming out can't reveal space that isn't occupied by content)

The minimum-scale default is really small and it's pretty common to have horizontal overflow from fixed-width elements, so you actually see LV >> ICB frequently on the web.

Metadata

Metadata

Assignees

No one assigned

    Type

    No type

    Projects

    No projects

    Milestone

    No milestone

    Relationships

    None yet

    Development

    No branches or pull requests

    Issue actions