In iOS Safari, “Hide toolbar” increases the height of the ICB

[simevidas]

I just made this discovery, so I wanted to check if the people working on viewport interop knew about this.

Basically, in iOS Safari, when the user scrolls down the page, and Safari’s UI retracts, the ICB does not grow. However, if the user chooses the “Hide Toolbar” option in the page settings menu (AA icon on the left side of the URL bar), Safari’s UI retracts in the same manner, but this time the ICB does grow.

This was quite surprising because I assumed that the ICB cannot have the “large viewport size” in a mobile browser. Apparently, it can.

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