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Re: [csswg-drafts] [css-nav-1] Revise selecting best candidate policy (#3386)

From: Jihye Hong via GitHub <sysbot+gh@w3.org>
Date: Thu, 29 Aug 2019 05:48:36 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-526033969-1567057714-sysbot+gh@w3.org>
The remaining issue here is the focusable element inside the search origin(currently focused element) is unreachable via spatial navigation.

This can be divided into two cases:

Case 1.  The search origin is the general focusable element
Case 2.  The search origin generates the fragmented elements
     (Elaborated in https://github.com/w3c/csswg-drafts/issues/3386#issuecomment-443619274)

I think Case 2 is already covered in the spec because the spec mentions that the focus will move to each fragment separately.
(Step 1 in https://drafts.csswg.org/css-nav-1/#find-focusable-areas )

However, Case 1 isn't considered in the current spec.
While selecting the candidate, the focusable elements are filtered if its geometric center is outside of the half-plane whose boundary goes through the geometric center of the search origin and is perpendicular to the navigation direction.

For example, A, B, and C are the focusable elements.
Let the focus is on the C. If up arrow key is pressed, B isn't selected as a candidate.
Also, even if both A and B are selected as candidates, it's unclear to decide which one will take higher priority because the values of [distance function](https://drafts.csswg.org/css-nav-1/#find-the-shortest-distance) are the same.

Therefore I think the spec should add description such as:
* Select the focusable element as a candidate depending on the edge of element.
   * If the navigation direction is up, the candidate would be the element which bottom edge is on the upper-side of the bottom edge of the search origin.
   * If the navigation direction is right, the candidate would be the element which left edge is on the right side of the left edge of the search origin.
   * Similar rules when the direction is down or left
* If there is any visually full-overlapped element with the search origin, it will take higher priority than the element which is outside of the search origin.

GitHub Notification of comment by jihyerish
Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/3386#issuecomment-526033969 using your GitHub account
Received on Thursday, 29 August 2019 05:48:38 UTC

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