Bug 253454 – Web Inspector: Box model should indicate that a margin has been "trimmed" by its containing block's `margin-trim` property

• Status: RESOLVED
• Resolution: FIXED
• Component: Layout and Rendering

[Sammy Gill]

Web Inspector currently does not take into account the rendered box for showing the element’s box model, but with `margin-trim`, the computed margins may no longer be the same as the used margins, as they might be trimmed by the parent container. We should provide some sort of treatment to indicate this - we should also think a bit more deeply about how to do so, since we currently allow editing margins in the box model, but now that edit may not visually affect anything if that margin was trimmed.

Without this work, the box model may show a margin for an edge of an element where no margin was applied at layout time. Not a horrible regression, but odd.

[Sammy Gill]

I think the solution for this will be to update the margin computed value when we do any trimming

[Sammy Gill]

rdar://103374677

[Brent Fulgham]

All subtasks are now complete.