The "the correct answer is to find the smaller of the start- and end-aligned sizes, then double that, aligning it to the abspos containing block edge that was chosen." thing seems a bit weird to me though. https://github.com/w3c/csswg-drafts/issues/1432#issuecomment-513028325 Why not simply use the center position and make the size the distance from there to the relevant CB edge?
Bug 1682641 Comment 7 Edit History
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The "the correct answer is to find the smaller of the start- and end-aligned sizes, then double that, aligning it to the abspos containing block edge that was chosen." thing seems a bit weird to me though. https://github.com/w3c/csswg-drafts/issues/1432#issuecomment-513028325 Why not simply use the center position and make the size the distance from there to the relevant CB edge (times two)?