- From: Aleksandar Totic via GitHub <sysbot+gh@w3.org>
- Date: Mon, 14 Oct 2019 23:21:01 +0000
- To: public-css-archive@w3.org

atotic has just created a new issue for https://github.com/w3c/csswg-drafts: == [css-tables-3] Tall cell height redistribution algorithm == I am reimplementing tables in Chrome. Height redistribution algorithm for tall cells (rowspan > 1) is not fully defined in current spec. I've investigated what Chrome and other browsers currently do. Every browser does something different. It'd be nice to spec a web compatible algorithm, so that implementations can converge. I expect row group and table height redistribution algorithms to be similar. Based upon Chrome's behavior, I came up with a following algorithm. ## Algorithm 1) Compute row groups. * Group1 are rows shorter than intrinsic height. These are percentage heights, as row layout algorithm (first pass) has already added fixed heights to row height. * Group2 are unconstrained cells. * Group3 are all cells. 1) If there are any rows in Group1, distribute excess heights until rows reach their existing height. Distribution of heights is not proportional to %ge (like columns). It is greedy. Cells are traversed, and each cell is resized to its desired %ge height. When we run out of excess height, distribution stops. Example: <tr height:100%> // this row gets all the excess height, because it is 100%. <tr height:100%> // this row gets nothing, because there is nothing left 2) If there is excess height left over distribute to Group2, or Group3 if Group2 is empty. Zero-height rows do not grow. Excess height is distributed in proportion to existing cell size. Current spec: https://drafts.csswg.org/css-tables-3/#height-distribution-principles https://drafts.csswg.org/css-tables-3/#row-layout I also have a w-p-t tentative testcase computing-row-measure-2.tentative.html Chrome passes (I modeled the algorithm on Chrome's behavior) PASS Unconstrained cells heights are distributed proportionally. PASS Constrained fixed cells not resized if unconstrained exist. PASS Constrained %ge cells grow to %ge size, but no more. PASS %ge grow greedily. PASS Zero height rows do not grow. PASS Unconstrained cells are redistributed proportionally Firefox has trouble with growing %ge cells: FAIL Constrained %ge cells grow to %ge size, but no more. expected 30 but got 19 FAIL %ge grow greedily. assert_equals: expected 60 but got 19 Safari, like FF, does not like to grow %ge cells. I am unclear how Safari decides on which cell to grow. FAIL Unconstrained cells heights are distributed proportionally. assert_equals: expected 50 but got 18 FAIL Constrained %ge cells grow to %ge size, but no more. assert_equals: expected 30 but got 18 FAIL %ge grow greedily. assert_equals: expected 60 but got 18 FAIL Unconstrained cells are redistributed proportionally assert_equals: expected 75 but got 30 Edge 17: Edge grows %ge cells beyond its intrinsic height, and does not grow greedily. FAIL Constrained fixed cells not resized if unconstrained exist. expected 30, got 62 FAIL Constrained %ge cells grow to %ge size, but no more. expected 30, got 50 FAIL %ge grow greedily. expected 60, got 33 Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/4418 using your GitHub account

Received on Monday, 14 October 2019 23:21:03 UTC