RESOLVED FIXED 48600
Multi-column layout unbalanced 
https://bugs.webkit.org/show_bug.cgi?id=48600
Summary Multi-column layout unbalanced
Steven Wittens
Reported 2010-10-28 17:08:16 PDT
WebKit's multi-column balancer appears to be buggy. I've attached two test-cases that show problematic behavior. Each test case shows a single multi-column container with one div inside. Clicking the button below adds additional divs to the container. As items are added, the columns are reflowed and various problems appear/disappear. Note: due to apparent lack of support for "-webkit-column-break-inside: avoid" in WebKit, the test-cases look weird when items < columns. For the purposes of this bug report, these scenarios may be ignored. When the number of items is not divisible by the number of columns, the columns are not balanced from left-to-right as one would expect. Instead, the excess items are either added to the last column or 'dithered' between columns. There also appear to be related off-by-one errors where a column is wrapped one pixel too soon or late, which might be the reason for the unbalanced layout. Column-test-1: Each item is a simple div with text. Result: - 2 columns: off-by-one error - 3 columns: unbalanced last column, off-by-one error - 4 columns: dithering - 5 columns: dithering - 6 columns: unbalanced last two columns, dithering, off-by-one errors - 7 columns: unbalanced last two columns, dithering, off-by-one error - 8 columns: unbalanced last column, dithering, off-by-one errors Column-test-2: Each item contains two elements, one of which floats. Result: - 2 columns: last column unbalanced - 3 columns: last column twice unbalanced - 4 columns: last 2 columns unbalanced - 5 columns: last 3 columns unbalanced - 6 columns: last 3 columns unbalanced - 7 columns: last 4 columns unbalanced - 8 columns: last 5 columns unbalanced
Attachments
Test case 1 (751 bytes, text/html)
2010-10-28 17:08 PDT, Steven Wittens 		no flags
Details
Test case 2 (956 bytes, text/html)
2010-10-28 17:09 PDT, Steven Wittens 		no flags
Details
View All Add attachment proposed patch, testcase, etc.
Steven Wittens
Comment 1 2010-10-28 17:08:45 PDT
Created attachment 72264 [details] Test case 1
Steven Wittens
Comment 2 2010-10-28 17:09:01 PDT
Created attachment 72265 [details] Test case 2
Steven Wittens
Comment 3 2010-10-28 20:12:51 PDT
My apologies. After poking some more, I realized I was testing with vanilla Safari instead of the nightly. The bug as reported no longer exists. However, the nightly's new behavior does make the lack of "webkit-column-break-inside" all the more problematic.
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