Bug 311064 – Table with fixed-height cells and border-spacing doesn't respect specified height

• Component: Tables
• Status: RESOLVED DUPLICATE

[Karl Dubost]

A table with height: 500px, border-spacing: 0 50px, and two rows with fixed-height cells (td { height: 20px }) renders at 418px in Safari instead of the specified 500px. Chrome and
Firefox both correctly render the table at 500px.

The root cause is in RenderTableSection::distributeRemainingExtraLogicalHeight (RenderTableSection.cpp). The function distributes extra height proportionally using m_rowPos[totalRows]
  as the denominator, but this value includes the initial m_rowPos[0] offset which is set to vBorderSpacing() for the top section. The code has a FIXME acknowledging this:

// FIXME: m_rowPos[totalRows] - m_rowPos[0] is the total rows' size.
LayoutUnit totalRowSize = m_rowPos[totalRows];

The sum of all row-slice numerators in the loop equals m_rowPos[totalRows] - m_rowPos[0], which is less than the denominator m_rowPos[totalRows]. This means a fraction of the extra
height proportional to m_rowPos[0] / m_rowPos[totalRows] is never distributed, leaving the table shorter than specified.

For the test case: m_rowPos is [50, 120, 190]. The extra height to distribute is 500 - 190 = 310px. The sum of numerators is (120-50) + (190-120) = 140, but the denominator is 190.
Only 310 * 140/190 ≈ 228px gets distributed, yielding a final height of 190 + 228 = 418px instead of 500px.

The fix is to change the denominator to m_rowPos[totalRows] - m_rowPos[0], matching what the FIXME describes.

Steps to Reproduce:
1. Create a table with height: 500px; border-spacing: 0 50px; border: none
2. Add two rows with td { height: 20px }
3. Compare table height across browsers

Expected: Table renders at 500px (Chrome, Firefox behavior)
Actual: Table renders at 418px in Safari

[Radar WebKit Bug Importer]

<rdar://problem/173665148>

[Karl Dubost]

Created attachment 478838 [details]
testcase

[Karl Dubost]

Pull request: https://github.com/WebKit/WebKit/pull/61659

[Karl Dubost]

*** This bug has been marked as a duplicate of bug 226002 ***