PowerPoint2007 Writer : Keep the borders a cell asked for

[dkulyk]

Description

Fixes #808

AbstractSlide::writeShapeTable() hands the edge shared by two neighbouring cells to one of them, which is sound. But it inspects the opposite side of the neighbour from the one it then copies:

// src/PhpPresentation/Writer/PowerPoint2007/AbstractSlide.php:530
if ($hasNextCellRight) {
    $nextCellRight = $shape->getRow($row)->getCell($cell + 1);
    if ($nextCellRight->getBorders()->getRight()->getHashCode() != $defaultBorder->getHashCode()) {
        $borderRight = $nextCellRight->getBorders()->getLeft();   // guard tested RIGHT, copies LEFT
    }
}
if ($hasNextRowBelow) {
    $nextCellBelow = $shape->getRow($row + 1)->getCell($cell);
    if ($nextCellBelow->getBorders()->getBottom()->getHashCode() != $defaultBorder->getHashCode()) {
        $borderBottom = $nextCellBelow->getBorders()->getTop();   // guard tested BOTTOM, copies TOP
    }
}

So a cell loses the borders it owns as soon as it has a neighbour on that side, and the rule that replaces them is whatever the neighbour has on the facing side — usually the default. Left and top are never overridden, which is exactly the "left works, bottom does not" shape of the report.

Measured

A two-column, three-row table where every cell sets its own right and bottom rule (LINE_THICKTHIN / LINE_DOUBLE):

cell	a:lnR before	a:lnB before	after
r0c0	sng	sng	thickThin / dbl
r0c1	thickThin	sng	thickThin / dbl
r1c0	sng	sng	thickThin / dbl
r1c1	thickThin	sng	thickThin / dbl
r2c0	sng	dbl	thickThin / dbl
r2c1	thickThin	dbl	thickThin / dbl

Eight of the twelve rules were dropped. Only the last column kept its right border and only the last row its bottom one — the two positions with no neighbour to be overridden by.

The fix

Inspect the side that is copied, the one facing this cell. The neighbour still wins the shared edge, but only when the neighbour is the one that asked for it — verified separately: a right neighbour that sets only its left border, and a cell below that sets only its top, both land on the top left cell as before.

Worth noting for anyone who worked around this: the old code required setting both sides of the neighbour — its right (to trip the guard) and its left (to supply the value). Setting just the facing side now works, and setting the border on the cell that owns it works too.

Checklist:

• My CI is 🟢
• I have covered by unit tests my new code (check build/coverage for coverage report)
  The existing testTableWithBorder passes unchanged, which is the problem — its XPath .../a:tr/a:tc/a:tcPr matches any cell in any row, so default borders satisfied it. PptSlidesTest::testTableWithBorderOnEveryCell and testTableWithBorderOwnedByTheNeighbour anchor on a:tr[1]/a:tc[1], the one cell that has both a neighbour to its right and a row below. Both fail on the current code and pass on the fix, and both are schema-validated.
• I have updated the documentation to describe the changes
  docs/usage/shapes/table.md said nothing about borders at all. New Define the borders section, including the sharing rule — which is what tells a caller which cell to set.
• I have updated the changelog

[coveralls]

coverage: 92.159%. remained the same — sapientpro:fix/table-cell-borders into PHPOffice:master