PowerPoint2007 Writer : Honour the format code of an axis

[dkulyk]

Description

writeAxis() writes the axis' format code and then immediately tells the renderer to ignore it:

// src/PhpPresentation/Writer/PowerPoint2007/PptCharts.php:2466
$objWriter->startElement('c:numFmt');
$objWriter->writeAttribute('formatCode', $oAxis->getFormatCode());
$objWriter->writeAttribute('sourceLinked', '1');   // ← take the format from the source data
$objWriter->endElement();

sourceLinked="1" means "the number format comes from the source data", so the formatCode sitting next to it is discarded by PowerPoint. The attribute is in the file, which is why the issue reads as "it still doesn't work" rather than "nothing is written".

Why '0' is the right value. The library already writes it correctly everywhere else — in the same file, all three data-label sites use sourceLinked="0":

line	what	sourceLinked
877	data labels (getDlblNumFormat())	0
1305	data labels	0
1445	data labels	0
2468	axis (getFormatCode())	1

The axis is the only one out of line. It has been hardcoded to '1' since b957fb9 (2016-03-02, the Gridlines implementation) and was never revisited.

The fix is not an unconditional '0' — that would take the inherited format away from every deck that never called the setter. Axis::DEFAULT_FORMAT_CODE is 'general', so:

$objWriter->writeAttribute('sourceLinked', Chart\Axis::DEFAULT_FORMAT_CODE === $oAxis->getFormatCode() ? '1' : '0');

• an axis nobody configured → byte-identical output to before;
• an axis with an explicit format code → the format code is finally honoured.

Fixes #632

Possibly related, deliberately not claimed here. #610 and #420 report chart series data not being formatted as numbers. They may share this cause, but I have not measured them.

The ODPresentation writer never reads getFormatCode() at all. ODF expresses a number format as a <number:number-style> element referenced through style:data-style-name, not as an attribute, and there is no such machinery in that writer today — that is separate work, not a matter of copying this line across. Hence the Available only on the PowerPoint2007 Writer note in the documentation, matching the existing one on Crossing.

Checklist:

• My CI is 🟢
• I have covered by unit tests my new code (check build/coverage for coverage report)
  Axis::setFormatCode() had no writer-side coverage at all — AxisTest only exercises the getter/setter, and numFmt appeared nowhere in the writer tests. PptChartsTest::testAxisFormatCode now covers both branches (default and explicit format code) and validates each against the ECMA-376 schema.
• I have updated the documentation to describe the changes
  setFormatCode was not mentioned anywhere in docs/. Added a Number format section to docs/usage/shapes/chart.md, next to Bounds and Crossing.
• I have updated the changelog

[coveralls]

coverage: 92.159%. remained the same — sapientpro:fix/chart-axis-format-code into PHPOffice:master