Add tests for previously-uncovered SparklineGroup setters (axis types,
manual limits, additional display options and colours) and a hand-crafted
Xlsx fixture exercising the reader's edge cases (non-sparkline ext, group
without sparklines, sparkline with empty sqref, missing colour elements).
Harden Reader/Xlsx/Sparklines against malformed input: guard the
sparklineGroup and sparkline iterations against a null children set so an
empty <x14:sparklineGroups> or <x14:sparklines> element no longer emits a
PHP warning.
Implements native sparkline support (line, column, and win/loss) in the
Xlsx reader and writer, resolving issue #4941.
- New model classes under Worksheet/Sparkline: Sparkline, SparklineGroup,
and the SparklineType enum.
- Worksheet gains a sparkline group collection with addSparkline(),
addSparklineGroup(), getSparklineGroupCollection(), and
removeSparklineGroupCollection(), plus deep-clone support.
- Reader/Xlsx/Sparklines parses x14:sparklineGroups from the sheet extLst.
- Writer/Xlsx/Worksheet emits x14:sparklineGroups; writeExtLst is
refactored so conditional-formatting data bars and sparklines share a
single extLst.
- Adds unit tests, an Xlsx round-trip test, a runnable sample, and docs.
saifulislamferoz