From 457023a2c690664cde77bc441fc965dbc8b773bd Mon Sep 17 00:00:00 2001
From: Elias H Aronsson <elias@andonlabs.com>
Date: Fri, 3 Jul 2026 20:11:42 -0700
Subject: [PATCH] Chart: emit single-level c:strRef categories and relative
 chart rel targets

Bar/line/area charts wrote single-level string categories as
c:multiLvlStrRef, and the slide->chart relationship Target as an absolute
/ppt/charts/chartN.xml. Both are valid OOXML that PowerPoint tolerates,
but they differ from what PowerPoint itself produces (and from the
pie/doughnut category code, which already uses c:strRef). Consequences in
other consumers: Google Slides and LibreOffice mis-render the category
axis, and strict parsers (e.g. pptxtojson) fail to read the labels or drop
the chart entirely.

- gen-charts.ts: emit single-level c:strRef when there is one category
  level; fall back to c:multiLvlStrRef only for genuine multi-level
  categories.
- gen-xml.ts: relativize the chart relationship Target in the slide rels
  to ../charts/chartN.xml, leaving the absolute Content_Types PartName
  (which requires the absolute form) unchanged.

No change to how PowerPoint renders these charts.
---
 src/gen-charts.ts | 13 +++++++++++++
 src/gen-xml.ts    |  7 ++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/gen-charts.ts b/src/gen-charts.ts
index 37f27396b..53a49cc23 100644
--- a/src/gen-charts.ts
+++ b/src/gen-charts.ts
@@ -955,6 +955,19 @@ function makeChartType (chartType: CHART_NAME, data: IOptsChartData[], opts: ICh
 						obj.labels[0].forEach((label, idx) => (strXml += `<c:pt idx="${idx}"><c:v>${encodeXmlEntities(label)}</c:v></c:pt>`))
 						strXml += '    </c:numCache>'
 						strXml += '  </c:numRef>'
+					} else if (obj.labels.length === 1) {
+						// Single-level string categories: emit the idiomatic single-level `c:strRef`
+						// (same form used by the pie/doughnut chart types below). A `c:multiLvlStrRef`
+						// with a single level is valid but non-idiomatic: PowerPoint tolerates it, but
+						// Google Slides / LibreOffice mis-render the category axis and strict parsers
+						// (e.g. pptxtojson) fail to read the labels.
+						strXml += '  <c:strRef>'
+						strXml += `    <c:f>Sheet1!$A$2:$A$${obj.labels[0].length + 1}</c:f>`
+						strXml += '    <c:strCache>'
+						strXml += `      <c:ptCount val="${obj.labels[0].length}"/>`
+						obj.labels[0].forEach((label, idx) => (strXml += `<c:pt idx="${idx}"><c:v>${encodeXmlEntities(label)}</c:v></c:pt>`))
+						strXml += '    </c:strCache>'
+						strXml += '  </c:strRef>'
 					} else {
 						strXml += '  <c:multiLvlStrRef>'
 						strXml += `    <c:f>Sheet1!$A$2:$${getExcelColName(obj.labels.length)}$${obj.labels[0].length + 1}</c:f>`
diff --git a/src/gen-xml.ts b/src/gen-xml.ts
index f1e3ecd9f..d3ea3390b 100644
--- a/src/gen-xml.ts
+++ b/src/gen-xml.ts
@@ -783,7 +783,12 @@ function slideObjectRelationsToXml (slide: PresSlide | SlideLayout, defaultRels:
 	})
 	; (slide._relsChart || []).forEach((rel: ISlideRelChart) => {
 		lastRid = Math.max(lastRid, rel.rId)
-		strXml += `<Relationship Id="rId${rel.rId}" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/chart" Target="${rel.Target}"/>`
+		// Relationship targets are relative to the slide part, e.g. "../charts/chartN.xml" (what
+		// PowerPoint writes). The stored `rel.Target` is the absolute "/ppt/charts/chartN.xml" form,
+		// which is reused verbatim as the absolute Content_Types PartName. Absolute relationship
+		// targets are valid but non-idiomatic and are mishandled by stricter consumers (e.g.
+		// pptxtojson resolves them to an invalid path and drops the chart), so relativize here only.
+		strXml += `<Relationship Id="rId${rel.rId}" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/chart" Target="${rel.Target.replace(/^\/ppt\//, '../')}"/>`
 	})
 	; (slide._relsMedia || []).forEach((rel: ISlideRelMedia) => {
 		const relRid = rel.rId.toString()