Charts: an automatic series colour follows the series' c:idx (#5963) (#5975)

* Charts: an automatic series colour follows the series' c:idx (#5963)

A series without its own colour took the accent for its place in the
file. Word picks it by the series' c:idx (c:order doesn't matter), so a
chart whose series aren't numbered 0, 1, 2... in file order, such as a
lone series with idx 2 after a deletion, got different colours.

c:idx is read strictly as the unsignedInt the schema says; a missing or
invalid value falls back to the place in the file.

* Charts: the renumbered test helper fails if ser's layout changes (#5963)

---------

Co-authored-by: kiwi4boy <kiwi4boy@gmail.com>
Co-authored-by: Martin Ball <martin.ball@ucscaregroup.co.uk>

ROADMAP.md

@@ -884,6 +884,7 @@ MATH glyphs that reference the same construction now share its immutable variant
 | 2026-11-06 | trivial | Progress log: Change Picture keeps the width and takes the new picture's aspect ratio (#5761) |
 | 2026-11-06 | trivial | Progress log: superscript and subscript text at 0.65 of its size rounded to the half point (Word for Mac) |
 | 2026-11-06 | trivial | Progress log: line numbers take the document's "Line Number" style |
+| 2026-11-07 | trivial | Charts: a series without its own colour takes the accent its `c:idx` picks, as Word does, not the one its place in the file picks (#5963) |
 | 2026-11-06 | trivial | Print helpers remove loaded PDF/settings files before driver work, tolerate prior removal and report cleanup errors; a held-driver regression checks the files are already absent (#5710) |
 | 2026-11-06 | trivial | Windows print submissions isolated per helper process; cancelled driver work cannot block a retry (#5710) |
 | 2026-11-06 | trivial | Progress log: print cancellation before sending, including without a document, and the Windows repeated-conversion limitation (#5710) |

crates/docx/src/read/chart/model.rs

@@ -66,6 +66,9 @@ pub(super) struct Axis {
 
 pub(super) struct Series {
     pub(super) name: String,
+    /// The series' `c:idx` (an `xsd:unsignedInt`), which picks its automatic colour; `None`
+    /// when missing or not a valid number.
+    pub(super) idx: Option<usize>,
     pub(super) color: Option<Rgb>,
     pub(super) line_w: f32,
     /// Whether the series is drawn as a line (scatter series without one get markers).

crates/docx/src/read/chart/parse.rs

@@ -91,8 +91,11 @@ impl Chart {
         self.accents.get(i % 6).copied().unwrap_or(Rgb::BLACK)
     }
 
+    /// Colour of series `j`: its own, else the accent its `c:idx` picks (as Word does; `c:order`
+    /// doesn't matter), else the one its place in the file picks.
     pub(super) fn series_colour(&self, j: usize) -> Rgb {
-        self.series.get(j).and_then(|s| s.color).unwrap_or_else(|| self.accent(j))
+        let s = self.series.get(j);
+        s.and_then(|s| s.color).unwrap_or_else(|| self.accent(s.and_then(|s| s.idx).unwrap_or(j)))
     }
 
     /// Colour of point `i` of series `j`: its `c:dPt` override, else the varied accent (pie) or
@@ -199,6 +202,7 @@ pub(super) fn text_size(space: &El) -> f32 {
 impl Series {
     fn parse(ser: &El, scatter: bool, theme: &[Rgb], cap: usize) -> Series {
         let name = ser.child("c:tx").and_then(|t| t.find("c:v")).map(|v| label(v.text().trim())).unwrap_or_default();
+        let idx = ser.child("c:idx").and_then(|e| e.attr("val")).and_then(|v| v.trim().parse::<u32>().ok()).and_then(|v| usize::try_from(v).ok());
         let sp = ser.child("c:spPr");
         let ln = sp.and_then(|p| p.child("a:ln"));
         let marker = ser.child("c:marker").and_then(|m| m.child("c:spPr")).and_then(|p| fill_colour(p, theme));
@@ -219,7 +223,7 @@ impl Series {
             }
         }
         let labels = show_values(ser.child("c:dLbls"));
-        Series { name, color, line_w, line, values, xs, points, fmt, x_fmt, labels, raw: Vec::new() }
+        Series { name, idx, color, line_w, line, values, xs, points, fmt, x_fmt, labels, raw: Vec::new() }
     }
 }
 

crates/docx/src/read/chart/tests.rs

@@ -528,3 +528,65 @@ fn negative_sections_and_scientific_numbers() {
     assert_eq!(format_value(0.0, "0.00E+00", 1.0), "0.00E+00");
     assert_eq!(format_value(-12345.0, "0.0E-00", 1.0), "-1.2E04");
 }
+
+// An automatic series colour follows the series' `c:idx`, not its place in the file (#5963), as
+// measured in Word: `idx` 3 then 0 are accent4 then accent1, a lone `idx` 2 is accent3, and
+// `c:order` changes nothing.
+
+/// The fill colours of the bars of a column chart of `sers`, and of its legend swatches.
+fn column_colours(sers: &[String]) -> (Vec<Rgb>, Vec<Rgb>) {
+    let plot = format!(
+        r#"<c:barChart><c:barDir val="col"/><c:grouping val="clustered"/><c:varyColors val="0"/>{}<c:axId val="1"/><c:axId val="2"/></c:barChart><c:catAx><c:axId val="1"/></c:catAx><c:valAx><c:axId val="2"/></c:valAx>"#,
+        sers.concat()
+    );
+    let items = with_legend(&plot, "r", 300.0, 200.0);
+    let bars = filled(&items).iter().map(|b| b.0).collect();
+    let keys = items
+        .iter()
+        .filter_map(|it| if let GraphicItem::Shape { rect, fill, .. } = it { (rect[2] == SWATCH).then_some(*fill).flatten() } else { None })
+        .collect();
+    (bars, keys)
+}
+
+/// `ser` with its `c:idx` / `c:order` replaced by `idx_order` (an empty string drops them).
+fn renumbered(ser: &str, idx_order: &str) -> String {
+    let start = ser.find("<c:idx").expect("ser writes c:idx");
+    let end = ser.find("<c:tx>").expect("ser writes c:tx");
+    format!("{}{idx_order}{}", &ser[..start], &ser[end..])
+}
+
+#[test]
+fn automatic_series_colours_follow_c_idx() {
+    let accent = |k: usize| theme()[4 + k];
+    let a = ser(0, "A", None, &["Q1"], &["1"]);
+    let b = ser(1, "B", None, &["Q1"], &["2"]);
+    // idx 3 first, idx 0 second: accent4, accent1, in the bars and the legend.
+    let sers = [renumbered(&a, r#"<c:idx val="3"/><c:order val="0"/>"#), renumbered(&b, r#"<c:idx val="0"/><c:order val="1"/>"#)];
+    assert_eq!(column_colours(&sers), (vec![accent(3), accent(0)], vec![accent(3), accent(0)]));
+    // A lone series with idx 2 is accent3.
+    let lone = [renumbered(&a, r#"<c:idx val="2"/><c:order val="0"/>"#)];
+    assert_eq!(column_colours(&lone).0, [accent(2)]);
+    // c:order doesn't matter: idx 0 and 1 stay accent1 and accent2 with their orders swapped.
+    let swapped = [renumbered(&a, r#"<c:idx val="0"/><c:order val="1"/>"#), renumbered(&b, r#"<c:idx val="1"/><c:order val="0"/>"#)];
+    assert_eq!(column_colours(&swapped).0, [accent(0), accent(1)]);
+    // A series' own colour still wins.
+    let own = [renumbered(&ser(0, "A", Some("FF0000"), &["Q1"], &["1"]), r#"<c:idx val="3"/><c:order val="0"/>"#)];
+    assert_eq!(column_colours(&own).0, [Rgb(0xFF, 0, 0)]);
+}
+
+#[test]
+fn series_without_a_usable_c_idx_take_their_place() {
+    let accent = |k: usize| theme()[4 + k];
+    let a = ser(0, "A", None, &["Q1"], &["1"]);
+    let b = ser(1, "B", None, &["Q1"], &["2"]);
+    // No c:idx at all: the place in the file.
+    assert_eq!(column_colours(&[renumbered(&a, ""), renumbered(&b, "")]).0, [accent(0), accent(1)]);
+    // Junk, negative and out-of-range values: no panic, the place in the file.
+    for junk in ["x", "-1", "1e3", "99999999999999999999999"] {
+        let sers = [renumbered(&a, &format!(r#"<c:idx val="{junk}"/>"#)), renumbered(&b, &format!(r#"<c:idx val="{junk}"/>"#))];
+        assert_eq!(column_colours(&sers).0, [accent(0), accent(1)], "{junk:?}");
+    }
+    // The largest unsignedInt `c:idx` allows draws, without a panic.
+    let big = [renumbered(&a, &format!(r#"<c:idx val="{}"/>"#, u32::MAX))];
+    assert_eq!(column_colours(&big).0.len(), 1);
+}

docs/file-format-parity.md

@@ -133,7 +133,7 @@ Measured by grepping `crates/docx/src/read` and `src/write` for the OOXML elemen
 | Group shapes (`wpg:`), drawing canvas (`wpc:`) | ✅ | ✅ | Groups (#267) and canvases (#344) with pictures, shapes, freeforms (custom geometry, #743; a path drawn back to its start without `a:close` is filled, as in Word) and text boxes; nested groups flattened; members' `a:grpFill` takes their group's fill, and a canvas background (`wpc:bg`) may be a gradient or transparent (#1500). The canvas schema has no transform, so a turned or flipped canvas keeps its turn in our own `wpc:extLst` extension (`urn:wordcraft:canvas-xfrm`; Word shows it unturned). Legacy VML canvases (`v:group editas="canvas"`) aren't read as canvases |
 | VML (`w:pict`, `v:shape`, `v:textbox`) | 🟡 | 🟡 | Pictures, text boxes, lines (with arrowheads, their kind, width and length kept), rectangles and ovals, best effort (#242, #611); `v:fill` opacity and gradients (`type="gradient"`/`gradientRadial`, `color2`, `colors`, `angle`, `focus`, `focusposition`, `o:opacity2`), saved as DrawingML (#1500). Preset shapes (`v:shape` whose `o:spt`, own or from its `v:shapetype`, or Word's shapetype id `_x0000_tNN`, names a preset; [MS-ODRAW] §2.4.24 numbers) are drawn and saved like the DrawingML preset of the same shape: exactly for rectangle, rounded rectangle, ellipse, diamond, isosceles triangle, five-point star, right arrow, line and straight connector, heart, text box, and the flowchart process, decision and connector; the others as their nearest shape, as for DrawingML (left/up/down arrows as the arrow, right triangle as the triangle, callouts as their box). Picture frames without a picture aren't drawn. Fill, outline and size come from the shape, else its shapetype; text inside keeps the shape around it (#1377). Adjust values (`adj`) aren't read: presets use WordCraft's proportions. Text boxes keep their internal margins (`inset`, unless `o:insetmode="auto"`), Resize shape to fit text (`mso-fit-shape-to-text`) and vertical alignment (`v-text-anchor`). Hidden shapes (`visibility:hidden`, like DrawingML's `wp:docPr/@hidden`) are kept and saved but neither drawn nor laid out, as in Word for Windows (Word for Mac draws them). Picture `gain` and `blacklevel` on `v:imagedata` (Word's picture watermark "Washout") are read as brightness and contrast (#1711). Saving as DOCX writes them as DrawingML `a:lum`; saving as Word 2003 XML writes them back as VML `gain`/`blacklevel` (transparency has no place on `v:imagedata` and is dropped there). Text-box text direction is read as Word reads it: `mso-layout-flow-alt:bottom-to-top` as `vert270` whatever `layout-flow` says, else `layout-flow:vertical` or `vertical-ideographic` as `vert`, else horizontal (#5193). Word's text watermark (a `v:textpath` shape in a header or footer, recognised by Word's `PowerPlusWaterMarkObject` id or by being centred on the page both ways) becomes the document's watermark: text, font, fill colour, semitransparent (`v:fill` `opacity`) and diagonal (any turn); drawn with WordCraft's own size and angle, on every page even when only some sections' headers (or only the first-page header) have it (#1290). Saving writes the watermark back the same way: a `v:textpath` shape centred on the margins, behind the text, at the start of every header's first paragraph; a section whose pages would show no header gets a header holding only the watermark (default, and first-page or even-page ones when those are on), while sections linked to an earlier header stay linked. Freeforms (`v:shape` with its own `path`: moves, lines, Béziers and closes in its `coordsize`/`coordorigin` space, `nf`/`ns`, `v:stroke` opacity) are read as freeforms and saved as DrawingML custom geometry; fill opacity kept (no fill at 0); arcs are drawn straight; shapes whose path uses formulas (`@n`) and paths inherited from a `v:shapetype` aren't read. Word signature lines (Insert › Signature Line: a VML picture with an `o:signatureline`) are shown as their picture and saved back whole with it, at the size set in WordCraft, so they stay signable in Word instead of becoming plain pictures. Other VML is written only for OLE object pictures and signature lines. Other VML WordArt (Word 2007's: `v:textpath` in the body, or a header logo) becomes a text box without fill or outline holding its `string`, in the textpath's font, the shape's fill colour and a size from the shape's height; its WordArt shape (`o:spt` 136–175) becomes the DrawingML text warp of the same shape (#2875). Its outline, shadow and 3-D effects aren't read |
 | Alt text of drawings (`wp:docPr`/`cNvPr` `descr` and `title`, decorative mark `adec:decorative` from [MS-ODRAWXML]) and tables (`w:tblCaption`, `w:tblDescription`) | ✅ | ✅ | Pictures, shapes, text boxes, groups and their members, charts and SmartArt; OLE objects get theirs written into the kept XML (#386) |
-| Charts (`c:chart`), SmartArt (`dgm`) | ✅ | ✅ | Drawn from the chart's cached data and SmartArt's stored drawing (#292), with data labels (`c:showVal`); their text (title, axis labels, legend) is drawn in the document's body font, and characters it lacks (Chinese in Calibri's substitute) in a fallback face that covers them, one face per run as in body text (#4720); a chart of only types not drawn yet (radar, stock, bubble, surface, 3-D, pie of pie) shows a placeholder in its frame with its title and type (#998). Charts made in WordCraft (Insert › Chart, #409) are written as a `c:chartSpace` part with their data as literals (`c:strLit`/`c:numLit`, no embedded workbook, so Word shows them and offers to create a workbook on Edit Data) and read back as editable; a chart part holding anything more (any chart from Word, or one re-saved by Word) stays read-only. Saved back as read, with every part they reach (chart, embedded workbook, colours and style; diagram data, layout, quick style, colours and drawing) and their content types; a moved or resized one keeps its new frame, and a pasted copy gets its own parts (#319). SmartArt made in WordCraft (#497) is written from its model: data (`dgm:dataModel` points and connections), our own layout, quick-style and colour definitions under the built-in layout identifiers, and a `dsp:drawing` with every shape placed; it reads back editable only when its data part is exactly what WordCraft writes |
+| Charts (`c:chart`), SmartArt (`dgm`) | ✅ | ✅ | Drawn from the chart's cached data and SmartArt's stored drawing (#292), with data labels (`c:showVal`); a series without its own colour takes the accent its `c:idx` picks, as Word does (#5963); their text (title, axis labels, legend) is drawn in the document's body font, and characters it lacks (Chinese in Calibri's substitute) in a fallback face that covers them, one face per run as in body text (#4720); a chart of only types not drawn yet (radar, stock, bubble, surface, 3-D, pie of pie) shows a placeholder in its frame with its title and type (#998). Charts made in WordCraft (Insert › Chart, #409) are written as a `c:chartSpace` part with their data as literals (`c:strLit`/`c:numLit`, no embedded workbook, so Word shows them and offers to create a workbook on Edit Data) and read back as editable; a chart part holding anything more (any chart from Word, or one re-saved by Word) stays read-only. Saved back as read, with every part they reach (chart, embedded workbook, colours and style; diagram data, layout, quick style, colours and drawing) and their content types; a moved or resized one keeps its new frame, and a pasted copy gets its own parts (#319). SmartArt made in WordCraft (#497) is written from its model: data (`dgm:dataModel` points and connections), our own layout, quick-style and colour definitions under the built-in layout identifiers, and a `dsp:drawing` with every shape placed; it reads back editable only when its data part is exactly what WordCraft writes |
 | OLE objects (`w:object`: embedded or linked files, ActiveX) | 🟡 | ✅ | Shown as their picture (VML or DrawingML); saved back whole with the embedding and picture parts, at the size, rotation and flips set in WordCraft (#319, #332). Can't be opened or edited |
 | Native Word ink (`w14:contentPart`, InkML) | 🟡 | 🟡 | Drawing-level ink kept opaque with its InkML part, relationship and content type; direct run-level `w:contentPart` and run-level `mc:AlternateContent` keep the native branch and VML picture fallback. Direct content parts remain direct through repeated save/reopen cycles, without a native rendering. Drawing-level ink shows the preview or a missing-picture box. Ink members of groups (`wpg:wgp`, nested groups too) and drawing canvases (`wpc:wpc`), bare or in `mc:AlternateContent` with a `pic:pic` fallback, keep their markup, part, relationship and place among the members; they are written at the member's current position in the group and drawn from their fallback picture. Such a group can't be ungrouped yet (Ungroup is unavailable, so the ink is never left in a form it can't be saved in). Their part is dropped with the group (no orphan part); ink whose part is missing or isn't InkML gives way to its fallback, else is dropped. No native stroke rendering, eraser, conversion or replay |
 | 3D models | ❌ | ❌ | Dropped on read, not preserved on save |
@@ -335,6 +335,7 @@ For field results, the engine parser treats a backslash in quoted arguments as e
 | Date | Change | Summary |
 |---|---|---|
 | 2026-11-08 | trivial | XML text and CDATA read with their line ends normalised (XML 1.0 §2.11): CR LF and a lone CR are one line feed, `
` stays a CR, so a line break inside `w:t` in a file saved with Windows line ends is one space, not two (#5897) |
+| 2026-11-07 | trivial | Charts: a series without its own colour takes the accent its `c:idx` picks, as Word does, not the one its place in the file picks (#5963) |
 | 2026-11-05 | trivial | ODT: text of another size in a heading, title or code paragraph keeps it. Every run's size went with the style, on screen and in LibreOffice after a save Text at the heading's size goes with the style, stated or not, and a percentage is of the heading's size. Text in a heading style that states no size keeps a size it states. |
 | 2026-11-05 | trivial | ODT: a table row kept from breaking across pages (`fo:keep-together` on the row) is read and written; it came back from a save free to break A row whose style doesn't say follows the default style. A row free to break says so where the file's default row style, which stays, keeps rows together. |
 | 2026-11-05 | trivial | ODT: a watermark added, changed or removed, and Different Odd & Even Pages turned on or off, in a file read from ODT are saved. The file's own page definitions were written back whatever happened to these, so the change was gone from the saved file (`odt::tests_more::headers`). Such a change writes the page definitions from the model, as other changes to what a page is made of do, so what WordCraft doesn't model of the page (a header's background) doesn't survive that save. Over 79 LibreOffice-authored files with a watermark added: all 79 have it, with the same page count in LibreOffice 26.8. |

docs/gaps.md

@@ -208,6 +208,7 @@ Page Setup's margin, paper-size and document-grid number boxes scroll long text
 | 2026-11-02 | trivial | #26 narrowed: MHT opens and `w:altChunk` content is brought in on open; saving MHT remains |
 | 2026-11-01 | trivial | Preserve table rows and cells inside selected alternate-content branches (#5219); readiness estimates unchanged. |
 | 2026-11-07 | trivial | Empty paragraph deletion preserves following paragraph/mark formatting (Leaf #152); synthetic regressions only, no ranked gap closed or estimate changed. |
+| 2026-11-07 | trivial | Charts: a series without its own colour takes the accent its `c:idx` picks, as Word does, not the one its place in the file picks (#5963) |
 | 2026-11-06 | trivial | Print helpers remove loaded PDF/settings files before driver work, tolerate prior removal and report cleanup errors; a held-driver regression checks the files are already absent (#5710) |
 | 2026-11-06 | trivial | Windows print submissions use a separate helper per job, preserving provider serialization inside the helper. An acknowledged cancellation stops that helper, so a stalled cancelled driver cannot block a later job; normal shutdown reaps helpers and removes temporary PDFs. The helper erases its plaintext inputs before driver work; a hard app crash during startup can still leave private temporary files. Startup requires an explicit start grant; after sending begins, jobs complete (#5710) |
 | 2026-11-06 | trivial | Gap 6: File › Print: before sending starts, Cancel printing (`ui.printCancel`) stops a waiting job and frees the Print page while keeping its settings, including after the last document closes; a successfully cancelled job is never sent. Quitting cancels waiting jobs and joins jobs already sending (#5710). On Windows, winprint repeats the DEVMODE conversion after sending starts. A stall during that repeat prevents cancellation and can keep shutdown waiting, even before a native job exists. No ranked gap changed; readiness estimates unchanged |