Charts: draw data-point fills on columns and bars, smoothed lines, and the file's chart text colour

crates/pptx/src/read/chart.rs

@@ -281,10 +281,33 @@ pub(crate) fn chart_from(root: &El) -> Option<Chart> {
     // the chart): the axes' and legend's, else the whole chart's; the title's own.
     let chart_size = text_size(root.child("txPr"));
     c.text_size = [val_ax, cat_ax, ch.child("legend")].into_iter().flatten().find_map(|e| text_size(e.child("txPr"))).or(chart_size);
+    // Text colour likewise: the axes' and legend's, else the whole chart's.
+    c.text_color = [val_ax, cat_ax, ch.child("legend"), Some(root)].into_iter().flatten().find_map(|e| text_color(e.child("txPr")));
     c.title_size = ch.child("title").and_then(|t| text_size(t.child("tx").and_then(|x| x.child("rich"))).or_else(|| text_size(t.child("txPr"))));
     Some(c)
 }
 
+/// The colour of the first `a:defRPr` or `a:rPr` with a solid fill under `e`.
+fn text_color(e: Option<&El>) -> Option<deckcraft_model::ColorRef> {
+    fn rec(e: &El, depth: usize) -> Option<deckcraft_model::ColorRef> {
+        if depth > 8 {
+            return None;
+        }
+        for c in e.elements() {
+            if (c.is("defRPr") || c.is("rPr"))
+                && let Some(Fill::Solid { color }) = simple_fill(Some(c))
+            {
+                return Some(color);
+            }
+            if let Some(v) = rec(c, depth + 1) {
+                return Some(v);
+            }
+        }
+        None
+    }
+    rec(e?, 0)
+}
+
 /// The size in points of the first `a:defRPr` or `a:rPr` with one under `e` (`sz` in hundredths).
 fn text_size(e: Option<&El>) -> Option<f64> {
     fn rec(e: &El, depth: usize) -> Option<f64> {
@@ -363,6 +386,14 @@ mod tests {
         assert!(c.series.iter().all(|s| !s.secondary_axis));
     }
 
+    #[test]
+    fn text_colour_is_read_from_the_axes() {
+        // LibreOffice's templates set light axis text for dark slides on the axes' c:txPr.
+        let xml = r#"<c:chartSpace xmlns:c="http://schemas.openxmlformats.org/drawingml/2006/chart" xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main"><c:chart><c:plotArea><c:barChart><c:barDir val="col"/><c:ser><c:idx val="0"/><c:val><c:numRef><c:numCache><c:ptCount val="1"/><c:pt idx="0"><c:v>1</c:v></c:pt></c:numCache></c:numRef></c:val></c:ser><c:axId val="1"/><c:axId val="2"/></c:barChart><c:catAx><c:axId val="1"/><c:txPr><a:bodyPr/><a:p><a:pPr><a:defRPr sz="1000"><a:solidFill><a:srgbClr val="FFFFFF"/></a:solidFill></a:defRPr></a:pPr></a:p></c:txPr></c:catAx><c:valAx><c:axId val="2"/></c:valAx></c:plotArea></c:chart></c:chartSpace>"#;
+        let c = read_chart_xml(xml.as_bytes()).unwrap();
+        assert_eq!(c.text_color, Some(deckcraft_model::ColorRef::rgb(deckcraft_color::Rgba::rgb(255, 255, 255))));
+    }
+
     #[test]
     fn text_sizes_are_read_from_the_file() {
         // PowerPoint's new charts set the axes' and legend's text to 11.97 pt and the title's to

crates/render/src/chart.rs

@@ -36,6 +36,43 @@ fn series_fill(ctx: &Ctx, c: &Chart, i: usize, s: Option<&deckcraft_model::chart
     }
 }
 
+/// The fill of point `k` of a series: its own (`c:dPt`) where the file gives one, else the series'.
+fn point_fill(ctx: &Ctx, c: &Chart, i: usize, s: &deckcraft_model::chart::Series, k: usize) -> Rgba {
+    match s.point_fills.iter().find(|(p, _)| *p == k).map(|(_, f)| f) {
+        Some(Fill::Solid { color: cc }) => ctx.color(cc, None),
+        _ => series_fill(ctx, c, i, Some(s)),
+    }
+}
+
+fn polyline(pts: &[Point]) -> BezPath {
+    let mut p = BezPath::new();
+    for (k, q) in pts.iter().enumerate() {
+        if k == 0 {
+            p.move_to(*q);
+        } else {
+            p.line_to(*q);
+        }
+    }
+    p
+}
+
+/// A smoothed line (`c:smooth`) through `pts`: a Catmull-Rom spline as cubic Béziers, the curve
+/// PowerPoint draws, passing through every point.
+pub(crate) fn smooth_path(pts: &[Point]) -> BezPath {
+    let mut p = BezPath::new();
+    let Some(first) = pts.first() else { return p };
+    p.move_to(*first);
+    for k in 0..pts.len() - 1 {
+        let p0 = pts[k.saturating_sub(1)];
+        let (p1, p2) = (pts[k], pts[k + 1]);
+        let p3 = pts[(k + 2).min(pts.len() - 1)];
+        let c1 = p1 + (p2 - p0) / 6.0;
+        let c2 = p2 - (p3 - p1) / 6.0;
+        p.curve_to(c1, c2, p2);
+    }
+    p
+}
+
 /// A line series' colour: its line's own (where PowerPoint keeps it), else its fill's, else the
 /// palette's.
 fn series_line(ctx: &Ctx, c: &Chart, i: usize, s: &deckcraft_model::chart::Series) -> Rgba {
@@ -418,7 +455,7 @@ pub fn draw(ctx: &mut RenderContext, rctx: &Ctx, c: &Chart, m: Affine, w: f64, h
                     Rect::new(plot.x0 + start, to_axis(sec, b), plot.x0 + start + bar, to_axis(sec, a))
                 };
                 ctx.set_transform(m);
-                ctx.set_paint(color(series_fill(rctx, c, *si, Some(s)), 1.0));
+                ctx.set_paint(color(point_fill(rctx, c, *si, s, i), 1.0));
                 ctx.fill_rect(&r.abs());
                 if c.data_labels {
                     let t = c.data_label(s, s.values.get(i).copied().flatten().unwrap_or(0.0));
@@ -480,14 +517,7 @@ pub fn draw(ctx: &mut RenderContext, rctx: &Ctx, c: &Chart, m: Affine, w: f64, h
         if pts.is_empty() {
             continue;
         }
-        let mut p = BezPath::new();
-        for (k, q) in pts.iter().enumerate() {
-            if k == 0 {
-                p.move_to(*q);
-            } else {
-                p.line_to(*q);
-            }
-        }
+        let p = if s.smooth && !area_kind && pts.len() > 2 { smooth_path(&pts) } else { polyline(&pts) };
         ctx.set_transform(m);
         if area_kind {
             let mut a = p.clone();

crates/render/src/tests.rs

@@ -155,6 +155,30 @@ fn combo_chart_draws_columns_and_a_line_on_its_own_axis() {
     assert!(col[0] < 250 || col[1] < 250 || col[2] < 250, "no column: {col:?}");
 }
 
+#[test]
+fn column_points_take_their_own_fill_and_smooth_lines_curve() {
+    // One column series where only the middle point is given a red c:dPt fill.
+    let mut c = Chart::sample(ChartType::Column);
+    c.title = None;
+    c.legend = None;
+    c.series.truncate(1);
+    c.categories = vec!["A".into(), "B".into(), "C".into()];
+    c.series[0].values = vec![Some(10.0), Some(10.0), Some(10.0)];
+    c.series[0].point_fills = vec![(1, deckcraft_model::style::Fill::solid(ColorRef::rgb(deckcraft_color::Rgba::rgb(255, 0, 0))))];
+    let sh = Shape { id: ShapeId(621), xfrm: Some(Xfrm::new(0.0, 0.0, 960.0, 540.0)), kind: ShapeKind::Chart(Box::new(c)), ..Default::default() };
+    let img = render_slide(&deck_with(vec![sh]), 0, &RenderOpts { scale: 1.0, ..Default::default() });
+    let red = |x: u32| (300..500).any(|y| img.pixel(x, y)[..3] == [255, 0, 0]);
+    assert!(red(480), "the middle column takes its point's fill");
+    assert!(!red(200) && !red(760), "the others keep the series colour");
+
+    // A smoothed line through a peak overshoots no point but leaves the straight chord.
+    let pts = [kurbo::Point::new(0.0, 0.0), kurbo::Point::new(10.0, 10.0), kurbo::Point::new(20.0, 0.0)];
+    let p = crate::chart::smooth_path(&pts);
+    assert_eq!(p.elements().len(), 3, "a cubic per segment");
+    let mid = kurbo::ParamCurve::eval(&p.segments().next().unwrap(), 0.5);
+    assert!(mid.y > mid.x, "the first half bows towards the peak instead of following the chord: {mid:?}");
+}
+
 #[test]
 fn placeholder_prompts_only_in_edit_view() {
     let p = Presentation::default();