Charts: a chart frame with no width no longer panics

crates/render/src/chart.rs

@@ -264,9 +264,9 @@ pub fn draw(ctx: &mut RenderContext, rctx: &Ctx, c: &Chart, m: Affine, w: f64, h
     } else if c.y_hidden {
         base * 0.5
     } else {
-        label_w(false, (min, max, step)).clamp(base * 1.5, area.width() * 0.3)
+        label_w(false, (min, max, step)).min(area.width() * 0.3).max(base * 1.5)
     };
-    let gutter_r = second.filter(|_| !c.y2_hidden).map(|sc| label_w(true, sc).clamp(base * 1.5, area.width() * 0.3)).unwrap_or(0.0);
+    let gutter_r = second.filter(|_| !c.y2_hidden).map(|sc| label_w(true, sc).min(area.width() * 0.3).max(base * 1.5)).unwrap_or(0.0);
     let plot = if horiz {
         Rect::new(area.x0 + gutter, area.y0, area.x1, area.y1 - base * 1.6)
     } else {
@@ -378,7 +378,7 @@ pub fn draw(ctx: &mut RenderContext, rctx: &Ctx, c: &Chart, m: Affine, w: f64, h
             );
         }
     }
-    let zero = to_v(0.0f64.clamp(min, max));
+    let zero = to_v(0.0f64.max(min).min(max));
     if let Some(bk) = bar_kind {
         let bars: Vec<(usize, &deckcraft_model::chart::Series)> =
             c.series.iter().enumerate().filter(|(_, s)| c.series_kind(s).is_bar_like()).collect();

crates/render/src/tests.rs

@@ -1711,3 +1711,51 @@ fn east_asian_vertical_text_stands_ideographs_upright() {
     let (w, h) = ink(deckcraft_model::text::TextDir::Vertical);
     assert!(h > w * 3, "vert: stroke on its side {w}x{h}");
 }
+
+#[test]
+fn charts_in_degenerate_frames_draw_without_panicking() {
+    // A chart frame squashed to no width (cx="0" in a generated file) made the value labels'
+    // gutter clamp panic (its upper bound, a share of the width, fell below its lower bound).
+    // Every chart type and legend position must survive any frame size.
+    let p = Presentation::default();
+    let rctx = Ctx::for_slide(&p, &p.slides[0]).unwrap();
+    let kinds = [
+        ChartType::Column,
+        ChartType::StackedColumn,
+        ChartType::PercentColumn,
+        ChartType::Bar,
+        ChartType::StackedBar,
+        ChartType::PercentBar,
+        ChartType::Line,
+        ChartType::LineMarkers,
+        ChartType::StackedLine,
+        ChartType::Area,
+        ChartType::StackedArea,
+        ChartType::Pie,
+        ChartType::Doughnut,
+        ChartType::Scatter,
+        ChartType::Bubble,
+        ChartType::Radar,
+        ChartType::FilledRadar,
+        ChartType::Stock,
+        ChartType::Surface,
+        ChartType::Histogram,
+        ChartType::Pareto,
+        ChartType::BoxWhisker,
+        ChartType::Waterfall,
+        ChartType::Funnel,
+        ChartType::Treemap,
+        ChartType::Sunburst,
+        ChartType::Combo,
+    ];
+    let mut ctx = vello_cpu::RenderContext::new(64, 64);
+    for k in kinds {
+        for (w, h) in [(0.0, 403.0), (403.0, 0.0), (0.0, 0.0), (2.0, 400.0), (400.0, 2.0), (12.0, 12.0)] {
+            for legend in [None, Some("b"), Some("t"), Some("r"), Some("l"), Some("tr")] {
+                let mut c = Chart::sample(k);
+                c.legend = legend.map(String::from);
+                crate::chart::draw(&mut ctx, &rctx, &c, kurbo::Affine::IDENTITY, w, h);
+            }
+        }
+    }
+}