fix: determine point/band scale domain from interval

gka · gka · commit 19780531e566 · 2025-05-27T19:56:43.000+02:00
diff --git a/src/lib/helpers/autoTicks.ts b/src/lib/helpers/autoTicks.ts
@@ -1,6 +1,6 @@
 import type { RawValue, ScaleType } from '$lib/types.js';
 import { maybeTimeInterval } from './time.js';
-import { range as rangei } from 'd3-array';
+import { extent, range as rangei } from 'd3-array';
 
 export function maybeInterval(interval: null | number | string | (<T>(d: T) => T)) {
     if (interval == null) return;
@@ -38,11 +38,11 @@ export function autoTicks(
     scaleFn,
     count: number
 ) {
-    return ticks
-        ? ticks
-        : interval
-          ? maybeInterval(interval, type).range(domain[0], domain[1])
-          : typeof scaleFn.ticks === 'function'
-            ? scaleFn.ticks(count)
-            : [];
+    if (ticks) return ticks;
+    if (interval) {
+        const [lo, hi] = extent(domain);
+        const I = maybeInterval(interval, type);
+        return I.range(lo, I.offset(hi));
+    }
+    return typeof scaleFn.ticks === 'function' ? scaleFn.ticks(count) : [];
 }
diff --git a/src/lib/helpers/scales.ts b/src/lib/helpers/scales.ts
@@ -29,6 +29,7 @@ import type {
 import isDataRecord from './isDataRecord.js';
 
 import { createProjection } from './projection.js';
+import { maybeInterval } from './autoTicks.js';
 
 /**
  * compute the plot scales
@@ -302,7 +303,7 @@ export function createScale<T extends ScaleOptions>(
     const valueArray =
         type === 'quantile' || type === 'quantile-cont' ? allDataValues.toSorted() : valueArr;
 
-    const domain = scaleOptions.domain
+    let domain = scaleOptions.domain
         ? isOrdinal
             ? scaleOptions.domain
             : extent(scaleOptions.zero ? [0, ...scaleOptions.domain] : scaleOptions.domain)
@@ -317,6 +318,16 @@ export function createScale<T extends ScaleOptions>(
               : valueArray
           : extent(scaleOptions.zero ? [0, ...valueArray] : valueArray);
 
+    if (scaleOptions.interval) {
+        if (isOrdinal) {
+            domain = domainFromInterval(domain, scaleOptions.interval);
+        } else {
+            throw new Error(
+                'Setting interval via axis options is only supported for ordinal scales'
+            );
+        }
+    }
+
     if (!scaleOptions.scale) {
         throw new Error(`No scale function defined for ${name}`);
     }
@@ -350,6 +361,12 @@ export function createScale<T extends ScaleOptions>(
     };
 }
 
+function domainFromInterval(domain: RawValue[], interval: string | number) {
+    const interval_ = maybeInterval(interval);
+    const [lo, hi] = extent(domain);
+    return interval_.range(lo, interval_.offset(hi));
+}
+
 /**
  * Infer a scale type based on the scale name, the data values mapped to it and
  * the mark types that are bound to the scale
