fix: wire distribution through string-stat geoms (#56)

Author: mcanouil

CHANGELOG.md

@@ -12,6 +12,7 @@
 - feat: `labs()` fields default to `auto`; pass `none` to suppress an axis or legend title and reclaim the space it reserved. (#12)
 - feat: `element-blank()` on a text surface (axis, plot, or legend title) collapses the space the text would reserve. (#12)
 - feat: `width`/`height` accept `auto` to fill the available space of a bounded container. (#10)
+- fix: `geom-qq()`/`geom-qq-line()` honour the `distribution` argument (`uniform`/`exponential`) instead of always plotting against the normal reference. (#56)
 - fix: the `font` set on `element-text`/`element-typst`/`element-geom` is applied to every text surface and to the text-drawing geoms, inheriting the base `text` font when unset. (#54)
 - fix: a `stage`/`after-scale` channel now trains its scale on the marker's source column, so the closure receives the channel's scale-resolved value as documented. (#52)
 - fix: grouped geoms (e.g., `geom-smooth`) no longer panic when a grouping aesthetic is mapped via `after-scale` or `stage`. (#51)

src/render.typ

@@ -9,7 +9,7 @@
 )
 #import "scale/expansion.typ": DISCRETE-AUTO-DATA-PAD, normalise-expansion
 #import "scale/oob.typ": filter-oob
-#import "stat/apply.typ": apply-stat, setup-stat, stat-default-params
+#import "stat/apply.typ": apply-stat, resolve-stat-spec, setup-stat
 #import "stat/info.typ": stat-info
 #import "position/apply.typ": apply-position, position-name-of
 #import "theme/current.typ": _theme-state
@@ -400,14 +400,9 @@
   // its own name and params. Match the same pattern used for `position:` below.
   let stat-spec = layer.at("stat", default: "identity")
   let params = layer.at("params", default: (:))
-  let stat-name = if type(stat-spec) == str {
-    stat-spec
-  } else { stat-spec.at("name", default: "identity") }
-  let stat-params = if type(stat-spec) == str {
-    stat-default-params(stat-name)
-  } else {
-    stat-spec.at("params", default: (:))
-  }
+  let resolved-stat = resolve-stat-spec(stat-spec, params)
+  let stat-name = resolved-stat.name
+  let stat-params = resolved-stat.params
   let stripped = _strip-mapping-refs(mapping)
 
   let stat-identity = stat-name == none or stat-name == "identity"

src/stat/apply.typ

@@ -153,6 +153,21 @@
   if ctor == none { (:) } else { ctor().params }
 }
 
+// Resolve a layer's `stat:` field into a `(name, params)` pair. A string name
+// inherits the geom's own params over the stat constructor defaults, mirroring
+// the `position:` string form, so geom params such as `distribution` reach the
+// stat. A `stat-*()` dict carries its own name and params instead.
+#let resolve-stat-spec(stat-spec, geom-params) = {
+  if type(stat-spec) == str {
+    (name: stat-spec, params: stat-default-params(stat-spec) + geom-params)
+  } else {
+    (
+      name: stat-spec.at("name", default: "identity"),
+      params: stat-spec.at("params", default: (:)),
+    )
+  }
+}
+
 #let setup-stat(name, data, mapping, params) = {
   let entry = _STATS.at(name, default: none)
   if entry == none { return params }

tests/unit/test-qq.typ

@@ -1,7 +1,9 @@
 // Q-Q statistic and helper tests.
 
 #import "../../src/utils/normal.typ": qnorm, theoretical-quantile
-#import "../../src/stat/apply.typ": apply-stat
+#import "../../src/stat/apply.typ": apply-stat, resolve-stat-spec
+#import "../../src/geom/qq.typ": geom-qq
+#import "../../src/geom/qq-line.typ": geom-qq-line
 
 // --- qnorm: classic 95 % quantile -----------------------------------------
 // Acklam's approximation matches the standard z to about 1.15e-9.
@@ -123,4 +125,31 @@
     < 1e-9,
 )
 
+// --- resolve-stat-spec: string stat inherits the geom's own params --------
+// Regression: geom-qq stores `distribution` in its params and dispatches the
+// stat by string name, so the resolver must forward those params to the stat
+// rather than dropping them for the constructor defaults.
+
+#let qq-layer = geom-qq(distribution: "uniform")
+#let qq-resolved = resolve-stat-spec(qq-layer.stat, qq-layer.params)
+#assert.eq(qq-resolved.name, "qq")
+#assert.eq(qq-resolved.params.distribution, "uniform")
+
+#let qq-line-layer = geom-qq-line(distribution: "exponential")
+#let qq-line-resolved = resolve-stat-spec(
+  qq-line-layer.stat,
+  qq-line-layer.params,
+)
+#assert.eq(qq-line-resolved.name, "qq-line")
+#assert.eq(qq-line-resolved.params.distribution, "exponential")
+
+// --- resolve-stat-spec: stat-*() dict carries its own name and params ------
+
+#let dict-resolved = resolve-stat-spec(
+  (kind: "stat", name: "boxplot", params: (coefficient: 1.0)),
+  (width: 0.6),
+)
+#assert.eq(dict-resolved.name, "boxplot")
+#assert.eq(dict-resolved.params.coefficient, 1.0)
+
 QQ tests passed.