Merge pull request #1630

Apply alphaMod and alphaOff in ColorRef::alpha

crates/model/src/style.rs

@@ -55,10 +55,12 @@ impl ColorRef {
         };
         deckcraft_color::apply(base, &self.mods)
     }
-    /// Alpha (0–1) from an `alpha` transform, if any.
+    /// Alpha (0–1) from the `alpha`, `alphaMod` and `alphaOff` transforms, applied in order.
     pub fn alpha(&self) -> f64 {
         self.mods.iter().fold(1.0, |a, m| match m {
             ColorTransform::Alpha(v) => (*v as f64 / 100_000.0).clamp(0.0, 1.0),
+            ColorTransform::AlphaMod(v) => (a * *v as f64 / 100_000.0).clamp(0.0, 1.0),
+            ColorTransform::AlphaOff(v) => (a + *v as f64 / 100_000.0).clamp(0.0, 1.0),
             _ => a,
         })
     }

crates/model/src/tests.rs

@@ -327,3 +327,15 @@ fn only_web_and_mail_links_are_safe_to_open() {
         assert!(!safe_url(url), "{url}");
     }
 }
+
+#[test]
+fn colour_alpha_follows_alpha_mod_and_off() {
+    use deckcraft_color::{ColorTransform, Rgba};
+    let base = || ColorRef::rgb(Rgba::rgb(1, 2, 3));
+    let mod_half = base().with(ColorTransform::AlphaMod(50000));
+    assert!((mod_half.alpha() - 0.5).abs() < 1e-9, "{}", mod_half.alpha());
+    let off = base().with(ColorTransform::AlphaOff(-50000));
+    assert!((off.alpha() - 0.5).abs() < 1e-9, "{}", off.alpha());
+    let both = base().with(ColorTransform::Alpha(40000)).with(ColorTransform::AlphaMod(50000));
+    assert!((both.alpha() - 0.2).abs() < 1e-9, "{}", both.alpha());
+}