test(gpu): assert Cut Away 100 is fully transparent

crates/gpu/src/tests.rs

@@ -446,12 +446,16 @@ pub(crate) fn effect_direct(id: &str, vals: &[(&str, Value)], adjustment: bool)
     for (k, v) in vals {
         params.values.insert(k.to_string(), v.clone());
     }
+    let expect_empty = id == "ec.distort.ccblobbylize" && vals.iter().any(|(k, v)| *k == "cutAway" && matches!(v, Value::Scalar(x) if *x == 100.0));
     for scale in [1.0, 0.5] {
         let img = pattern(7, (size[0] * scale) as u32, (size[1] * scale) as u32);
         let buf = effectcraft_effects::Buf { img, offset: [0.0, 0.0], scale };
         let ctx = || effectcraft_effects::EffectCtx { params: &params, time: 0.25, layer_size: size, seed: 11, adjustment, env: Default::default() };
         let cpu = (spec.render)(&ctx(), buf.clone());
         let out = effectcraft_render::Accelerator::effects(g, &[effectcraft_render::FxStep { spec, ctx: ctx() }], &buf, None).expect("the GPU runs the effect");
+        if expect_empty {
+            assert!(out.img.data.iter().all(|p| p[3] == 0.0), "{id} {vals:?} adj {adjustment} scale {scale}: Cut Away 100 produced non-zero alpha");
+        }
         assert_eq!((out.offset, out.scale), (cpu.offset, cpu.scale), "{id}: geometry");
         let d = diff(&cpu.img, &out.img, 1e-3);
         let allow = if on_gl() { (d.total as f64 * GL_BOUNDARY_FLIPS) as usize } else { 0 };