fix: handle MIST movie timer actions and verify skipping

frontend/src/player/screens.ts

@@ -2046,7 +2046,12 @@ export class ScreenManager {
       Image: shape("image"),
       AlphaMask: shape("alphamask"),
     };
-    out.If = (condition: any, yes: any = null, no: any = null) => (truthy(condition) ? yes : no);
+    out.If = (...a: any[]) => {
+      const kw = kwOf(a), args = a.filter((value) => !value?.__kw);
+      const condition = args.length ? args[0] : kw.expression;
+      return truthy(condition) ? (args.length > 1 ? args[1] : kw.true ?? null)
+        : (args.length > 2 ? args[2] : kw.false ?? null);
+    };
     out.GetTooltip = () => this.tooltip;
     out.StaticValue = (value: number, range = 1) => new BarValue(() => value, () => range);
     out.AnimatedValue = out.StaticValue;

frontend/tests/mist-runtime.test.mjs

@@ -19,12 +19,14 @@ test("MIST's actual movie Skip survives a queued redraw and returns before its t
     engine.newStore();
     Object.assign(engine.store, { movielength: 63, movieplaying: "images/animations/movies/Intro_Movie.webm" });
     const completed = engine.exec({ op: "call_screen", name: "custommoviescreen", args: [], kw: {} });
+    await until(() => root.querySelector(".pg-sadd")?.dataset.seen);
     const button = [...root.querySelectorAll(".pg-sbtn")].find((element) => element.textContent === "Skip");
     assert.ok(button);
     assert.equal(button.classList.contains("pg-sdisabled"), false);
     engine.screens.refresh();
     window.dispatchEvent(new window.Event("pointerdown"));
-    await until(() => engine.store.movielength < 63);
+    const remaining = engine.store.movielength;
+    await until(() => engine.store.movielength < remaining);
     assert.equal(button.isConnected, true);
     window.dispatchEvent(new window.Event("pointerup"));
     click(button);

frontend/tests/screens.test.mjs

@@ -55,6 +55,22 @@ const buttons = (root) => [...root.querySelectorAll(".pg-sbtn")];
 const click = (el) => el.onclick({ stopPropagation() {}, preventDefault() {} });
 const settle = () => wait(15);
 
+test("If accepts named true/false actions used by MIST's movie timer", () => {
+  const { manager, store } = setup();
+  try {
+    const { If, SetVariable } = manager.builtins();
+    const yes = SetVariable("branch", "yes"), no = SetVariable("branch", "no");
+    manager.run(If(true, { __kw: { true: yes, false: no } }), null);
+    assert.equal(store.branch, "yes");
+    manager.run(If(false, { __kw: { true: yes, false: no } }), null);
+    assert.equal(store.branch, "no");
+    assert.equal(If(true, yes, no), yes);
+    assert.equal(If(false, yes, no), no);
+    assert.equal(If(true, null, { __kw: { false: no } }), null);
+    assert.equal(If({ __kw: { expression: false, true: yes, false: no } }), no);
+  } finally { manager.destroy(); }
+});
+
 test("a screen renders its widgets, conditions, loops and interpolated text", () => {
   const { manager } = setup();
   manager.show("hud", [2]);