dice js: Make s.anim_id be possibly null

We might not have requested an animation frame.  If so we shouldn't
cancel it.  Nor, if we have already cancelled it, or if it has
occurred.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/templates/script.ts b/templates/script.ts
index 5268aac192ad0ae14f0bc225fd1929e179797fab..464387e00e9acb010753d7c1a5e06a1faf5d50d6 100644 (file)
--- a/templates/script.ts
+++ b/templates/script.ts
@@ -2263,7 +2263,7 @@ function startup() {
 }
 
 type DieSpecialRendering = SpecialRendering & {
-  anim_id: number,
+  anim_id: number | null,
 };
 special_renderings['Die'] = function(piece: PieceId, p: PieceInfo,
                                     s: DieSpecialRendering) {
@@ -2274,11 +2274,15 @@ special_renderings['Die'] = function(piece: PieceId, p: PieceInfo,
 } as any;
 function die_render_frame(piece: PieceId, p: PieceInfo,
                          s: DieSpecialRendering, ts: DOMHighResTimeStamp) {
+  s.anim_id = null;
   console.log('DIE RENDER', piece, ts);
 }
 function die_rendering_stop(piece: PieceId, p: PieceInfo,
                            s: DieSpecialRendering) {
-  window.cancelAnimationFrame(s.anim_id);
+  let anim_id = s.anim_id;
+  if (anim_id == null) return;
+  s.anim_id = null;
+  window.cancelAnimationFrame(anim_id);
 }    
 
 declare var wasm_input : any;