userscript/manga-bookmark.user.js

@@ -1019,6 +1019,16 @@
       fab.style.bottom = "auto";
     });
 
+    function snapToEdge() {
+      const w = fab.offsetWidth, h = fab.offsetHeight;
+      const r = fab.getBoundingClientRect();
+      const side = r.left + w / 2 < window.innerWidth / 2 ? "left" : "right";
+      const y = clamp(r.top, FAB_MARGIN, window.innerHeight - h - FAB_MARGIN);
+      fab.style.transition = "left .2s ease, right .2s ease, top .2s ease";
+      applyFabPos(fab, side, y);
+      saveFabPos(side, y / window.innerHeight);
+    }
+
     fab.addEventListener("pointerup", (e) => {
       if (!down) return;
       const didDrag = moved, didScroll = scrolling;
@@ -1029,16 +1039,15 @@
       }
       if (!didDrag) return; // tap — let the click handler toggle the panel
       fab.dataset.dragged = "1"; // suppress the click that trails this drag
-      const w = fab.offsetWidth, h = fab.offsetHeight;
-      const r = fab.getBoundingClientRect();
-      const side = r.left + w / 2 < window.innerWidth / 2 ? "left" : "right";
-      const y = clamp(r.top, FAB_MARGIN, window.innerHeight - h - FAB_MARGIN);
-      fab.style.transition = "left .2s ease, right .2s ease, top .2s ease";
-      applyFabPos(fab, side, y);
-      saveFabPos(side, y / window.innerHeight);
+      snapToEdge();
     });
 
-    fab.addEventListener("pointercancel", reset);
+    fab.addEventListener("pointercancel", () => {
+      if (!down) return;
+      const didDrag = moved;
+      reset();
+      if (didDrag) snapToEdge(); // OS claimed the gesture mid-drag — don't strand the FAB
+    });
   }
 
   // ============================================================