Merge pull request #334 from inokawa/refactor-calculate-jump

Refactor calculateJump
inokawa · Jan 21, 2024 · e166a4f · e166a4f
2 parents ec679a0 + 45a8c2d
commit e166a4f
Showing 1 changed file with 13 additions and 32 deletions.
diff --git a/src/core/store.ts b/src/core/store.ts
@@ -14,9 +14,6 @@ import { isIOSWebKit } from "./environment";
 import type { CacheSnapshot } from "./types";
 import { abs, clamp, max, min } from "./utils";
 
-// Scroll offset and sizes can have sub-pixel value if window.devicePixelRatio has decimal value
-const SUBPIXEL_THRESHOLD = 1.5; // 0.5 * 3
-
 /** @internal */
 export const SCROLL_IDLE = 0;
 /** @internal */
@@ -125,17 +122,9 @@ export const overscanEndIndex = (
   );
 };
 
-const calculateJump = (
-  cache: Cache,
-  items: readonly ItemResize[],
-  keepEnd?: boolean
-): number => {
+const calculateJump = (cache: Cache, items: readonly ItemResize[]): number => {
   return items.reduce((acc, [index, size]) => {
-    const diff = size - getItemSize(cache, index);
-    if (!keepEnd || diff > 0) {
-      acc += diff;
-    }
-    return acc;
+    return acc + size - getItemSize(cache, index);
   }, 0);
 };
 
@@ -315,26 +304,18 @@ export const createVirtualStore = (
 
           // Calculate jump
           // Should maintain visible position to minimize junks in appearance
-          let diff = 0;
-
-          if (scrollOffset === 0) {
-            // Do nothing to stick to the start
-          } else if (scrollOffset > getMaxScrollOffset() - SUBPIXEL_THRESHOLD) {
-            // Keep end to stick to the end
-            diff = calculateJump(cache, updated, true);
+          let diff: number;
+          if (_scrollMode === SCROLL_BY_PREPENDING) {
+            // Keep distance from end immediately after prepending
+            // We can assume jumps occurred on the upper outside
+            diff = calculateJump(cache, updated);
           } else {
-            if (_scrollMode === SCROLL_BY_PREPENDING) {
-              // Keep distance from end immediately after prepending
-              // We can assume jumps occurred on the upper outside
-              diff = calculateJump(cache, updated);
-            } else {
-              // Keep start at mid
-              const [startIndex] = _prevRange;
-              diff = calculateJump(
-                cache,
-                updated.filter(([index]) => index < startIndex)
-              );
-            }
+            // Keep start at mid
+            const [startIndex] = _prevRange;
+            diff = calculateJump(
+              cache,
+              updated.filter(([index]) => index < startIndex)
+            );
           }
 
           if (diff) {