fix: 让显影参数覆盖完整范围

src/main.ts

@@ -74,10 +74,10 @@ app.innerHTML = `
           <label class="control" for="retention-control">
             <span class="control__heading">
               <span>显影</span>
-              <output id="retention-value">14%</output>
+              <output id="retention-value">15%</output>
             </span>
             <span class="control__hint">留下多少原文词语</span>
-            <input id="retention-control" type="range" min="5" max="40" value="14" />
+            <input id="retention-control" type="range" min="0" max="100" value="15" />
           </label>
 
           <label class="control" for="volume-control">

src/mosaic.test.ts

@@ -36,6 +36,14 @@ describe('selectKeywords', () => {
 
     expect(candidates.some((candidate) => candidate.selected)).toBe(true)
   })
+
+  it('显影 0% 不保留词语，100% 保留全部候选词', () => {
+    const hidden = selectKeywords(SOURCE, 0, 1)
+    const revealed = selectKeywords(SOURCE, 100, 1)
+
+    expect(hidden.some((candidate) => candidate.selected)).toBe(false)
+    expect(revealed.every((candidate) => candidate.selected)).toBe(true)
+  })
 })
 
 describe('generateMosaic', () => {

src/mosaic.ts

@@ -345,13 +345,13 @@ export function selectKeywords(
     return candidates
   }
 
-  const desiredCount = Math.min(
-    candidates.length,
-    Math.max(
-      candidates.length >= 4 ? 2 : 1,
-      Math.round(candidates.length * (retention / 100)),
-    ),
-  )
+  const desiredCount =
+    retention <= 0
+      ? 0
+      : Math.min(
+          candidates.length,
+          Math.max(1, Math.ceil(candidates.length * (retention / 100))),
+        )
   const ranked = [...candidates].sort(
     (left, right) => right.score - left.score || left.start - right.start,
   )