Improve text input performance with apply/cancel

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 - Split the big app file into smaller TypeScript modules and add `tsc` typechecking
 - Add PDF upload support (extract all text client-side for speed reading)
+- Improve text editor performance by applying changes explicitly instead of reprocessing on each keystroke
 
 ### 2026-02-02: 1.0.5
 

src/App.tsx

@@ -42,6 +42,7 @@ export default function App() {
   const positionsRef = useRef<PositionsMap>(savedSettings?.positions || {});
 
   const [text, setText] = useState(() => savedSettings?.text || DEFAULT_TEXT);
+  const [draftText, setDraftText] = useState(() => savedSettings?.text || DEFAULT_TEXT);
   const [words, setWords] = useState(() =>
     splitWords(savedSettings?.text || DEFAULT_TEXT),
   );
@@ -100,6 +101,24 @@ export default function App() {
   const prevTextRef = useRef(text);
   const fileInputRef = useRef<HTMLInputElement | null>(null);
 
+  const toggleTextInput = useCallback(() => {
+    setShowTextInput((prev) => {
+      const next = !prev;
+      if (next) setDraftText(text);
+      return next;
+    });
+  }, [text]);
+
+  const applyDraftText = useCallback(() => {
+    setText(draftText);
+    setShowTextInput(false);
+  }, [draftText]);
+
+  const cancelDraftText = useCallback(() => {
+    setDraftText(text);
+    setShowTextInput(false);
+  }, [text]);
+
   const togglePlay = useCallback(() => {
     if (currentIndex >= words.length - 1) {
       setCurrentIndex(0);
@@ -281,6 +300,7 @@ export default function App() {
         case "Escape":
           setShowInfo(false);
           setShowShortcuts(false);
+          setDraftText(text);
           setShowTextInput(false);
           setShowSettings(false);
           break;
@@ -389,7 +409,7 @@ export default function App() {
     <div style={styles.container}>
       <TopBar
         showTextInput={showTextInput}
-        onToggleTextInput={() => setShowTextInput((prev) => !prev)}
+        onToggleTextInput={toggleTextInput}
         fileInputRef={fileInputRef}
         onFileUpload={handleFileUpload}
         fileAccept=".epub,.pdf,.txt"
@@ -406,8 +426,17 @@ export default function App() {
 
       {showTextInput && (
         <TextInputOverlay
-          text={text}
+          text={draftText}
-          onChangeText={(e) => setText(e.target.value)}
+          onChangeText={(e) => setDraftText(e.target.value)}
+          onKeyDown={(e) => {
+            if (e.key === "Enter" && (e.ctrlKey || e.metaKey)) {
+              e.preventDefault();
+              applyDraftText();
+            }
+          }}
+          isDirty={draftText !== text}
+          onApply={applyDraftText}
+          onCancel={cancelDraftText}
         />
       )}
 

src/components/TextInputOverlay.tsx

@@ -1,25 +1,65 @@
-import type { ChangeEventHandler } from "react";
+import type { ChangeEventHandler, KeyboardEventHandler } from "react";
 import { styles } from "../styles";
 
 type Props = {
   text: string;
   onChangeText: ChangeEventHandler<HTMLTextAreaElement>;
+  onKeyDown?: KeyboardEventHandler<HTMLTextAreaElement>;
+  isDirty: boolean;
+  onApply: () => void;
+  onCancel: () => void;
 };
 
-export function TextInputOverlay({ text, onChangeText }: Props) {
+export function TextInputOverlay({
+  text,
+  onChangeText,
+  onKeyDown,
+  isDirty,
+  onApply,
+  onCancel,
+}: Props) {
   return (
     <div style={styles.textInputOverlay}>
       <div style={styles.textInputPanel}>
         <textarea
           value={text}
           onChange={onChangeText}
+          onKeyDown={onKeyDown}
           style={styles.textarea}
           placeholder="Paste your text here..."
           rows={8}
           autoFocus
         />
+
+        <div style={styles.textInputActions}>
+          <div style={styles.textInputHint}>
+            Changes won't affect the reader until you apply.
+          </div>
+          <div style={styles.textInputButtons}>
+            <button
+              onClick={onCancel}
+              style={styles.textInputBtnSecondary}
+              className="icon-btn"
+              type="button"
+            >
+              Cancel
+            </button>
+            <button
+              onClick={onApply}
+              style={{
+                ...styles.textInputBtnPrimary,
+                ...(isDirty ? {} : styles.textInputBtnPrimaryDisabled),
+              }}
+              className="icon-btn"
+              type="button"
+              disabled={!isDirty}
+              title={isDirty ? "Apply changes" : "No changes to apply"}
+            >
+              Apply
+            </button>
+          </div>
+        </div>
       </div>
     </div>
   );
 }
-

src/lib/reading.ts

@@ -21,6 +21,7 @@ export function getWordDelay(word: string, baseDelayMs: number): number {
 }
 
 export function formatReadingTime(minutes: number): string {
+  minutes = Math.round(minutes);
   if (minutes < 1) return "< 1 min";
   if (minutes < 60) return `${Math.round(minutes)} min`;
   const hours = Math.floor(minutes / 60);
@@ -28,4 +29,3 @@ export function formatReadingTime(minutes: number): string {
   if (mins === 0) return `${hours}h`;
   return `${hours}h ${mins}m`;
 }
-

src/styles.ts

@@ -117,6 +117,48 @@ export const styles: Record<string, CSSProperties> =
     padding: "4px",
     border: "1px solid #222",
   },
+  textInputActions: {
+    display: "flex",
+    alignItems: "center",
+    justifyContent: "space-between",
+    gap: "12px",
+    padding: "10px 12px 12px 12px",
+    borderTop: "1px solid #1a1a1a",
+  },
+  textInputHint: {
+    fontSize: "0.75rem",
+    color: "#888",
+    lineHeight: 1.3,
+  },
+  textInputButtons: {
+    display: "flex",
+    alignItems: "center",
+    gap: "10px",
+  },
+  textInputBtnPrimary: {
+    backgroundColor: "#ff6b6b",
+    color: "#0a0a0a",
+    border: "none",
+    borderRadius: "8px",
+    padding: "10px 12px",
+    fontSize: "0.85rem",
+    fontWeight: 700,
+    cursor: "pointer",
+  },
+  textInputBtnPrimaryDisabled: {
+    opacity: 0.45,
+    cursor: "not-allowed",
+  },
+  textInputBtnSecondary: {
+    backgroundColor: "transparent",
+    color: "#bbb",
+    border: "1px solid #2a2a2a",
+    borderRadius: "8px",
+    padding: "10px 12px",
+    fontSize: "0.85rem",
+    fontWeight: 600,
+    cursor: "pointer",
+  },
   textarea: {
     width: "100%",
     padding: "16px",