refactor: extract debounce logic into shared composable

- Create useDebounce composable to avoid code duplication
- Apply debounce to TextSettings margin/padding inputs
- Harmonize debounce delay to 500ms across all components
- Fix input lag when typing values like "30mm"

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/ElementPopup.vue

@@ -274,6 +274,7 @@
 import { ref, computed, watch } from 'vue';
 import { useStylesheetStore } from '../stores/stylesheet';
 import { usePopupPosition } from '../composables/usePopupPosition';
+import { useDebounce } from '../composables/useDebounce';
 import NumberInput from './ui/NumberInput.vue';
 import Coloris from '@melloware/coloris';
 import '@melloware/coloris/dist/coloris.css';
@@ -307,7 +308,7 @@ const colorInput = ref(null);
 const backgroundInput = ref(null);
 
 let isUpdatingFromStore = false;
-let updateTimer = null;
+const { debouncedUpdate } = useDebounce(500);
 
 // Style properties
 const fontFamily = ref({ value: 'Alegreya Sans' });
@@ -320,11 +321,6 @@ const background = ref({ value: 'transparent' });
 const marginOuter = ref({ value: 0, unit: 'mm' });
 const paddingInner = ref({ value: 0, unit: 'mm' });
 
-const debouncedUpdate = (callback) => {
-  clearTimeout(updateTimer);
-  updateTimer = setTimeout(callback, 1000);
-};
-
 const immediateUpdate = (callback) => {
   callback();
 };

src/components/PagePopup.vue

@@ -285,6 +285,7 @@
 import { ref, computed, watch, onMounted } from 'vue';
 import { useStylesheetStore } from '../stores/stylesheet';
 import { usePopupPosition } from '../composables/usePopupPosition';
+import { useDebounce } from '../composables/useDebounce';
 import NumberInput from './ui/NumberInput.vue';
 import Coloris from '@melloware/coloris';
 import '@melloware/coloris/dist/coloris.css';
@@ -312,7 +313,7 @@ const inheritanceLocked = ref(true);
 const backgroundColorInput = ref(null);
 
 let isUpdatingFromStore = false;
-let updateTimer = null;
+const { debouncedUpdate } = useDebounce(500);
 
 const margins = ref({
   top: { value: 0, unit: 'mm' },
@@ -328,11 +329,6 @@ const background = ref({
 
 const pattern = ref('');
 
-const debouncedUpdate = (callback) => {
-  clearTimeout(updateTimer);
-  updateTimer = setTimeout(callback, 1000);
-};
-
 const immediateUpdate = (callback) => {
   callback();
 };

src/components/editor/PageSettings.vue

@@ -288,16 +288,17 @@
 <script setup>
 import { ref, computed, watch, onMounted, inject } from 'vue';
 import { useStylesheetStore } from '../../stores/stylesheet';
+import { useDebounce } from '../../composables/useDebounce';
 import Coloris from '@melloware/coloris';
 import NumberInput from '../ui/NumberInput.vue';
 import '@melloware/coloris/dist/coloris.css';
 
 const stylesheetStore = useStylesheetStore();
+const { debouncedUpdate } = useDebounce(500);
 const backgroundColorInput = ref(null);
 const activeTab = inject('activeTab', ref('document'));
 
 let isUpdatingFromStore = false;
-let updateTimer = null;
 
 const pageFormat = ref('A4');
 
@@ -328,11 +329,6 @@ const pattern = ref('');
 const pageNumbers = ref(false);
 const runningTitle = ref(false);
 
-const debouncedUpdate = (callback) => {
-  clearTimeout(updateTimer);
-  updateTimer = setTimeout(callback, 1000);
-};
-
 const immediateUpdate = (callback) => {
   callback();
 };

src/components/editor/TextSettings.vue

@@ -130,9 +130,11 @@ import InputWithUnit from '../ui/InputWithUnit.vue';
 import MarginEditor from '../ui/MarginEditor.vue';
 import { useCssUpdater } from '../../composables/useCssUpdater';
 import { useCssSync } from '../../composables/useCssSync';
+import { useDebounce } from '../../composables/useDebounce';
 
 const { updateStyle, setMargin, setDetailedMargins, setPadding, setDetailedPadding } = useCssUpdater();
 const { extractValue, extractNumericValue, extractSpacing } = useCssSync();
+const { debouncedUpdate } = useDebounce(500);
 
 // Constants
 const fonts = ['Alegreya Sans', 'Arial', 'Georgia', 'Helvetica', 'Times New Roman'];
@@ -203,26 +205,32 @@ watch(weight, (val) => {
 
 watch(fontSize, (val) => {
   if (isUpdatingFromStore) return;
-  updateStyle('p', 'font-size', `${val.value}${val.unit}`);
+  debouncedUpdate(() => {
+    updateStyle('p', 'font-size', `${val.value}${val.unit}`);
+  });
 }, { deep: true });
 
 // Margin/Padding handlers
 const handleMarginOuterChange = ({ type, simple, detailed }) => {
   if (isUpdatingFromStore) return;
-  if (type === 'simple') {
-    setMargin('p', simple.value, simple.unit);
-  } else {
-    setDetailedMargins('p', detailed.top, detailed.right, detailed.bottom, detailed.left);
-  }
+  debouncedUpdate(() => {
+    if (type === 'simple') {
+      setMargin('p', simple.value, simple.unit);
+    } else {
+      setDetailedMargins('p', detailed.top, detailed.right, detailed.bottom, detailed.left);
+    }
+  });
 };
 
 const handleMarginInnerChange = ({ type, simple, detailed }) => {
   if (isUpdatingFromStore) return;
-  if (type === 'simple') {
-    setPadding('p', simple.value, simple.unit);
-  } else {
-    setDetailedPadding('p', detailed.top, detailed.right, detailed.bottom, detailed.left);
-  }
+  debouncedUpdate(() => {
+    if (type === 'simple') {
+      setPadding('p', simple.value, simple.unit);
+    } else {
+      setDetailedPadding('p', detailed.top, detailed.right, detailed.bottom, detailed.left);
+    }
+  });
 };
 
 // Sync from store

src/composables/useDebounce.js

@@ -0,0 +1,15 @@
+/**
+ * Composable for debounced updates
+ * @param {number} delay - Debounce delay in milliseconds (default: 500ms)
+ * @returns {Function} debouncedUpdate function
+ */
+export function useDebounce(delay = 500) {
+  let timer = null;
+
+  const debouncedUpdate = (callback) => {
+    clearTimeout(timer);
+    timer = setTimeout(callback, delay);
+  };
+
+  return { debouncedUpdate };
+}