Enhance TemplatePreview Component with Scroll and Iframe Resizing Features

- Refactored the TemplatePreview component to improve iframe content size handling and scrolling behavior.
- Introduced a new ScrollBox component to manage scroll position and enhance user experience.
- Implemented a ResizeObserver to dynamically adjust iframe size based on content, ensuring better display of HTML previews.
- Added cleanup logic for the observer to prevent memory leaks during component unmounting.

src/components/Dashboard/common/TemplatePreview.jsx

@@ -1,10 +1,18 @@
-import { useState, useContext, useEffect, useRef, useCallback } from 'react'
+import {
+  useState,
+  useContext,
+  useEffect,
+  useLayoutEffect,
+  useRef,
+  useCallback
+} from 'react'
 import PropTypes from 'prop-types'
 import { Flex, Button, Input, Select } from 'antd'
 import PlusIcon from '../../Icons/PlusIcon.jsx'
 import MinusIcon from '../../Icons/MinusIcon.jsx'
 import InfoCircleIcon from '../../Icons/InfoCircleIcon.jsx'
 import ObjectProperty from '../common/ObjectProperty.jsx'
+import ScrollBox from './ScrollBox.jsx'
 import { ApiServerContext } from '../context/ApiServerContext.jsx'
 
 const noop = () => {}
@@ -20,6 +28,9 @@ const TemplatePreview = ({
   showPreviewSwitch = true
 }) => {
   const iframeRef = useRef(null)
+  const scrollElementRef = useRef(null)
+  const savedScrollRef = useRef({ top: 0, left: 0 })
+  const iframeSizeObserverRef = useRef(null)
   const previewRequestIdRef = useRef(0)
   const { fetchTemplatePreview, fetchTemplatePDF } =
     useContext(ApiServerContext)
@@ -28,23 +39,112 @@ const TemplatePreview = ({
   const [reloadLoading, setReloadLoading] = useState(false)
   const [previewScale, setPreviewScale] = useState(1)
   const [previewType, setPreviewType] = useState('HTML')
+  const [iframeSize, setIframeSize] = useState({
+    width: '100%',
+    height: 'auto'
+  })
+
+  const applyIframeContentSize = useCallback(() => {
+    const iframe = iframeRef.current
+    const doc = iframe?.contentDocument
+    if (!iframe || !doc?.documentElement) {
+      return
+    }
+
+    const documentEl =
+      doc.querySelector('.previewDocument') ||
+      doc.querySelector('.previewWrapper') ||
+      doc.body
+    const container = doc.querySelector('.previewContainer')
+    const wrapper = doc.querySelector('.previewWrapper')
+    const visual = documentEl.getBoundingClientRect()
+    if (visual.width <= 0 && visual.height <= 0) {
+      return
+    }
+
+    if (wrapper) {
+      wrapper.style.width = `${visual.width}px`
+      wrapper.style.height = `${visual.height}px`
+    }
+
+    let padX = 0
+    let padY = 0
+    if (container) {
+      const containerStyle = doc.defaultView.getComputedStyle(container)
+      padX =
+        parseFloat(containerStyle.paddingLeft) +
+        parseFloat(containerStyle.paddingRight)
+      padY =
+        parseFloat(containerStyle.paddingTop) +
+        parseFloat(containerStyle.paddingBottom)
+    }
+
+    const contentWidth = Math.ceil(visual.width + padX)
+    const contentHeight = Math.ceil(visual.height + padY)
+
+    if (!doc.head?.querySelector('style[data-preview-outer-scroll]')) {
+      const styleEl = doc.createElement('style')
+      styleEl.setAttribute('data-preview-outer-scroll', 'true')
+      styleEl.textContent =
+        'html, body { overflow: hidden !important; height: auto !important; }'
+      doc.head?.appendChild(styleEl)
+    }
+
+    setIframeSize((prev) => {
+      const width = `${contentWidth}px`
+      const height = `${contentHeight}px`
+      if (prev.width === width && prev.height === height) {
+        return prev
+      }
+      return { width, height }
+    })
+  }, [])
+
+  const restoreScrollPosition = useCallback(() => {
+    const scrollEl = scrollElementRef.current
+    if (!scrollEl) {
+      return
+    }
+    scrollEl.scrollTo(savedScrollRef.current.left, savedScrollRef.current.top)
+  }, [])
+
+  const handleIframeLoad = useCallback(() => {
+    iframeSizeObserverRef.current?.disconnect()
+    iframeSizeObserverRef.current = null
+
+    if (previewType != 'HTML') {
+      return
+    }
+
+    applyIframeContentSize()
+
+    const doc = iframeRef.current?.contentDocument
+    const observed =
+      doc?.querySelector('.previewDocument') ||
+      doc?.querySelector('.previewContainer') ||
+      doc?.body
+    if (observed && typeof ResizeObserver === 'function') {
+      const observer = new ResizeObserver(() => {
+        applyIframeContentSize()
+      })
+      observer.observe(observed)
+      iframeSizeObserverRef.current = observer
+    }
+  }, [applyIframeContentSize, previewType])
+
+  useLayoutEffect(() => {
+    restoreScrollPosition()
+  }, [iframeSize, restoreScrollPosition])
 
   const updatePreviewContentHTML = (html) => {
-    if (iframeRef.current) {
-      // Save current scroll position
-      const scrollY = iframeRef.current.contentWindow.scrollY
-      const scrollX = iframeRef.current.contentWindow.scrollX
-
-      // Update srcDoc
+    const scrollEl = scrollElementRef.current
+    if (scrollEl) {
+      savedScrollRef.current = {
+        top: scrollEl.scrollTop,
+        left: scrollEl.scrollLeft
+      }
+    }
     setPreviewContentHTML(html)
-
-      // Restore scroll position after iframe loads new content
-      const handleLoad = () => {
-        iframeRef.current.contentWindow.scrollTo(scrollX, scrollY)
-        iframeRef.current.removeEventListener('load', handleLoad)
-      }
-      iframeRef.current.addEventListener('load', handleLoad)
-    }
   }
 
   const reloadPreviewPDF = useCallback(
@@ -84,12 +184,7 @@ const TemplatePreview = ({
 
       const requestId = ++previewRequestIdRef.current
       setReloadLoading(true)
-      fetchTemplatePreview(
-        templateId,
-        content,
-        testObject,
-        scale,
-        (result) => {
+      fetchTemplatePreview(templateId, content, testObject, scale, (result) => {
         if (requestId !== previewRequestIdRef.current) {
           return
         }
@@ -100,8 +195,7 @@ const TemplatePreview = ({
           updatePreviewContentHTML(result.html)
           onPreviewMessage('No issues found.', false)
         }
-        }
-      )
+      })
     },
     [fetchTemplatePreview, onPreviewMessage, documentTemplate?._id]
   )
@@ -136,6 +230,12 @@ const TemplatePreview = ({
     reloadPreviewPDF
   ])
 
+  useEffect(() => {
+    return () => {
+      iframeSizeObserverRef.current?.disconnect()
+    }
+  }, [])
+
   return (
     <Flex vertical gap={'middle'} style={{ height: '100%' }}>
       <Flex gap={'small'}>
@@ -149,6 +249,7 @@ const TemplatePreview = ({
                 objectData={objectData}
                 disabled={!isEditing || objectData?.global}
                 type={'object'}
+                style={{ minWidth: 0 }}
               />
             ) : (
               <div style={{ flexGrow: 1 }}>
@@ -205,18 +306,50 @@ const TemplatePreview = ({
         ) : null}
       </Flex>
 
+      <div
+        style={{
+          flex: '1 1 auto',
+          minHeight: 0,
+          border: '1px solid #85858541'
+        }}
+      >
+        {previewType == 'HTML' ? (
+          <ScrollBox scrollableNodeProps={{ ref: scrollElementRef }}>
+            <div
+              style={{
+                width: iframeSize.width,
+                height: iframeSize.height
+              }}
+            >
               <iframe
                 ref={iframeRef}
-        srcDoc={previewType == 'HTML' ? previewContentHTML : undefined}
-        src={previewType == 'PDF' ? pdfBlob : undefined}
+                srcDoc={previewContentHTML}
+                onLoad={handleIframeLoad}
+                scrolling='no'
                 frameBorder='0'
                 style={{
                   width: '100%',
-          flexGrow: 1,
-          border: '1px solid #85858541',
-          overflow: 'auto'
+                  height: iframeSize.height === 'auto' ? 150 : '100%',
+                  display: 'block',
+                  border: 0,
+                  overflow: 'hidden'
                 }}
               />
+            </div>
+          </ScrollBox>
+        ) : (
+          <iframe
+            ref={iframeRef}
+            src={pdfBlob}
+            frameBorder='0'
+            style={{
+              width: '100%',
+              height: '100%',
+              border: 0
+            }}
+          />
+        )}
+      </div>
     </Flex>
   )
 }