From ded941b7b92e1266084dbaec01facb465768a905 Mon Sep 17 00:00:00 2001
From: one <wangan.cs@gmail.com>
Date: Sun, 17 Aug 2025 13:22:59 +0800
Subject: [PATCH] refactor(Mermaid): render mermaid in shadow dom (#9187)

* refactor(Mermaid): render mermaid in shadow dom

* refactor: pass style overrides to renderSvgInShadowHost

* refactor(MermaidPreview): separate measurement from rendering

* refactor: rename hostCss to customCss

* refactor: use custom properties in shadow host

* test: update snapshots

* fix: remove svg max-width

* refactor: add viewBox to svg (experimental)

* Revert "refactor: add viewBox to svg (experimental)"

This reverts commit 8a265fa8a48d34b098fc050c516686ae5029a4e9.
---
 .../components/Preview/GraphvizPreview.tsx    | 17 +++---
 .../src/components/Preview/MermaidPreview.tsx | 53 ++++++++++++-------
 .../components/Preview/PlantUmlPreview.tsx    |  3 +-
 .../src/components/Preview/SvgPreview.tsx     |  3 +-
 .../GraphvizPreview.test.tsx.snap             |  7 ++-
 .../MermaidPreview.test.tsx.snap              |  7 ++-
 .../PlantUmlPreview.test.tsx.snap             |  8 ++-
 .../__snapshots__/SvgPreview.test.tsx.snap    |  8 ++-
 src/renderer/src/components/Preview/styles.ts | 12 +++++
 src/renderer/src/components/Preview/utils.ts  | 10 ++--
 10 files changed, 84 insertions(+), 44 deletions(-)

diff --git a/src/renderer/src/components/Preview/GraphvizPreview.tsx b/src/renderer/src/components/Preview/GraphvizPreview.tsx
index c3c5c641a2..578a35450b 100644
--- a/src/renderer/src/components/Preview/GraphvizPreview.tsx
+++ b/src/renderer/src/components/Preview/GraphvizPreview.tsx
@@ -1,9 +1,9 @@
 import { AsyncInitializer } from '@renderer/utils/asyncInitializer'
 import React, { memo, useCallback } from 'react'
-import styled from 'styled-components'
 
 import { useDebouncedRender } from './hooks/useDebouncedRender'
 import ImagePreviewLayout from './ImagePreviewLayout'
+import { ShadowWhiteContainer } from './styles'
 import { BasicPreviewHandles, BasicPreviewProps } from './types'
 import { renderSvgInShadowHost } from './utils'
 
@@ -13,8 +13,10 @@ const vizInitializer = new AsyncInitializer(async () => {
   return await module.instance()
 })
 
-/** 预览 Graphviz 图表
- * 使用 usePreviewRenderer hook 大幅简化组件逻辑
+/**
+ * 预览 Graphviz 图表
+ * - 使用 useDebouncedRender 改善体验
+ * - 使用 shadow dom 渲染 SVG
  */
 const GraphvizPreview = ({
   children,
@@ -41,16 +43,9 @@ const GraphvizPreview = ({
       ref={ref}
       imageRef={containerRef}
       source="graphviz">
-      <StyledGraphviz ref={containerRef} className="graphviz special-preview" />
+      <ShadowWhiteContainer ref={containerRef} className="graphviz special-preview" />
     </ImagePreviewLayout>
   )
 }
 
-const StyledGraphviz = styled.div`
-  overflow: auto;
-  position: relative;
-  width: 100%;
-  height: 100%;
-`
-
 export default memo(GraphvizPreview)
diff --git a/src/renderer/src/components/Preview/MermaidPreview.tsx b/src/renderer/src/components/Preview/MermaidPreview.tsx
index b4bd1b148e..86e0339c2f 100644
--- a/src/renderer/src/components/Preview/MermaidPreview.tsx
+++ b/src/renderer/src/components/Preview/MermaidPreview.tsx
@@ -1,15 +1,17 @@
 import { nanoid } from '@reduxjs/toolkit'
 import { useMermaid } from '@renderer/hooks/useMermaid'
 import React, { memo, useCallback, useEffect, useRef, useState } from 'react'
-import styled from 'styled-components'
 
 import { useDebouncedRender } from './hooks/useDebouncedRender'
 import ImagePreviewLayout from './ImagePreviewLayout'
+import { ShadowTransparentContainer } from './styles'
 import { BasicPreviewHandles, BasicPreviewProps } from './types'
+import { renderSvgInShadowHost } from './utils'
 
-/** 预览 Mermaid 图表
- * 使用 usePreviewRenderer hook 重构，同时保留必要的可见性检测逻辑
- * FIXME: 等将来 mermaid-js 修复可见性问题后可以进一步简化
+/**
+ * 预览 Mermaid 图表
+ * - 使用 useDebouncedRender 改善体验
+ * - 使用 shadow dom 渲染 SVG
  */
 const MermaidPreview = ({
   children,
@@ -20,17 +22,39 @@ const MermaidPreview = ({
   const diagramId = useRef<string>(`mermaid-${nanoid(6)}`).current
   const [isVisible, setIsVisible] = useState(true)
 
-  // 定义渲染函数
+  /**
+   * 定义渲染函数，在临时容器中测量，在 shadow dom 中渲染。
+   * 如果这个方案有问题，可以回退到 innerHTML。
+   */
   const renderMermaid = useCallback(
     async (content: string, container: HTMLDivElement) => {
       // 验证语法，提前抛出异常
       await mermaid.parse(content)
 
-      const { svg } = await mermaid.render(diagramId, content, container)
+      // 获取容器宽度
+      const { width } = container.getBoundingClientRect()
+      if (width === 0) return
 
-      // 避免不可见时产生 undefined 和 NaN
-      const fixedSvg = svg.replace(/translate\(undefined,\s*NaN\)/g, 'translate(0, 0)')
-      container.innerHTML = fixedSvg
+      // 创建临时的 div 用于 mermaid 测量
+      const measureEl = document.createElement('div')
+      measureEl.style.position = 'absolute'
+      measureEl.style.left = '-9999px'
+      measureEl.style.top = '-9999px'
+      measureEl.style.width = `${width}px`
+      document.body.appendChild(measureEl)
+
+      try {
+        const { svg } = await mermaid.render(diagramId, content, measureEl)
+
+        // 避免不可见时产生 undefined 和 NaN
+        const fixedSvg = svg.replace(/translate\(undefined,\s*NaN\)/g, 'translate(0, 0)')
+
+        // 有问题可以回退到 innerHTML
+        renderSvgInShadowHost(fixedSvg, container)
+        // container.innerHTML = fixedSvg
+      } finally {
+        document.body.removeChild(measureEl)
+      }
     },
     [diagramId, mermaid]
   )
@@ -63,7 +87,7 @@ const MermaidPreview = ({
       const element = containerRef.current
       if (!element) return
 
-      const currentlyVisible = element.offsetParent !== null
+      const currentlyVisible = element.offsetParent !== null && element.offsetWidth > 0 && element.offsetHeight > 0
       setIsVisible(currentlyVisible)
     }
 
@@ -105,16 +129,9 @@ const MermaidPreview = ({
       ref={ref}
       imageRef={containerRef}
       source="mermaid">
-      <StyledMermaid ref={containerRef} className="mermaid special-preview" />
+      <ShadowTransparentContainer ref={containerRef} className="mermaid special-preview" />
     </ImagePreviewLayout>
   )
 }
 
-const StyledMermaid = styled.div`
-  overflow: auto;
-  position: relative;
-  width: 100%;
-  height: 100%;
-`
-
 export default memo(MermaidPreview)
diff --git a/src/renderer/src/components/Preview/PlantUmlPreview.tsx b/src/renderer/src/components/Preview/PlantUmlPreview.tsx
index b94b87e187..f29a0c1ffc 100644
--- a/src/renderer/src/components/Preview/PlantUmlPreview.tsx
+++ b/src/renderer/src/components/Preview/PlantUmlPreview.tsx
@@ -4,6 +4,7 @@ import React, { memo, useCallback, useEffect } from 'react'
 
 import { useDebouncedRender } from './hooks/useDebouncedRender'
 import ImagePreviewLayout from './ImagePreviewLayout'
+import { ShadowWhiteContainer } from './styles'
 import { BasicPreviewHandles, BasicPreviewProps } from './types'
 import { renderSvgInShadowHost } from './utils'
 
@@ -128,7 +129,7 @@ const PlantUmlPreview = ({
       ref={ref}
       imageRef={containerRef}
       source="plantuml">
-      <div ref={containerRef} className="plantuml-preview special-preview" />
+      <ShadowWhiteContainer ref={containerRef} className="plantuml-preview special-preview" />
     </ImagePreviewLayout>
   )
 }
diff --git a/src/renderer/src/components/Preview/SvgPreview.tsx b/src/renderer/src/components/Preview/SvgPreview.tsx
index d9a4689fcd..2122ebe091 100644
--- a/src/renderer/src/components/Preview/SvgPreview.tsx
+++ b/src/renderer/src/components/Preview/SvgPreview.tsx
@@ -2,6 +2,7 @@ import { memo, useCallback } from 'react'
 
 import { useDebouncedRender } from './hooks/useDebouncedRender'
 import ImagePreviewLayout from './ImagePreviewLayout'
+import { ShadowWhiteContainer } from './styles'
 import { BasicPreviewHandles } from './types'
 import { renderSvgInShadowHost } from './utils'
 
@@ -34,7 +35,7 @@ const SvgPreview = ({ children, enableToolbar = false, className, ref }: SvgPrev
       ref={ref}
       imageRef={containerRef}
       source="svg">
-      <div ref={containerRef} className={className ?? 'svg-preview special-preview'}></div>
+      <ShadowWhiteContainer ref={containerRef} className={className ?? 'svg-preview special-preview'} />
     </ImagePreviewLayout>
   )
 }
diff --git a/src/renderer/src/components/Preview/__tests__/__snapshots__/GraphvizPreview.test.tsx.snap b/src/renderer/src/components/Preview/__tests__/__snapshots__/GraphvizPreview.test.tsx.snap
index 923f35b9e7..5ac34bfadd 100644
--- a/src/renderer/src/components/Preview/__tests__/__snapshots__/GraphvizPreview.test.tsx.snap
+++ b/src/renderer/src/components/Preview/__tests__/__snapshots__/GraphvizPreview.test.tsx.snap
@@ -2,10 +2,9 @@
 
 exports[`GraphvizPreview > basic rendering > should match snapshot 1`] = `
 .c0 {
-  overflow: auto;
-  position: relative;
-  width: 100%;
-  height: 100%;
+  --shadow-host-background-color: white;
+  --shadow-host-border: 0.5px solid var(--color-code-background);
+  --shadow-host-border-radius: 8px;
 }
 
 <div>
diff --git a/src/renderer/src/components/Preview/__tests__/__snapshots__/MermaidPreview.test.tsx.snap b/src/renderer/src/components/Preview/__tests__/__snapshots__/MermaidPreview.test.tsx.snap
index 01e98a63cd..1f87a151a8 100644
--- a/src/renderer/src/components/Preview/__tests__/__snapshots__/MermaidPreview.test.tsx.snap
+++ b/src/renderer/src/components/Preview/__tests__/__snapshots__/MermaidPreview.test.tsx.snap
@@ -2,10 +2,9 @@
 
 exports[`MermaidPreview > basic rendering > should match snapshot 1`] = `
 .c0 {
-  overflow: auto;
-  position: relative;
-  width: 100%;
-  height: 100%;
+  --shadow-host-background-color: transparent;
+  --shadow-host-border: unset;
+  --shadow-host-border-radius: unset;
 }
 
 <div>
diff --git a/src/renderer/src/components/Preview/__tests__/__snapshots__/PlantUmlPreview.test.tsx.snap b/src/renderer/src/components/Preview/__tests__/__snapshots__/PlantUmlPreview.test.tsx.snap
index 34d7840cb4..eb398f4cf5 100644
--- a/src/renderer/src/components/Preview/__tests__/__snapshots__/PlantUmlPreview.test.tsx.snap
+++ b/src/renderer/src/components/Preview/__tests__/__snapshots__/PlantUmlPreview.test.tsx.snap
@@ -1,6 +1,12 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
 exports[`PlantUmlPreview > basic rendering > should match snapshot 1`] = `
+.c0 {
+  --shadow-host-background-color: white;
+  --shadow-host-border: 0.5px solid var(--color-code-background);
+  --shadow-host-border-radius: 8px;
+}
+
 <div>
   <div
     data-source="plantuml"
@@ -15,7 +21,7 @@ exports[`PlantUmlPreview > basic rendering > should match snapshot 1`] = `
       data-testid="preview-content"
     >
       <div
-        class="plantuml-preview special-preview"
+        class="c0 plantuml-preview special-preview"
       />
     </div>
   </div>
diff --git a/src/renderer/src/components/Preview/__tests__/__snapshots__/SvgPreview.test.tsx.snap b/src/renderer/src/components/Preview/__tests__/__snapshots__/SvgPreview.test.tsx.snap
index 00ee51b0e6..b96c8def5d 100644
--- a/src/renderer/src/components/Preview/__tests__/__snapshots__/SvgPreview.test.tsx.snap
+++ b/src/renderer/src/components/Preview/__tests__/__snapshots__/SvgPreview.test.tsx.snap
@@ -1,6 +1,12 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
 exports[`SvgPreview > basic rendering > should match snapshot 1`] = `
+.c0 {
+  --shadow-host-background-color: white;
+  --shadow-host-border: 0.5px solid var(--color-code-background);
+  --shadow-host-border-radius: 8px;
+}
+
 <div>
   <div
     data-source="svg"
@@ -15,7 +21,7 @@ exports[`SvgPreview > basic rendering > should match snapshot 1`] = `
       data-testid="preview-content"
     >
       <div
-        class="svg-preview special-preview"
+        class="c0 svg-preview special-preview"
       />
     </div>
   </div>
diff --git a/src/renderer/src/components/Preview/styles.ts b/src/renderer/src/components/Preview/styles.ts
index aa8718b34e..521b96e225 100644
--- a/src/renderer/src/components/Preview/styles.ts
+++ b/src/renderer/src/components/Preview/styles.ts
@@ -33,3 +33,15 @@ export const PreviewContainer = styled(Flex).attrs({ role: 'alert' })`
     }
   }
 `
+
+export const ShadowWhiteContainer = styled.div`
+  --shadow-host-background-color: white;
+  --shadow-host-border: 0.5px solid var(--color-code-background);
+  --shadow-host-border-radius: 8px;
+`
+
+export const ShadowTransparentContainer = styled.div`
+  --shadow-host-background-color: transparent;
+  --shadow-host-border: unset;
+  --shadow-host-border-radius: unset;
+`
diff --git a/src/renderer/src/components/Preview/utils.ts b/src/renderer/src/components/Preview/utils.ts
index e400062911..476a3b913a 100644
--- a/src/renderer/src/components/Preview/utils.ts
+++ b/src/renderer/src/components/Preview/utils.ts
@@ -28,11 +28,15 @@ export function renderSvgInShadowHost(svgContent: string, hostElement: HTMLEleme
   const style = document.createElement('style')
   style.textContent = `
     :host {
+      --shadow-host-background-color: white;
+      --shadow-host-border: 0.5px solid var(--color-code-background);
+      --shadow-host-border-radius: 8px;
+
+      background-color: var(--shadow-host-background-color);
+      border: var(--shadow-host-border);
+      border-radius: var(--shadow-host-border-radius);
       padding: 1em;
-      background-color: white;
       overflow: hidden; /* Prevent scrollbars, as scaling is now handled */
-      border: 0.5px solid var(--color-code-background);
-      border-radius: 8px;
       display: block;
       position: relative;
       width: 100%;