From 289017bcb28c049c8258b2ffd7da0ec3e6ef120b Mon Sep 17 00:00:00 2001
From: Ruben Fiszel <ruben@windmill.dev>
Date: Wed, 1 Jul 2026 14:05:30 +0200
Subject: [PATCH] feat(frontend): add zoom and download to Mermaid graphs
 (#9859)

* feat(frontend): add zoom and download to Mermaid graphs

Mermaid diagrams in the AI chat could only be viewed inline with
horizontal scroll. Add a download-as-SVG button and an expand button
that opens a fullscreen modal with pan/drag and zoom (mouse wheel plus
in/out/reset controls), reusing the existing `panzoom` dependency.

Fixes WIN-2117

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(frontend): guard panzoom action against close-before-import race

Address review nit: if the modal closes before the dynamic
import('panzoom') resolves, destroy() ran while instance was still
undefined (disposing nothing) and the late .then() built a leaked
panzoom on a detached node. A disposed flag makes the cleanup airtight.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 .../copilot/chat/script/MermaidDisplay.svelte | 147 ++++++++++++++++--
 1 file changed, 134 insertions(+), 13 deletions(-)

diff --git a/frontend/src/lib/components/copilot/chat/script/MermaidDisplay.svelte b/frontend/src/lib/components/copilot/chat/script/MermaidDisplay.svelte
index 4adf86e76d..dda1892baa 100644
--- a/frontend/src/lib/components/copilot/chat/script/MermaidDisplay.svelte
+++ b/frontend/src/lib/components/copilot/chat/script/MermaidDisplay.svelte
@@ -2,8 +2,10 @@
 	import { randomUUID } from '$lib/utils/uuid'
 	import { useIsDarkMode } from '$lib/components/DarkModeObserver.svelte'
 	import { Button } from '$lib/components/common'
-	import { copyToClipboard } from '$lib/utils'
-	import { ClipboardCopy } from 'lucide-svelte'
+	import Modal from '$lib/components/common/modal/Modal.svelte'
+	import { copyToClipboard, download } from '$lib/utils'
+	import { ClipboardCopy, Download, Maximize2, Minus, Plus, RotateCcw } from 'lucide-svelte'
+	import type { PanZoom } from 'panzoom'
 
 	let { code }: { code: string } = $props()
 
@@ -18,6 +20,8 @@
 	// overwrite the result of a newer one (out-of-order async on rapid code/theme changes).
 	let renderSeq = 0
 
+	let expanded = $state(false)
+
 	async function render(source: string, dark: boolean) {
 		const seq = ++renderSeq
 		if (!source?.trim()) {
@@ -52,26 +56,143 @@
 
 	// Only show the diagram while it corresponds to the current source.
 	let showSvg = $derived(svg !== undefined && renderedCode === code)
+
+	function downloadSvg() {
+		if (svg) {
+			download('mermaid.svg', svg, 'image/svg+xml')
+		}
+	}
+
+	// Pan/zoom is only wired up inside the fullscreen modal so the inline preview
+	// stays a plain, non-interactive thumbnail.
+	let panzoomInstance = $state<PanZoom | undefined>(undefined)
+	let panzoomNode: HTMLElement | undefined = undefined
+
+	function panzoomAction(node: HTMLElement) {
+		let instance: PanZoom | undefined
+		// Guard the async import against a close-before-resolve: without it,
+		// destroy() (instance still undefined) disposes nothing and the late
+		// .then() would build a leaked panzoom on an already-detached node.
+		let disposed = false
+		panzoomNode = node
+		import('panzoom').then(({ default: panzoom }) => {
+			if (disposed) return
+			instance = panzoom(node, {
+				bounds: true,
+				boundsPadding: 0.1,
+				maxZoom: 8,
+				minZoom: 0.2,
+				zoomDoubleClickSpeed: 1,
+				smoothScroll: false
+			})
+			panzoomInstance = instance
+		})
+		return {
+			destroy() {
+				disposed = true
+				instance?.dispose()
+				panzoomInstance = undefined
+				panzoomNode = undefined
+			}
+		}
+	}
+
+	function zoomBy(ratio: number) {
+		if (!panzoomInstance || !panzoomNode) return
+		// smoothZoom anchors on client coordinates — zoom around the viewport center.
+		const rect = panzoomNode.getBoundingClientRect()
+		panzoomInstance.smoothZoom(rect.left + rect.width / 2, rect.top + rect.height / 2, ratio)
+	}
+
+	function resetZoom() {
+		if (!panzoomInstance) return
+		panzoomInstance.moveTo(0, 0)
+		panzoomInstance.zoomAbs(0, 0, 1)
+	}
 </script>
 
 {#if showSvg}
 	<div class="relative">
-		<Button
-			wrapperClasses="absolute top-2 right-2 z-20"
-			onclick={() => copyToClipboard(code)}
-			color="light"
-			size="xs2"
-			startIcon={{
-				icon: ClipboardCopy
-			}}
-			iconOnly
-			title="Copy to clipboard"
-		/>
+		<div class="absolute top-2 right-2 z-20 flex flex-row gap-1">
+			<Button
+				onclick={() => copyToClipboard(code)}
+				color="light"
+				size="xs2"
+				startIcon={{ icon: ClipboardCopy }}
+				iconOnly
+				title="Copy diagram source"
+			/>
+			<Button
+				onclick={downloadSvg}
+				color="light"
+				size="xs2"
+				startIcon={{ icon: Download }}
+				iconOnly
+				title="Download as SVG"
+			/>
+			<Button
+				onclick={() => (expanded = true)}
+				color="light"
+				size="xs2"
+				startIcon={{ icon: Maximize2 }}
+				iconOnly
+				title="Expand and zoom"
+			/>
+		</div>
 		<div class="p-2 flex justify-center overflow-x-auto">
 			<!-- eslint-disable-next-line svelte/no-at-html-tags -->
 			{@html svg}
 		</div>
 	</div>
+
+	<Modal bind:open={expanded} title="Diagram" kind="X" class="sm:max-w-none w-[92vw]">
+		{#snippet settings()}
+			<div class="flex flex-row gap-1 mr-8">
+				<Button
+					onclick={() => zoomBy(1 / 1.3)}
+					color="light"
+					size="xs2"
+					startIcon={{ icon: Minus }}
+					iconOnly
+					title="Zoom out"
+				/>
+				<Button
+					onclick={() => zoomBy(1.3)}
+					color="light"
+					size="xs2"
+					startIcon={{ icon: Plus }}
+					iconOnly
+					title="Zoom in"
+				/>
+				<Button
+					onclick={resetZoom}
+					color="light"
+					size="xs2"
+					startIcon={{ icon: RotateCcw }}
+					iconOnly
+					title="Reset zoom"
+				/>
+				<Button
+					onclick={downloadSvg}
+					color="light"
+					size="xs2"
+					startIcon={{ icon: Download }}
+					iconOnly
+					title="Download as SVG"
+				/>
+			</div>
+		{/snippet}
+		<div
+			class="relative w-full h-[78vh] overflow-hidden rounded border cursor-grab bg-surface-secondary"
+		>
+			{#if expanded}
+				<div use:panzoomAction class="w-full h-full flex items-center justify-center">
+					<!-- eslint-disable-next-line svelte/no-at-html-tags -->
+					{@html svg}
+				</div>
+			{/if}
+		</div>
+	</Modal>
 {:else}
 	<!-- Fallback while loading or when rendering fails: show the raw source -->
 	<pre class="overflow-auto max-h-screen text-xs p-2">{code}</pre>