From 7ae62ee727142af5696648e21600b12f6dc6c69d Mon Sep 17 00:00:00 2001
From: KenLiu <kenliu.mason@gmail.com>
Date: Wed, 13 May 2026 16:09:37 +0800
Subject: [PATCH] fix: highlight same-net schematic traces on hover

---
 lib/components/SchematicViewer.tsx     | 17 ++++++
 lib/hooks/useTraceNetHoverHighlight.ts | 79 ++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 lib/hooks/useTraceNetHoverHighlight.ts

diff --git a/lib/components/SchematicViewer.tsx b/lib/components/SchematicViewer.tsx
index ab4fd20..dfc96af 100644
--- a/lib/components/SchematicViewer.tsx
+++ b/lib/components/SchematicViewer.tsx
@@ -5,6 +5,7 @@ import {
 import { su } from "@tscircuit/soup-util"
 import { useChangeSchematicComponentLocationsInSvg } from "lib/hooks/useChangeSchematicComponentLocationsInSvg"
 import { useChangeSchematicTracesForMovedComponents } from "lib/hooks/useChangeSchematicTracesForMovedComponents"
+import { useTraceNetHoverHighlight } from "lib/hooks/useTraceNetHoverHighlight"
 import { useSchematicGroupsOverlay } from "lib/hooks/useSchematicGroupsOverlay"
 import { enableDebug } from "lib/utils/debug"
 import { useCallback, useEffect, useMemo, useRef, useState } from "react"
@@ -345,6 +346,11 @@ export const SchematicViewer = ({
     editEvents: editEventsWithUnappliedEditEvents,
   })
 
+  useTraceNetHoverHighlight({
+    svgDivRef,
+    circuitJsonKey,
+  })
+
   // Add group overlays when enabled
   useSchematicGroupsOverlay({
     svgDivRef,
@@ -396,6 +402,17 @@ export const SchematicViewer = ({
 
   return (
     <MouseTracker>
+      <style>
+        {`
+          g.trace.trace-net-hover,
+          g.trace-overlays.trace-net-hover {
+            filter: invert(1);
+          }
+          g.trace-overlays.trace-net-hover .trace-crossing-outline {
+            opacity: 0;
+          }
+        `}
+      </style>
       {onSchematicComponentClicked && (
         <style>
           {`.schematic-component-clickable [data-schematic-component-id]:hover { cursor: pointer !important; }`}
diff --git a/lib/hooks/useTraceNetHoverHighlight.ts b/lib/hooks/useTraceNetHoverHighlight.ts
new file mode 100644
index 0000000..182e289
--- /dev/null
+++ b/lib/hooks/useTraceNetHoverHighlight.ts
@@ -0,0 +1,79 @@
+import { useEffect, useRef } from "react"
+
+const TRACE_NET_HOVER_CLASS = "trace-net-hover"
+
+const escapeAttributeValue = (value: string) =>
+  value.replace(/\\/g, "\\\\").replace(/"/g, '\\"')
+
+export const useTraceNetHoverHighlight = ({
+  svgDivRef,
+  circuitJsonKey,
+}: {
+  svgDivRef: React.RefObject<HTMLDivElement | null>
+  circuitJsonKey: string
+}) => {
+  const activeNetKeyRef = useRef<string | null>(null)
+  const activeElementsRef = useRef<SVGElement[]>([])
+
+  useEffect(() => {
+    const svgDiv = svgDivRef.current
+    if (!svgDiv) return
+
+    const clearHighlight = () => {
+      for (const element of activeElementsRef.current) {
+        element.classList.remove(TRACE_NET_HOVER_CLASS)
+      }
+      activeElementsRef.current = []
+      activeNetKeyRef.current = null
+    }
+
+    const getNetKeyFromTarget = (target: EventTarget | null) => {
+      if (!(target instanceof Element)) return null
+      return (
+        target
+          .closest<SVGElement>('[data-circuit-json-type="schematic_trace"]')
+          ?.getAttribute("data-subcircuit-connectivity-map-key") ?? null
+      )
+    }
+
+    const applyHighlight = (netKey: string) => {
+      if (activeNetKeyRef.current === netKey) return
+
+      clearHighlight()
+      activeNetKeyRef.current = netKey
+
+      const escapedNetKey = escapeAttributeValue(netKey)
+      const selector = `[data-circuit-json-type="schematic_trace"][data-subcircuit-connectivity-map-key="${escapedNetKey}"]`
+      const elements = Array.from(svgDiv.querySelectorAll<SVGElement>(selector))
+      for (const element of elements) {
+        element.classList.add(TRACE_NET_HOVER_CLASS)
+      }
+      activeElementsRef.current = elements
+    }
+
+    const handleMouseOver = (event: MouseEvent) => {
+      const netKey = getNetKeyFromTarget(event.target)
+      if (!netKey) return
+      applyHighlight(netKey)
+    }
+
+    const handleMouseOut = (event: MouseEvent) => {
+      const currentNetKey = getNetKeyFromTarget(event.target)
+      if (!currentNetKey) return
+
+      const nextNetKey = getNetKeyFromTarget(event.relatedTarget)
+      if (nextNetKey === currentNetKey) return
+
+      clearHighlight()
+    }
+
+    svgDiv.addEventListener("mouseover", handleMouseOver)
+    svgDiv.addEventListener("mouseout", handleMouseOut)
+
+    return () => {
+      svgDiv.removeEventListener("mouseover", handleMouseOver)
+      svgDiv.removeEventListener("mouseout", handleMouseOut)
+      clearHighlight()
+    }
+  }, [svgDivRef, circuitJsonKey])
+}