From df5e4d0614afc8c857717d59a2e565119e00e4fb Mon Sep 17 00:00:00 2001
From: KAYEB <KAYEB@users.noreply.github.com>
Date: Wed, 20 May 2026 11:08:26 -0700
Subject: [PATCH] Highlight connected schematic traces on hover

---
 lib/components/SchematicViewer.tsx            |  10 ++
 .../useHighlightConnectedTracesOnHover.ts     | 111 ++++++++++++++++++
 2 files changed, 121 insertions(+)
 create mode 100644 lib/hooks/useHighlightConnectedTracesOnHover.ts

diff --git a/lib/components/SchematicViewer.tsx b/lib/components/SchematicViewer.tsx
index ab4fd20..9a4822c 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 { useHighlightConnectedTracesOnHover } from "lib/hooks/useHighlightConnectedTracesOnHover"
 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,
   })
 
+  useHighlightConnectedTracesOnHover({
+    svgDivRef,
+    circuitJson,
+  })
+
   // Add group overlays when enabled
   useSchematicGroupsOverlay({
     svgDivRef,
@@ -396,6 +402,10 @@ export const SchematicViewer = ({
 
   return (
     <MouseTracker>
+      <style>
+        {`[data-circuit-json-type="schematic_trace"].same-net-trace-hover { filter: invert(1); }
+[data-circuit-json-type="schematic_trace"].same-net-trace-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/useHighlightConnectedTracesOnHover.ts b/lib/hooks/useHighlightConnectedTracesOnHover.ts
new file mode 100644
index 0000000..d1bc765
--- /dev/null
+++ b/lib/hooks/useHighlightConnectedTracesOnHover.ts
@@ -0,0 +1,111 @@
+import { useEffect } from "react"
+import { su } from "@tscircuit/soup-util"
+import type { CircuitJson } from "circuit-json"
+
+const HOVER_CLASS = "same-net-trace-hover"
+
+export const useHighlightConnectedTracesOnHover = ({
+  svgDivRef,
+  circuitJson,
+}: {
+  svgDivRef: React.RefObject<HTMLDivElement | null>
+  circuitJson: CircuitJson
+}) => {
+  useEffect(() => {
+    const svg = svgDivRef.current
+    if (!svg) return
+
+    let hoveredTraceGroupKey: string | null = null
+    const traceGroupKeyBySchematicTraceId = new Map<string, string>()
+
+    try {
+      const sourceTraceById = new Map<string, any>()
+      for (const trace of su(circuitJson).source_trace.list()) {
+        sourceTraceById.set(trace.source_trace_id, trace)
+      }
+
+      for (const trace of su(circuitJson).schematic_trace.list()) {
+        if (!trace.schematic_trace_id || !trace.source_trace_id) continue
+        const sourceTrace = sourceTraceById.get(trace.source_trace_id)
+        const sourceNetIds = [...(sourceTrace?.connected_source_net_ids ?? [])]
+          .filter(Boolean)
+          .sort()
+        const traceGroupKey =
+          sourceNetIds.length > 0
+            ? `source_net:${sourceNetIds.join("|")}`
+            : `source_trace:${trace.source_trace_id}`
+
+        traceGroupKeyBySchematicTraceId.set(
+          trace.schematic_trace_id,
+          traceGroupKey,
+        )
+      }
+    } catch (err) {
+      console.error("Failed to derive schematic trace ids", err)
+      return
+    }
+
+    const traceGroups = () =>
+      svg.querySelectorAll<SVGElement>(
+        '[data-circuit-json-type="schematic_trace"][data-schematic-trace-id]',
+      )
+
+    const clearHoverClasses = () => {
+      for (const traceGroup of Array.from(traceGroups())) {
+        traceGroup.classList.remove(HOVER_CLASS)
+      }
+    }
+
+    const setHoveredTraceGroupKey = (traceGroupKey: string | null) => {
+      if (traceGroupKey === hoveredTraceGroupKey) return
+      hoveredTraceGroupKey = traceGroupKey
+      clearHoverClasses()
+
+      if (!traceGroupKey) return
+
+      for (const traceGroup of Array.from(traceGroups())) {
+        const schematicTraceId = traceGroup.getAttribute(
+          "data-schematic-trace-id",
+        )
+        if (
+          schematicTraceId &&
+          traceGroupKeyBySchematicTraceId.get(schematicTraceId) ===
+            traceGroupKey
+        ) {
+          traceGroup.classList.add(HOVER_CLASS)
+        }
+      }
+    }
+
+    const handlePointerMove = (event: PointerEvent) => {
+      const target = event.target
+      if (!(target instanceof Element)) {
+        setHoveredTraceGroupKey(null)
+        return
+      }
+
+      const traceGroup = target.closest<SVGElement>(
+        '[data-circuit-json-type="schematic_trace"][data-schematic-trace-id]',
+      )
+      const schematicTraceId = traceGroup?.getAttribute(
+        "data-schematic-trace-id",
+      )
+      const traceGroupKey = schematicTraceId
+        ? (traceGroupKeyBySchematicTraceId.get(schematicTraceId) ?? null)
+        : null
+
+      setHoveredTraceGroupKey(traceGroupKey)
+    }
+
+    const handlePointerLeave = () => setHoveredTraceGroupKey(null)
+
+    svg.addEventListener("pointermove", handlePointerMove)
+    svg.addEventListener("pointerleave", handlePointerLeave)
+
+    return () => {
+      svg.removeEventListener("pointermove", handlePointerMove)
+      svg.removeEventListener("pointerleave", handlePointerLeave)
+      clearHoverClasses()
+    }
+  }, [svgDivRef, circuitJson])
+}