fix: align link hit-test DPR source with canvas in queryLinkSegmentAtPoint

processMouseDown's isPointInStroke fallback uses this.dpr, but
layoutStore.queryLinkSegmentAtPoint was reading raw window.devicePixelRatio.
With the DPR migration in place these two hit-test paths can now disagree
on low-DPR displays, making alt/shift-click link detection depend on which
path wins.

Thread an optional dpr argument through queryLinkSegmentAtPoint /
queryLinkAtPoint and the LayoutStore interface, and pass this.dpr from
processMouseDown so both hit-test paths share the canvas-owned DPR.
Window fallback is preserved for legacy callers without a canvas reference.

Addresses review feedback:
https://github.com/Comfy-Org/ComfyUI_frontend/pull/11498#pullrequestreview-4151044800

src/lib/litegraph/src/LGraphCanvas.ts

@@ -2540,8 +2540,15 @@ export class LGraphCanvas implements CustomEventDispatcher<LGraphCanvasEventMap>
       this.ctx.lineWidth = this.connections_width + 7
       const dpi = this.dpr
 
-      // Try layout store for segment hit testing first (more precise)
-      const hitSegment = layoutStore.queryLinkSegmentAtPoint({ x, y }, this.ctx)
+      // Try layout store for segment hit testing first (more precise).
+      // Pass this.dpr so the layout-store hit-test uses the same DPR as the
+      // isPointInStroke fallback below; otherwise the two paths can disagree
+      // on low-DPR displays (e.g. chromium-0.5x).
+      const hitSegment = layoutStore.queryLinkSegmentAtPoint(
+        { x, y },
+        this.ctx,
+        this.dpr
+      )
 
       for (const linkSegment of this.renderedPaths) {
         const centre = linkSegment._pos

src/renderer/core/layout/store/layoutStore.ts

@@ -661,10 +661,17 @@ class LayoutStoreImpl implements LayoutStore {
 
   /**
    * Query link segment at point (returns structured data)
+   *
+   * @param dpr Device pixel ratio used to map the CSS-space point into the
+   *   canvas's device-pixel-scaled stroke space. Pass the active
+   *   `LGraphCanvas.dpr` so this hit-test agrees with `processMouseDown`'s
+   *   `isPointInStroke` fallback. Falls back to `window.devicePixelRatio`
+   *   for legacy callers without a canvas reference.
    */
   queryLinkSegmentAtPoint(
     point: Point,
-    ctx?: CanvasRenderingContext2D
+    ctx?: CanvasRenderingContext2D,
+    dpr?: number
   ): { linkId: LinkId; rerouteId: RerouteId | null } | null {
     // Determine tolerance from current canvas state (if available)
     // - Use the caller-provided ctx.lineWidth (LGraphCanvas sets this to connections_width + padding)
@@ -695,9 +702,12 @@ class LayoutStoreImpl implements LayoutStore {
       if (!segmentLayout) continue
 
       if (ctx && segmentLayout.path) {
-        // TODO: Migrate to canvas.dpr once layoutStore has access to the active viewport
+        // Prefer the caller-supplied DPR (the active LGraphCanvas.dpr) so
+        // this hit-test stays in lockstep with processMouseDown's fallback
+        // path; fall back to window.devicePixelRatio for legacy callers.
         const dpi =
-          (typeof window !== 'undefined' && window?.devicePixelRatio) || 1
+          dpr ??
+          ((typeof window !== 'undefined' && window?.devicePixelRatio) || 1)
         const hit = ctx.isPointInStroke(
           segmentLayout.path,
           point.x * dpi,
@@ -732,10 +742,11 @@ class LayoutStoreImpl implements LayoutStore {
    */
   queryLinkAtPoint(
     point: Point,
-    ctx?: CanvasRenderingContext2D
+    ctx?: CanvasRenderingContext2D,
+    dpr?: number
   ): LinkId | null {
     // Invoke segment query and return just the linkId
-    const segment = this.queryLinkSegmentAtPoint(point, ctx)
+    const segment = this.queryLinkSegmentAtPoint(point, ctx, dpr)
     return segment ? segment.linkId : null
   }
 

src/renderer/core/layout/types.ts

@@ -274,10 +274,15 @@ export interface LayoutStore {
   queryNodesInBounds(bounds: Bounds): NodeId[]
 
   // Hit testing queries for links, slots, and reroutes
-  queryLinkAtPoint(point: Point, ctx?: CanvasRenderingContext2D): LinkId | null
+  queryLinkAtPoint(
+    point: Point,
+    ctx?: CanvasRenderingContext2D,
+    dpr?: number
+  ): LinkId | null
   queryLinkSegmentAtPoint(
     point: Point,
-    ctx?: CanvasRenderingContext2D
+    ctx?: CanvasRenderingContext2D,
+    dpr?: number
   ): { linkId: LinkId; rerouteId: RerouteId | null } | null
   querySlotAtPoint(point: Point): SlotLayout | null
   queryRerouteAtPoint(point: Point): RerouteLayout | null