fix mmb navigation when click starts on Vue nodes (#5921)

## Summary

Fixes https://github.com/Comfy-Org/ComfyUI_frontend/issues/5860
by updating Vue node pointer interactions to forward middle mouse button
events to canvas instead of handling them locally.

## Review Focus

Middle mouse button event detection logic using both `button` property
and `buttons` bitmask for cross-browser compatibility. Test coverage for
pointer event forwarding behavior.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5921-fix-mmb-navigation-when-click-starts-on-Vue-nodes-2826d73d3650819688eec4600666755d)
by [Unito](https://www.unito.io)

---------

Co-authored-by: DrJKL <DrJKL@users.noreply.github.com>

knip.config.ts

@@ -23,7 +23,7 @@ const config: KnipConfig = {
       project: ['src/**/*.{js,ts}']
     }
   },
-  ignoreBinaries: ['python3'],
+  ignoreBinaries: ['python3', 'stylelint'],
   ignoreDependencies: [
     // Weird importmap things
     '@iconify/json',
@@ -32,7 +32,8 @@ const config: KnipConfig = {
     '@primeuix/utils',
     '@primevue/icons',
     // Dev
-    '@trivago/prettier-plugin-sort-imports'
+    '@trivago/prettier-plugin-sort-imports',
+    'stylelint'
   ],
   ignore: [
     // Auto generated manager types

src/base/pointerUtils.ts

@@ -0,0 +1,22 @@
+/**
+ * Utilities for pointer event handling
+ */
+
+/**
+ * Checks if a pointer or mouse event is a middle button input
+ * @param event - The pointer or mouse event to check
+ * @returns true if the event is from the middle button/wheel
+ */
+export function isMiddlePointerInput(
+  event: PointerEvent | MouseEvent
+): boolean {
+  if ('button' in event && event.button === 1) {
+    return true
+  }
+
+  if ('buttons' in event && typeof event.buttons === 'number') {
+    return event.buttons === 4
+  }
+
+  return false
+}

src/renderer/core/canvas/useCanvasInteractions.ts

@@ -1,5 +1,6 @@
 import { computed } from 'vue'
 
+import { isMiddlePointerInput } from '@/base/pointerUtils'
 import { useSettingStore } from '@/platform/settings/settingStore'
 import { useCanvasStore } from '@/renderer/core/canvas/canvasStore'
 import { app } from '@/scripts/app'
@@ -59,6 +60,11 @@ export function useCanvasInteractions() {
    * be forwarded to canvas (e.g., space+drag for panning)
    */
   const handlePointer = (event: PointerEvent) => {
+    if (isMiddlePointerInput(event)) {
+      forwardEventToCanvas(event)
+      return
+    }
+
     // Check if canvas exists using established pattern
     const canvas = getCanvas()
     if (!canvas) return

src/renderer/extensions/vueNodes/composables/useNodePointerInteractions.test.ts

@@ -4,10 +4,12 @@ import { nextTick, ref } from 'vue'
 import type { VueNodeData } from '@/composables/graph/useGraphNodeManager'
 import { useNodePointerInteractions } from '@/renderer/extensions/vueNodes/composables/useNodePointerInteractions'
 
+const forwardEventToCanvasMock = vi.fn()
+
 // Mock the dependencies
 vi.mock('@/renderer/core/canvas/useCanvasInteractions', () => ({
   useCanvasInteractions: () => ({
-    forwardEventToCanvas: vi.fn(),
+    forwardEventToCanvas: forwardEventToCanvasMock,
     shouldHandleNodePointerEvents: ref(true)
   })
 }))
@@ -69,6 +71,7 @@ const createMouseEvent = (
 describe('useNodePointerInteractions', () => {
   beforeEach(() => {
     vi.clearAllMocks()
+    forwardEventToCanvasMock.mockClear()
   })
 
   it('should only start drag on left-click', async () => {
@@ -100,6 +103,34 @@ describe('useNodePointerInteractions', () => {
     )
   })
 
+  it('forwards middle mouse interactions to the canvas', () => {
+    const mockNodeData = createMockVueNodeData()
+    const mockOnPointerUp = vi.fn()
+
+    const { pointerHandlers } = useNodePointerInteractions(
+      ref(mockNodeData),
+      mockOnPointerUp
+    )
+
+    const middlePointerDown = createPointerEvent('pointerdown', { button: 1 })
+    pointerHandlers.onPointerdown(middlePointerDown)
+    expect(forwardEventToCanvasMock).toHaveBeenCalledWith(middlePointerDown)
+
+    forwardEventToCanvasMock.mockClear()
+
+    const middlePointerMove = createPointerEvent('pointermove', { buttons: 4 })
+    pointerHandlers.onPointermove(middlePointerMove)
+    expect(forwardEventToCanvasMock).toHaveBeenCalledWith(middlePointerMove)
+
+    forwardEventToCanvasMock.mockClear()
+
+    const middlePointerUp = createPointerEvent('pointerup', { button: 1 })
+    pointerHandlers.onPointerup(middlePointerUp)
+    expect(forwardEventToCanvasMock).toHaveBeenCalledWith(middlePointerUp)
+
+    expect(mockOnPointerUp).not.toHaveBeenCalled()
+  })
+
   it('should distinguish drag from click based on distance threshold', async () => {
     const mockNodeData = createMockVueNodeData()
     const mockOnPointerUp = vi.fn()

src/renderer/extensions/vueNodes/composables/useNodePointerInteractions.ts

@@ -1,5 +1,6 @@
 import { type MaybeRefOrGetter, computed, onUnmounted, ref, toValue } from 'vue'
 
+import { isMiddlePointerInput } from '@/base/pointerUtils'
 import type { VueNodeData } from '@/composables/graph/useGraphNodeManager'
 import { useCanvasInteractions } from '@/renderer/core/canvas/useCanvasInteractions'
 import { layoutStore } from '@/renderer/core/layout/store/layoutStore'
@@ -34,6 +35,12 @@ export function useNodePointerInteractions(
   const { forwardEventToCanvas, shouldHandleNodePointerEvents } =
     useCanvasInteractions()
 
+  const forwardMiddlePointerIfNeeded = (event: PointerEvent) => {
+    if (!isMiddlePointerInput(event)) return false
+    forwardEventToCanvas(event)
+    return true
+  }
+
   // Drag state for styling
   const isDragging = ref(false)
   const dragStyle = computed(() => {
@@ -52,6 +59,8 @@ export function useNodePointerInteractions(
       return
     }
 
+    if (forwardMiddlePointerIfNeeded(event)) return
+
     const stopNodeDragTarget =
       event.target instanceof HTMLElement
         ? event.target.closest('[data-capture-node="true"]')
@@ -90,6 +99,8 @@ export function useNodePointerInteractions(
   }
 
   const handlePointerMove = (event: PointerEvent) => {
+    if (forwardMiddlePointerIfNeeded(event)) return
+
     if (isDragging.value) {
       void handleDrag(event)
     }
@@ -129,6 +140,8 @@ export function useNodePointerInteractions(
   }
 
   const handlePointerUp = (event: PointerEvent) => {
+    if (forwardMiddlePointerIfNeeded(event)) return
+
     if (isDragging.value) {
       handleDragTermination(event, 'drag end')
     }