fix: collapsed node connection link positions (#10641)

## Summary

Fix connection links rendering at wrong positions when nodes are
collapsed in Vue nodes mode.

## Changes

- **What**: Fall back to `clientPosToCanvasPos` for collapsed node slot
positioning since DOM-relative scale derivation is invalid when layout
store preserves expanded size. Clear stale `cachedOffset` on collapse
and defer sync when canvas is not yet initialized.
- 3 unit tests for collapsed node slot sync fallback
(clientPosToCanvasPos, cachedOffset clearing, canvas-not-initialized
deferral)
- 3 E2E tests for collapsed node link positions (within bounds, after
position change, after expand recovery)

## Review Focus

- `clientPosToCanvasPos` fallback is safe for collapsed nodes because
collapse is user-initiated (no loading-time transform desync risk that
#9121 originally fixed)
- `cachedOffset` clearing prevents stale expanded-state offsets during
collapsed node drag
- Regression from #9121 (DOM-relative scale) combined with #9680
(collapsed node ResizeObserver skip)

## Screenshots 
Before
<img width="1030" height="434" alt="image"
src="https://github.com/user-attachments/assets/2f8b8a1f-ed22-4588-ab62-72b89880e53f"
/>

After
<img width="1029" height="476" alt="image"
src="https://github.com/user-attachments/assets/52dbbf7c-61ed-465b-ae19-a9781513e7e8"
/>


┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10641-fix-collapsed-node-connection-link-positions-3316d73d365081f4aee3fecb92c83b91)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Alexander Brown <drjkl@comfy.org>
Co-authored-by: Alexander Brown <DrJKL0424@gmail.com>

browser_tests/tests/collapsedNodeLinks.spec.ts

@@ -0,0 +1,68 @@
+import { expect } from '@playwright/test'
+
+import { comfyPageFixture as test } from '../fixtures/ComfyPage'
+import { assertNodeSlotsWithinBounds } from '../fixtures/utils/slotBoundsUtil'
+
+const NODE_ID = '3'
+const NODE_TITLE = 'KSampler'
+
+test.describe(
+  'Collapsed node link positions',
+  { tag: ['@canvas', '@node'] },
+  () => {
+    test.beforeEach(async ({ comfyPage }) => {
+      await comfyPage.settings.setSetting('Comfy.VueNodes.Enabled', true)
+      await comfyPage.workflow.loadWorkflow('default')
+      await comfyPage.vueNodes.waitForNodes()
+    })
+
+    test.afterEach(async ({ comfyPage }) => {
+      await comfyPage.canvasOps.resetView()
+    })
+
+    test('link endpoints stay within collapsed node bounds', async ({
+      comfyPage
+    }) => {
+      const node = await comfyPage.vueNodes.getFixtureByTitle(NODE_TITLE)
+      await node.toggleCollapse()
+      await comfyPage.nextFrame()
+
+      await assertNodeSlotsWithinBounds(comfyPage.page, NODE_ID)
+    })
+
+    test('links follow collapsed node after drag', async ({ comfyPage }) => {
+      const node = await comfyPage.vueNodes.getFixtureByTitle(NODE_TITLE)
+      await node.toggleCollapse()
+      await comfyPage.nextFrame()
+
+      const box = await node.boundingBox()
+      expect(box).not.toBeNull()
+      await comfyPage.page.mouse.move(
+        box!.x + box!.width / 2,
+        box!.y + box!.height / 2
+      )
+      await comfyPage.page.mouse.down()
+      await comfyPage.page.mouse.move(
+        box!.x + box!.width / 2 + 200,
+        box!.y + box!.height / 2 + 100,
+        { steps: 10 }
+      )
+      await comfyPage.page.mouse.up()
+      await comfyPage.nextFrame()
+
+      await assertNodeSlotsWithinBounds(comfyPage.page, NODE_ID)
+    })
+
+    test('links recover correct positions after expand', async ({
+      comfyPage
+    }) => {
+      const node = await comfyPage.vueNodes.getFixtureByTitle(NODE_TITLE)
+      await node.toggleCollapse()
+      await comfyPage.nextFrame()
+      await node.toggleCollapse()
+      await comfyPage.nextFrame()
+
+      await assertNodeSlotsWithinBounds(comfyPage.page, NODE_ID)
+    })
+  }
+)

browser_tests/tests/subgraph/subgraphSlots.spec.ts

@@ -7,6 +7,10 @@ import type { ComfyWorkflowJSON } from '@/platform/workflow/validation/schemas/w
 
 import { comfyPageFixture as test, comfyExpect } from '../../fixtures/ComfyPage'
 import { SubgraphHelper } from '../../fixtures/helpers/SubgraphHelper'
+import {
+  expectSlotsWithinBounds,
+  measureNodeSlotOffsets
+} from '../../fixtures/utils/slotBoundsUtil'
 
 // Constants
 const RENAMED_INPUT_NAME = 'renamed_input'
@@ -19,20 +23,6 @@ const SELECTORS = {
   promptDialog: '.graphdialog input'
 } as const
 
-interface SlotMeasurement {
-  key: string
-  offsetX: number
-  offsetY: number
-}
-
-interface NodeSlotData {
-  nodeId: string
-  isSubgraph: boolean
-  nodeW: number
-  nodeH: number
-  slots: SlotMeasurement[]
-}
-
 test.describe('Subgraph Slots', { tag: ['@slow', '@subgraph'] }, () => {
   test.beforeEach(async ({ comfyPage }) => {
     await comfyPage.settings.setSetting('Comfy.UseNewMenu', 'Disabled')
@@ -604,71 +594,19 @@ test.describe('Subgraph Slots', { tag: ['@slow', '@subgraph'] }, () => {
       )
       await comfyPage.nextFrame()
 
-      // Wait for slot elements to appear in DOM
       await comfyPage.page.locator('[data-slot-key]').first().waitFor()
 
-      const result: NodeSlotData[] = await comfyPage.page.evaluate(() => {
-        const nodes = window.app!.graph._nodes
-        const slotData: NodeSlotData[] = []
+      const nodeIds = await comfyPage.page.evaluate(() =>
+        window
+          .app!.graph._nodes.filter((n) => !!n.isSubgraphNode?.())
+          .map((n) => String(n.id))
+      )
+      expect(nodeIds.length).toBeGreaterThan(0)
 
-        for (const node of nodes) {
-          const nodeId = String(node.id)
-          const nodeEl = document.querySelector(
-            `[data-node-id="${nodeId}"]`
-          ) as HTMLElement | null
-          if (!nodeEl) continue
-
-          const slotEls = nodeEl.querySelectorAll('[data-slot-key]')
-          if (slotEls.length === 0) continue
-
-          const slots: SlotMeasurement[] = []
-
-          const nodeRect = nodeEl.getBoundingClientRect()
-          for (const slotEl of slotEls) {
-            const slotRect = slotEl.getBoundingClientRect()
-            const slotKey = (slotEl as HTMLElement).dataset.slotKey ?? 'unknown'
-            slots.push({
-              key: slotKey,
-              offsetX: slotRect.left + slotRect.width / 2 - nodeRect.left,
-              offsetY: slotRect.top + slotRect.height / 2 - nodeRect.top
-            })
-          }
-
-          slotData.push({
-            nodeId,
-            isSubgraph: !!node.isSubgraphNode?.(),
-            nodeW: nodeRect.width,
-            nodeH: nodeRect.height,
-            slots
-          })
-        }
-
-        return slotData
-      })
-
-      const subgraphNodes = result.filter((n) => n.isSubgraph)
-      expect(subgraphNodes.length).toBeGreaterThan(0)
-
-      for (const node of subgraphNodes) {
-        for (const slot of node.slots) {
-          expect(
-            slot.offsetX,
-            `Slot ${slot.key} on node ${node.nodeId}: X offset ${slot.offsetX} outside node width ${node.nodeW}`
-          ).toBeGreaterThanOrEqual(-SLOT_BOUNDS_MARGIN)
-          expect(
-            slot.offsetX,
-            `Slot ${slot.key} on node ${node.nodeId}: X offset ${slot.offsetX} outside node width ${node.nodeW}`
-          ).toBeLessThanOrEqual(node.nodeW + SLOT_BOUNDS_MARGIN)
-
-          expect(
-            slot.offsetY,
-            `Slot ${slot.key} on node ${node.nodeId}: Y offset ${slot.offsetY} outside node height ${node.nodeH}`
-          ).toBeGreaterThanOrEqual(-SLOT_BOUNDS_MARGIN)
-          expect(
-            slot.offsetY,
-            `Slot ${slot.key} on node ${node.nodeId}: Y offset ${slot.offsetY} outside node height ${node.nodeH}`
-          ).toBeLessThanOrEqual(node.nodeH + SLOT_BOUNDS_MARGIN)
-        }
+      for (const nodeId of nodeIds) {
+        const data = await measureNodeSlotOffsets(comfyPage.page, nodeId)
+        expect(data, `Node ${nodeId} not found in DOM`).not.toBeNull()
+        expectSlotsWithinBounds(data!, SLOT_BOUNDS_MARGIN, `Node ${nodeId}`)
       }
     })
   })