[feat] TransformPane - Viewport synchronization layer for Vue nodes (#4304)

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Benjamin Lu <benceruleanlu@proton.me>
Co-authored-by: github-actions <github-actions@github.com>

src/components/graph/TransformPane.vue

@@ -0,0 +1,133 @@
+<!-- eslint-disable @intlify/vue-i18n/no-raw-text -->
+<template>
+  <div
+    class="transform-pane"
+    :class="{ 'transform-pane--interacting': isInteracting }"
+    :style="transformStyle"
+    @pointerdown="handlePointerDown"
+  >
+    <!-- Vue nodes will be rendered here -->
+    <slot />
+
+    <!-- DEV ONLY: Viewport bounds visualization -->
+    <div
+      v-if="props.showDebugOverlay"
+      class="viewport-debug-overlay"
+      :style="{
+        position: 'absolute',
+        left: '10px',
+        top: '10px',
+        border: '2px solid red',
+        width: (props.viewport?.width || 0) - 20 + 'px',
+        height: (props.viewport?.height || 0) - 20 + 'px',
+        pointerEvents: 'none',
+        opacity: 0.5
+      }"
+    >
+      <div
+        style="
+          position: absolute;
+          top: 0;
+          left: 0;
+          background: red;
+          color: white;
+          padding: 2px 5px;
+          font-size: 10px;
+        "
+      >
+        Viewport: {{ props.viewport?.width }}x{{ props.viewport?.height }} DPR:
+        {{ devicePixelRatio }}
+      </div>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { computed, provide } from 'vue'
+
+import { useTransformState } from '@/composables/element/useTransformState'
+import { useCanvasTransformSync } from '@/composables/graph/useCanvasTransformSync'
+import { useTransformSettling } from '@/composables/graph/useTransformSettling'
+import { LGraphCanvas } from '@/lib/litegraph/src/litegraph'
+
+interface TransformPaneProps {
+  canvas?: LGraphCanvas
+  viewport?: { width: number; height: number }
+  showDebugOverlay?: boolean
+}
+
+const props = defineProps<TransformPaneProps>()
+
+// Get device pixel ratio for display
+const devicePixelRatio = window.devicePixelRatio || 1
+
+// Transform state management
+const {
+  camera,
+  transformStyle,
+  syncWithCanvas,
+  canvasToScreen,
+  screenToCanvas,
+  isNodeInViewport
+} = useTransformState()
+
+// Transform settling detection for re-rasterization optimization
+const canvasElement = computed(() => props.canvas?.canvas)
+const { isTransforming } = useTransformSettling(canvasElement, {
+  settleDelay: 200,
+  trackPan: true
+})
+
+// Use isTransforming for the CSS class (aliased for clarity)
+const isInteracting = isTransforming
+
+// Provide transform utilities to child components
+provide('transformState', {
+  camera,
+  canvasToScreen,
+  screenToCanvas,
+  isNodeInViewport
+})
+
+// Event delegation for node interactions
+const handlePointerDown = (event: PointerEvent) => {
+  const target = event.target as HTMLElement
+  const nodeElement = target.closest('[data-node-id]')
+
+  if (nodeElement) {
+    // TODO: Emit event for node interaction
+    // Node interaction with nodeId will be handled in future implementation
+  }
+}
+
+// Canvas transform synchronization
+const emit = defineEmits<{
+  rafStatusChange: [active: boolean]
+  transformUpdate: [time: number]
+}>()
+
+useCanvasTransformSync(props.canvas, syncWithCanvas, {
+  onStart: () => emit('rafStatusChange', true),
+  onUpdate: (duration) => emit('transformUpdate', duration),
+  onStop: () => emit('rafStatusChange', false)
+})
+</script>
+
+<style scoped>
+.transform-pane {
+  position: absolute;
+  inset: 0;
+  contain: layout style paint;
+  transform-origin: 0 0;
+  pointer-events: none;
+}
+
+.transform-pane--interacting {
+  will-change: transform;
+}
+
+/* Allow pointer events on nodes */
+.transform-pane :deep([data-node-id]) {
+  pointer-events: auto;
+}
+</style>