feat(canvas): add proximity magnet target resolver

components/canvas/__tests__/canvas-connection-drop-target.test.tsx

@@ -7,7 +7,6 @@ import { resolveDroppedConnectionTarget } from "@/components/canvas/canvas-helpe
 
 function createNode(overrides: Partial<RFNode> & Pick<RFNode, "id">): RFNode {
   return {
-    id: overrides.id,
     position: { x: 0, y: 0 },
     data: {},
     ...overrides,
@@ -40,6 +39,34 @@ function makeNodeElement(id: string, rect: Partial<DOMRect> = {}): HTMLElement {
   return element;
 }
 
+function makeHandleElement(args: {
+  nodeId: string;
+  handleType: "source" | "target";
+  handleId?: string;
+  rect: Partial<DOMRect>;
+}): HTMLElement {
+  const element = document.createElement("div");
+  element.className = "react-flow__handle";
+  element.dataset.nodeId = args.nodeId;
+  element.dataset.handleType = args.handleType;
+  if (args.handleId !== undefined) {
+    element.dataset.handleId = args.handleId;
+  }
+  vi.spyOn(element, "getBoundingClientRect").mockReturnValue({
+    x: args.rect.left ?? 0,
+    y: args.rect.top ?? 0,
+    top: args.rect.top ?? 0,
+    left: args.rect.left ?? 0,
+    right: args.rect.right ?? 10,
+    bottom: args.rect.bottom ?? 10,
+    width: args.rect.width ?? 10,
+    height: args.rect.height ?? 10,
+    toJSON: () => ({}),
+  } as DOMRect);
+  document.body.appendChild(element);
+  return element;
+}
+
 describe("resolveDroppedConnectionTarget", () => {
   afterEach(() => {
     vi.restoreAllMocks();
@@ -144,6 +171,169 @@ describe("resolveDroppedConnectionTarget", () => {
     });
   });
 
+  it("resolves nearest valid target handle even without a node body hit", () => {
+    const sourceNode = createNode({
+      id: "node-source",
+      type: "image",
+      position: { x: 0, y: 0 },
+    });
+    const compareNode = createNode({
+      id: "node-compare",
+      type: "compare",
+      position: { x: 320, y: 200 },
+    });
+    Object.defineProperty(document, "elementsFromPoint", {
+      value: vi.fn(() => []),
+      configurable: true,
+    });
+
+    makeHandleElement({
+      nodeId: "node-compare",
+      handleType: "target",
+      handleId: "left",
+      rect: { left: 358, top: 252, width: 12, height: 12, right: 370, bottom: 264 },
+    });
+    makeHandleElement({
+      nodeId: "node-compare",
+      handleType: "target",
+      handleId: "right",
+      rect: { left: 438, top: 332, width: 12, height: 12, right: 450, bottom: 344 },
+    });
+
+    const result = resolveDroppedConnectionTarget({
+      point: { x: 364, y: 258 },
+      fromNodeId: "node-source",
+      fromHandleType: "source",
+      nodes: [sourceNode, compareNode],
+      edges: [],
+    });
+
+    expect(result).toEqual({
+      sourceNodeId: "node-source",
+      targetNodeId: "node-compare",
+      sourceHandle: undefined,
+      targetHandle: "left",
+    });
+  });
+
+  it("skips a closer invalid handle and picks the nearest valid handle", () => {
+    const sourceNode = createNode({
+      id: "node-source",
+      type: "image",
+      position: { x: 0, y: 0 },
+    });
+    const mixerNode = createNode({
+      id: "node-mixer",
+      type: "mixer",
+      position: { x: 320, y: 200 },
+    });
+    Object.defineProperty(document, "elementsFromPoint", {
+      value: vi.fn(() => []),
+      configurable: true,
+    });
+
+    makeHandleElement({
+      nodeId: "node-mixer",
+      handleType: "target",
+      handleId: "base",
+      rect: { left: 358, top: 252, width: 12, height: 12, right: 370, bottom: 264 },
+    });
+    makeHandleElement({
+      nodeId: "node-mixer",
+      handleType: "target",
+      handleId: "overlay",
+      rect: { left: 386, top: 278, width: 12, height: 12, right: 398, bottom: 290 },
+    });
+
+    const result = resolveDroppedConnectionTarget({
+      point: { x: 364, y: 258 },
+      fromNodeId: "node-source",
+      fromHandleType: "source",
+      nodes: [sourceNode, mixerNode],
+      edges: [
+        createEdge({
+          id: "edge-base-taken",
+          source: "node-source",
+          target: "node-mixer",
+          targetHandle: "base",
+        }),
+      ],
+    });
+
+    expect(result).toEqual({
+      sourceNodeId: "node-source",
+      targetNodeId: "node-mixer",
+      sourceHandle: undefined,
+      targetHandle: "overlay",
+    });
+  });
+
+  it("prefers the actually nearest handle for compare and mixer targets", () => {
+    const sourceNode = createNode({
+      id: "node-source",
+      type: "image",
+      position: { x: 0, y: 0 },
+    });
+    const compareNode = createNode({
+      id: "node-compare",
+      type: "compare",
+      position: { x: 320, y: 200 },
+    });
+    const mixerNode = createNode({
+      id: "node-mixer",
+      type: "mixer",
+      position: { x: 640, y: 200 },
+    });
+    Object.defineProperty(document, "elementsFromPoint", {
+      value: vi.fn(() => []),
+      configurable: true,
+    });
+
+    makeHandleElement({
+      nodeId: "node-compare",
+      handleType: "target",
+      handleId: "left",
+      rect: { left: 358, top: 252, width: 12, height: 12, right: 370, bottom: 264 },
+    });
+    makeHandleElement({
+      nodeId: "node-compare",
+      handleType: "target",
+      handleId: "right",
+      rect: { left: 438, top: 332, width: 12, height: 12, right: 450, bottom: 344 },
+    });
+    makeHandleElement({
+      nodeId: "node-mixer",
+      handleType: "target",
+      handleId: "base",
+      rect: { left: 678, top: 252, width: 12, height: 12, right: 690, bottom: 264 },
+    });
+    makeHandleElement({
+      nodeId: "node-mixer",
+      handleType: "target",
+      handleId: "overlay",
+      rect: { left: 678, top: 292, width: 12, height: 12, right: 690, bottom: 304 },
+    });
+
+    const compareResult = resolveDroppedConnectionTarget({
+      point: { x: 364, y: 258 },
+      fromNodeId: "node-source",
+      fromHandleType: "source",
+      nodes: [sourceNode, compareNode, mixerNode],
+      edges: [],
+    });
+
+    const mixerResult = resolveDroppedConnectionTarget({
+      point: { x: 684, y: 299 },
+      fromNodeId: "node-source",
+      fromHandleType: "source",
+      nodes: [sourceNode, compareNode, mixerNode],
+      edges: [],
+    });
+
+    expect(compareResult?.targetHandle).toBe("left");
+    expect(mixerResult?.targetHandle).toBe("overlay");
+  });
+
   it("reverses the connection when the drag starts from a target handle", () => {
     const droppedNode = createNode({
       id: "node-dropped",
@@ -177,4 +367,44 @@ describe("resolveDroppedConnectionTarget", () => {
       targetHandle: "target-handle",
     });
   });
+
+  it("resolves nearest source handle when drag starts from target handle", () => {
+    const fromNode = createNode({
+      id: "node-compare-target",
+      type: "compare",
+      position: { x: 0, y: 0 },
+    });
+    const compareNode = createNode({
+      id: "node-compare-source",
+      type: "compare",
+      position: { x: 320, y: 200 },
+    });
+    Object.defineProperty(document, "elementsFromPoint", {
+      value: vi.fn(() => []),
+      configurable: true,
+    });
+
+    makeHandleElement({
+      nodeId: "node-compare-source",
+      handleType: "source",
+      handleId: "compare-out",
+      rect: { left: 478, top: 288, width: 12, height: 12, right: 490, bottom: 300 },
+    });
+
+    const result = resolveDroppedConnectionTarget({
+      point: { x: 484, y: 294 },
+      fromNodeId: "node-compare-target",
+      fromHandleId: "left",
+      fromHandleType: "target",
+      nodes: [fromNode, compareNode],
+      edges: [],
+    });
+
+    expect(result).toEqual({
+      sourceNodeId: "node-compare-source",
+      targetNodeId: "node-compare-target",
+      sourceHandle: "compare-out",
+      targetHandle: "left",
+    });
+  });
 });

components/canvas/canvas-connection-magnetism.ts

@@ -0,0 +1,198 @@
+import type { Connection, Edge as RFEdge, Node as RFNode } from "@xyflow/react";
+
+import { validateCanvasConnectionPolicy } from "@/lib/canvas-connection-policy";
+
+export const HANDLE_GLOW_RADIUS_PX = 56;
+export const HANDLE_SNAP_RADIUS_PX = 40;
+
+export type CanvasMagnetTarget = {
+  nodeId: string;
+  handleId?: string;
+  handleType: "source" | "target";
+  centerX: number;
+  centerY: number;
+  distancePx: number;
+};
+
+type HandleCandidate = CanvasMagnetTarget & {
+  index: number;
+};
+
+function isOptimisticEdgeId(id: string): boolean {
+  return id.startsWith("optimistic_edge_");
+}
+
+function normalizeHandleId(value: string | undefined): string | undefined {
+  if (value === undefined || value === "") {
+    return undefined;
+  }
+  return value;
+}
+
+function isValidConnectionCandidate(args: {
+  connection: Connection;
+  nodes: RFNode[];
+  edges: RFEdge[];
+}): boolean {
+  const { connection, nodes, edges } = args;
+  if (!connection.source || !connection.target) {
+    return false;
+  }
+  if (connection.source === connection.target) {
+    return false;
+  }
+
+  const sourceNode = nodes.find((node) => node.id === connection.source);
+  const targetNode = nodes.find((node) => node.id === connection.target);
+  if (!sourceNode || !targetNode) {
+    return false;
+  }
+
+  const incomingEdges = edges.filter(
+    (edge) =>
+      edge.className !== "temp" &&
+      !isOptimisticEdgeId(edge.id) &&
+      edge.target === connection.target,
+  );
+
+  return (
+    validateCanvasConnectionPolicy({
+      sourceType: sourceNode.type ?? "",
+      targetType: targetNode.type ?? "",
+      targetHandle: connection.targetHandle,
+      targetIncomingCount: incomingEdges.length,
+      targetIncomingHandles: incomingEdges.map((edge) => edge.targetHandle),
+    }) === null
+  );
+}
+
+function collectHandleCandidates(args: {
+  point: { x: number; y: number };
+  expectedHandleType: "source" | "target";
+  maxDistancePx: number;
+  handleElements?: Element[];
+}): HandleCandidate[] {
+  const { point, expectedHandleType, maxDistancePx } = args;
+  const handleElements =
+    args.handleElements ??
+    (typeof document === "undefined"
+      ? []
+      : Array.from(document.querySelectorAll("[data-node-id][data-handle-type]")));
+
+  const candidates: HandleCandidate[] = [];
+  let index = 0;
+  for (const element of handleElements) {
+    if (!(element instanceof HTMLElement)) {
+      continue;
+    }
+    if (element.dataset.handleType !== expectedHandleType) {
+      continue;
+    }
+
+    const nodeId = element.dataset.nodeId;
+    if (!nodeId) {
+      continue;
+    }
+
+    const rect = element.getBoundingClientRect();
+    const centerX = rect.left + rect.width / 2;
+    const centerY = rect.top + rect.height / 2;
+    const distancePx = Math.hypot(point.x - centerX, point.y - centerY);
+
+    if (distancePx > maxDistancePx) {
+      continue;
+    }
+
+    candidates.push({
+      index,
+      nodeId,
+      handleId: normalizeHandleId(element.dataset.handleId),
+      handleType: expectedHandleType,
+      centerX,
+      centerY,
+      distancePx,
+    });
+    index += 1;
+  }
+
+  return candidates;
+}
+
+function toConnectionFromCandidate(args: {
+  fromNodeId: string;
+  fromHandleId?: string;
+  fromHandleType: "source" | "target";
+  candidate: HandleCandidate;
+}): Connection {
+  if (args.fromHandleType === "source") {
+    return {
+      source: args.fromNodeId,
+      sourceHandle: args.fromHandleId ?? null,
+      target: args.candidate.nodeId,
+      targetHandle: args.candidate.handleId ?? null,
+    };
+  }
+
+  return {
+    source: args.candidate.nodeId,
+    sourceHandle: args.candidate.handleId ?? null,
+    target: args.fromNodeId,
+    targetHandle: args.fromHandleId ?? null,
+  };
+}
+
+export function resolveCanvasMagnetTarget(args: {
+  point: { x: number; y: number };
+  fromNodeId: string;
+  fromHandleId?: string;
+  fromHandleType: "source" | "target";
+  nodes: RFNode[];
+  edges: RFEdge[];
+  maxDistancePx?: number;
+  handleElements?: Element[];
+}): CanvasMagnetTarget | null {
+  const expectedHandleType = args.fromHandleType === "source" ? "target" : "source";
+  const maxDistancePx = args.maxDistancePx ?? HANDLE_GLOW_RADIUS_PX;
+
+  const candidates = collectHandleCandidates({
+    point: args.point,
+    expectedHandleType,
+    maxDistancePx,
+    handleElements: args.handleElements,
+  }).filter((candidate) => {
+    const connection = toConnectionFromCandidate({
+      fromNodeId: args.fromNodeId,
+      fromHandleId: args.fromHandleId,
+      fromHandleType: args.fromHandleType,
+      candidate,
+    });
+
+    return isValidConnectionCandidate({
+      connection,
+      nodes: args.nodes,
+      edges: args.edges,
+    });
+  });
+
+  if (candidates.length === 0) {
+    return null;
+  }
+
+  candidates.sort((a, b) => {
+    const distanceDelta = a.distancePx - b.distancePx;
+    if (Math.abs(distanceDelta) > Number.EPSILON) {
+      return distanceDelta;
+    }
+    return a.index - b.index;
+  });
+
+  const winner = candidates[0];
+  return {
+    nodeId: winner.nodeId,
+    handleId: winner.handleId,
+    handleType: winner.handleType,
+    centerX: winner.centerX,
+    centerY: winner.centerY,
+    distancePx: winner.distancePx,
+  };
+}

components/canvas/canvas-helpers.ts

@@ -8,6 +8,7 @@ import {
   getSourceImageFromGraph,
 } from "@/lib/canvas-render-preview";
 import { NODE_HANDLE_MAP } from "@/lib/canvas-utils";
+import { resolveCanvasMagnetTarget } from "@/components/canvas/canvas-connection-magnetism";
 
 export const OPTIMISTIC_NODE_PREFIX = "optimistic_";
 export const OPTIMISTIC_EDGE_PREFIX = "optimistic_edge_";
@@ -421,17 +422,7 @@ export function resolveDroppedConnectionTarget(args: {
       ? []
       : document.elementsFromPoint(args.point.x, args.point.y);
   const nodeElement = getNodeElementAtClientPoint(args.point, elementsAtPoint);
-  if (!nodeElement) {
+  if (nodeElement) {
-    logCanvasConnectionDebug("drop-target:node-missed", {
-      point: args.point,
-      fromNodeId: args.fromNodeId,
-      fromHandleId: args.fromHandleId ?? null,
-      fromHandleType: args.fromHandleType,
-      elementsAtPoint: elementsAtPoint.slice(0, 6).map(describeConnectionDebugElement),
-    });
-    return null;
-  }
-
     const targetNodeId = nodeElement.dataset.id;
     if (!targetNodeId) {
       logCanvasConnectionDebug("drop-target:node-missing-data-id", {
@@ -511,6 +502,65 @@ export function resolveDroppedConnectionTarget(args: {
     return droppedConnection;
   }
 
+  const magnetTarget = resolveCanvasMagnetTarget({
+    point: args.point,
+    fromNodeId: args.fromNodeId,
+    fromHandleId: args.fromHandleId,
+    fromHandleType: args.fromHandleType,
+    nodes: args.nodes,
+    edges: args.edges,
+  });
+
+  if (!magnetTarget) {
+    logCanvasConnectionDebug("drop-target:node-missed", {
+      point: args.point,
+      fromNodeId: args.fromNodeId,
+      fromHandleId: args.fromHandleId ?? null,
+      fromHandleType: args.fromHandleType,
+      elementsAtPoint: elementsAtPoint.slice(0, 6).map(describeConnectionDebugElement),
+    });
+    return null;
+  }
+
+  if (args.fromHandleType === "source") {
+    const droppedConnection = {
+      sourceNodeId: args.fromNodeId,
+      targetNodeId: magnetTarget.nodeId,
+      sourceHandle: args.fromHandleId,
+      targetHandle: magnetTarget.handleId,
+    };
+
+    logCanvasConnectionDebug("drop-target:magnet-detected", {
+      point: args.point,
+      fromNodeId: args.fromNodeId,
+      fromHandleId: args.fromHandleId ?? null,
+      fromHandleType: args.fromHandleType,
+      magnetTarget,
+      resolvedConnection: droppedConnection,
+    });
+
+    return droppedConnection;
+  }
+
+  const droppedConnection = {
+    sourceNodeId: magnetTarget.nodeId,
+    targetNodeId: args.fromNodeId,
+    sourceHandle: magnetTarget.handleId,
+    targetHandle: args.fromHandleId,
+  };
+
+  logCanvasConnectionDebug("drop-target:magnet-detected", {
+    point: args.point,
+    fromNodeId: args.fromNodeId,
+    fromHandleId: args.fromHandleId ?? null,
+    fromHandleType: args.fromHandleType,
+    magnetTarget,
+    resolvedConnection: droppedConnection,
+  });
+
+  return droppedConnection;
+}
+
 /** Kanten-Split nach Drag: wartet auf echte Node-ID, wenn der Knoten noch optimistisch ist. */
 export type PendingEdgeSplit = {
   intersectedEdgeId: Id<"edges">;

lib/canvas-utils.ts

@@ -102,7 +102,9 @@ export function convexEdgeToRF(edge: Doc<"edges">): RFEdge {
  * Akzentfarben der Handles je Node-Typ (s. jeweilige Node-Komponente).
  * Für einen dezenten Glow entlang der Kante (drop-shadow am Pfad).
  */
-const SOURCE_NODE_GLOW_RGB: Record<string, readonly [number, number, number]> = {
+type RgbColor = readonly [number, number, number];
+
+const SOURCE_NODE_GLOW_RGB: Record<string, RgbColor> = {
   prompt: [139, 92, 246],
   "video-prompt": [124, 58, 237],
   "ai-image": [139, 92, 246],
@@ -123,21 +125,59 @@ const SOURCE_NODE_GLOW_RGB: Record<string, readonly [number, number, number]> =
   render: [14, 165, 233],
   agent: [245, 158, 11],
   "agent-output": [245, 158, 11],
+  mixer: [100, 116, 139],
 };
 
 /** Compare: Ziel-Handles blau/smaragd, Quelle compare-out grau (wie in compare-node.tsx). */
-const COMPARE_HANDLE_CONNECTION_RGB: Record<
+const COMPARE_HANDLE_CONNECTION_RGB: Record<string, RgbColor> = {
-  string,
-  readonly [number, number, number]
-> = {
   left: [59, 130, 246],
   right: [16, 185, 129],
   "compare-out": [100, 116, 139],
 };
 
-const CONNECTION_LINE_FALLBACK_RGB: readonly [number, number, number] = [
+const MIXER_HANDLE_CONNECTION_RGB: Record<string, RgbColor> = {
-  13, 148, 136,
+  base: [14, 165, 233],
-];
+  overlay: [236, 72, 153],
+  "mixer-out": [100, 116, 139],
+};
+
+const CONNECTION_LINE_FALLBACK_RGB: RgbColor = [13, 148, 136];
+
+export function canvasHandleAccentRgb(args: {
+  nodeType: string | undefined;
+  handleId?: string | null;
+  handleType: "source" | "target";
+}): RgbColor {
+  const nodeType = args.nodeType;
+  const handleId = args.handleId ?? undefined;
+  const handleType = args.handleType;
+
+  if (nodeType === "compare" && handleId) {
+    if (handleType === "target" && handleId === "compare-out") {
+      return SOURCE_NODE_GLOW_RGB.compare;
+    }
+    const byHandle = COMPARE_HANDLE_CONNECTION_RGB[handleId];
+    if (byHandle) {
+      return byHandle;
+    }
+  }
+
+  if (nodeType === "mixer" && handleId) {
+    if (handleType === "target" && handleId === "mixer-out") {
+      return SOURCE_NODE_GLOW_RGB.mixer;
+    }
+    const byHandle = MIXER_HANDLE_CONNECTION_RGB[handleId];
+    if (byHandle) {
+      return byHandle;
+    }
+  }
+
+  if (!nodeType) {
+    return CONNECTION_LINE_FALLBACK_RGB;
+  }
+
+  return SOURCE_NODE_GLOW_RGB[nodeType] ?? CONNECTION_LINE_FALLBACK_RGB;
+}
 
 /**
  * RGB für die temporäre Verbindungslinie (Quell-Node + optional Handle, z. B. Reconnect).
@@ -145,13 +185,12 @@ const CONNECTION_LINE_FALLBACK_RGB: readonly [number, number, number] = [
 export function connectionLineAccentRgb(
   nodeType: string | undefined,
   handleId: string | null | undefined,
-): readonly [number, number, number] {
+): RgbColor {
-  if (nodeType === "compare" && handleId) {
+  return canvasHandleAccentRgb({
-    const byHandle = COMPARE_HANDLE_CONNECTION_RGB[handleId];
+    nodeType,
-    if (byHandle) return byHandle;
+    handleId,
-  }
+    handleType: "source",
-  if (!nodeType) return CONNECTION_LINE_FALLBACK_RGB;
+  });
-  return SOURCE_NODE_GLOW_RGB[nodeType] ?? CONNECTION_LINE_FALLBACK_RGB;
 }
 
 export type EdgeGlowColorMode = "light" | "dark";