From c310bb05c82e666c502edf46a3716ad7a65af46c Mon Sep 17 00:00:00 2001
From: Victor Giers <mail@victorgiers.com>
Date: Thu, 2 Apr 2026 23:01:06 +0200
Subject: [PATCH] Add viewport transient state management

---
 .../viewport-transient-state.ts               | 54 +++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 src/viewport-three/viewport-transient-state.ts

diff --git a/src/viewport-three/viewport-transient-state.ts b/src/viewport-three/viewport-transient-state.ts
new file mode 100644
index 00000000..6f5cabde
--- /dev/null
+++ b/src/viewport-three/viewport-transient-state.ts
@@ -0,0 +1,54 @@
+import type { Vec3 } from "../core/vector";
+import type { ViewportPanelId } from "./viewport-layout";
+
+export interface BoxCreateViewportToolPreview {
+  kind: "box-create";
+  sourcePanelId: ViewportPanelId;
+  center: Vec3 | null;
+}
+
+export type ViewportToolPreview = BoxCreateViewportToolPreview | { kind: "none" };
+
+export interface ViewportTransientState {
+  toolPreview: ViewportToolPreview;
+}
+
+export function createDefaultViewportTransientState(): ViewportTransientState {
+  return {
+    toolPreview: {
+      kind: "none"
+    }
+  };
+}
+
+export function cloneViewportToolPreview(toolPreview: ViewportToolPreview): ViewportToolPreview {
+  if (toolPreview.kind === "none") {
+    return toolPreview;
+  }
+
+  return {
+    kind: "box-create",
+    sourcePanelId: toolPreview.sourcePanelId,
+    center: toolPreview.center === null ? null : { ...toolPreview.center }
+  };
+}
+
+export function areViewportToolPreviewsEqual(left: ViewportToolPreview, right: ViewportToolPreview): boolean {
+  if (left.kind !== right.kind) {
+    return false;
+  }
+
+  if (left.kind === "none" || right.kind === "none") {
+    return true;
+  }
+
+  if (left.sourcePanelId !== right.sourcePanelId) {
+    return false;
+  }
+
+  if (left.center === null || right.center === null) {
+    return left.center === right.center;
+  }
+
+  return left.center.x === right.center.x && left.center.y === right.center.y && left.center.z === right.center.z;
+}