Add pre-size and inverse coordinates calculation APIs

.gitignore

@@ -2,6 +2,7 @@
 !/.gitignore
 !/.github
 
+build
 dist
 node_modules
 playwright-report

package.json

@@ -19,10 +19,10 @@
 	],
 	"scripts": {
 		"build": "tsx build.ts",
-		"build:watch": "tsx build.ts --watch",
+		"watch": "tsx build.ts --watch",
 		"clean": "rm -rf dist",
-		"test": "playwright test tests/integration tests/unit",
-		"test:perf": "playwright test --workers=1 ./benchmarks",
+		"test": "tsx test.ts",
+		"bench": "playwright test --workers=1 ./benchmarks",
 		"example": "tsx serve.ts",
 		"deploy": "tsx deploy.ts",
 		"lint": "biome lint src tests",
@@ -34,6 +34,7 @@
 		"@playwright/test": "^1.57.0",
 		"@types/node": "^22.10.5",
 		"esbuild": "^0.27.2",
+		"monocart-coverage-reports": "^2.12.2",
 		"tsx": "^4.21.0",
 		"typescript": "^5.9.3"
 	}

src/layout/types.ts → src/core/types.ts

@@ -95,6 +95,13 @@ export interface LayoutPath {
 	layout: Layout;
 }
 
+/**
+ * The detail payload of the `regular-layout-resize-before` event.
+ */
+export interface PresizeDetail {
+	calculatePresizePaths(): Record<string, LayoutPath>;
+}
+
 /**
  * An empty `Layout` with no panels.
  */

src/extensions.ts

@@ -11,7 +11,7 @@
 
 import { RegularLayout } from "./regular-layout.ts";
 import { RegularLayoutFrame } from "./regular-layout-frame.ts";
-import type { Layout } from "./layout/types.ts";
+import type { Layout, PresizeDetail } from "./core/types.ts";
 import { RegularLayoutTab } from "./regular-layout-tab.ts";
 
 customElements.define("regular-layout", RegularLayout);
@@ -59,6 +59,12 @@ declare global {
 			options?: { signal: AbortSignal },
 		): void;
 
+		addEventListener(
+			name: "regular-layout-resize-before",
+			cb: (e: RegularLayoutPresizeEvent) => void,
+			options?: { signal: AbortSignal },
+		): void;
+
 		removeEventListener(
 			name: "regular-layout-update",
 			cb: (e: RegularLayoutEvent) => void,
@@ -68,7 +74,13 @@ declare global {
 			name: "regular-layout-before-update",
 			cb: (e: RegularLayoutEvent) => void,
 		): void;
+
+		removeEventListener(
+			name: "regular-layout-resize-before",
+			cb: (e: RegularLayoutPresizeEvent) => void,
+		): void;
 	}
 }
 
 export type RegularLayoutEvent = CustomEvent<Layout>;
+export type RegularLayoutPresizeEvent = CustomEvent<PresizeDetail>;

src/index.ts

@@ -59,10 +59,12 @@
  * @packageDocumentation
  */
 
-export type * from "./layout/types.ts";
+export type * from "./core/types.ts";
 
 export { RegularLayout } from "./regular-layout.ts";
 export { RegularLayoutFrame } from "./regular-layout-frame.ts";
 
+export type * from "./extensions.ts";
+
 // Side effects
 import "./extensions.ts";

src/layout/calculate_edge.ts

@@ -9,15 +9,15 @@
 // ┃  *  [Apache License 2.0](https://www.apache.org/licenses/LICENSE-2.0). *  ┃
 // ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
 
-import { DEFAULT_PHYSICS, type Physics } from "./constants";
+import { DEFAULT_PHYSICS, type Physics } from "../core/constants";
 import { insert_child } from "./insert_child";
 import type {
 	Layout,
 	LayoutPath,
 	LayoutPathTraversal,
 	Orientation,
 	ViewWindow,
-} from "./types";
+} from "../core/types";
 
 /**
  * Calculates an insertion point (which may involve splitting a single

src/layout/calculate_intersect.ts

@@ -15,7 +15,7 @@ import type {
 	Layout,
 	ViewWindow,
 	LayoutPathTraversal,
-} from "./types.ts";
+} from "../core/types.ts";
 
 const VIEW_WINDOW = {
 	row_start: 0,
@@ -130,7 +130,10 @@ function calculate_intersection_recursive(
 		}
 
 		// Check if position falls within this child's bounds
-		if (position >= current_pos && position < next_pos) {
+		if (
+			position >= current_pos &&
+			(position < next_pos || i === panel.children.length - 1)
+		) {
 			return calculate_intersection_recursive(
 				column,
 				row,