refactor: collapse mask definition registry to a single keyed registry

The freeform mask was assembled on every getMaskDefinition("freeform") call,
re-spreading params and injecting a wrong SquareIcon placeholder, with a type
cast to suppress the structural mismatch. Root cause: MasksRegistry was keyed
on BuiltinMaskType, so freeform had no entry.

- Re-key MasksRegistry from BuiltinMaskType to MaskType
- Register freeform alongside builtins in registerDefaultMasks, with
  PenToolAddIcon as its menu icon
- getMaskDefinition and getMaskDefinitionsForMenu become plain registry
  lookups with no branching, no manual spreading, no cast
- Rename RegisteredBuiltinMaskDefinition to RegisteredMaskDefinition and
  tighten computeParamUpdate return type to Partial<BaseMaskParams>

Co-authored-by: Cursor <cursoragent@cursor.com>

3 files changed, 30 insertions, 47 deletions

diff --git a/apps/web/src/masks/builtin/definitions/index.ts b/apps/web/src/masks/builtin/definitions/index.ts
index 9f722876..5deb4e3f 100644
--- a/apps/web/src/masks/builtin/definitions/index.ts
+++ b/apps/web/src/masks/builtin/definitions/index.ts
@@ -1,6 +1,6 @@
 import {
-	builtinMasksRegistry,
-	type BuiltinMaskDefinitionForRegistration,
+	masksRegistry,
+	type MaskDefinitionForRegistration,
 	type MaskIconProps,
 } from "../../registry";
 import { cinematicBarsMaskDefinition } from "./cinematic-bars";
@@ -11,6 +11,7 @@ import { rectangleMaskDefinition } from "./rectangle";
 import { splitMaskDefinition } from "./split";
 import { starMaskDefinition } from "./star";
 import { textMaskDefinition } from "./text";
+import { freeformMaskDefinition } from "../../freeform/definition";
 import {
 	MinusSignIcon,
 	PanelRightDashedIcon,
@@ -20,23 +21,24 @@ import {
 	DiamondIcon,
 	StarsIcon,
 	TextFontIcon,
+	PenToolAddIcon,
 } from "@hugeicons/core-free-icons";
 
 function registerDefaultMask({
 	definition,
 	icon,
 }: {
-	definition: BuiltinMaskDefinitionForRegistration;
+	definition: MaskDefinitionForRegistration;
 	icon: MaskIconProps;
 }) {
-	if (builtinMasksRegistry.has(definition.type)) {
+	if (masksRegistry.has(definition.type)) {
 		return;
 	}
 
-	builtinMasksRegistry.registerMask({ definition, icon });
+	masksRegistry.registerMask({ definition, icon });
 }
 
-export function registerBuiltinMasks(): void {
+export function registerDefaultMasks(): void {
 	registerDefaultMask({
 		definition: splitMaskDefinition,
 		icon: { icon: PanelRightDashedIcon, strokeWidth: 1 },
@@ -69,4 +71,8 @@ export function registerBuiltinMasks(): void {
 		definition: textMaskDefinition,
 		icon: { icon: TextFontIcon },
 	});
+	registerDefaultMask({
+		definition: freeformMaskDefinition,
+		icon: { icon: PenToolAddIcon },
+	});
 }
diff --git a/apps/web/src/masks/index.ts b/apps/web/src/masks/index.ts
index be5faef7..994f05f2 100644
--- a/apps/web/src/masks/index.ts
+++ b/apps/web/src/masks/index.ts
@@ -1,15 +1,9 @@
 import type { Mask, MaskDefaultContext, MaskType } from "@/masks/types";
-import {
-	BASE_MASK_PARAM_DEFINITIONS,
-	builtinMasksRegistry,
-	type RegisteredBuiltinMaskDefinition,
-} from "./registry";
-import { freeformMaskDefinition } from "./freeform/definition";
+import { masksRegistry } from "./registry";
 import { generateUUID } from "@/utils/id";
-import { SquareIcon } from "@hugeicons/core-free-icons";
 
-export { builtinMasksRegistry } from "./registry";
-export { registerBuiltinMasks as registerDefaultMasks } from "./builtin/definitions";
+export { masksRegistry } from "./registry";
+export { registerDefaultMasks } from "./builtin/definitions";
 
 type MaskWithoutId = Mask extends infer TMask
 	? TMask extends Mask
@@ -40,28 +34,12 @@ function withMaskId({ mask, id }: { mask: MaskWithoutId; id: string }): Mask {
 	}
 }
 
-export function getMaskDefinition(maskType: MaskType): RegisteredBuiltinMaskDefinition {
-	if (maskType === "freeform") {
-		return {
-			...freeformMaskDefinition,
-			params: [...freeformMaskDefinition.params, ...BASE_MASK_PARAM_DEFINITIONS],
-			icon: { icon: SquareIcon },
-		} as RegisteredBuiltinMaskDefinition;
-	}
-
-	return builtinMasksRegistry.get(maskType);
+export function getMaskDefinition(maskType: MaskType) {
+	return masksRegistry.get(maskType);
 }
 
 export function getMaskDefinitionsForMenu() {
-	return [
-		...builtinMasksRegistry.getAll(),
-		{
-			...freeformMaskDefinition,
-			name: "Pen tool",
-			params: [...freeformMaskDefinition.params, ...BASE_MASK_PARAM_DEFINITIONS],
-			icon: { icon: SquareIcon },
-		},
-	];
+	return masksRegistry.getAll();
 }
 
 export function buildDefaultMaskInstance({
@@ -71,7 +49,7 @@ export function buildDefaultMaskInstance({
 	maskType: MaskType;
 	elementSize?: { width: number; height: number };
 }): Mask {
-	const definition = getMaskDefinition(maskType);
+	const definition = masksRegistry.get(maskType);
 	const context: MaskDefaultContext = { elementSize };
 	return withMaskId({
 		mask: definition.buildDefault(context),
diff --git a/apps/web/src/masks/registry.ts b/apps/web/src/masks/registry.ts
index 77861926..35d215c6 100644
--- a/apps/web/src/masks/registry.ts
+++ b/apps/web/src/masks/registry.ts
@@ -2,7 +2,6 @@ import { MAX_FEATHER } from "@/masks/feather";
 import type { ParamDefinition } from "@/params";
 import type {
 	BaseMaskParams,
-	BuiltinMaskType,
 	Mask,
 	MaskDefaultContext,
 	MaskDefinition,
@@ -24,9 +23,9 @@ type RegisteredMaskWithoutId = Mask extends infer TMask
 		: never
 	: never;
 
-export type BuiltinMaskDefinitionForRegistration = {
-	[TType in BuiltinMaskType]: MaskDefinition<TType>;
-}[BuiltinMaskType];
+export type MaskDefinitionForRegistration = {
+	[TType in MaskType]: MaskDefinition<TType>;
+}[MaskType];
 
 export const BASE_MASK_PARAM_DEFINITIONS: ParamDefinition<
 	keyof BaseMaskParams & string
@@ -58,7 +57,7 @@ export const BASE_MASK_PARAM_DEFINITIONS: ParamDefinition<
 	},
 ];
 
-export interface RegisteredBuiltinMaskDefinition {
+export interface RegisteredMaskDefinition {
 	type: MaskType;
 	name: string;
 	features: MaskDefinition["features"];
@@ -69,13 +68,13 @@ export interface RegisteredBuiltinMaskDefinition {
 	buildDefault(context: MaskDefaultContext): RegisteredMaskWithoutId;
 	computeParamUpdate(
 		args: MaskParamUpdateArgs<BaseMaskParams>,
-	): ReturnType<MaskDefinition["computeParamUpdate"]>;
+	): Partial<BaseMaskParams>;
 	icon: MaskIconProps;
 }
 
-export class BuiltinMasksRegistry extends DefinitionRegistry<
-	BuiltinMaskType,
-	RegisteredBuiltinMaskDefinition
+export class MasksRegistry extends DefinitionRegistry<
+	MaskType,
+	RegisteredMaskDefinition
 > {
 	constructor() {
 		super("mask");
@@ -85,10 +84,10 @@ export class BuiltinMasksRegistry extends DefinitionRegistry<
 		definition,
 		icon,
 	}: {
-		definition: BuiltinMaskDefinitionForRegistration;
+		definition: MaskDefinitionForRegistration;
 		icon: MaskIconProps;
 	}): void {
-		const withBaseParams: RegisteredBuiltinMaskDefinition = {
+		const withBaseParams: RegisteredMaskDefinition = {
 			type: definition.type,
 			name: definition.name,
 			features: definition.features,
@@ -107,4 +106,4 @@ export class BuiltinMasksRegistry extends DefinitionRegistry<
 	}
 }
 
-export const builtinMasksRegistry = new BuiltinMasksRegistry();
+export const masksRegistry = new MasksRegistry();