Decode structs without Object.defineProperties

WINDOWKIT.md

@@ -14,6 +14,8 @@ dependent names its URL:
 | Patch | Upstream |
 | --- | --- |
 | `getVariation()` for fonts in WOFF and WOFF2 containers (#1) | [foliojs/fontkit#389](https://github.com/foliojs/fontkit/pull/389) |
+| Decoded structs hold their hidden fields in private fields of a class, not `Object.defineProperties`: a face's first shaping takes a third less time (#4, `src/restructure.js`) | Not offered. The change belongs in [restructure](https://github.com/foliojs/restructure)'s `Struct#_setup` ([sidorares/ntk#437](https://github.com/sidorares/ntk/issues/437)) |
+| Builds for Chrome 91 rather than 70, so those private fields stay native instead of being compiled to WeakMaps (#4) | Fork only |
 
 When upstream releases a version with everything in this table, the fork
 has done its job: point the dependent back at `fontkit` on npm.

package.json

@@ -41,27 +41,27 @@
       "source": "src/node.js",
       "context": "browser",
       "engines": {
-        "browsers": "chrome >= 70"
+        "browsers": "chrome >= 91"
       }
     },
     "node-module": {
       "source": "src/node.js",
       "isLibrary": true,
       "includeNodeModules": false,
       "engines": {
-        "browsers": "chrome >= 70"
+        "browsers": "chrome >= 91"
       }
     },
     "module": {
       "source": "src/index.js",
       "engines": {
-        "browsers": "chrome >= 70"
+        "browsers": "chrome >= 91"
       }
     },
     "browser": {
       "source": "src/index.js",
       "engines": {
-        "browsers": "chrome >= 70"
+        "browsers": "chrome >= 91"
       }
     }
   },

src/DFont.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from './restructure';
 import TTFFont from './TTFFont';
 
 let DFontName = new r.String(r.uint8);

src/TrueTypeCollection.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from './restructure';
 import TTFFont from './TTFFont';
 import Directory from './tables/directory';
 import tables from './tables';

src/WOFF2Font.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from './restructure';
 import brotli from 'brotli/decompress.js';
 import TTFFont from './TTFFont';
 import TTFGlyph, { Point } from './glyph/TTFGlyph';

src/cff/CFFTop.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import { resolveLength } from 'restructure';
 import CFFDict from './CFFDict';
 import CFFIndex from './CFFIndex';

src/glyph/SBIXGlyph.js

@@ -1,5 +1,5 @@
 import TTFGlyph from './TTFGlyph';
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let SBIXImage = new r.Struct({
   originX: r.uint16,

src/glyph/TTFGlyph.js

@@ -1,7 +1,7 @@
 import Glyph from './Glyph';
 import Path from './Path';
 import BBox from './BBox';
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 // The header for both simple and composite glyphs
 let GlyfHeader = new r.Struct({

src/glyph/TTFGlyphEncoder.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 // Flags for simple glyphs
 const ON_CURVE        = 1 << 0;

src/restructure.js

@@ -0,0 +1,91 @@
+// restructure, with the structs fontkit decodes made without
+// Object.defineProperties.
+//
+// restructure gives every struct it decodes four hidden fields (parent,
+// _startOffset, _currentOffset, _length) with one Object.defineProperties
+// call, which is a runtime call, and fontkit decodes thousands of structs in
+// a face's first shaping and a glyph's first outline. The structs made here
+// keep the four in private fields of a class and read them through accessors
+// on its prototype, which takes a fifth to two fifths off a face's first
+// shaping, more for a face with more lookups (sidorares/ntk#437).
+//
+// They are only fast where the private fields are native: package.json's
+// targets are Chrome 91 rather than 70 for that, since below it the build
+// compiles them to WeakMaps.
+//
+// Everything that reads them reads the same: they stay out of Object.keys,
+// for...in, JSON.stringify and Object.assign, `struct.parent` reads, and a
+// write to it throws in strict code. What differs is that they are no longer
+// own properties (hasOwnProperty, getOwnPropertyNames), and that a decoded
+// struct's prototype is DecodedStruct's rather than Object.prototype.
+//
+// This is a module of its own rather than a change to restructure's
+// prototype because restructure is shared by everything in the process that
+// uses it: only the structs fontkit declares are made this way. Files that
+// declare structs import restructure from here, which test/restructure.js
+// checks.
+import * as r from 'restructure';
+
+// By name, not `export * from 'restructure'`: the parcel this builds with
+// drops a star re-export of an external package from a module it wraps, and
+// it wraps this one. test/restructure.js checks the list is all of them.
+export {
+  Array, Bitfield, Boolean, Buffer, DecodeStream, EncodeStream, Enum, Fixed,
+  LazyArray, Number, Optional, Pointer, PropertyDescriptor, Reserved, String,
+  VoidPointer, double, doublebe, doublele, fixed16, fixed16be, fixed16le,
+  fixed32, fixed32be, fixed32le, float, floatbe, floatle, int16, int16be,
+  int16le, int24, int24be, int24le, int32, int32be, int32le, int8,
+  resolveLength, uint16, uint16be, uint16le, uint24, uint24be, uint24le,
+  uint32, uint32be, uint32le, uint8
+} from 'restructure';
+
+export class DecodedStruct {
+  #parent;
+  #startOffset;
+  #currentOffset;
+  #length;
+
+  constructor(parent, startOffset, length) {
+    this.#parent = parent;
+    this.#startOffset = startOffset;
+    this.#currentOffset = 0;
+    this.#length = length;
+  }
+
+  // An object made with Object.create(DecodedStruct.prototype) has none of
+  // the fields, which is what a deep copy by the clone package is (subsets
+  // copy maxp, head and hhea that way). It reads them as undefined, as a
+  // copy of one of restructure's own structs does.
+
+  get parent() {
+    return #parent in this ? this.#parent : undefined;
+  }
+
+  get _startOffset() {
+    return #startOffset in this ? this.#startOffset : undefined;
+  }
+
+  get _currentOffset() {
+    return #currentOffset in this ? this.#currentOffset : undefined;
+  }
+
+  set _currentOffset(value) {
+    this.#currentOffset = value;
+  }
+
+  get _length() {
+    return #length in this ? this.#length : undefined;
+  }
+}
+
+export class Struct extends r.Struct {
+  _setup(stream, parent, length) {
+    return new DecodedStruct(parent, stream.pos, length);
+  }
+}
+
+export class VersionedStruct extends r.VersionedStruct {
+  _setup(stream, parent, length) {
+    return new DecodedStruct(parent, stream.pos, length);
+  }
+}

src/tables/BASE.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import {ScriptList, FeatureList, LookupList, Coverage, ClassDef, Device} from './opentype';
 import {ItemVariationStore} from './variations';
 

src/tables/COLR.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let LayerRecord = new r.Struct({
   gid: r.uint16,          // Glyph ID of layer glyph (must be in z-order from bottom to top).

src/tables/CPAL.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let ColorRecord = new r.Struct({
   blue: r.uint8,

src/tables/DSIG.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let Signature = new r.Struct({
   format: r.uint32,

src/tables/EBDT.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 export let BigMetrics = new r.Struct({
   height: r.uint8,

src/tables/EBLC.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import {BigMetrics} from './EBDT';
 
 let SBitLineMetrics = new r.Struct({

src/tables/GDEF.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import {ScriptList, FeatureList, LookupList, Coverage, ClassDef, Device} from './opentype';
 import {ItemVariationStore} from './variations';
 

src/tables/GPOS.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import {ScriptList, FeatureList, LookupList, Coverage, ClassDef, Device, Context, ChainingContext} from './opentype';
 import {FeatureVariations} from './variations';
 

src/tables/GSUB.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import {ScriptList, FeatureList, LookupList, Coverage, ClassDef, Device, Context, ChainingContext} from './opentype';
 import {FeatureVariations} from './variations';
 

src/tables/HVAR.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import { resolveLength } from 'restructure';
 import { ItemVariationStore } from './variations';
 

src/tables/JSTF.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import { ScriptList, FeatureList, LookupList, Coverage, ClassDef, Device } from './opentype';
 import { GPOSLookup } from './GPOS';
 

src/tables/LTSH.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 // Linear Threshold table
 // Records the ppem for each glyph at which the scaling becomes linear again,

src/tables/OS2.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 var OS2 = new r.VersionedStruct(r.uint16, {
   header: {

src/tables/PCLT.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 // PCL 5 Table
 // NOTE: The PCLT table is strongly discouraged for OpenType fonts with TrueType outlines

src/tables/VDMX.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 // VDMX tables contain ascender/descender overrides for certain (usually small)
 // sizes. This is needed in order to match font metrics on Windows.

src/tables/VORG.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let VerticalOrigin = new r.Struct({
   glyphIndex:   r.uint16,

src/tables/WOFF2Directory.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 const Base128 = {
   decode(stream) {

src/tables/WOFFDirectory.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import tables from './';
 
 let WOFFDirectoryEntry = new r.Struct({

src/tables/aat.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 class UnboundedArrayAccessor {
   constructor(type, stream, parent) {

src/tables/avar.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let shortFrac = new r.Fixed(16, 'BE', 14);
 

src/tables/bsln.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import { LookupTable } from './aat';
 
 let BslnSubtable = new r.VersionedStruct('format', {

src/tables/cmap.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let SubHeader = new r.Struct({
   firstCode:      r.uint16,

src/tables/cvt.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 // An array of predefined values accessible by instructions
 export default new r.Struct({

src/tables/directory.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import Tables from './';
 
 let TableEntry = new r.Struct({

src/tables/feat.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let Setting = new r.Struct({
   setting: r.uint16,

src/tables/fpgm.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 // A list of instructions that are executed once when a font is first used.
 // These instructions are known as the font program. The main use of this table

src/tables/fvar.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let Axis = new r.Struct({
   axisTag: new r.String(4),

src/tables/gasp.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let GaspRange = new r.Struct({
   rangeMaxPPEM:       r.uint16,                  // Upper limit of range, in ppem

src/tables/gvar.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let shortFrac = new r.Fixed(16, 'BE', 14);
 class Offset {

src/tables/hdmx.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let DeviceRecord = new r.Struct({
   pixelSize:      r.uint8,

src/tables/head.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 // font header
 export default new r.Struct({

src/tables/hhea.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 // horizontal header
 export default new r.Struct({

src/tables/hmtx.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let HmtxEntry = new r.Struct({
   advance: r.uint16,

src/tables/just.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 import { LookupTable, StateTable1 } from './aat';
 
 let ClassTable = new r.Struct({

src/tables/kern.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let KernPair = new r.Struct({
   left:   r.uint16,

src/tables/loca.js

@@ -1,4 +1,4 @@
-import * as r from 'restructure';
+import * as r from '../restructure';
 
 let loca = new r.VersionedStruct('head.indexToLocFormat', {
   0: {