minimap: prebake small fonts to reduce runtime perf

src/vs/editor/browser/viewParts/minimap/minimapCharRendererFactory.ts

@@ -5,6 +5,7 @@
 
 import { MinimapCharRenderer } from 'vs/editor/browser/viewParts/minimap/minimapCharRenderer';
 import { allCharCodes } from 'vs/editor/browser/viewParts/minimap/minimapCharSheet';
+import { prebakedMiniMaps } from 'vs/editor/browser/viewParts/minimap/minimapPreBaked';
 import { Constants } from './minimapCharSheet';
 
 /**
@@ -28,10 +29,16 @@ export class MinimapCharRendererFactory {
 			return this.lastCreated;
 		}
 
-		const factory = MinimapCharRendererFactory.createFromSampleData(
-			MinimapCharRendererFactory.createSampleData(fontFamily).data,
-			scale
-		);
+		let factory: MinimapCharRenderer;
+		if (prebakedMiniMaps[scale]) {
+			factory = new MinimapCharRenderer(prebakedMiniMaps[scale](), scale);
+		} else {
+			factory = MinimapCharRendererFactory.createFromSampleData(
+				MinimapCharRendererFactory.createSampleData(fontFamily).data,
+				scale
+			);
+		}
+
 		this.lastFontFamily = fontFamily;
 		this.lastCreated = factory;
 		return factory;

src/vs/editor/browser/viewParts/minimap/minimapPreBaked.ts

+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { once } from 'vs/base/common/functional';
+
+const charTable: { [hex: string]: number } = {
+	'0': 0,
+	'1': 1,
+	'2': 2,
+	'3': 3,
+	'4': 4,
+	'5': 5,
+	'6': 6,
+	'7': 7,
+	'8': 8,
+	'9': 9,
+	A: 10,
+	B: 11,
+	C: 12,
+	D: 13,
+	E: 14,
+	F: 15
+};
+
+const decodeData = (str: string) => {
+	const output = new Uint8ClampedArray(str.length / 2);
+	for (let i = 0; i < str.length; i += 2) {
+		output[i >> 1] = (charTable[str[i]] << 4) | (charTable[str[i + 1]] & 0xF);
+	}
+
+	return output;
+};
+
+/*
+const encodeData = (data: Uint8ClampedArray, length: string) => {
+	const chars = '0123456789ABCDEF';
+	let output = '';
+	for (let i = 0; i < data.length; i++) {
+		output += chars[data[i] >> 4] + chars[data[i] & 0xf];
+	}
+	return output;
+};
+*/
+
+/**
+ * Map of minimap scales to prebaked sample data at those scales. We don't
+ * sample much larger data, because then font family becomes visible, which
+ * is use-configurable.
+ */
+export const prebakedMiniMaps: { [scale: number]: () => Uint8ClampedArray } = {
+	1: once(() =>
+		decodeData(
+			'0000511D6300CF609C709645A78432005642574171487021003C451900274D35D762755E8B629C5BA856AF57BA649530C167D1512A272A3F6038604460398526BCA2A968DB6F8957C768BE5FBE2FB467CF5D8D5B795DC7625B5DFF50DE64C466DB2FC47CD860A65E9A2EB96CB54CE06DA763AB2EA26860524D3763536601005116008177A8705E53AB738E6A982F88BAA35B5F5B626D9C636B449B737E5B7B678598869A662F6B5B8542706C704C80736A607578685B70594A49715A4522E792'
+		)
+	),
+	2: once(() =>
+		decodeData(
+			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
+		)
+	)
+};