Introduce is256Color helper

src/renderer/atlas/CharAtlasUtils.ts

@@ -6,6 +6,7 @@
 import { ITerminal } from '../../Types';
 import { IColorSet } from '../Types';
 import { ICharAtlasConfig } from '../../shared/atlas/Types';
+import { DEFAULT_COLOR } from './Types';
 
 export function generateConfig(scaledCharWidth: number, scaledCharHeight: number, terminal: ITerminal, colors: IColorSet): ICharAtlasConfig {
   // null out some fields that don't matter
@@ -51,3 +52,7 @@ export function configEquals(a: ICharAtlasConfig, b: ICharAtlasConfig): boolean
       a.colors.foreground === b.colors.foreground &&
       a.colors.background === b.colors.background;
 }
+
+export function is256Color(colorCode: number): boolean {
+  return colorCode < DEFAULT_COLOR;
+}

src/renderer/atlas/StaticCharAtlas.ts

@@ -7,6 +7,7 @@ import { DIM_OPACITY, IGlyphIdentifier, DEFAULT_COLOR } from './Types';
 import { CHAR_ATLAS_CELL_SPACING, ICharAtlasConfig } from '../../shared/atlas/Types';
 import { generateStaticCharAtlasTexture } from '../../shared/atlas/CharAtlasGenerator';
 import BaseCharAtlas from './BaseCharAtlas';
+import { is256Color } from './CharAtlasUtils';
 
 export default class StaticCharAtlas extends BaseCharAtlas {
   private _texture: HTMLCanvasElement | ImageBitmap;
@@ -58,7 +59,7 @@ export default class StaticCharAtlas extends BaseCharAtlas {
     }
 
     let colorIndex = 0;
-    if (glyph.fg < DEFAULT_COLOR) {
+    if (is256Color(glyph.fg)) {
       colorIndex = 2 + glyph.fg + (glyph.bold ? 16 : 0);
     } else if (glyph.fg === DEFAULT_COLOR) {
       // If default color and bold