Avatar defaults and colors

ts/util/avatarTextSizeCalculator.ts

@@ -0,0 +1,52 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import * as grapheme from './grapheme';
+import { getEmojiCount } from '../components/emoji/lib';
+
+type FontSizes = {
+  diameter: number;
+  singleEmoji: number;
+  smol: number;
+  text: number;
+};
+
+type RectSize = {
+  height: number;
+  width: number;
+};
+
+export function getFontSizes(bubbleSize: number): FontSizes {
+  return {
+    diameter: Math.ceil(bubbleSize * 0.75),
+    singleEmoji: Math.ceil(bubbleSize * 0.6),
+    smol: Math.ceil(bubbleSize * 0.05),
+    text: Math.ceil(bubbleSize * 0.45),
+  };
+}
+
+export function getFittedFontSize(
+  bubbleSize: number,
+  text: string,
+  measure: (candidateFontSize: number) => RectSize
+): number {
+  const sizes = getFontSizes(bubbleSize);
+
+  let candidateFontSize = sizes.text;
+  if (grapheme.count(text) === 1 && getEmojiCount(text) === 1) {
+    candidateFontSize = sizes.singleEmoji;
+  }
+
+  for (
+    candidateFontSize;
+    candidateFontSize >= sizes.smol;
+    candidateFontSize -= 1
+  ) {
+    const { height, width } = measure(candidateFontSize);
+    if (width < sizes.diameter && height < sizes.diameter) {
+      return candidateFontSize;
+    }
+  }
+
+  return candidateFontSize;
+}