Don't rescale powerline or nerd fonts

src/browser/renderer/shared/RendererUtils.ts

@@ -23,23 +23,40 @@ export function isRestrictedPowerlineGlyph(codepoint: number): boolean {
   return 0xE0B0 <= codepoint && codepoint <= 0xE0B7;
 }
 
+function isNerdFontGlyph(codepoint: number): boolean {
+  return 0xE000 <= codepoint && codepoint <= 0xF8FF;
+}
+
 function isBoxOrBlockGlyph(codepoint: number): boolean {
   return 0x2500 <= codepoint && codepoint <= 0x259F;
 }
 
 export function isEmoji(codepoint: number): boolean {
   return (
     codepoint >= 0x1F600 && codepoint <= 0x1F64F || // Emoticons
-    codepoint >= 0x1F300 && codepoint <= 0x1F5FF ||  // Misc Symbols and Pictographs
-    codepoint >= 0x1F680 && codepoint <= 0x1F6FF ||  // Transport and Map
-    codepoint >= 0x2600 && codepoint <= 0x26FF ||    // Misc symbols
-    codepoint >= 0x2700 && codepoint <= 0x27BF ||    // Dingbats
-    codepoint >= 0xFE00 && codepoint <= 0xFE0F ||    // Variation Selectors
-    codepoint >= 0x1F900 && codepoint <= 0x1F9FF ||  // Supplemental Symbols and Pictographs
+    codepoint >= 0x1F300 && codepoint <= 0x1F5FF || // Misc Symbols and Pictographs
+    codepoint >= 0x1F680 && codepoint <= 0x1F6FF || // Transport and Map
+    codepoint >= 0x2600  && codepoint <= 0x26FF  || // Misc symbols
+    codepoint >= 0x2700  && codepoint <= 0x27BF  || // Dingbats
+    codepoint >= 0xFE00  && codepoint <= 0xFE0F  || // Variation Selectors
+    codepoint >= 0x1F900 && codepoint <= 0x1F9FF || // Supplemental Symbols and Pictographs
     codepoint >= 0x1F1E6 && codepoint <= 0x1F1FF
   );
 }
 
+export function allowRescaling(codepoint: number | undefined, width: number, glyphSizeX: number, deviceCellWidth: number): boolean {
+  return (
+    // Is single cell width
+    width === 1 &&
+    // Glyph exceeds cell bounds, + 1 to avoid hurting readability
+    glyphSizeX > deviceCellWidth + 1 &&
+    // Never rescale emoji
+    codepoint !== undefined && !isEmoji(codepoint) &&
+    // Never rescale powerline or nerd fonts
+    !isPowerlineGlyph(codepoint) && !isNerdFontGlyph(codepoint)
+  );
+}
+
 export function treatGlyphAsBackgroundColor(codepoint: number): boolean {
   return isPowerlineGlyph(codepoint) || isBoxOrBlockGlyph(codepoint);
 }

typings/xterm-headless.d.ts

@@ -144,8 +144,14 @@ declare module '@xterm/headless' {
      * Whether to rescale glyphs horizontally that are a single cell wide but
      * have glyphs that would overlap following cell(s). This typically happens
      * for ambiguous width characters (eg. the roman numeral characters U+2160+)
-     * which aren't featured in monospace fonts. Emoji glyphs are never
-     * rescaled. This is an important feature for achieving GB18030 compliance.
+     * which aren't featured in monospace fonts. This is an important feature
+     * for achieving GB18030 compliance.
+     *
+     * The following glyphs will never be rescaled:
+     *
+     * - Emoji glyphs
+     * - Powerline glyphs
+     * - Nerd font glyphs
      *
      * Note that this doesn't work with the DOM renderer. The default is false.
      */

typings/xterm.d.ts

@@ -213,8 +213,14 @@ declare module '@xterm/xterm' {
      * Whether to rescale glyphs horizontally that are a single cell wide but
      * have glyphs that would overlap following cell(s). This typically happens
      * for ambiguous width characters (eg. the roman numeral characters U+2160+)
-     * which aren't featured in monospace fonts. Emoji glyphs are never
-     * rescaled. This is an important feature for achieving GB18030 compliance.
+     * which aren't featured in monospace fonts. This is an important feature
+     * for achieving GB18030 compliance.
+     *
+     * The following glyphs will never be rescaled:
+     *
+     * - Emoji glyphs
+     * - Powerline glyphs
+     * - Nerd font glyphs
      *
      * Note that this doesn't work with the DOM renderer. The default is false.
      */