disable font kerning

src/browser/renderer/dom/DomRenderer.ts

@@ -138,6 +138,7 @@ export class DomRenderer extends Disposable implements IRenderer {
       ` color: ${colors.foreground.css};` +
       ` font-family: ${this._optionsService.rawOptions.fontFamily};` +
       ` font-size: ${this._optionsService.rawOptions.fontSize}px;` +
+      ` font-kerning: none;` +
       ` white-space: pre` +
       `}`;
     styles +=

src/browser/renderer/dom/SpacingCache.ts

@@ -40,6 +40,8 @@ export class SpacingCache implements IDisposable {
     this._container.style.top = '-50000px';
     this._container.style.width = '50000px';
     this._container.style.whiteSpace = 'pre';
+    // avoid undercuts in non-monospace fonts from kerning
+    this._container.style.fontKerning = 'none';
 
     const regular = _document.createElement('span');