respect dpr/charWidth changes, more accurate base measuring

src/browser/renderer/dom/DomRenderer.ts

@@ -233,6 +233,7 @@ export class DomRenderer extends Disposable implements IRenderer {
 
   public handleDevicePixelRatioChange(): void {
     this._updateDimensions();
+    this._widthCache.clear();
   }
 
   private _refreshRowElements(cols: number, rows: number): void {
@@ -255,6 +256,7 @@ export class DomRenderer extends Disposable implements IRenderer {
 
   public handleCharSizeChanged(): void {
     this._updateDimensions();
+    this._widthCache.clear();
   }
 
   public handleBlur(): void {

src/browser/renderer/dom/DomRendererRowFactory.ts

@@ -391,6 +391,11 @@ export class DomRendererRowFactory {
       }
       // apply letter-spacing rule
       if (spacing) {
+        /**
+         * TODO:
+         * - check if we can ignore tiny spacings here (saves ~400ms)
+         * - check if we can apply a global spacing to rows element
+         */
         charElement.style.letterSpacing = `${spacing}px`;
       }