Add API to clear canvas renderer texture atlas

Fixes #3455

src/browser/renderer/BaseRenderLayer.ts

@@ -138,6 +138,10 @@ export abstract class BaseRenderLayer implements IRenderLayer {
 
   public abstract reset(): void;
 
+  public clearTextureAtlas(): void {
+    this._charAtlas?.clear();
+  }
+
   /**
    * Fills 1+ cells completely. This uses the existing fillStyle on the context.
    * @param x The column to start at.

src/browser/renderer/Renderer.ts

@@ -149,6 +149,12 @@ export class Renderer extends Disposable implements IRenderer {
     }
   }
 
+  public clearTextureAtlas(): void {
+    for (const layer of this._renderLayers) {
+      layer.clearTextureAtlas();
+    }
+  }
+
   /**
    * Recalculates the character and canvas dimensions.
    */

src/browser/renderer/Types.d.ts

@@ -52,6 +52,7 @@ export interface IRenderer extends IDisposable {
   onOptionsChanged(): void;
   clear(): void;
   renderRows(start: number, end: number): void;
+  clearTextureAtlas?(): void;
 }
 
 export interface IRenderLayer extends IDisposable {
@@ -100,4 +101,9 @@ export interface IRenderLayer extends IDisposable {
    * Clear the state of the render layer.
    */
   reset(): void;
+
+  /**
+   * Clears the texture atlas.
+   */
+  clearTextureAtlas(): void;
 }

src/browser/renderer/atlas/BaseCharAtlas.ts

@@ -28,6 +28,8 @@ export abstract class BaseCharAtlas implements IDisposable {
    */
   private _doWarmUp(): void { }
 
+  public clear(): void { }
+
   /**
    * Called when we start drawing a new frame.
    *

src/browser/renderer/atlas/DynamicCharAtlas.ts

@@ -119,6 +119,16 @@ export class DynamicCharAtlas extends BaseCharAtlas {
     this._drawToCacheCount = 0;
   }
 
+  public clear(): void {
+    if (this._cacheMap.size > 0) {
+      const capacity = this._width * this._height;
+      this._cacheMap = new LRUMap(capacity);
+      this._cacheMap.prealloc(capacity);
+    }
+    this._cacheCtx.clearRect(0, 0, TEXTURE_WIDTH, TEXTURE_HEIGHT);
+    this._tmpCtx.clearRect(0, 0, this._config.scaledCharWidth, this._config.scaledCharHeight);
+  }
+
   public draw(
     ctx: CanvasRenderingContext2D,
     glyph: IGlyphIdentifier,