feat(core): add `begin` and `end` renderer methods to track change detection

packages/core/src/render/api.ts

@@ -127,6 +127,8 @@ export interface RendererType2 {
  */
 export abstract class RendererFactory2 {
   abstract createRenderer(hostElement: any, type: RendererType2|null): Renderer2;
+  abstract begin?(): void;
+  abstract end?(): void;
 }
 
 /**

packages/core/src/view/refs.ts

@@ -239,7 +239,16 @@ export class ViewRef_ implements EmbeddedViewRef<any>, InternalViewRef {
 
   markForCheck(): void { markParentViewsForCheck(this._view); }
   detach(): void { this._view.state &= ~ViewState.Attached; }
-  detectChanges(): void { Services.checkAndUpdateView(this._view); }
+  detectChanges(): void {
+    const fs = this._view.root.rendererFactory;
+    if (fs.begin) {
+      fs.begin();
+    }
+    Services.checkAndUpdateView(this._view);
+    if (fs.end) {
+      fs.end();
+    }
+  }
   checkNoChanges(): void { Services.checkNoChangesView(this._view); }
 
   reattach(): void { this._view.state |= ViewState.Attached; }

packages/core/src/view/services.ts

@@ -456,6 +456,17 @@ class DebugRendererFactory2 implements RendererFactory2 {
   createRenderer(element: any, renderData: RendererType2|null): Renderer2 {
     return new DebugRenderer2(this.delegate.createRenderer(element, renderData));
   }
+
+  begin() {
+    if (this.delegate.begin) {
+      this.delegate.begin();
+    }
+  }
+  end() {
+    if (this.delegate.end) {
+      this.delegate.end();
+    }
+  }
 }
 
 

packages/core/test/linker/change_detection_integration_spec.ts

@@ -666,6 +666,22 @@ export function main() {
 
     });
 
+    describe('RendererFactory', () => {
+      it('should call the begin and end methods on the renderer factory when change detection is called',
+         fakeAsync(() => {
+           const ctx = createCompFixture('<div testDirective [a]="42"></div>');
+           const rf = TestBed.get(RendererFactory2);
+           spyOn(rf, 'begin');
+           spyOn(rf, 'end');
+           expect(rf.begin).not.toHaveBeenCalled();
+           expect(rf.end).not.toHaveBeenCalled();
+
+           ctx.detectChanges(false);
+           expect(rf.begin).toHaveBeenCalled();
+           expect(rf.end).toHaveBeenCalled();
+         }));
+    });
+
     describe('change notification', () => {
       describe('updating directives', () => {
         it('should happen without invoking the renderer', fakeAsync(() => {

packages/platform-browser/animations/src/animation_renderer.ts

@@ -25,6 +25,17 @@ export class AnimationRendererFactory implements RendererFactory2 {
         trigger => this._engine.registerTrigger(trigger, namespaceify(namespaceId, trigger.name)));
     return new AnimationRenderer(delegate, this._engine, this._zone, namespaceId);
   }
+
+  begin() {
+    if (this.delegate.begin) {
+      this.delegate.begin();
+    }
+  }
+  end() {
+    if (this.delegate.end) {
+      this.delegate.end();
+    }
+  }
 }
 
 export class AnimationRenderer implements Renderer2 {

packages/platform-browser/src/dom/dom_renderer.ts

@@ -94,6 +94,9 @@ export class DomRendererFactory2 implements RendererFactory2 {
       }
     }
   }
+
+  begin() {}
+  end() {}
 }
 
 class DefaultDomRenderer2 implements Renderer2 {

packages/platform-server/src/server_renderer.ts

@@ -52,6 +52,9 @@ export class ServerRendererFactory2 implements RendererFactory2 {
       }
     }
   }
+
+  begin() {}
+  end() {}
 }
 
 class DefaultServerRenderer2 implements Renderer2 {

packages/platform-webworker/src/web_workers/worker/renderer.ts

@@ -81,6 +81,9 @@ export class WebWorkerRendererFactory2 implements RendererFactory2 {
     return renderer;
   }
 
+  begin() {}
+  end() {}
+
   callUI(fnName: string, fnArgs: FnArg[]) {
     const args = new UiArguments(fnName, fnArgs);
     this._messageBroker.runOnService(args, null);

tools/public_api_guard/core/core.d.ts

@@ -846,7 +846,9 @@ export declare abstract class Renderer2 {
 
 /** @experimental */
 export declare abstract class RendererFactory2 {
+    abstract begin?(): void;
     abstract createRenderer(hostElement: any, type: RendererType2 | null): Renderer2;
+    abstract end?(): void;
 }
 
 /** @experimental */