feat(previewer): add beforePreview and afterPreview hooks

README.md

@@ -117,6 +117,10 @@ New handlers can be registered from `import { registerHandlers } from 'pagedjs'`
 Handlers have methods that correspond to the hooks for the parsing, layout and rendering of the Chunker and Polisher. Returning an promise or `async` function from a method in a handler will complete that task before continuing with the other registered methods for that hook.
 
 ```js
+// Previewer
+beforePreview(content, renderTo)
+afterPreview(pages)
+
 // Chunker
 beforeParsed(content)
 afterParsed(parsed)

src/polyfill/previewer.js

 import EventEmitter from "event-emitter";
 
+import Hook from "../utils/hook";
 import Chunker from "../chunker/chunker";
 import Polisher from "../polisher/polisher";
 
@@ -17,6 +18,8 @@ class Previewer {
 
 		// Hooks
 		this.hooks = {};
+		this.hooks.beforeAll = new Hook(this);
+		this.hooks.afterAll = new Hook(this);
 
 		// Handlers
 		this.handlers = this.initializeHandlers();
@@ -119,6 +122,8 @@ class Previewer {
 
 	async preview(content, stylesheets, renderTo) {
 
+		await this.hooks.beforePreview.trigger(content, renderTo);
+
 		if (!content) {
 			content = this.wrapContent();
 		}
@@ -143,6 +148,8 @@ class Previewer {
 
 		this.emit("rendered", flow);
 
+		await this.hooks.afterPreview.trigger(flow.pages);
+
 		return flow;
 	}
 }