feat(renderers): add restoreFocus setting

This controls where focus should be restored when a dialog closes.
By default focus is restored to the last element that was active when
the dialog opened.

src/dialog-settings.ts

@@ -92,6 +92,14 @@ export interface DialogSettings {
    * When invoked the function is passed the dialog container and the dialog overlay elements.
    */
   position?: (dialogContainer: Element, dialogOverlay?: Element) => void;
+
+  /**
+   * This function is called when a dialog closes to restore focus to the last
+   * element that was focused when the dialog opened. It can be overridden in
+   * general settings, or on a case by case basis by providing an override when
+   * a particular dialog is opened.
+   */
+  restoreFocus?: (lastActiveElement: HTMLElement) => void;
 }
 
 /**
@@ -105,4 +113,5 @@ export class DefaultDialogSettings implements DialogSettings {
   public rejectOnCancel = false;
   public ignoreTransitions = false;
   public position?: (dialogContainer: Element, dialogOverlay: Element) => void;
+  public restoreFocus = (lastActiveElement: HTMLElement) => lastActiveElement.focus();
 }

src/renderers/native-dialog-renderer.ts

@@ -47,6 +47,7 @@ export class NativeDialogRenderer implements Renderer {
   private dialogCancel: (e: Event) => void;
 
   public dialogContainer: HTMLDialogElement;
+  public lastActiveElement: HTMLElement;
   public host: Element;
   public anchor: Element;
 
@@ -62,6 +63,8 @@ export class NativeDialogRenderer implements Renderer {
   }
 
   private attach(dialogController: DialogController): void {
+    this.lastActiveElement = DOM.activeElement as HTMLElement;
+
     const spacingWrapper = DOM.createElement('div'); // TODO: check if redundant
     spacingWrapper.appendChild(this.anchor);
     this.dialogContainer = DOM.createElement(containerTagName) as HTMLDialogElement;
@@ -92,6 +95,9 @@ export class NativeDialogRenderer implements Renderer {
     if (!NativeDialogRenderer.dialogControllers.length) {
       this.host.classList.remove('ux-dialog-open');
     }
+    if (dialogController.settings.restoreFocus) {
+      dialogController.settings.restoreFocus(this.lastActiveElement);
+    }
   }
 
   private setAsActive(): void {

src/renderers/ux-dialog-renderer.ts

@@ -105,6 +105,7 @@ export class DialogRenderer implements Renderer {
 
   public dialogContainer: HTMLElement;
   public dialogOverlay: HTMLElement;
+  public lastActiveElement: HTMLElement;
   public host: Element;
   public anchor: Element;
 
@@ -120,6 +121,8 @@ export class DialogRenderer implements Renderer {
   }
 
   private attach(dialogController: DialogController): void {
+    this.lastActiveElement = DOM.activeElement as HTMLElement;
+
     const spacingWrapper = DOM.createElement('div'); // TODO: check if redundant
     spacingWrapper.appendChild(this.anchor);
 
@@ -156,6 +159,9 @@ export class DialogRenderer implements Renderer {
     if (!DialogRenderer.dialogControllers.length) {
       host.classList.remove('ux-dialog-open');
     }
+    if (dialogController.settings.restoreFocus) {
+      dialogController.settings.restoreFocus(this.lastActiveElement);
+    }
   }
 
   private setAsActive(): void {

test/unit/native-dialog-renderer.spec.ts

@@ -182,6 +182,18 @@ describe('native-dialog-renderer.spec.ts', () => {
         done();
       });
     });
+
+    describe('"restoreFocus"', () => {
+      it('and calls the given callback on close', async done => {
+        let restoreCalled = false;
+        const renderer = createRenderer({ restoreFocus: () => restoreCalled = true });
+        await show(done, renderer);
+        expect(restoreCalled).toBe(false);
+        await hide(done, renderer);
+        expect(restoreCalled).toBe(true);
+        done();
+      });
+    });
   });
 
   describe('on first open dialog', () => {

test/unit/ux-dialog-renderer.spec.ts

@@ -185,6 +185,18 @@ describe('ux-dialog-renderer.spec.ts', () => {
         done();
       });
     });
+
+    describe('"restoreFocus"', () => {
+      it('and calls the given callback on close', async done => {
+        let restoreCalled = false;
+        const renderer = createRenderer({ restoreFocus: () => restoreCalled = true });
+        await show(done, renderer);
+        expect(restoreCalled).toBe(false);
+        await hide(done, renderer);
+        expect(restoreCalled).toBe(true);
+        done();
+      });
+    });
   });
 
   describe('on first open dialog', () => {