fix(window level): The window level value is not displayed by default on all the viewports when selecting common/custom layout and TMTV. (#5865)

* fix(window level): Set up listener for viewport availability such that the initial window level can be read and displayed.

* PR feedback.

* PR feedback.

---------

Co-authored-by: Bill Wallace <wayfarer3130@gmail.com>

tests/WindowLevelOverlayText.spec.ts

@@ -0,0 +1,40 @@
+import { expect, test, visitStudy } from './utils';
+
+test('should display the window level text as an overlay in various viewport layouts', async ({
+  page,
+  mainToolbarPageObject,
+  viewportPageObject,
+}) => {
+  const studyInstanceUID = '1.3.6.1.4.1.25403.345050719074.3824.20170125095258.1';
+  const mode = 'viewer';
+  await visitStudy(page, studyInstanceUID, mode, 2000);
+
+  await expect(viewportPageObject.getNth(0).overlayText.bottomLeft.windowLevel).toBeVisible();
+
+  await mainToolbarPageObject.layoutSelection.click();
+  await page.getByTestId('Layout-3-0').click();
+
+  for (let i = 0; i < 3; i++) {
+    await expect(viewportPageObject.getNth(i).overlayText.bottomLeft.windowLevel).toBeVisible();
+  }
+
+  await mainToolbarPageObject.layoutSelection.click();
+  await page.getByTestId('Layout-1-1').click();
+
+  for (let i = 0; i < 3; i++) {
+    await expect(viewportPageObject.getNth(i).overlayText.bottomLeft.windowLevel).toBeVisible();
+  }
+});
+
+test('should display the window level text as an overlay in the various TMTV viewports', async ({
+  page,
+  viewportPageObject,
+}) => {
+  const studyInstanceUID = '1.3.6.1.4.1.14519.5.2.1.7009.2403.871108593056125491804754960339';
+  const mode = 'tmtv';
+  await visitStudy(page, studyInstanceUID, mode, 2000);
+
+  for (let i = 0; i < 9; i++) {
+    await expect(viewportPageObject.getNth(i).overlayText.bottomLeft.windowLevel).toBeVisible();
+  }
+});