[Discover] Improve doc viewer source tab performance by limiting height (#127439) (#128125)

(cherry picked from commit f5533008dd)

src/plugins/discover/public/services/doc_views/components/doc_viewer_source/get_height.test.tsx

@@ -0,0 +1,50 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+import { monaco } from '@kbn/monaco';
+import { getHeight } from './get_height';
+
+describe('getHeight', () => {
+  window.innerHeight = 500;
+  const getMonacoMock = (lineCount: number) => {
+    return {
+      getDomNode: jest.fn(() => {
+        return {
+          getBoundingClientRect: jest.fn(() => {
+            return {
+              top: 200,
+            };
+          }),
+        };
+      }),
+      getOption: jest.fn(() => 10),
+      getModel: jest.fn(() => ({ getLineCount: jest.fn(() => lineCount) })),
+      getTopForLineNumber: jest.fn((line) => line * 10),
+    } as unknown as monaco.editor.IStandaloneCodeEditor;
+  };
+  test('when using document explorer, returning the available height in the flyout', () => {
+    const monacoMock = getMonacoMock(500);
+
+    const height = getHeight(monacoMock, true);
+    expect(height).toBe(275);
+  });
+
+  test('when using classic table, its displayed inline without scrolling', () => {
+    const monacoMock = getMonacoMock(100);
+
+    const height = getHeight(monacoMock, false);
+    expect(height).toBe(1020);
+  });
+
+  test('when using classic table, limited height > 500 lines to allow scrolling', () => {
+    const monacoMock = getMonacoMock(1000);
+
+    const height = getHeight(monacoMock, false);
+    expect(height).toBe(5020);
+  });
+});

src/plugins/discover/public/services/doc_views/components/doc_viewer_source/get_height.tsx

@@ -0,0 +1,32 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+import { monaco } from '@kbn/monaco';
+import { MARGIN_BOTTOM, MAX_LINES_CLASSIC_TABLE } from './source';
+
+export function getHeight(editor: monaco.editor.IStandaloneCodeEditor, useDocExplorer: boolean) {
+  const editorElement = editor?.getDomNode();
+  if (!editorElement) {
+    return 0;
+  }
+
+  let result;
+  if (useDocExplorer) {
+    // assign a good height filling the available space of the document flyout
+    const position = editorElement.getBoundingClientRect();
+    result = window.innerHeight - position.top - MARGIN_BOTTOM;
+  } else {
+    // takes care of the classic table, display a maximum of 500 lines
+    // why not display it all? Due to performance issues when the browser needs to render it all
+    const lineHeight = editor.getOption(monaco.editor.EditorOption.lineHeight);
+    const lineCount = editor.getModel()?.getLineCount() || 1;
+    const displayedLineCount =
+      lineCount > MAX_LINES_CLASSIC_TABLE ? MAX_LINES_CLASSIC_TABLE : lineCount;
+    result = editor.getTopForLineNumber(displayedLineCount + 1) + lineHeight;
+  }
+  return result > 0 ? result : 0;
+}

src/plugins/discover/public/services/doc_views/components/doc_viewer_source/source.tsx

@@ -14,10 +14,11 @@ import { EuiButton, EuiEmptyPrompt, EuiLoadingSpinner, EuiSpacer, EuiText } from
 import { i18n } from '@kbn/i18n';
 import { useDiscoverServices } from '../../../../utils/use_discover_services';
 import { JSONCodeEditorCommonMemoized } from '../../../../components/json_code_editor/json_code_editor_common';
-import { SEARCH_FIELDS_FROM_SOURCE } from '../../../../../common';
+import { DOC_TABLE_LEGACY, SEARCH_FIELDS_FROM_SOURCE } from '../../../../../common';
 import { useEsDocSearch } from '../../../../utils/use_es_doc_search';
 import { DataView } from '../../../../../../data_views/common';
 import { ElasticRequestState } from '../../../../application/doc/types';
+import { getHeight } from './get_height';
 
 interface SourceViewerProps {
   id: string;
@@ -27,6 +28,12 @@ interface SourceViewerProps {
   width?: number;
 }
 
+// Ihe number of lines displayed without scrolling used for classic table, which renders the component
+// inline limitation was necessary to enable virtualized scrolling, which improves performance
+export const MAX_LINES_CLASSIC_TABLE = 500;
+// Displayed margin of the code editor to the window bottom when rendered in the document explorer flyout
+export const MARGIN_BOTTOM = 25;
+
 export const DocViewerSource = ({
   id,
   index,
@@ -38,6 +45,7 @@ export const DocViewerSource = ({
   const [jsonValue, setJsonValue] = useState<string>('');
   const { uiSettings } = useDiscoverServices();
   const useNewFieldsApi = !uiSettings.get(SEARCH_FIELDS_FROM_SOURCE);
+  const useDocExplorer = !uiSettings.get(DOC_TABLE_LEGACY);
   const [reqState, hit, requestData] = useEsDocSearch({
     id,
     index,
@@ -62,16 +70,18 @@ export const DocViewerSource = ({
       return;
     }
 
-    const lineHeight = editor.getOption(monaco.editor.EditorOption.lineHeight);
-    const lineCount = editor.getModel()?.getLineCount() || 1;
-    const height = editor.getTopForLineNumber(lineCount + 1) + lineHeight;
+    const height = getHeight(editor, useDocExplorer);
+    if (height === 0) {
+      return;
+    }
+
     if (!jsonValue || jsonValue === '') {
       editorElement.style.height = '0px';
     } else {
       editorElement.style.height = `${height}px`;
     }
     editor.layout();
-  }, [editor, jsonValue]);
+  }, [editor, jsonValue, useDocExplorer]);
 
   const loadingState = (
     <div className="sourceViewer__loading">