Add keyboard navigation to repository overview list (#2146)

A new api is introduced to allow focus-based list iteration through keyboard shortcuts. The api is initially considered closed and only used in the repository overview.

Co-authored-by: Eduard Heimbuch <eduard.heimbuch@cloudogu.com>

docs/de/user/shortcuts/index.md

@@ -5,7 +5,8 @@ Der SCM-Manager unterstützt Tastaturinteraktion und -navigation durch zusätzli
 
 ### Übersicht
 
-Während sie den SCM-Manager verwenden, können sie eine Übersicht aller dem aktiven Benutzer auf der aktuellen Seite verfügbaren Tastenkürzel mittels der `?`-Taste aufrufen.
+Während Sie den SCM-Manager verwenden, können Sie eine Übersicht aller
+verfügbaren Tastenkürzel mittels der `?`-Taste aufrufen.
 
 ### Globale Tastenkürzel
 
@@ -18,20 +19,31 @@ Während sie den SCM-Manager verwenden, können sie eine Übersicht aller dem ak
 | alt g           | Navigiere zur Gruppenübersicht      |
 | alt a           | Navigiere zur Administration        |
 
+### Navigation von Listen
+
+Einige Seiten mit Listen erlauben die Navigation per Tastatur.
+Wenn die Seite dieses unterstützt, tauchen die Tastaturkürzel in der Übersicht im SCM-Manager
+auf (`?`).
+
+| Key Combination | Description                                       |
+|-----------------|---------------------------------------------------|
+| j               | Bewege den Fokus auf den nächsten Listeneintrag   |
+| k               | Bewege den Fokus auf den vorherigen Listeneintrag |
+
 ### Repositoryspezifische Tastenkürzel
 
-| Key Combination | Description   |
+| Key Combination | Description                  |
-|-----------------|---------------|
+|-----------------|------------------------------|
-| g i             | Info          |
+| g i             | Wechsel zur Repository-Info  |
-| g b             | Branches      |
+| g b             | Wechsel zu den Branches      |
-| g t             | Tags          |
+| g t             | Wechsel zu den Tags          |
-| g c             | Code          |
+| g c             | Wechsel zum Code             |
-| g s             | Einstellungen |
+| g s             | Wechsel zu den Einstellungen |
 
 ### Tastenkürzel aus Plugin
 
 Plugins können selbst neue Tastenkürzel definieren.
 Diese können global oder repository-spezifisch sein oder in einem komplett anderen Kontext angewandt werden.
 Sie werden automatisch in der Übersicht im SCM-Manager mit aufgelistet.
-Um die Tastenkürzel eines Plugins innerhalb der Benutzerdokumentation zu finden, verweisen wir hier auf die Dokumentation
+Um die Tastenkürzel eines Plugins innerhalb der Benutzerdokumentation zu finden, verweisen wir hier auf die
-des jeweiligen Plugins.
+Dokumentation des jeweiligen Plugins.

docs/en/user/shortcuts/index.md

@@ -19,15 +19,25 @@ from anywhere by pressing the `?` key.
 | alt g           | Navigate to Groups         |
 | alt a           | Navigate to Administration |
 
+### List Navigation
+
+Some pages with lists on them support keyboard navigation.
+If the page supports this feature, the shortcuts show up in the shortcut overview dialog (`?`).
+
+| Key Combination | Description              |
+|-----------------|--------------------------|
+| j               | Focus next list item     |
+| k               | Focus previous list item |
+
 ### Repository-specific Shortcuts
 
-| Key Combination | Description |
+| Key Combination | Description               |
-|-----------------|-------------|
+|-----------------|---------------------------|
-| g i             | Info        |
+| g i             | Switch to repository info |
-| g b             | Branches    |
+| g b             | Switch to branches        |
-| g t             | Tags        |
+| g t             | Switch to tags            |
-| g c             | Code        |
+| g c             | Switch to code            |
-| g s             | Settings    |
+| g s             | Switch to settings        |
 
 ### Plugin Shortcuts
 

gradle/changelog/repo_overview_navigation.yaml

@@ -0,0 +1,2 @@
+- type: added
+  description: Add keyboard navigation to repository overview list ([#2146](https://github.com/scm-manager/scm-manager/pull/2146))

scm-ui/ui-components/src/layout/GroupEntry.tsx

@@ -26,6 +26,7 @@ import { Link } from "react-router-dom";
 import classNames from "classnames";
 import styled from "styled-components";
 import { useTranslation } from "react-i18next";
+import { useKeyboardIteratorTarget } from "@scm-manager/ui-shortcuts";
 
 const StyledGroupEntry = styled.div`
   max-height: calc(90px - 1.5rem);
@@ -82,9 +83,11 @@ type Props = {
 
 const GroupEntry: FC<Props> = ({ link, avatar, title, name, description, contentRight, ariaLabel }) => {
   const [t] = useTranslation("repos");
+  const ref = useKeyboardIteratorTarget();
   return (
     <div className="is-relative">
       <OverlayLink
+        ref={ref}
         to={link}
         className="has-hover-background-blue"
         aria-label={t("overview.ariaLabel", { name: ariaLabel })}

scm-ui/ui-shortcuts/package.json

@@ -12,10 +12,13 @@
   "scripts": {
     "build": "tsup ./src/index.ts -d build --format esm,cjs --dts",
     "lint": "eslint src",
-    "typecheck": "tsc"
+    "typecheck": "tsc",
+    "depcheck": "depcheck",
+    "test": "jest"
   },
   "peerDependencies": {
-    "react": "17"
+    "react": "17",
+    "react-i18next": "10"
   },
   "dependencies": {
     "mousetrap": "1.6.5"
@@ -25,7 +28,9 @@
     "@scm-manager/babel-preset": "^2.13.1",
     "@scm-manager/prettier-config": "^2.10.1",
     "@scm-manager/eslint-config": "^2.16.0",
-    "@scm-manager/tsconfig": "^2.13.0"
+    "@scm-manager/tsconfig": "^2.13.0",
+    "@testing-library/react-hooks": "8.0.1",
+    "@testing-library/react": "12.1.5"
   },
   "babel": {
     "presets": [

scm-ui/ui-shortcuts/src/index.ts

@@ -25,3 +25,4 @@
 export { default as useShortcut } from "./useShortcut";
 export { default as useShortcutDocs, ShortcutDocsContextProvider } from "./useShortcutDocs";
 export { default as usePauseShortcuts } from "./usePauseShortcuts";
+export { useKeyboardIteratorTarget, KeyboardIterator } from "./iterator/keyboardIterator";

scm-ui/ui-shortcuts/src/iterator/keyboardIterator.test.tsx

@@ -0,0 +1,240 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020-present Cloudogu GmbH and Contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+import { renderHook } from "@testing-library/react-hooks";
+import React, { FC } from "react";
+import { KeyboardIteratorContextProvider, useKeyboardIteratorCallback } from "./keyboardIterator";
+import { render } from "@testing-library/react";
+import { ShortcutDocsContextProvider } from "../useShortcutDocs";
+import Mousetrap from "mousetrap";
+
+jest.mock("react-i18next", () => ({
+  useTranslation: () => [jest.fn()],
+}));
+
+const Wrapper: FC<{ initialIndex?: number }> = ({ children, initialIndex }) => {
+  return (
+    <ShortcutDocsContextProvider>
+      <KeyboardIteratorContextProvider initialIndex={initialIndex}>{children}</KeyboardIteratorContextProvider>
+    </ShortcutDocsContextProvider>
+  );
+};
+
+const DocsWrapper: FC = ({ children }) => <ShortcutDocsContextProvider>{children}</ShortcutDocsContextProvider>;
+
+const createWrapper =
+  (initialIndex?: number): FC =>
+  ({ children }) =>
+    <Wrapper initialIndex={initialIndex}>{children}</Wrapper>;
+
+const Item: FC<{ callback: () => void }> = ({ callback }) => {
+  useKeyboardIteratorCallback(callback);
+  return <li>example</li>;
+};
+
+const List: FC<{ callbacks: Array<() => void> }> = ({ callbacks }) => {
+  return (
+    <ul data-testid="list">
+      {callbacks.map((cb, idx) => (
+        <Item key={idx} callback={cb} />
+      ))}
+    </ul>
+  );
+};
+
+describe("shortcutIterator", () => {
+  beforeEach(() => Mousetrap.reset());
+
+  it("should not call callback upon registration", () => {
+    const callback = jest.fn();
+
+    renderHook(() => useKeyboardIteratorCallback(callback), {
+      wrapper: Wrapper,
+    });
+
+    expect(callback).not.toHaveBeenCalled();
+  });
+
+  it("should not throw if not inside keyboard iterator context", () => {
+    const callback = jest.fn();
+
+    const { result, unmount } = renderHook(() => useKeyboardIteratorCallback(callback), {
+      wrapper: DocsWrapper,
+    });
+
+    unmount();
+
+    expect(result.error).toBeUndefined();
+  });
+
+  it("should call last callback upon pressing forward in initial state", async () => {
+    const callback = jest.fn();
+    const callback2 = jest.fn();
+    const callback3 = jest.fn();
+
+    render(
+      <Wrapper>
+        <List callbacks={[callback, callback2, callback3]} />
+      </Wrapper>
+    );
+
+    Mousetrap.trigger("j");
+
+    expect(callback).not.toHaveBeenCalled();
+    expect(callback2).not.toHaveBeenCalled();
+    expect(callback3).toHaveBeenCalledTimes(1);
+  });
+
+  it("should call first callback once upon pressing backward in initial state", async () => {
+    const callback = jest.fn();
+    const callback2 = jest.fn();
+    const callback3 = jest.fn();
+
+    render(
+      <Wrapper>
+        <List callbacks={[callback, callback2, callback3]} />
+      </Wrapper>
+    );
+
+    Mousetrap.trigger("k");
+    Mousetrap.trigger("k");
+
+    expect(callback).toHaveBeenCalledTimes(1);
+    expect(callback2).not.toHaveBeenCalled();
+    expect(callback3).not.toHaveBeenCalled();
+  });
+
+  it("should not allow moving past the end of the callback array", async () => {
+    const callback = jest.fn();
+    const callback2 = jest.fn();
+    const callback3 = jest.fn();
+
+    render(
+      <Wrapper initialIndex={1}>
+        <List callbacks={[callback, callback2, callback3]} />
+      </Wrapper>
+    );
+
+    Mousetrap.trigger("j");
+    Mousetrap.trigger("j");
+
+    expect(callback).not.toHaveBeenCalled();
+    expect(callback2).not.toHaveBeenCalled();
+    expect(callback3).toHaveBeenCalledTimes(1);
+  });
+
+  it("should move to existing index when active index is at the end and last callback is deregistered", async () => {
+    const callback = jest.fn();
+    const callback2 = jest.fn();
+    const callback3 = jest.fn();
+
+    const { rerender } = render(<List callbacks={[callback, callback2, callback3]} />, {
+      wrapper: createWrapper(2),
+    });
+
+    expect(callback).not.toHaveBeenCalled();
+    expect(callback2).not.toHaveBeenCalled();
+    expect(callback3).not.toHaveBeenCalled();
+
+    rerender(<List callbacks={[callback, callback2]} />);
+
+    expect(callback).not.toHaveBeenCalled();
+    expect(callback2).toHaveBeenCalledTimes(1);
+    expect(callback3).not.toHaveBeenCalled();
+  });
+
+  it("should move to existing index when active index is at the beginning and first callback is deregistered", async () => {
+    const callback = jest.fn();
+    const callback2 = jest.fn();
+    const callback3 = jest.fn();
+
+    const { rerender } = render(<List callbacks={[callback, callback2, callback3]} />, {
+      wrapper: createWrapper(0),
+    });
+
+    expect(callback).not.toHaveBeenCalled();
+    expect(callback2).not.toHaveBeenCalled();
+    expect(callback3).not.toHaveBeenCalled();
+
+    rerender(<List callbacks={[callback2, callback3]} />);
+
+    expect(callback).not.toHaveBeenCalled();
+    expect(callback2).toHaveBeenCalledTimes(1);
+    expect(callback3).not.toHaveBeenCalled();
+  });
+
+  it("should move to existing index when active index is at the end and first callback is deregistered", async () => {
+    const callback = jest.fn();
+    const callback2 = jest.fn();
+    const callback3 = jest.fn();
+
+    const { rerender } = render(<List callbacks={[callback, callback2, callback3]} />, {
+      wrapper: createWrapper(2),
+    });
+
+    expect(callback).not.toHaveBeenCalled();
+    expect(callback2).not.toHaveBeenCalled();
+    expect(callback3).not.toHaveBeenCalled();
+
+    rerender(<List callbacks={[callback, callback2]} />);
+
+    expect(callback).not.toHaveBeenCalled();
+    expect(callback2).toHaveBeenCalledTimes(1);
+    expect(callback3).not.toHaveBeenCalled();
+  });
+
+  it("should not move on deregistration if iterator is not active", async () => {
+    const callback = jest.fn();
+    const callback2 = jest.fn();
+    const callback3 = jest.fn();
+
+    const { rerender } = render(<List callbacks={[callback, callback2, callback3]} />, {
+      wrapper: createWrapper(),
+    });
+
+    expect(callback).not.toHaveBeenCalled();
+    expect(callback2).not.toHaveBeenCalled();
+    expect(callback3).not.toHaveBeenCalled();
+
+    rerender(<List callbacks={[callback, callback2]} />);
+
+    expect(callback).not.toHaveBeenCalled();
+    expect(callback2).not.toHaveBeenCalled();
+    expect(callback3).not.toHaveBeenCalled();
+  });
+
+  it("should not explode if the last item in the list is removed", async () => {
+    const callback = jest.fn();
+
+    const { rerender } = render(<List callbacks={[callback]} />, {
+      wrapper: createWrapper(),
+    });
+
+    expect(callback).not.toHaveBeenCalled();
+
+    rerender(<List callbacks={[]} />);
+
+    expect(callback).not.toHaveBeenCalled();
+  });
+});

scm-ui/ui-shortcuts/src/iterator/keyboardIterator.tsx

@@ -0,0 +1,150 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020-present Cloudogu GmbH and Contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+import React, { FC, useCallback, useContext, useEffect, useMemo, useRef } from "react";
+import { useTranslation } from "react-i18next";
+import { useShortcut } from "../index";
+
+type Callback = () => void;
+
+type KeyboardIteratorContextType = {
+  register: (callback: Callback) => number;
+  deregister: (index: number) => void;
+};
+
+const KeyboardIteratorContext = React.createContext<KeyboardIteratorContextType>({
+  register: () => {
+    if (process.env.NODE_ENV === "development") {
+      // eslint-disable-next-line no-console
+      console.warn("Keyboard iterator targets have to be declared inside a KeyboardIterator");
+    }
+    return 0;
+  },
+  deregister: () => {
+    if (process.env.NODE_ENV === "development") {
+      // eslint-disable-next-line no-console
+      console.warn("Keyboard iterator targets have to be declared inside a KeyboardIterator");
+    }
+  },
+});
+
+export const KeyboardIteratorContextProvider: FC<{ initialIndex?: number }> = ({ children, initialIndex = -1 }) => {
+  const [t] = useTranslation("commons");
+  const callbacks = useRef<Array<Callback>>([]);
+  const activeIndex = useRef<number>(initialIndex);
+  const executeCallback = useCallback((index: number) => callbacks.current[index](), []);
+
+  const navigateBackward = useCallback(() => {
+    if (activeIndex.current === -1) {
+      activeIndex.current = 0;
+      executeCallback(activeIndex.current);
+    } else if (activeIndex.current > 0) {
+      activeIndex.current -= 1;
+      executeCallback(activeIndex.current);
+    }
+  }, [executeCallback]);
+
+  const navigateForward = useCallback(() => {
+    if (activeIndex.current === -1) {
+      activeIndex.current = callbacks.current.length - 1;
+      executeCallback(activeIndex.current);
+    } else if (activeIndex.current < callbacks.current.length - 1) {
+      activeIndex.current += 1;
+      executeCallback(activeIndex.current);
+    }
+  }, [executeCallback]);
+
+  const value = useMemo(
+    () => ({
+      register: (callback: () => void) => callbacks.current.push(callback) - 1,
+      deregister: (index: number) => {
+        callbacks.current.splice(index, 1);
+        if (callbacks.current.length === 0) {
+          activeIndex.current = -1;
+        } else if (activeIndex.current === index || activeIndex.current >= callbacks.current.length) {
+          if (activeIndex.current > 0) {
+            activeIndex.current -= 1;
+          }
+          executeCallback(activeIndex.current);
+        }
+      },
+    }),
+    [executeCallback]
+  );
+
+  useShortcut("k", navigateBackward, {
+    description: t("shortcuts.iterator.previous"),
+  });
+
+  useShortcut("j", navigateForward, {
+    description: t("shortcuts.iterator.next"),
+  });
+
+  useShortcut("tab", () => {
+    activeIndex.current = -1;
+
+    return true;
+  });
+
+  return <KeyboardIteratorContext.Provider value={value}>{children}</KeyboardIteratorContext.Provider>;
+};
+
+export const useKeyboardIteratorCallback = (callback: Callback) => {
+  const { register, deregister } = useContext(KeyboardIteratorContext);
+  useEffect(() => {
+    const index = register(callback);
+    return () => deregister(index);
+  }, [callback, register, deregister]);
+};
+
+/**
+ * Use the {@link React.RefObject} returned from this hook to register a target to the nearest enclosing {@link KeyboardIterator}.
+ *
+ * @example
+ * const ref = useKeyboardIteratorTarget();
+ * const target = <button ref={ref}>My Iteration Target</button>
+ */
+export function useKeyboardIteratorTarget(): React.RefCallback<HTMLElement> {
+  const ref = useRef<HTMLElement>();
+  const callback = useCallback(() => ref.current?.focus(), []);
+  const refCallback: React.RefCallback<HTMLElement> = useCallback((el) => {
+    if (el) {
+      ref.current = el;
+    }
+  }, []);
+  useKeyboardIteratorCallback(callback);
+  return refCallback;
+}
+
+/**
+ * Allows keyboard users to iterate through a list of items, defined by enclosed {@link useKeyboardIteratorTarget} invocations.
+ *
+ * The order is determined by the render order of the target hooks.
+ *
+ * Press `k` to navigate backwards and `j` to navigate forward.
+ * Pressing `tab` will reset the iterator to its initial state.
+ */
+export const KeyboardIterator: FC = ({ children }) => (
+  <KeyboardIteratorContextProvider>{children}</KeyboardIteratorContextProvider>
+);

scm-ui/ui-webapp/public/locales/de/commons.json

@@ -278,6 +278,10 @@
     "users": "Navigiere zur Benutzerübersicht",
     "groups": "Navigiere zur Gruppenübersicht",
     "admin": "Navigiere zur Administration",
-    "docs": "Öffne die Tastaturkürzelübersicht"
+    "docs": "Öffne die Tastaturkürzelübersicht",
+    "iterator": {
+      "next": "Fokussiere den nächsten Listeneintrag",
+      "previous": "Fokussiere den vorherigen Listeneintrag"
+    }
   }
 }

scm-ui/ui-webapp/public/locales/en/commons.json

@@ -279,6 +279,10 @@
     "users": "Navigate to Users",
     "groups": "Navigate to Groups",
     "admin": "Navigate to Administration",
-    "docs": "Open the shortcut summary"
+    "docs": "Open the shortcut summary",
+    "iterator": {
+      "next": "Focus next list item",
+      "previous": "Focus previous list item"
+    }
   }
 }

scm-ui/ui-webapp/src/repos/components/list/RepositoryList.tsx

@@ -28,6 +28,7 @@ import { NamespaceCollection, Repository } from "@scm-manager/ui-types";
 import groupByNamespace from "./groupByNamespace";
 import RepositoryGroupEntry from "./RepositoryGroupEntry";
 import { ExtensionPoint, extensionPoints } from "@scm-manager/ui-extensions";
+import { KeyboardIterator } from "@scm-manager/ui-shortcuts";
 
 type Props = {
   repositories: Repository[];
@@ -50,12 +51,14 @@ class RepositoryList extends React.Component<Props> {
           props={{
             page,
             search,
-            namespace
+            namespace,
           }}
         />
-        {groups.map(group => {
+        <KeyboardIterator>
-          return <RepositoryGroupEntry group={group} key={group.name} />;
+          {groups.map((group) => {
-        })}
+            return <RepositoryGroupEntry group={group} key={group.name} />;
+          })}
+        </KeyboardIterator>
       </div>
     );
   }

yarn.lock

@@ -3522,6 +3522,14 @@
     lz-string "^1.4.4"
     pretty-format "^27.0.2"
 
+"@testing-library/react-hooks@8.0.1":
+  version "8.0.1"
+  resolved "https://registry.yarnpkg.com/@testing-library/react-hooks/-/react-hooks-8.0.1.tgz#0924bbd5b55e0c0c0502d1754657ada66947ca12"
+  integrity sha512-Aqhl2IVmLt8IovEVarNDFuJDVWVvhnr9/GCU6UUnrYXwgDFF9h2L2o2P9KBni1AST5sT6riAyoukFLyjQUgD/g==
+  dependencies:
+    "@babel/runtime" "^7.12.5"
+    react-error-boundary "^3.1.0"
+
 "@testing-library/react-hooks@^5.0.3":
   version "5.1.3"
   resolved "https://registry.yarnpkg.com/@testing-library/react-hooks/-/react-hooks-5.1.3.tgz#f722cc526025be2c16966a9a081edf47a2528721"
@@ -3534,7 +3542,7 @@
     filter-console "^0.1.1"
     react-error-boundary "^3.1.0"
 
-"@testing-library/react@^12.1.5":
+"@testing-library/react@12.1.5", "@testing-library/react@^12.1.5":
   version "12.1.5"
   resolved "https://registry.yarnpkg.com/@testing-library/react/-/react-12.1.5.tgz#bb248f72f02a5ac9d949dea07279095fa577963b"
   integrity sha512-OfTXCJUFgjd/digLUuPxa0+/3ZxsQmE7ub9kcbW/wi96Bh3o/p5vrETcBGfP17NWPGqeYYl5LTRpwyGoMC4ysg==