Support expandable images (#31)

Closes #26

Eject `MDXComponents/Img` using Docusaurus swizzling. Adapt the expandable
image logic from the `Image` component in `gravitational/docs` to the
Docusaurus site, copying the `ModalImage` and `PlainImage` components,
plus their supporting hooks, into the ejected `MDXImg` component.

package.json

@@ -43,6 +43,7 @@
     "@docusaurus/theme-classic": "^3.5.0",
     "@inkeep/widgets": "^0.2.288",
     "@mdx-js/react": "^3.0.0",
+    "classnames": "^2.3",
     "clsx": "^2.1.1",
     "date-fns": "^3.6.0",
     "prism-react-renderer": "^2.3.0",

src/theme/MDXComponents/Img/index.tsx

@@ -0,0 +1,124 @@
+import cn from "classnames";
+import { React, useEffect, useState, useCallback, useRef } from "react";
+import clsx from "clsx";
+import type { Props } from "@theme/MDXComponents/Img";
+
+import styles from "./styles.module.css";
+
+function useClickInside(ref, handler) {
+  useEffect(() => {
+    const listener = (e: MouseEvent) => {
+      if (ref.current) {
+        handler(e);
+      }
+    };
+    document.addEventListener("mousedown", listener);
+    return () => {
+      document.removeEventListener("mousedown", listener);
+    };
+  }, [ref, handler]);
+}
+
+function useEscape(handler) {
+  useEffect(() => {
+    const listener = (e: KeyboardEvent) => {
+      if (e.key === "Escape") {
+        handler(e);
+      }
+    };
+    document.addEventListener("keydown", listener);
+    return () => {
+      document.removeEventListener("keydown", listener);
+    };
+  }, [handler]);
+}
+
+function useDisableBodyScroll(shouldDisable) {
+  useEffect(() => {
+    if (shouldDisable) {
+      document.body.style.overflow = "hidden";
+    } else {
+      document.body.style.overflow = "unset";
+    }
+  }, [shouldDisable]);
+}
+
+function transformImgClassName(className?: string): string {
+  return clsx(className, styles.img);
+}
+
+//** Maximum width of content block where images are placed.
+/* If the original image is smaller, then there is no sense to expand the image by clicking. */
+const MAX_CONTENT_WIDTH = 900;
+
+type ModalImageProps = {
+  setShowExpandedImage: Dispatch<SetStateAction<boolean>>;
+} & ImageProps;
+
+const ModalImage = ({ setShowExpandedImage, ...props }: ModalImageProps) => {
+  const closeHandler = useCallback(
+    () => setShowExpandedImage(false),
+    [setShowExpandedImage]
+  );
+  const modalRef = useRef<HTMLDivElement>();
+  useClickInside(modalRef, closeHandler);
+  useEscape(closeHandler);
+
+  return (
+    <div ref={modalRef}>
+      <div className={styles.overlay} />
+      <div className={styles.dialog}>
+        <img
+          decoding="async"
+          loading="lazy"
+          {...props}
+          className={transformImgClassName(props.className)}
+        />
+      </div>
+    </div>
+  );
+};
+
+export default function MDXImg(props: Props): JSX.Element {
+  const [showExpandedImage, setShowExpandedImage] = useState(false);
+  const shouldExpand = props.width > MAX_CONTENT_WIDTH;
+  useDisableBodyScroll(showExpandedImage);
+  const handleClickImage = () => {
+    if (shouldExpand) {
+      setShowExpandedImage(true);
+    }
+  };
+  const PlainImage = () => {
+    if (shouldExpand) {
+      return (
+        <button onClick={handleClickImage} className={styles.zoomable}>
+          <img
+            decoding="async"
+            loading="lazy"
+            {...props}
+            className={transformImgClassName(props.className)}
+          />
+        </button>
+      );
+    } else
+      return (
+        <img
+          decoding="async"
+          loading="lazy"
+          {...props}
+          className={transformImgClassName(props.className)}
+        />
+      );
+  };
+
+  return (
+    <>
+      <span className={cn(styles.wrapper)}>
+        <PlainImage />
+      </span>
+      {showExpandedImage && (
+        <ModalImage setShowExpandedImage={setShowExpandedImage} {...props} />
+      )}
+    </>
+  );
+}

src/theme/MDXComponents/Img/styles.module.css

@@ -0,0 +1,45 @@
+.img {
+  height: auto;
+}
+
+.overlay {
+  background-color: rgba(0, 0, 0, 0.7);
+  width: 100vw;
+  height: 100%;
+  min-width: 100%;
+  top: 50%;
+  left: 50%;
+  z-index: 3002;
+  transform: translate(-50%, -50%);
+  position: fixed;
+  cursor: zoom-out;
+}
+
+.zoomable {
+  /*
+   * The background-color and border styles override browser defaults for the
+   * button element.
+   */
+  background-color: inherit;
+  border: inherit;
+
+  cursor: zoom-in;
+  cursor: -moz-zoom-in;
+  cursor: -webkit-zoom-in;
+}
+
+.dialog {
+  position: fixed;
+  top: 50%;
+  left: 50%;
+  transform: translate(-50%, -50%);
+  background: rgba(0,0,0,0);
+  cursor: zoom-out;
+  cursor: -moz-zoom-out;
+  cursor: -webkit-zoom-out;
+  z-index: 3002;
+  & .img {
+    max-width: 95vw;
+    max-height: 95vh;
+  }
+}

yarn.lock

@@ -5138,6 +5138,11 @@ ci-info@^3.2.0:
   resolved "https://registry.yarnpkg.com/ci-info/-/ci-info-3.9.0.tgz#4279a62028a7b1f262f3473fc9605f5e218c59b4"
   integrity sha512-NIxF55hv4nSqQswkAeiOi1r83xy8JldOFDTWiug55KBu9Jnblncd2U6ViHmYgHf01TPZS77NJBhBMKdWj9HQMQ==
 
+classnames@^2.3:
+  version "2.5.1"
+  resolved "https://registry.yarnpkg.com/classnames/-/classnames-2.5.1.tgz#ba774c614be0f016da105c858e7159eae8e7687b"
+  integrity sha512-saHYOzhIQs6wy2sVxTM6bUDsQO4F50V9RQ22qBpEdCW+I+/Wmke2HOl6lS6dTpdxVhb88/I6+Hs+438c3lfUow==
+
 clean-css@^5.2.2, clean-css@^5.3.2, clean-css@~5.3.2:
   version "5.3.3"
   resolved "https://registry.yarnpkg.com/clean-css/-/clean-css-5.3.3.tgz#b330653cd3bd6b75009cc25c714cae7b93351ccd"