Copy over styles fixing the layout issues

frontend/src/components/Notes/RenderInWindow.js

@@ -1,49 +1,135 @@
-import React, {useState, useEffect,useRef} from 'react'
-import ReactDOM from "react-dom";
+import ReactDOM from 'react-dom';
+import { useState, useEffect, useRef, useCallback } from 'react';
 
 export default function RenderInWindow(props) {
   const [container, setContainer] = useState(null);
   const newWindow = useRef(null);
 
+  // `copyStyles`, `fixUrlForRule` and `getKeyFrameText` taken from
+  // https://github.com/rmariuzzo/react-new-window/blob/master/src/NewWindow.js
+  const fixUrlForRule = useCallback(
+    (cssRule) =>
+      cssRule.cssText
+        .split('url(')
+        .map((line) => {
+          if (line[1] === '/') {
+            return `${line.slice(0, 1)}${window.location.origin}${line.slice(
+              1
+            )}`;
+          }
+          return line;
+        })
+        .join('url('),
+    []
+  );
+
+  const getKeyFrameText = useCallback((cssRule) => {
+    const tokens = ['@keyframes', cssRule.name, '{'];
+    Array.from(cssRule.cssRules).forEach((cssRule) => {
+      // type === CSSRule.KEYFRAME_RULE should always be true
+      tokens.push(cssRule.keyText, '{', cssRule.style.cssText, '}');
+    });
+    tokens.push('}');
+    return tokens.join(' ');
+  }, []);
+
+  const copyStyles = useCallback(
+    (source, target) => {
+      // Store style tags, avoid reflow in the loop
+      const headFrag = target.createDocumentFragment();
+
+      Array.from(source.styleSheets).forEach((styleSheet) => {
+        // For <style> elements
+        let rules;
+        try {
+          rules = styleSheet.cssRules;
+        } catch (err) {
+          console.error(err);
+        }
+        if (rules) {
+          // IE11 is very slow for appendChild, so use plain string here
+          const ruleText = [];
+
+          // Write the text of each rule into the body of the style element
+          Array.from(styleSheet.cssRules).forEach((cssRule) => {
+            const { type } = cssRule;
+
+            // Skip unknown rules
+            if (type === CSSRule.UNKNOWN_RULE) {
+              return;
+            }
+
+            let returnText = '';
+
+            if (type === CSSRule.KEYFRAMES_RULE) {
+              // IE11 will throw error when trying to access cssText property, so we
+              // need to assemble them
+              returnText = getKeyFrameText(cssRule);
+            } else if (
+              [CSSRule.IMPORT_RULE, CSSRule.FONT_FACE_RULE].includes(type)
+            ) {
+              // Check if the cssRule type is CSSImportRule (3) or CSSFontFaceRule (5)
+              // to handle local imports on a about:blank page
+              // '/custom.css' turns to 'http://my-site.com/custom.css'
+              returnText = fixUrlForRule(cssRule);
+            } else {
+              returnText = cssRule.cssText;
+            }
+            ruleText.push(returnText);
+          });
+
+          const newStyleEl = target.createElement('style');
+          newStyleEl.textContent = ruleText.join('\n');
+          headFrag.appendChild(newStyleEl);
+        } else if (styleSheet.href) {
+          // for <link> elements loading CSS from a URL
+          const newLinkEl = target.createElement('link');
+
+          newLinkEl.rel = 'stylesheet';
+          newLinkEl.href = styleSheet.href;
+          headFrag.appendChild(newLinkEl);
+        }
+      });
+
+      target.head.appendChild(headFrag);
+    },
+    [fixUrlForRule, getKeyFrameText]
+  );
+
   useEffect(() => {
     // Create container element on client-side
-    setContainer(document.createElement("div"));
+    setContainer(document.createElement('div'));
   }, []);
 
   useEffect(() => {
     // When container is ready
     if (container) {
       // Create window
       newWindow.current = window.open(
-        "",
-        "",
-        "width=600,height=400,left=200,top=200"
+        '',
+        '',
+        'width=600,height=400,left=200,top=200'
       );
 
-      newWindow.current.document.head.innerHTML = window.document.head.innerHTML;
+      newWindow.current.document.head.innerHTML =
+        window.document.head.innerHTML;
       // Append container
       newWindow.current.document.body.appendChild(container);
 
-      // Save reference to window for cleanup
-      const curWindow = newWindow.current;
-
-      setupBeforeUnloadListener();
-
-      // Return cleanup function
-      return () => {
-        curWindow.close();
-    }
-    }
-  }, [container]);
+      // Copy styles
+      setTimeout(() => {
+        copyStyles(document, newWindow.current.document);
+      }, 0);
 
-  const setupBeforeUnloadListener = () => {
-    newWindow.current.addEventListener("beforeunload", (ev) => {
-        ev.preventDefault();
+      newWindow.current.addEventListener('beforeunload', (e) => {
+        e.preventDefault();
         props.closeMarkdownWindow();
-
-    });
-};
+      });
 
+      // Return cleanup function
+      return () => newWindow.current?.close();
+    }
+  }, [container, copyStyles, props]);
 
   return container && ReactDOM.createPortal(props.children, container);
-};
+}