Split into multiple files

edit-context/html-editor/converter.js

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+// The EditContext object only knows about character offsets. But out editor
+// view renders HTML tokens as DOM nodes. This function finds DOM node tokens
+// that are in the provided EditContext offset range.
+export function fromOffsetsToRenderedTokenNodes(renderedTokens, start, end) {
+  const tokenNodes = [];
+
+  for (let offset = start; offset < end; offset++) {
+    const token = renderedTokens.find(
+      (token) => token.pos <= offset && token.pos + token.value.length > offset
+    );
+    if (token) {
+      tokenNodes.push({
+        node: token.node,
+        nodeOffset: token.pos,
+        charOffset: offset,
+      });
+    }
+  }
+
+  return tokenNodes;
+}
+
+// The EditContext object only knows about a plain text string and about
+// character offsets. However, our editor view renders the text by using
+// DOM nodes. So we sometimes need to convert between the two.
+// This function converts from a DOM selection object to character offsets.
+export function fromSelectionToOffsets(selection, editorEl) {
+  const treeWalker = document.createTreeWalker(editorEl, NodeFilter.SHOW_TEXT);
+
+  let anchorNodeFound = false;
+  let extentNodeFound = false;
+  let anchorOffset = 0;
+  let extentOffset = 0;
+
+  while (treeWalker.nextNode()) {
+    const node = treeWalker.currentNode;
+    if (node === selection.anchorNode) {
+      anchorNodeFound = true;
+      anchorOffset += selection.anchorOffset;
+    }
+
+    if (node === selection.extentNode) {
+      extentNodeFound = true;
+      extentOffset += selection.extentOffset;
+    }
+
+    if (!anchorNodeFound) {
+      anchorOffset += node.textContent.length;
+    }
+    if (!extentNodeFound) {
+      extentOffset += node.textContent.length;
+    }
+  }
+
+  if (!anchorNodeFound || !extentNodeFound) {
+    return null;
+  }
+
+  return { start: anchorOffset, end: extentOffset };
+}
+
+// The EditContext object only knows about a plain text string and about
+// character offsets. However, our editor view renders the text by using
+// DOM nodes. So we sometimes need to convert between the two.
+// This function converts character offsets to a DOM selection object.
+export function fromOffsetsToSelection(start, end, editorEl) {
+  const treeWalker = document.createTreeWalker(editorEl, NodeFilter.SHOW_TEXT);
+
+  let offset = 0;
+  let anchorNode = null;
+  let anchorOffset = 0;
+  let extentNode = null;
+  let extentOffset = 0;
+
+  while (treeWalker.nextNode()) {
+    const node = treeWalker.currentNode;
+
+    if (!anchorNode && offset + node.textContent.length >= start) {
+      anchorNode = node;
+      anchorOffset = start - offset;
+    }
+
+    if (!extentNode && offset + node.textContent.length >= end) {
+      extentNode = node;
+      extentOffset = end - offset;
+    }
+
+    if (anchorNode && extentNode) {
+      break;
+    }
+
+    offset += node.textContent.length;
+  }
+
+  return { anchorNode, anchorOffset, extentNode, extentOffset };
+}

edit-context/html-editor/editor.js

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+import { tokenizeHTML } from "./tokenizer.js";
+import {
+  fromOffsetsToRenderedTokenNodes,
+  fromSelectionToOffsets,
+  fromOffsetsToSelection,
+} from "./converter.js";
+
+const IS_EDIT_CONTEXT_SUPPORTED = "EditContext" in window;
+const IS_CUSTOM_HIGHLIGHT_SUPPORTED = "Highlight" in window;
+
+// The editor element.
+const editorEl = document.getElementById("html-editor");
+
+// The current tokens from the html text.
+let currentTokens = [];
+
+// Instances of CSS custom Highlight objects, used to render
+// the IME composition text formats.
+const imeHighlights = {
+  "solid-thin": null,
+  "solid-thick": null,
+  "dotted-thin": null,
+  "dotted-thick": null,
+  "dashed-thin": null,
+  "dashed-thick": null,
+  "wavy-thin": null,
+  "wavy-thick": null,
+  "squiggle-thin": null,
+  "squiggle-thick": null,
+};
+if (IS_CUSTOM_HIGHLIGHT_SUPPORTED) {
+  for (const [key, value] of Object.entries(imeHighlights)) {
+    imeHighlights[key] = new Highlight();
+    CSS.highlights.set(`ime-${key}`, imeHighlights[key]);
+  }
+} else {
+  console.warn(
+    "Custom highlights are not supported in this browser. IME formats will not be rendered."
+  );
+}
+
+(function () {
+  if (!IS_EDIT_CONTEXT_SUPPORTED) {
+    editorEl.textContent =
+      "Sorry, your browser doesn't support the EditContext API. This demo will not work.";
+    return;
+  }
+
+  // Instantiate the EditContext object.
+  const editContext = new EditContext({
+    text: "<html>\n  <body id=foo>\n    <h1 id='header'>Cool Title</h1>\n    <p class=\"wow\">hello<br/>How are you? test</p>\n  </body>\n</html>",
+  });
+
+  // Attach the EditContext object to the editor element.
+  // This makes the element focusable and able to receive text input.
+  editorEl.editContext = editContext;
+
+  // Update the control bounds (i.e. where the editor is on the screen)
+  // now, and when the window is resized.
+  // This helps the OS position the IME composition window correctly.
+  function updateControlBounds() {
+    const editorBounds = editorEl.getBoundingClientRect();
+    editContext.updateControlBounds(editorBounds);
+  }
+  updateControlBounds();
+  window.addEventListener("resize", updateControlBounds);
+
+  // Update the selection and selection bounds in the EditContext object.
+  // This helps the OS position the IME composition window correctly.
+  function updateSelection(start, end) {
+    editContext.updateSelection(start, end);
+    // Get the bounds of the selection.
+    editContext.updateSelectionBounds(
+      document.getSelection().getRangeAt(0).getBoundingClientRect()
+    );
+  }
+
+  // The render function is used to update the view of the editor.
+  // The EditContext object is our "model", and the editorEl is our "view".
+  // The render function's job is to update the view when the model changes.
+  function render(text, selectionStart, selectionEnd) {
+    // Empty the editor. We're re-rendering everything.
+    editorEl.innerHTML = "";
+
+    // Tokenize the text.
+    currentTokens = tokenizeHTML(text);
+
+    // Render each token.
+    for (const token of currentTokens) {
+      const span = document.createElement("span");
+      span.classList.add(`token-${token.type}`);
+      span.textContent = token.value;
+      span.dataset.tokenPos = token.pos;
+      editorEl.appendChild(span);
+
+      // Store the node in the token so we can find it later.
+      token.node = span;
+    }
+
+    // Move the selection to the correct location.
+    // It was lost when we updated the DOM.
+    // The EditContext API gives us the selection as text offsets.
+    // Convert it into a DOM selection.
+    const { anchorNode, anchorOffset, extentNode, extentOffset } =
+      fromOffsetsToSelection(selectionStart, selectionEnd, editorEl);
+    document
+      .getSelection()
+      .setBaseAndExtent(anchorNode, anchorOffset, extentNode, extentOffset);
+  }
+
+  // Listen to the EditContext's textupdate event.
+  // This tells us when text input happens. We use it to re-render the view.
+  editContext.addEventListener("textupdate", (e) => {
+    render(editContext.text, e.selectionStart, e.selectionEnd);
+  });
+
+  // Visually show when we're composing text, like when using an IME,
+  // or voice dictation.
+  editContext.addEventListener("compositionstart", (e) => {
+    editorEl.classList.add("is-composing");
+  });
+  editContext.addEventListener("compositionend", (e) => {
+    editorEl.classList.remove("is-composing");
+  });
+
+  // Update the character bounds when the EditContext needs it.
+  editContext.addEventListener("characterboundsupdate", (e) => {
+    const tokenNodes = fromOffsetsToRenderedTokenNodes(
+      currentTokens,
+      e.rangeStart,
+      e.rangeEnd
+    );
+
+    const charBounds = tokenNodes.map(({ node, nodeOffset, charOffset }) => {
+      const range = document.createRange();
+      range.setStart(node.firstChild, charOffset - nodeOffset);
+      range.setEnd(node.firstChild, charOffset - nodeOffset + 1);
+      return range.getBoundingClientRect();
+    });
+
+    editContext.updateCharacterBounds(e.rangeStart, charBounds);
+  });
+
+  // Draw IME composition text formats if needed.
+  editContext.addEventListener("textformatupdate", (e) => {
+    const formats = e.getTextFormats();
+
+    for (const format of formats) {
+      const { rangeStart, rangeEnd, underlineStyle, underlineThickness } =
+        format;
+
+      // Find the nodes in the view that are in the range.
+      const { anchorNode, anchorOffset, extentNode, extentOffset } =
+        fromOffsetsToSelection(rangeStart, rangeEnd, editorEl);
+      const highlight =
+        imeHighlights[
+          `${format.underlineStyle.toLowerCase()}-${format.underlineThickness.toLowerCase()}`
+        ];
+      if (highlight) {
+        const range = document.createRange();
+        range.setStart(anchorNode, anchorOffset);
+        range.setEnd(extentNode, extentOffset);
+        highlight.add(range);
+      }
+    }
+  });
+
+  // Handle key presses that are not already handled by the EditContext.
+  editorEl.addEventListener("keydown", (e) => {
+    const start = Math.min(
+      editContext.selectionStart,
+      editContext.selectionEnd
+    );
+    const end = Math.max(editContext.selectionStart, editContext.selectionEnd);
+
+    if (e.key === "Tab") {
+      e.preventDefault();
+      editContext.updateText(start, end, "\t");
+      updateSelection(start + 1, start + 1);
+      render(
+        editContext.text,
+        editContext.selectionStart,
+        editContext.selectionEnd
+      );
+    } else if (e.key === "Enter") {
+      editContext.updateText(start, end, "\n");
+      updateSelection(start + 1, start + 1);
+      render(
+        editContext.text,
+        editContext.selectionStart,
+        editContext.selectionEnd
+      );
+    }
+  });
+
+  // Listen to selectionchange events to let the EditContext know where it is.
+  document.addEventListener("selectionchange", () => {
+    const selection = document.getSelection();
+    const offsets = fromSelectionToOffsets(selection, editorEl);
+    if (offsets) {
+      updateSelection(offsets.start, offsets.end);
+    }
+  });
+
+  // Render the initial view.
+  render(
+    editContext.text,
+    editContext.selectionStart,
+    editContext.selectionEnd
+  );
+})();