Update dictionary sample to use sidePanel.open() (GoogleChrome#1087)

* Update dictionary sample to use sidePanel.open()

Updates the dictionary side panel example to use the
sidePanel.open() API. This means we are also able to demonstrate
a way of safely passing data to the side panel without hitting
any race conditions.

* Address feedback

functional-samples/sample.sidepanel-dictionary/README.md

@@ -4,18 +4,23 @@ This example allows users to right-click on a word and see the definition on the
 
 NOTE: This example only defines the word extensions and popup.
 
+## Implementation Notes
+
+When the user selects a word, we need to send it to the side panel, but that
+may not be open yet. To handle this we store the word in
+`chrome.storage.session`, which results in the following:
+
+- If the side panel is already open, the `storage.session.onChanged` event
+  will fire in the side panel.
+- Otherwise, the value will be loaded from storage when the side panel opens.
+
 ## Running this extension
 
 1. Clone this repository.
 2. Load this directory in Chrome as an [unpacked extension](https://developer.chrome.com/docs/extensions/mv3/getstarted/development-basics/#load-unpacked).
-3. Open the side panel UI
-4. Choose the "Dictionary side panel".
-
-<img src="https://wd.imgix.net/image/BhuKGJaIeLNPW9ehns59NfwqKxF2/9QJK3CNx71t67M3MlIUY.png?auto=format&w=385" alt="Dictionary side panel">
-
-5. Go to https://developer.chrome.com/docs/extensions/
-6. Right-click on the "Extensions" word.
-7. Choose the "Define" context menu
+3. Go to https://developer.chrome.com/docs/extensions/
+4. Right-click on the "Extensions" word.
+5. Choose the "Define" context menu
 
 You should see the definition on the side panel
 

functional-samples/sample.sidepanel-dictionary/manifest.json

@@ -13,5 +13,5 @@
   "side_panel": {
     "default_path": "sidepanel.html"
   },
-  "permissions": ["sidePanel", "contextMenus"]
+  "permissions": ["sidePanel", "contextMenus", "storage"]
 }

functional-samples/sample.sidepanel-dictionary/service-worker.js

@@ -24,9 +24,10 @@ chrome.runtime.onInstalled.addListener(() => {
   setupContextMenu();
 });
 
-chrome.contextMenus.onClicked.addListener((data) => {
-  chrome.runtime.sendMessage({
-    name: 'define-word',
-    data: { value: data.selectionText }
-  });
+chrome.contextMenus.onClicked.addListener((data, tab) => {
+  // Store the last word in chrome.storage.session.
+  chrome.storage.session.set({ lastWord: data.selectionText });
+
+  // Make sure the side panel is open.
+  chrome.sidePanel.open({ tabId: tab.id });
 });

functional-samples/sample.sidepanel-dictionary/sidepanel.js

@@ -19,14 +19,31 @@ const words = {
     "A UI surface which appears when an extension's action icon is clicked."
 };
 
-chrome.runtime.onMessage.addListener(({ name, data }) => {
-  if (name === 'define-word') {
-    // Hide instructions.
-    document.body.querySelector('#select-a-word').style.display = 'none';
-
-    // Show word and definition.
-    document.body.querySelector('#definition-word').innerText = data.value;
-    document.body.querySelector('#definition-text').innerText =
-      words[data.value.toLowerCase()];
+chrome.storage.session.get('lastWord', ({ lastWord }) => {
+  updateDefinition(lastWord);
+});
+
+chrome.storage.session.onChanged.addListener((changes) => {
+  const lastWordChange = changes['lastWord'];
+
+  if (!lastWordChange) {
+    return;
   }
+
+  updateDefinition(lastWordChange.newValue);
 });
+
+function updateDefinition(word) {
+  // If the side panel was opened manually, rather than using the context menu,
+  // we might not have a word to show the definition for.
+  if (!word) return;
+
+  // Hide instructions.
+  document.body.querySelector('#select-a-word').style.display = 'none';
+
+  // Show word and definition.
+  document.body.querySelector('#definition-word').innerText = word;
+  document.body.querySelector('#definition-text').innerText =
+    words[word.toLowerCase()] ??
+    `Unknown word! Supported words: ${Object.keys(words).join(', ')}`;
+}