Add support for Electron 5 and above

Starting with Electron 5.0.0, the function `webFrame.setSpellCheckProvider` has a different signature, in order to support asynchronous spell checkers. For more information on this change in Electron, see electron/electron#14032.

This diff updates `SpellCheckHandler` to use the new interface if running on Electron 5.0.0 and above. However, it still checks the spelling synchronously like before.

If running on Electron versions below 5.0.0, the `SpellCheckHandler` still works.

Closes electron-userland#144.

src/spell-check-handler.js

@@ -140,11 +140,9 @@ module.exports = class SpellCheckHandler {
       this.currentSpellchecker = new Spellchecker();
       this.currentSpellcheckerLanguage = 'en-US';
 
+      d('DEBUG: Settings Spell Check Provider...');
       if (webFrame) {
-        webFrame.setSpellCheckProvider(
-          this.currentSpellcheckerLanguage,
-          this.shouldAutoCorrect,
-          { spellCheck: this.handleElectronSpellCheck.bind(this) });
+        this.setSpellCheckProvider(webFrame);
       }
       return;
     }
@@ -255,9 +253,9 @@ module.exports = class SpellCheckHandler {
     }
 
     let contentToCheck = Observable.merge(
-        this.spellingErrorOccurred,
-        initialInputText,
-        possiblySwitchedCharacterSets)
+      this.spellingErrorOccurred,
+      initialInputText,
+      possiblySwitchedCharacterSets)
       .mergeMap(() => {
         if (lastInputText.length < 8) return Observable.empty();
         return Observable.of(lastInputText);
@@ -295,16 +293,13 @@ module.exports = class SpellCheckHandler {
       let prevSpellCheckLanguage;
 
       disp.add(this.currentSpellcheckerChanged
-          .startWith(true)
+        .startWith(true)
         .filter(() => this.currentSpellcheckerLanguage)
         .subscribe(() => {
           if (prevSpellCheckLanguage === this.currentSpellcheckerLanguage) return;
 
           d('Actually installing spell check provider to Electron');
-          webFrame.setSpellCheckProvider(
-            this.currentSpellcheckerLanguage,
-            this.shouldAutoCorrect,
-            { spellCheck: this.handleElectronSpellCheck.bind(this) });
+          this.setSpellCheckProvider(webFrame);
 
           prevSpellCheckLanguage = this.currentSpellcheckerLanguage;
         }));
@@ -388,7 +383,7 @@ module.exports = class SpellCheckHandler {
     let dict = null;
 
     this.isMisspelledCache.reset();
-    
+
     // Set language on macOS
     if (isMac && this.currentSpellchecker) {
       d(`Setting current spellchecker to ${langCode}`);
@@ -449,7 +444,7 @@ module.exports = class SpellCheckHandler {
     return await Observable.of(...alternatives)
       .concatMap((l) => {
         return Observable.defer(() =>
-            Observable.fromPromise(this.dictionarySync.loadDictionaryForLanguage(l, cacheOnly)))
+          Observable.fromPromise(this.dictionarySync.loadDictionaryForLanguage(l, cacheOnly)))
           .map((d) => ({language: l, dictionary: d}))
           .do(({language}) => {
             alternatesTable[langCode] = language;
@@ -463,10 +458,34 @@ module.exports = class SpellCheckHandler {
   }
 
   /**
-   *  The actual callout called by Electron to handle spellchecking
+   *  Sets the SpellCheckProvider on the given WebFrame. Handles API differences
+   *  in Electron.
+   *  @private
+   *  @param {*} webFrame
+   */
+  setSpellCheckProvider(webFrame) {
+    if (process.versions.electron >= '5.0.0') {
+      d('DEBUG: Setting provider for Electron 5');
+      // Electron 5 and above:
+      webFrame.setSpellCheckProvider(
+        this.currentSpellcheckerLanguage,
+        { spellCheck: this.handleElectronSpellCheck.bind(this) });
+    } else {
+      d('DEBUG: Setting provider for Electron 4');
+      // Electron 4 and below:
+      webFrame.setSpellCheckProvider(
+        this.currentSpellcheckerLanguage,
+        this.shouldAutoCorrect,
+        { spellCheck: this.handleElectron4SpellCheck.bind(this) });
+    }
+  }
+
+  /**
+   *  The actual callout called by Electron version 4 and below to handle
+   *  spellchecking
    *  @private
    */
-  handleElectronSpellCheck(text) {
+  handleElectron4SpellCheck(text) {
     if (!this.currentSpellchecker) return true;
 
     if (isMac) {
@@ -480,6 +499,29 @@ module.exports = class SpellCheckHandler {
     return !result;
   }
 
+  /**
+   *  The actual callout called by Electron version 5 and above to handle 
+   *  spellchecking.
+   *  @private
+   */
+  handleElectronSpellCheck(words, callback) {
+    if (!this.currentSpellchecker) {
+      callback([]);
+      return;
+    }
+
+    let misspelled = words.filter(w => this.isMisspelled(w));
+
+    if (isMac) {
+      callback(misspelled);
+      return;
+    }
+
+    this.spellCheckInvoked.next(true);
+
+    misspelled.forEach(w => this.spellingErrorOccurred.next(w));
+  }
+
   /**
    * Calculates whether a word is missspelled, using an LRU cache to memoize
    * the callout to the actual spell check code.
@@ -652,4 +694,4 @@ module.exports = class SpellCheckHandler {
     d(`Result: ${JSON.stringify(ret)}`);
     return ret;
   }
-}
+};