MarkdownToolbar: Add buttons to navigate between words

lib/widgets/markdown_toolbar.dart

@@ -23,6 +23,14 @@ class MarkdownToolBar extends StatelessWidget {
           icon: const Text('B'),
           onPressed: () => _modifyCurrentWord('**'),
         ),
+        IconButton(
+          icon: const Icon(Icons.navigate_before),
+          onPressed: _navigateToPrevWord,
+        ),
+        IconButton(
+          icon: const Icon(Icons.navigate_next),
+          onPressed: _navigateToNextWord,
+        ),
       ],
     );
   }
@@ -34,6 +42,16 @@ class MarkdownToolBar extends StatelessWidget {
   void _modifyCurrentWord(String char) {
     textController.value = modifyCurrentWord(textController.value, char);
   }
+
+  void _navigateToPrevWord() {
+    var offset = nextWordPos(textController.value);
+    textController.selection = TextSelection.collapsed(offset: offset);
+  }
+
+  void _navigateToNextWord() {
+    var offset = prevWordPos(textController.value);
+    textController.selection = TextSelection.collapsed(offset: offset);
+  }
 }
 
 TextEditingValue modifyCurrentLine(
@@ -146,3 +164,28 @@ TextEditingValue modifyCurrentWord(
     selection: TextSelection.collapsed(offset: wordEndPos),
   );
 }
+
+// FIXME: This will fail in non space delimited languages
+int nextWordPos(TextEditingValue textEditingValue) {
+  var cursorPos = textEditingValue.selection.baseOffset;
+  var text = textEditingValue.text;
+
+  var nextSpacePos = text.indexOf(RegExp('\s'), cursorPos);
+  if (nextSpacePos == -1) {
+    return text.length;
+  }
+
+  return nextSpacePos;
+}
+
+int prevWordPos(TextEditingValue textEditingValue) {
+  var cursorPos = textEditingValue.selection.baseOffset;
+  var text = textEditingValue.text;
+
+  var lastSpacePos = text.lastIndexOf(RegExp('\s'), cursorPos);
+  if (lastSpacePos == -1) {
+    return 0;
+  }
+
+  return lastSpacePos;
+}

test/markdown_toolbar_test.dart

@@ -166,4 +166,40 @@ void main() {
       char: '**',
     );
   });
+
+  //
+  // Navigation
+  //
+  test('Navigation with only 1 word', () {
+    var val = const TextEditingValue(
+      text: 'Hello',
+      selection: TextSelection.collapsed(offset: 3),
+    );
+
+    expect(nextWordPos(val), 5);
+
+    val = const TextEditingValue(
+      text: 'Hello',
+      selection: TextSelection.collapsed(offset: 5),
+    );
+
+    expect(nextWordPos(val), 5);
+
+    val = const TextEditingValue(
+      text: 'Hello',
+      selection: TextSelection.collapsed(offset: 3),
+    );
+
+    expect(prevWordPos(val), 0);
+
+    val = const TextEditingValue(
+      text: 'Hello',
+      selection: TextSelection.collapsed(offset: 5),
+    );
+
+    expect(prevWordPos(val), 0);
+  });
+
+  // Test for navigating between punctuations
+  // Test for navigating between newlines
 }