add comment to explain bad behaviour with firstNonWhitespaceCharacterIndex, #2560

src/vs/vscode.d.ts

@@ -73,7 +73,7 @@ declare namespace vscode {
 
 		/**
 		 * The offset of the first character which is not a whitespace character as defined
-		 * by `/\s/`.
+		 * by `/\s/`. **Note** that if a line is all whitespaces the length of the line is returned.
 		 *
 		 * @readonly
 		 */