added PosGenerator class

example/blue/lib/main.dart

-import 'dart:async';
-import 'dart:convert';
 import 'package:esc_pos_printer/esc_pos_printer.dart';
 import 'package:flutter/material.dart';
-// import 'package:flutter_bluetooth_basic/flutter_bluetooth_basic.dart';
 import 'package:oktoast/oktoast.dart';
 
 void main() => runApp(MyApp());
@@ -59,7 +56,20 @@ class _MyHomePageState extends State<MyHomePage> {
 
   void _testPrint(PrinterBluetooth printer) async {
     printerManager.selectPrinter(printer);
-    printerManager.printLine('====== @@@ hello\n\n\n').then((val) {
+
+    // printerManager.addText('left', styles: PosStyles(align: PosTextAlign.left));
+    // printerManager.addText('center',
+    //     styles: PosStyles(align: PosTextAlign.center));
+    // printerManager.addText('right',
+    //     styles: PosStyles(align: PosTextAlign.right), linesAfter: 3);
+
+    printerManager.addText(
+        'Regular: aA bB cC dD eE fF gG hH iI jJ kK lL mM nN oO pP qQ rR sS tT uU vV wW xX yY zZ');
+    printerManager.addText('Special 1: àÀ èÈ éÉ ûÛ üÜ çÇ ôÔ',
+        styles: PosStyles(codeTable: PosCodeTable.westEur));
+    printerManager.addEmptyLines(3);
+
+    printerManager.printTicket().then((val) {
       showToast('Success!');
     }).catchError((dynamic e) {
       print('catched: ${e.toString()}');

lib/esc_pos_printer.dart

@@ -9,6 +9,7 @@ library esc_pos_printer;
 export './src/barcode.dart';
 export './src/enums.dart';
 export './src/pos_column.dart';
+export './src/pos_generator.dart';
 export './src/pos_styles.dart';
 export './src/printer.dart';
 export './src/printer_bluetooth_manager.dart';

lib/src/pos_generator.dart

+import 'dart:convert';
+// import 'dart:io';
+import 'dart:typed_data';
+// import 'package:gbk_codec/gbk_codec.dart';
+// import 'package:hex/hex.dart';
+// import 'package:image/image.dart';
+// import 'barcode.dart';
+import 'commands.dart';
+import 'enums.dart';
+// import 'pos_column.dart';
+import 'pos_styles.dart';
+
+class PosGenerator {
+  static List<int> emptyLines(int n) {
+    if (n > 0) {
+      return latin1.encode(List.filled(n, '\n').join());
+    }
+    return [];
+  }
+
+  static List<int> text(
+    String text, {
+    PosStyles styles = const PosStyles(),
+    int linesAfter = 0,
+  }) {
+    List<int> bytes = [];
+
+    bytes += latin1.encode(styles.align == PosTextAlign.left
+        ? cAlignLeft
+        : (styles.align == PosTextAlign.center ? cAlignCenter : cAlignRight));
+
+    // Set local code table
+    if (styles.codeTable != null) {
+      bytes += Uint8List.fromList(
+        List.from(cCodeTable.codeUnits)..add(styles.codeTable.value),
+      );
+    }
+    bytes += latin1.encode(text + '\n');
+    bytes += emptyLines(linesAfter);
+
+    return bytes;
+  }
+}

lib/src/printer_bluetooth_manager.dart

@@ -8,6 +8,7 @@
 
 import 'dart:async';
 import 'dart:convert';
+import 'package:esc_pos_printer/esc_pos_printer.dart';
 import 'package:rxdart/rxdart.dart';
 // import 'dart:convert';
 // import 'dart:io';
@@ -40,6 +41,7 @@ class PrinterBluetoothManager {
   StreamSubscription _scanResultsSubscription;
   StreamSubscription _isScanningSubscription;
   PrinterBluetooth _selectedPrinter;
+  List<int> _printBuffer = [];
 
   final BehaviorSubject<bool> _isScanning = BehaviorSubject.seeded(false);
   Stream<bool> get isScanningStream => _isScanning.stream;
@@ -80,7 +82,7 @@ class PrinterBluetoothManager {
     _selectedPrinter = printer;
   }
 
-  Future<void> printLine(String text) async {
+  Future<void> writeBytes(List<int> bytes) async {
     const int timeout = 5;
     if (_selectedPrinter == null) {
       throw Exception('Print failed (Select a printer first)');
@@ -108,7 +110,6 @@ class PrinterBluetoothManager {
           print('********************* CONNECTED');
           // To avoid double call
           if (!_isConnected) {
-            final List<int> bytes = latin1.encode(text).toList();
             await _bluetoothManager.writeData(bytes);
             // TODO Notify data sent
           }
@@ -137,4 +138,27 @@ class PrinterBluetoothManager {
       }
     });
   }
+
+  void addText(
+    String text, {
+    PosStyles styles = const PosStyles(),
+    int linesAfter = 0,
+  }) {
+    _printBuffer +=
+        PosGenerator.text(text, styles: styles, linesAfter: linesAfter);
+  }
+
+  void addEmptyLines(int n) {
+    _printBuffer += PosGenerator.emptyLines(n);
+  }
+
+  Future<void> printTicket() async {
+    if (_printBuffer.isNotEmpty) {
+      final Future<void> res = writeBytes(_printBuffer);
+      _printBuffer = [];
+      return res;
+    } else {
+      throw Exception('Print failed (print buffer is empty)');
+    }
+  }
 }