change style of save warning dialog buttons on Haiku for better integration

csgui/messageBox.py

@@ -1,4 +1,5 @@
-from PyQt5.QtWidgets import QApplication, QAction, QLabel, QDialogButtonBox, QDialog, QFileDialog, QMessageBox, QPushButton, QLineEdit, QCheckBox, QSpinBox, QDoubleSpinBox, QTableWidgetItem, QTabWidget, QComboBox, QWidget, QScrollArea, QMainWindow, QShortcut
+from PyQt5.QtWidgets import QApplication, QAction, QLabel, QDialogButtonBox, QDialog, QFileDialog, QMessageBox, QPushButton, QLineEdit, QCheckBox, QSpinBox, QDoubleSpinBox, QTableWidgetItem, QTabWidget, QComboBox, QWidget, QScrollArea, QMainWindow, QShortcut, QDialogButtonBox
+import sys
 
 class UnsavedMessageBox(QMessageBox):
     """
@@ -15,7 +16,12 @@ class UnsavedMessageBox(QMessageBox):
         self.setStandardButtons(
             QMessageBox.Save | QMessageBox.Discard | QMessageBox.Cancel)
         self.setDefaultButton(QMessageBox.Save)
-
+        
+        # If we are running on Haiku, use the MacOS button style to fit in more
+        # with native applications
+        if sys.platform.startswith("haiku"):
+            buttonBox = self.findChild(QDialogButtonBox)
+            buttonBox.setStyleSheet("* { button-layout: 1}")
 
 class UnreadableMessageBox(QMessageBox):
     """