Now the user is restricted to inputting only 0 and 1 and cant overwrite the separator character.

binary_text_edit.py

@@ -0,0 +1,20 @@
+#!/usr/bin/python3
+
+from PyQt6.QtWidgets import QPlainTextEdit
+
+
+class BinaryTextEdit(QPlainTextEdit):  # rewrite QPlainTextEdit.keyPressEvent because it has no .setValidator()
+    def keyPressEvent(self, event):
+        allowed_keys = {"", "0", "1"}
+
+        if event.text() in allowed_keys:
+            cursor = self.textCursor()
+            pos = cursor.position()
+
+            if (pos + 1) % 9 == 0 and event.text() not in {'', None}:  # dont overwrite the separator character
+                return
+
+            super().keyPressEvent(event)
+
+        else:
+            event.ignore()

file.py

@@ -1,6 +1,8 @@
 #!/usr/bin/python3
 
-from PyQt6.QtWidgets import QWidget, QPlainTextEdit, QFileDialog, QVBoxLayout
+from PyQt6.QtWidgets import QWidget, QFileDialog, QVBoxLayout
+from PyQt6.QtGui import QFont
+from binary_text_edit import BinaryTextEdit
 
 
 class FileActions:
@@ -80,9 +82,11 @@ class File:
         self.content_widget = QWidget(self.app.main_window.openFileTabs, objectName=path)
         self.content_widget_layout = QVBoxLayout()
 
-        self.content_binary_input = QPlainTextEdit(self.content_widget)
+        self.content_binary_input = BinaryTextEdit()
+        self.content_binary_input.setOverwriteMode(True)
         self.content_widget_layout.addWidget(self.content_binary_input)
         self.content_binary_input.setPlainText(self.app.utils.bstring_to_oz(file_content))
+        self.content_binary_input.setFont(QFont("Ubuntu Mono"))
         self.content_binary_input.textChanged.connect(self.on_edit)
 
         self.content_widget.setLayout(self.content_widget_layout)