Fix a crash when initialDirectory contains special characters on Linux

[TechnicJelle]

Today, I was testing my Flutter program, and happened to select a directory that has a non-ASCII character in it.

Specifically, this character: گ (Arabic letter Kaf with line, used for /g/)

The selecting part went okay, and I got the result back just fine.
However, my application stores the resulting path, and uses that as the initialDirectory for the next pick.
There, it would keep crashing:

Stacktrace

Performing hot restart...
Syncing files to device Linux...
Restarted application in 547ms.
[ERROR:flutter/runtime/dart_vm_initializer.cc(40)] Unhandled Exception: 'package:dbus/src/dbus_value.dart': Failed assertion: line 151 pos 16: 'value >= 0 && value <= 255': Byte must be in range [0, 255]
#0      _AssertionError._doThrowNew (dart:core-patch/errors_patch.dart:67:4)
#1      _AssertionError._throwNew (dart:core-patch/errors_patch.dart:49:5)
#2      new DBusByte (package:dbus/src/dbus_value.dart:151:16)
#3      new DBusArray.byte.<anonymous closure> (package:dbus/src/dbus_value.dart:919:51)
#4      MappedListIterable.elementAt (dart:_internal/iterable.dart:442:31)
#5      ListIterator.moveNext (dart:_internal/iterable.dart:371:26)
#6      new _GrowableList._ofEfficientLengthIterable (dart:core-patch/growable_array.dart:194:27)
#7      new _GrowableList.of (dart:core-patch/growable_array.dart:154:28)
#8      new List.of (dart:core-patch/array_patch.dart:39:18)
#9      ListIterable.toList (dart:_internal/iterable.dart:224:7)
#10     new DBusArray (package:dbus/src/dbus_value.dart:893:29)
#11     new DBusArray.byte (package:dbus/src/dbus_value.dart:918:12)
#12     FilePickerLinux.getDirectoryPath (package:file_picker/src/linux/file_picker_linux.dart:112:39)
#13     PathPickerButton.build.<anonymous closure> (package:bluemap_gui/project_view/configs/views/base.dart:117:60)
#14     _InkResponseState.handleTap (package:flutter/src/material/ink_well.dart:1224:21)
#15     GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:345:24)
#16     TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:758:11)
#17     BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:383:5)
#18     BaseTapGestureRecognizer.acceptGesture (package:flutter/src/gestures/tap.dart:353:7)
#19     GestureArenaManager.sweep (package:flutter/src/gestures/arena.dart:173:27)
#20     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:532:20)
#21     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:498:22)
#22     RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:473:11)
#23     GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:437:7)
#24     GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:394:5)
#25     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:341:7)
#26     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:308:9)
#27     _invoke1 (dart:ui/hooks.dart:372:13)
#28     PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:467:7)
#29     _dispatchPointerDataPacket (dart:ui/hooks.dart:307:31)

The exact code it was crashing on was this:

List<int> tmp = [];
for (var i = 0; i < initialDirectory.length; i++) {
  tmp.add(initialDirectory[i].codeUnitAt(0));
}
tmp.add(0);
DBusArray directory = DBusArray.byte(tmp);

In that last line is an assert that ensures the ints of the tmp list are actually bytes, and not way too high.

However, that special character results in the value being 1711, as you can see in this screenshot of the debugger:

The full contents of the tmp list

And so, together with a friend, we concluded that the way that the tmp list is being constructed isn't completely proper.

This PR fixes that, by using Dart's built-in UTF-8 encoder to convert the string to a byte array.

I verified with the DBus docs, and DBus String are indeed only allowed to be UTF-8:

• https://dbus.freedesktop.org/doc/api/html/group__DBusString.html
• https://dbus.freedesktop.org/doc/api/html/group__DBusSyntax.html#ga7d98d5d9af66ff78e74d5dd1d8cd3390

I have tested this in my own program, and it does solve the issue.

Here's a pair of (somewhat crappy) videos demonstrating the issue and that the fix works:

The issue:

Peek.2026-03-10.21-41.mp4

The fix:

Peek.2026-03-10.21-35.mp4

[TechnicJelle]

I forked this from the tag v10.3.10, by the way.
Hope that's okay