Black screen when using GTK_PLUG mode on Linux

[AoEiuV020]

Description

When launching the Flutter application in GTK_PLUG mode on Linux (for embedding into other applications), the window becomes completely black if the project has window_manager as a dependency. This occurs even without calling any window_manager APIs.

Environment

• OS: Linux
• Flutter: 3.24.5
• window_manager version: ^0.4.3

Steps to Reproduce

1. Create a new Flutter project
2. Add window_manager as a dependency in pubspec.yaml
3. Run the application in GTK_PLUG mode using gtk_plug_new()
4. The window becomes completely black

Example Code

// Linux embedding code
GtkWidget* window = NULL;
if (self->plug_mode) {
  window = gtk_plug_new(0);
} else {
  window = GTK_WIDGET(gtk_application_window_new(GTK_APPLICATION(application)));
}

Expected Behavior

The application should display normally when running in GTK_PLUG mode, regardless of whether window_manager is included as a dependency.

Actual Behavior

The application window becomes completely black when running in GTK_PLUG mode if window_manager is included as a dependency, even without calling any of its APIs.

Additional Information

• The issue only occurs when window_manager is added as a dependency
• The application works normally in regular window mode
• The black screen appears immediately upon launch
• No error messages are displayed in the console

For reference, check my demo https://github.com/AoEiuV020/FlutterDemo/tree/fa72ddb5daf7e00a9d25499c5e4a1d4243f599c7

This project is a Flutter template project with modifications to ./linux/my_application.cc to support both normal window mode and plug mode operation.

I added a script ./embed_test/test.sh that compiles a wrapper window with a button to embed the Flutter demo. However, when embedded, the Flutter window shows only a black screen.

Comparing with the previous commit, the only change was adding the window_manager dependency - no other code changes were made. This single dependency addition caused the black screen issue.