The error code 0x0000059D translates to ERROR_NO_SYSTEM_MENU. This error occurs in Windows programs when you attempt to access or modify the system menu (the menu that appears when you click the icon in the top-left corner of a window) of a window that doesn’t have one.

Understanding System Menus:

• The system menu of a window provides basic window management options like minimize, maximize, close, and sometimes restore.
• Not all windows have system menus. Some specialized windows or dialog boxes might not require them.

Causes of ERROR_NO_SYSTEM_MENU:

• Accessing Menu of Window Without One: The most common cause is trying to use functions like GetSystemMenu or ModifyMenu on a window handle that doesn’t have a system menu.

• Code Errors: Mistakes in how you’re identifying the window type or using system menu functions can lead to this error.

Troubleshooting Steps:

1. Verify Window Type: Double-check if the window you’re working with actually has a system menu. Some dialog boxes or custom window types might not have them.

2. Handle Window Type Appropriately: If the window doesn’t have a system menu, adjust your code to handle this case gracefully. You might want to skip operations that rely on the system menu or provide alternative functionality.

3. Debug Window Handle: Use debugging tools to inspect the window handle you’re using. Ensure it refers to a valid window and not a handle that might not have a system menu by design.

4. Review System Menu Usage: Carefully examine how you’re using GetSystemMenu or ModifyMenu in your code. Make sure you’re targeting the correct window handle and handling potential cases where the window might not have a system menu.

5. Alternative Approaches: If you need to provide menu functionality for a window without a system menu, consider creating a custom context menu or using other UI elements like buttons or toolbars.

Additional Tips:

• Use comments in your code to document assumptions made about the window type and system menu availability.
• Consider using higher-level UI libraries or frameworks (if available) that might provide abstractions for window management, potentially hiding the need to directly interact with system menus.

By following these steps and understanding the reasons behind the ERROR_NO_SYSTEM_MENU error, you should be able to identify if the window you’re targeting has a system menu and adjust your code accordingly. If it doesn’t have one, implement alternative approaches to provide the desired functionality for your program.