The error code 0x000005A9 translates to ERROR_INVALID_SHOWWIN_COMMAND. This error occurs in Windows programs when you use the ShowWindow function with an invalid value in the nCmdShow parameter.

Understanding ShowWindow Function:

• The ShowWindow function controls how a window is displayed (shown, hidden, minimized, maximized, etc.).
• The nCmdShow parameter specifies the desired window visibility or state using predefined constants like:
  • SW_SHOW: Shows a hidden window.
  • SW_HIDE: Hides a visible window.
  • SW_MINIMIZE: Minimizes a window.

Causes of ERROR_INVALID_SHOWWIN_COMMAND:

• Incorrect Constant: The most common cause is using an invalid constant or a typo in the nCmdShow parameter. Ensure you’re using a valid constant defined for the ShowWindow function.

• Unsupported Flag: In some cases, attempting to use a flag that’s not applicable to the specific ShowWindow functionality you’re trying to achieve can also trigger this error (e.g., using flags specific to dialog boxes with a regular window).

• Code Errors: Mistakes in how you’re referencing constants or constructing the nCmdShow parameter can lead to this error.

Troubleshooting Steps:

1. Verify Constant Usage: Double-check the documentation for ShowWindow to ensure you’re using a valid constant for the desired window visibility or state. Refer to the list of supported SW_* constants.

2. Review Flag Compatibility: If you’re using multiple flags in the nCmdShow parameter, make sure they are compatible with each other and the specific ShowWindow usage.

3. Debug Function Call: Use debugging tools to inspect the value you’re passing for the nCmdShow parameter in the ShowWindow call. This can help identify typos or invalid flag combinations.

4. Consult Documentation: Refer to the documentation for ShowWindow to understand the supported SW_* constants, their meanings, and any usage guidelines or compatibility information.

5. Alternative Approaches: Consider alternative approaches for managing window visibility if the desired functionality can’t be achieved with a single ShowWindow call. This might involve using combinations of functions like IsWindowVisible and SetWindowPos to achieve the specific visual state.

Additional Tips:

• Use constants or well-defined variables to store the SW_* constants for different window visibility states. This improves code readability and reduces the risk of typos.
• Consider using higher-level UI libraries or frameworks (if available) that might provide abstractions for window management tasks, potentially simplifying window visibility control using ShowWindow.

By following these steps and understanding the reasons behind the ERROR_INVALID_SHOWWIN_COMMAND error, you should be able to identify the issue with your nCmdShow parameter and fix your code to use ShowWindow with valid constants to control the visibility or state of your windows as intended.