Problem

When gMKVExtractGUI is started directly, the detection of mmg/mkvmerge.exe is skipped if MKVToolnix Path in the .ini file is empty.

• If _Settings.MkvToolnixPath is empty, the existence check falls back to the current working directory.
• When the app is opened by double-click, the working directory happens to contain mkvmerge.exe, so it is detected.
• But when the app is opened by dragging an MKV file, the working directory is different, so mkvmerge.exe is not found.
• As a result, AutoDetectMkvToolnixPath is skipped entirely, leading to failure to detect MKVToolnix.

Root Cause

• MKVToolnix Path being empty in the .ini file.
• The existence check incorrectly succeeds or fails depending on the working directory.
• This caused inconsistent behavior:
  • Direct open → succeeds (due to working dir containing mkvmerge).
  • Drag-drop open → fails (different working dir).

Solution

Before performing the detection checks, explicitly verify that _Settings.MkvToolnixPath is not empty or whitespace.

• If empty → force AutoDetectMkvToolnixPath to run.
• Otherwise → continue with the normal path checks.

This ensures consistent detection regardless of how the program is started.