title: NSIS dual mode installer. Checking path validity
body: <p>I'm writing a NSIS installer which elevates only after user chooses a path installing to which requires admin privileges. Obviously, I included MUI_DIRECTORYPAGE_VERIFYONLEAVE define, to allow the "Next" button to stay active even when the user chooses such a path. After user changes installation directory, .onVerifyInstDir is called where I am supposed to check for path validity and call Abort for graying out "Next" button. The problem is, .onVerifyInstDir is called only for valid paths, so if user enters something like "sdfasdfas" the function won't be called, and the "Next" button will stay active. Of course, I can verify path on leaving the directory page, but what I want is an inactive "Next" button for such cases. Any ideas?</p>