NSIS安装程序：安装前在目录页面上运行功能

Question

I created a very simple installer that doesn't add any registry keys or anything. It just installs some files of some python executable program. The installer contains only 1 step where it asks about the installation directory and then installs the software.

The problem : In case a previous version of the program is installed or the directory chosen by the user contains files in it, I would like do some checks by running a function CleanInstallationDirectory before the installation begins .

My question is : How can I run that function when the user chooses the directory and not after the installation progress starts? I would like to run that function, and based on that function's return or based on that function internal calls display a message confirming that everything in that directory will be deleted, then if the user confirms, then the installation starts.

Alternative : If it's not possible to do that, then I'm OK with the following: If the user says "No" during the installation, the installer should go back to the directory page to ask about a different directory.

Here's the current NSIS installer script I have:

  Function CleanInstallationDirectory

## do stuff

  FunctionEnd


  Name "My Software"
  OutFile "GNOMEAcqInstaller.exe"

  InstallDir "D:\MySoftware"

  RequestExecutionLevel admin



  !define MUI_ABORTWARNING

  !insertmacro MUI_PAGE_DIRECTORY
  !insertmacro MUI_PAGE_INSTFILES

  !insertmacro MUI_LANGUAGE "English"



Section "Installation" InstallSection

  SetOutPath "$INSTDIR"

  Call CleanInstallationDirectory

  File /r "MyFiles\*"
SectionEnd

  LangString DESC_SecDummy ${LANG_ENGLISH} "A test section."

Thank you.

Answer 1

If you look in the "Page Custom Functions" section in the MUI documentation you will find the names of some defines you can set on a per-page basis that will call a custom function. You want MUI_PAGE_CUSTOMFUNCTION_SHOW or MUI_PAGE_CUSTOMFUNCTION_LEAVE depending on when you want your function to run.

!insertmacro MUI_PAGE_WELCOME
!define MUI_PAGE_CUSTOMFUNCTION_LEAVE CleanInstallationDirectory
!insertmacro MUI_PAGE_DIRECTORY
!insertmacro MUI_PAGE_INSTFILES
!insertmacro MUI_LANGUAGE "English"

You can prevent the installer from going to the next page if you call Abort in a custom leave function.