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## 4.7 Functions

Functions are similar to Sections in that they contain zero or more instructions. User functions are not called by the installer directly, instead they are called from Sections using the Call instruction. Callback functions will be called by the installer when a certain event occurs.

Functions must be declared outside of Sections or other Functions.

### 4.7.1 Function Commands

#### 4.7.1.1 Function

    [function_name]

Begins and opens a new function. Function names beginning with "." (e.g. ".Whatever") are generally reserved for callback functions. Function names beginning with "un." are functions that will be generated in the Uninstaller. Hence, normal install Sections and functions cannot call uninstall functions, and the Uninstall Section and uninstall functions cannot call normal functions.

    Function func

      # some commands

    FunctionEnd

    Section

      Call func

    SectionEnd

#### 4.7.1.2 FunctionEnd

This command closes the current open function.

### 4.7.2 Callback Functions

You can create callback functions which have special names, that will be called by the installer at certain points in the install. Below is a list of currently available callbacks:

#### 4.7.2.1 Install Callbacks

##### 4.7.2.1.1 .onGUIInit

This callback will be called just before the first page is loaded and the installer dialog is shown, allowing you to tweak the user interface.

Example:

     !include "WinMessages.nsh"

     Function .onGUIInit

       # 1028 is the id of the branding text control

       GetDlgItem $R0 $HWNDPARENT 1028

       CreateFont $R1 "Tahoma" 10 700

       SendMessage $R0 ${WM_SETFONT} $R1 0

       # set background color to white and text color to red

       SetCtlColors $R0 FFFFFF FF0000

     FunctionEnd

##### 4.7.2.1.2 .onInit

This callback will be called when the installer is nearly finished initializing. If the '.onInit' function calls Abort, the installer will quit instantly.

Here are two examples of how this might be used:

     Function .onInit

       MessageBox MB_YESNO "This will install. Continue?" IDYES NoAbort

         Abort ; causes installer to quit.

       NoAbort:

     FunctionEnd

or:

     Function .onInit

       ReadINIStr $INSTDIR $WINDIR\wincmd.ini Configuration InstallDir

       StrCmp $INSTDIR "" 0 NoAbort

         MessageBox MB_OK "Windows Commander not found. Unable to get install path."

         Abort ; causes installer to quit.

       NoAbort:

     FunctionEnd

##### 4.7.2.1.3 .onInstFailed

This callback is called when the user hits the 'cancel' button after the install has failed (if it could not extract a file, or the install script used the Abort command).

Example:

      Function .onInstFailed

        MessageBox MB_OK "Better luck next time."

      FunctionEnd

##### 4.7.2.1.4 .onInstSuccess

This callback is called when the install was successful, right before the install window closes (which may be after the user clicks 'Close' if AutoCloseWindow or SetAutoClose is set to false).

Example:

      Function .onInstSuccess

        MessageBox MB_YESNO "Congrats, it worked. View readme?" IDNO NoReadme

          Exec notepad.exe ; view readme or whatever, if you want.

        NoReadme:

      FunctionEnd

##### 4.7.2.1.5 .onGUIEnd

This callback is called right after the installer window closes. Use it to free any user interface related plug-ins if needed.

##### 4.7.2.1.6 .onMouseOverSection

This callback is called whenever the mouse position over the sections tree has changed. This allows you to set a description for each section for example. The section id on which the mouse is over currently is stored, temporarily, in $0.

Example:

      Function .onMouseOverSection

        FindWindow $R0 "#32770" "" $HWNDPARENT

        GetDlgItem $R0 $R0 1043 ; description item (must be added to the UI)

        StrCmp $0 0 "" +2

          SendMessage $R0 ${WM_SETTEXT} 0 "STR:first section description"

        StrCmp $0 1 "" +2

          SendMessage $R0 ${WM_SETTEXT} 0 "STR:second section description"

      FunctionEnd

##### 4.7.2.1.7 .onRebootFailed

This callback is called if Reboot fails. WriteUninstaller, plug-ins, File and WriteRegBin should not be used in this callback.

Example:

     Function .onRebootFailed

       MessageBox MB_OK|MB_ICONSTOP "Reboot failed. Please reboot manually." /SD IDOK

     FunctionEnd

##### 4.7.2.1.8 .onSelChange

Called when the selection changes on the component page. Useful for using with SectionSetFlags and SectionGetFlags.

Selection changes include both section selection and installation type change.

##### 4.7.2.1.9 .onUserAbort

This callback is called when the user hits the 'cancel' button, and the install hasn't already failed. If this function calls Abort, the install will not be aborted.

Example:

     Function .onUserAbort

       MessageBox MB_YESNO "Abort install?" IDYES NoCancelAbort

         Abort ; causes installer to not quit.

       NoCancelAbort:

     FunctionEnd

##### 4.7.2.1.10 .onVerifyInstDir

This callback enables control over whether or not an installation path is valid for your installer. This code will be called every time the user changes the install directory, so it shouldn't do anything crazy with MessageBox or the likes. If this function calls Abort, the installation path in $INSTDIR is deemed invalid.

Example:

      Function .onVerifyInstDir

        IfFileExists $INSTDIR\Winamp.exe PathGood

          Abort ; if $INSTDIR is not a winamp directory, don't let us install there

        PathGood:

      FunctionEnd

#### 4.7.2.2 Uninstall Callbacks

##### 4.7.2.2.1 un.onGUIInit

This callback will be called just before the first page is loaded and the installer dialog is shown, allowing you to tweak the user interface.

Have a look at .onGUIInit for an example.

##### 4.7.2.2.2 un.onInit

This callback will be called when the uninstaller is nearly finished initializing. If the 'un.onInit' function calls Abort, the uninstaller will quit instantly. Note that this function can verify and/or modify $INSTDIR if necessary.

Here are two examples of how this might be used:

      Function un.onInit

        MessageBox MB_YESNO "This will uninstall. Continue?" IDYES NoAbort

          Abort ; causes uninstaller to quit.

        NoAbort:

      FunctionEnd

or:

      Function un.onInit

        IfFileExists $INSTDIR\myfile.exe found

          Messagebox MB_OK "Uninstall path incorrect"

          Abort

        found:

      FunctionEnd

##### 4.7.2.2.3 un.onUninstFailed

This callback is called when the user hits the 'cancel' button after the uninstall has failed (if it used the Abort command or otherwise failed).

Example:

      Function un.onUninstFailed

        MessageBox MB_OK "Better luck next time."

      FunctionEnd

##### 4.7.2.2.4 un.onUninstSuccess

This callback is called when the uninstall was successful, right before the install window closes (which may be after the user clicks 'Close' if SetAutoClose is set to false)..

Example:

      Function un.onUninstSuccess

        MessageBox MB_OK "Congrats, it's gone."

      FunctionEnd

##### 4.7.2.2.5 un.onGUIEnd

This callback is called right after the uninstaller window closes. Use it to free any user interface related plug-ins if needed.

##### 4.7.2.2.6 un.onRebootFailed

This callback is called if Reboot fails. WriteUninstaller, plug-ins, File and WriteRegBin should not be used in this callback.

Example:

     Function un.onRebootFailed

       MessageBox MB_OK|MB_ICONSTOP "Reboot failed. Please reboot manually." /SD IDOK

     FunctionEnd

##### 4.7.2.2.7 un.onSelChange

Called when the selection changes on the component page. Useful for using with SectionSetFlags and SectionGetFlags.

Selection changes include both section selection and installation type change.

##### 4.7.2.2.8 un.onUserAbort

This callback is called when the user hits the 'cancel' button and the uninstall hasn't already failed. If this function calls Abort, the install will not be aborted.

Example:

      Function un.onUserAbort

        MessageBox MB_YESNO "Abort uninstall?" IDYES NoCancelAbort

          Abort ; causes uninstaller to not quit.

        NoCancelAbort:

      FunctionEnd

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