New customized Print button in the NSIS installer screen is not displaying

Question

My requirement is,

I wanted to add a new button ("Print") to the License Agreement custom screen. For this I have written the below code. It is compiling but is not showing the "Print" button.

Please help me to resolve this. And also is there any simplest way to create a new button on the installer screen?

; Pages

!insertmacro MUI_PAGE_WELCOME

;Customizing the License Page Text
!define MUI_TEXT_LICENSE_TITLE "End-User License Agreement"
!define MUI_TEXT_LICENSE_SUBTITLE "Please read the following license agreement carefully"
!define MUI_INNERTEXT_LICENSE_BOTTOM ""
!define MUI_INNERTEXT_LICENSE_TOP ""
!define MUI_INNERTEXT_LICENSE_BOTTOM_CHECKBOX ""
!define MUI_PAGE_CUSTOMFUNCTION_LICENSESHOW MyLicenseShowCallback

Function MyLicenseShowCallback

; You are supposed to use ChangeUI (or MUI_UI) and a modified ui file to add new buttons but this example adds the button at run-time...
GetDlgItem $0 $hwndparent 2 ; Find cancel button
System::Call *(i,i,i,i)i.r1
System::Call 'USER32::GetWindowRect(ir0,ir1)'
System::Call *$1(i.r2,i.r3,i.r4,i.r5)
IntOp $5 $5 - $3 ;height
IntOp $4 $4 - $2 ;width
System::Call 'USER32::ScreenToClient(i$hwndparent,ir1)'
System::Call *$1(i.r2,i.r3)
System::Free $1
IntOp $2 $2 + $4 ;x
IntOp $2 $2 + 8  ;x+padding
System::Call 'USER32::CreateWindowEx(i 0,t "Button",t "Print",i ${WS_CHILD}|${WS_VISIBLE}|${WS_TABSTOP},i r2,i r3,i r4,i r5,i $hwndparent,i 0x666,i 0,i 0)i.r0'

SendMessage $hwndparent ${WM_GETFONT} 0 0 $1
SendMessage $0 ${WM_SETFONT} $1 1

GetFunctionAddress $0 onmybtnclick
ButtonEvent::AddEventHandler 0x666 $0

SendMessage $mui.LicensePage.Text ${WM_SETTEXT} 0 "STR:$(MUI_TEXT_LICENSE_TITLE)"

FunctionEnd

Function onmybtnclick
MessageBox mb_ok "You clicked me!"
FunctionEnd

Answer 1

For this I have written the below code

Are you sure about that? Looks a lot like the code I wrote in a answer here.

You failed to properly read the MUI documentation and you failed to properly adapt the example code you found.

MyLicenseShowCallback is never executed because you used the wrong define, the correct name is MUI_PAGE_CUSTOMFUNCTION_SHOW.

The other problem is that the original code placed the new button next to the Cancel button in the classic NSIS UI but the Cancel button is in a different place in MUI and the button ends up off-screen.

This code just places the button on the left side of the UI

Var PrintBtn
!include MUI2.nsh
!include LogicLib.nsh

!define MUI_PAGE_CUSTOMFUNCTION_SHOW HidePrintButton
!insertmacro MUI_PAGE_WELCOME
!define MUI_PAGE_CUSTOMFUNCTION_SHOW MyLicenseShowCallback
!define MUI_PAGE_CUSTOMFUNCTION_LEAVE HidePrintButton
!insertmacro MUI_PAGE_LICENSE "${__FILE__}"
!insertmacro MUI_PAGE_DIRECTORY
!insertmacro MUI_PAGE_INSTFILES
!insertmacro MUI_LANGUAGE English

Function HidePrintButton
${IfThen} $PrintBtn P<> 0 ${|} SendMessage $PrintBtn ${WM_CLOSE} 0 0 ${|}
FunctionEnd

Function MyLicenseShowCallback
GetDlgItem $0 $hwndparent 2 ; Find cancel button so we can copy its size and y position.
System::Call *(i,i,i,i)p.r1
System::Call 'USER32::GetWindowRect(pr0,pr1)'
System::Call *$1(i.r2,i.r3,i.r4,i.r5)
IntOp $5 $5 - $3 ;height
IntOp $4 $4 - $2 ;width
System::Call 'USER32::ScreenToClient(p$hwndparent,pr1)'
System::Call *$1(i.r2,i.r3)
System::Free $1
IntOp $2 $4 / 5 ; Calculate x padding based on the width but you can put any value you want in $2
System::Call 'USER32::CreateWindowEx(i 0,t "Button",t "Print",i ${WS_CHILD}|${WS_VISIBLE}|${WS_TABSTOP},i r2,i r3,i r4,i r5,p $hwndparent,p 0x666,p 0,p 0)p.r0'
StrCpy $PrintBtn $0
SendMessage $hwndparent ${WM_GETFONT} 0 0 $1
SendMessage $0 ${WM_SETFONT} $1 1
GetFunctionAddress $0 onmybtnclick
ButtonEvent::AddEventHandler 0x666 $0
FunctionEnd

Function onmybtnclick
MessageBox mb_ok "You clicked me!"
FunctionEnd