How do I only disable a section in a certain InstType, but force it on otherwise (even in the "Custom" InstType)? - nsis

Question

I have a Section that is set to RO and occurs in all InstTypes except for a special one.
When the user first selects the special InstType and then selects "Custom" as the InstType the section is unchecked and can't be checked again in the "Custom" InstType.
So everything is fine except that when the users selects the "Custom" InstType the Section should always be checked again.
Only in the special InstType use case it should be unchecked.
How can I achieve this?

Answer 1

You can enforce whatever logic you want in .onSelChange:
!include WinMessages.nsh
!include LogicLib.nsh
!include Sections.nsh
Page Components
Page InstFiles
InstType "Normal1"
!define CIT_Special 1
InstType "Special"
InstType "Normal2"
Section Foo
SectionIn 1 2 3
SectionEnd
Section Bar SEC_Special
SectionIn 1 3
SectionIn RO
SectionEnd
Section Baz
SectionIn 1 2 ;3 << Not the same as Foo just to have some sort of difference
SectionEnd
Function .onSelChange
;Normally you would call GetCurInstType here, but it seems we need a little hack to detect the custom section
FindWindow $1 "#32770" "" $HWNDPARENT
GetDlgItem $1 $1 0x3F9
SendMessage $1 ${CB_GETCURSEL} 0 0 $2
SendMessage $1 ${CB_GETITEMDATA} $2 0 $2
${If} $2 = ${CIT_Special}
!insertmacro UnselectSection ${SEC_Special}
${Else}
!insertmacro SelectSection ${SEC_Special}
${EndIf}
FunctionEnd