How to simultaneously scroll two windows?

Question

I want to simultaneously scroll two windows, but the hotkey input method requires me to duplicate it multiple times. My idea is to use Function Hotkeys and A_ThisHotKey variable, but the WheelDown is disable in the program if using this script:

WheelDown::
ScrollKey := A_ThisHotKey
SetTitleMatchMode, 2
IfWinActive, Writer
{
        CoordMode, Mouse, Screen
        WinGet, active_id, ID, A
        IfWinExist, Sumatra
        {
                Send {ScrollKey}
                WinActivate ; Automatically uses the window found above.
                Send {ScrollKey}
                Send {ScrollKey}
                WinActivate, ahk_id %active_id%
        }
}
Else
{
        Send {A_ThisHotKey}
}
return

I want ScrollKey to match WheelUp, WheelDown, PgUp, PgDn, Up, Down.

Ideally, I think the script should detect how much the first program is scrolled, then apply that amount to the second one. Advantages:

• Scrolling will be seamless since the other program are scrolled in the background
• Clicking on the scrollbar works
• Different scrolling speeds don't affect the comparison
• Moving lines in text editors won't scroll pages in PDF viewers

Related:

• Send/SendRaw/SendInput/SendPlay/SendEvent: Send keys & clicks
• How to grab the scrolling amount in one window?

Answer 1

Try this

#SingleInstance Force
Process, Priority, , High

; SetTitleMatchMode, 2

GroupAdd, Scroll_Group, ahk_class Notepad
GroupAdd, Scroll_Group, ahk_class Notepad++

SetWinDelay 0

#If (WinActive("ahk_class Notepad") && WinExist("ahk_class Notepad++")) || (WinActive("ahk_class Notepad++") && WinExist("ahk_class Notepad"))

    WheelUp::
    WheelDown::
    PgUp::
    PgDn::
    Up::
    Down::  
        MouseGetPos, mX, mY
        Send {%A_ThisHotKey%}
        GroupActivate Scroll_Group  ; activate the next window of this group
        If (A_ThisHotKey = "WheelUp" || A_ThisHotKey = "WheelDown")
            MouseMove, 200, 200, 0  ; move the mouse over the currently active window 
        Send {%A_ThisHotKey%}   
        GroupActivate Scroll_Group
        MouseMove, mX, mY, 0
    return

#If