Mousewheel Graph Window Zoom

#pragma TextEncoding="UTF-8"
#pragma rtGlobals=3
#pragma DefaultTab={3,20,4}
#pragma version=1.60
#pragma IndependentModule=ScrollToZoom
#pragma IgorVersion=9
 
#define global
 
// key codes
// 2: shift; 4: option/alt; 8: command/ctrl
// On Windows, alt key is reserved for graph drag.
static constant kZoomKey   =  8
static constant kFasterKey =  2 // 0 to disable
static constant kZoomSpeed = 70
static constant kReverse   =  0 // 1 to reverse the direction of expansion
 
#ifdef global
 
static function AfterWindowCreatedHook(string win, variable type)
    if (type == 1)
        SetWindow $win hook(hScrollToZoom)=ScrollToZoom#hookScrollToZoom
    endif
    return 0
end
 
static function AfterFileOpenHook(variable refNum, string fileNameStr, string pathNameStr, string fileTypeStr, string fileCreatorStr, variable fileKind)
    if (filekind == 1 || filekind == 2) // opened an experiment
        SetHooks(1)
    endif
    return 0
end
 
static function SetHooks(int activate)
    wave/T wGraphs = ListToTextWave(WinList("*",";","WIN:1"), ";")
    for (string strWin : wGraphs)
        if (activate)
            SetWindow $strWin hook(hScrollToZoom)=ScrollToZoom#hookScrollToZoom
        else
            SetWindow $strWin hook(hScrollToZoom)=$""
        endif
    endfor
end
 
#endif
 
menu "Graph", dynamic
    ScrollToZoom#zoomMenu(), /Q, ScrollToZoom#toggleZoom()
end
 
menu "Panel", dynamic
    ScrollToZoom#zoomMenu(), /Q, ScrollToZoom#toggleZoom()
end
 
function/S zoomMenu()
    string strParent = ParseFilePath(0, WinName(0, 65), "#", 0, 0)
    if (!strlen(strParent))
        return ""
    endif
    GetWindow/Z $strParent hook(hScrollToZoom)
    return SelectString(strlen(s_value)>0, "", "!" + num2char(18)) + "Scroll-to-Zoom"
end
 
function toggleZoom()
    string strParent = ParseFilePath(0, WinName(0, 65), "#", 0, 0)
    if (strlen(strParent))
        GetWindow $strParent hook(hScrollToZoom)
        SetWindow $strParent hook(hScrollToZoom) = $SelectString(strlen(s_value)>0, "ScrollToZoom#hookScrollToZoom", "")
    endif
end
 
function hookScrollToZoom(STRUCT WMWinHookStruct &s)
    
    if (WinType(s.winName) != 1)
        return 0
    endif
    
    if (s.eventCode == 22 && s.eventMod&kZoomKey) // mousewheel/touchpad + zoom key
 
        string strAxes = AxisList(s.WinName), axis = "", type = "", info = ""
        int i, isHorizontal, isLog
        Make/D/free/N=3 wAx // free wave to hold axis minimum, maximum, axis value for mouse location
        variable expansion = 1 + sign(kReverse - 1) * s.wheelDy * kZoomSpeed / 5000
        if (s.eventMod & kFasterKey)
            if (kFasterKey==2 && s.wheelDy==0)
                // this works when shift key also transforms wheel.dY to wheel.dX
                s.wheelDy = s.wheelDx
            endif
            expansion = 1 + sign(kReverse - 1) * s.wheelDy * kZoomSpeed / 500
        endif
                
        for (i=ItemsInList(strAxes);i>=0;i--)
            axis = StringFromList(i, strAxes)
            info = AxisInfo(s.WinName, axis)
            type = StringByKey("AXTYPE", info)
            isHorizontal = (cmpstr(type, "bottom")==0 || cmpstr(type,"top")==0)
            isHorizontal = isHorizontal || (cmpstr(type[0,2],"/B=")==0 || cmpstr(type[0,2],"/T=")==0)
            isLog = (NumberByKey("log(x)", info, "="))
                    
            GetAxis/W=$s.WinName/Q $axis
            wAx = {v_min, v_max, AxisValFromPixel(s.WinName, axis, isHorizontal ? s.mouseLoc.h : s.mouseLoc.v)}
            if (WaveMax(wAx) == wAx[2] || WaveMin(wAx) == wAx[2])
                continue
            endif
                        
            if (isLog)
                wAx = log(wAx)
                wAx = wAx[2] - (wAx[2] - wAx[p]) * expansion
                wAx = alog(wAx)
            else
                wAx = wAx[2] - (wAx[2] - wAx[p]) * expansion
            endif
                    
            WaveStats/Q/M=1 wAx
            if ( (V_numNaNs+V_numInfs) || wAx[1]==wAx[0] )
                continue
            endif
            
            if (wAx[1] > wAx[0])
                SetAxis/W=$s.WinName $axis, wAx[0], wAx[1]
            else
                SetAxis/R/W=$s.WinName $axis, wAx[0], wAx[1]
            endif
        endfor
    endif
    return 0
end