// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Incoprea
// Locate a touch relative to a sampled rail
// Not compiled or tested in-world
// Setup: Put in the root of a spare owned object/linkset. Child touch handlers may consume events. Touch rail start, rail end, then a point to compare. Collect 3 owner touches; the next touch starts another measurement.
// Stop / restore: Reset clears collected points; disable/remove to stop. No geometry is changed.
// Notes: The rail is a finite segment; projection clamps at either endpoint. Results use actual touch positions in region coordinates, not hidden mesh dimensions.
// License: see LICENSE in this distribution.
// Original Incoprea. MIT. Live touch measurements only.
list points;
default
{
    touch_start(integer detectedCount)
    {
        if(llDetectedKey(0)!=llGetOwner())return;
        if(llDetectedTouchFace(0)<0)
        {
            llOwnerSay("Touch position unavailable.");
            return;
        }
        if(llGetListLength(points)>=3)points=[];
        points+=[llDetectedTouchPos(0)];
        integer collected=llGetListLength(points);
        if(collected<3)
        {
            llOwnerSay("Recorded point "+(string)collected+" of 3.");
            return;
        }
        vector a=llList2Vector(points,0);
        vector b=llList2Vector(points,1);
        vector c=llList2Vector(points,2);
        vector d=llList2Vector(points,3);
        vector rail=b-a;
        float den=rail*rail;
        if(den<0.000001)
        {
            llOwnerSay("Rail endpoints coincide.");
            return;
        }
        float t=((c-a)*rail)/den;
        if(t<0.0)t=0.0;
        if(t>1.0)t=1.0;
        vector point=a+t*rail;
        llOwnerSay("Along fraction="+(string)t+" rail point="+(string)point+" perpendicular/clamped distance="+(string)llVecDist(c,point));
    }
    changed(integer flags)
    {
        if(flags&CHANGED_OWNER)llResetScript();
    }
}