// SPDX-License-Identifier: MIT
// Copyright (c) 2026 Incoprea
// Align child top to root plane
// Not compiled or tested in-world
// Setup: Set TOP_HEIGHT. Use a nonphysical child with meaningful bounding-box dimensions. Owner-touch applies/restores.
// Stop / restore: Owner-touch again to restore the startup snapshot before removal or reset, unless setup describes a different cycle. Do not relink during a preview.
// Notes: Use a spare modifiable build. Saved state lives only in script memory. Useful for aligning shelf undersides or ceiling details. It uses projected bounding-box height, not exact mesh geometry.
// License: see LICENSE in this distribution.
// Original Incoprea. MIT. Not compiled or tested in-world.
integer preview;
float TOP_HEIGHT=1.0;
vector home;
default
{
    state_entry()
    {
        home=llGetLocalPos();
    }
    touch_start(integer n)
    {
        if(llDetectedKey(0)!=llGetOwner())return;
        if(llGetLinkNumber()<2||llGetStatus(STATUS_PHYSICS))return;
        preview=!preview;
        if(preview)
        {
            vector size=llGetScale();
            rotation r=llGetLocalRot();
            vector x=<1.0,0.0,0.0>*r;
            vector y=<0.0,1.0,0.0>*r;
            vector z=<0.0,0.0,1.0>*r;
            float half=(llFabs(x.z)*size.x+llFabs(y.z)*size.y+llFabs(z.z)*size.z)*0.5;
            vector p=home;
            p.z=TOP_HEIGHT-half;
            llSetLinkPrimitiveParamsFast(LINK_THIS,[PRIM_POS_LOCAL,p]);
        }
        else
        {
            llSetLinkPrimitiveParamsFast(LINK_THIS,[PRIM_POS_LOCAL,home]);
        }
    }
}