Texture Changer

// =====================================================================
//  Texture Changer
//  skimi3d script library
//  https://grid.skimi3d.com/scripts/texture-changer
//
//  Put several textures in a prim and click through them. The wall
//  colour of a house you are selling, the poster in a frame, the
//  painting over the fireplace, the sign outside a shop that changes
//  with the season.
//
//  It reads the textures out of the prim's own Contents, so adding one
//  more is dropping one more in. Nothing to edit.
//
//  Plain LSL.
// =====================================================================


// ---------------------------------------------------------------------
//  Settings
// ---------------------------------------------------------------------

// Which face changes. -1 means every face of the prim. Give a single
// face number to change only the front of a picture frame and leave the
// wood alone.
integer FACE = -1;

// How it is chosen:
//   0 = one click, next texture
//   1 = a menu, so people can pick by name
integer MODE = 0;

// Change every prim in the linkset rather than just this one. Useful
// for a wall built from six prims that should redecorate together.
integer WHOLE_LINKSET = FALSE;

// Which texture it starts on, counting from 0. Contents is kept in
// alphabetical order, so naming them 1 Oak, 2 Pine, 3 Ash puts them in
// the order you meant.
integer START_AT = 0;

// Say the name of each texture as it comes up. Handy while you are
// setting up, noisy afterwards.
integer ANNOUNCE = FALSE;

// Who may change it. 0 = everyone, 1 = only the owner, 2 = same group.
integer WHO_MAY_CHANGE = 0;


// ---------------------------------------------------------------------
//  Everything below here is the machinery
// ---------------------------------------------------------------------

float PATIENCE = 60.0;      // how long a menu waits for an answer
integer PER_PAGE = 9;       // a dialog holds nine buttons and no more

list    gTextures = [];
integer gAt       = 0;
integer gChannel  = 0;
integer gListen   = 0;
integer gPage     = 0;


list findTextures()
{
    list out = [];
    integer n = llGetInventoryNumber(INVENTORY_TEXTURE);
    integer i;

    for (i = 0; i < n; ++i)
    {
        out += [llGetInventoryName(INVENTORY_TEXTURE, i)];
    }

    return out;
}


show(integer at)
{
    integer n = llGetListLength(gTextures);
    if (n == 0) return;

    // Wrap both ways, so a click past the end comes back to the start.
    while (at < 0)  at += n;
    while (at >= n) at -= n;
    gAt = at;

    string tex = llList2String(gTextures, at);

    integer link = LINK_THIS;
    if (WHOLE_LINKSET) link = LINK_SET;

    llSetLinkPrimitiveParamsFast(link, [PRIM_TEXTURE, FACE, tex,
                                        <1.0, 1.0, 0.0>, ZERO_VECTOR, 0.0]);

    if (ANNOUNCE) llOwnerSay("Now showing: " + tex);
}


integer privateChannel(key who)
{
    return -1 - (integer)("0x" + llGetSubString((string)who, 0, 6));
}


list page(integer n)
{
    integer total = llGetListLength(gTextures);
    if (total <= PER_PAGE) return gTextures;

    integer room  = PER_PAGE - 2;
    integer pages = (total + room - 1) / room;

    if (n < 0) n = pages - 1;
    if (n >= pages) n = 0;
    gPage = n;

    integer from = n * room;
    integer to   = from + room - 1;
    if (to > total - 1) to = total - 1;

    return llList2List(gTextures, from, to) + ["< Back", "Next >"];
}


menu(key who, integer n)
{
    if (gListen) llListenRemove(gListen);

    gChannel = privateChannel(who);
    gListen  = llListen(gChannel, "", who, "");

    llDialog(who, "Which one?", page(n), gChannel);
    llSetTimerEvent(PATIENCE);
}


shut()
{
    if (gListen) llListenRemove(gListen);
    gListen = 0;
    gPage   = 0;
    llSetTimerEvent(0.0);
}


integer mayChange(key who)
{
    if (WHO_MAY_CHANGE == 1) return who == llGetOwner();
    if (WHO_MAY_CHANGE == 2) return llSameGroup(who);
    return TRUE;
}


default
{
    state_entry()
    {
        shut();
        gTextures = findTextures();

        if (llGetListLength(gTextures) == 0)
        {
            llOwnerSay("I have no textures in my Contents. Drop some in and I will start working.");
            return;
        }

        show(START_AT);
    }

    touch_start(integer total)
    {
        key who = llDetectedKey(0);

        if (!mayChange(who))
        {
            llRegionSayTo(who, 0, "This one is not yours to change.");
            return;
        }

        if (llGetListLength(gTextures) == 0)
        {
            llRegionSayTo(who, 0, "There is nothing here to show yet.");
            return;
        }

        if (MODE == 1)
        {
            menu(who, 0);
            return;
        }

        show(gAt + 1);
    }

    listen(integer channel, string name, key who, string message)
    {
        if (message == "Next >")
        {
            menu(who, gPage + 1);
            return;
        }

        if (message == "< Back")
        {
            menu(who, gPage - 1);
            return;
        }

        shut();

        integer at = llListFindList(gTextures, [message]);
        if (at != -1) show(at);
    }

    timer()
    {
        shut();
    }

    changed(integer what)
    {
        // Dropping another texture in should be all it takes. Holding
        // the current one by NAME rather than by number means the
        // picture on the wall does not jump when a new texture sorts
        // itself in ahead of it.
        if (what & CHANGED_INVENTORY)
        {
            string was = llList2String(gTextures, gAt);
            gTextures = findTextures();

            integer at = llListFindList(gTextures, [was]);
            if (at == -1) at = 0;
            gAt = at;
        }
    }

    on_rez(integer start)
    {
        llResetScript();
    }
}