How to use Trackables!

[Black-Hole]

Trackables
A trackable is just something like a doodad, let's say. But it is different as it can't be selected, it can't be moved, it can't die, and it can't be eliminated. It doesn't even have to be seen if you don't want it to.
The point of a trackable is to harness the mouse detection for usage in triggers. Mouse detection just means the game registers when your mouse pointer moves over an object, or clicks it.

FAQ
As I get more questions, I will answer them here so you don't have to sift through the posts.

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Q. Do trackables work in multiplayer maps?
A. Yes, they work fine. As for tracking which player triggered the trackable, you would need a handler system for that.

Limitations
Although Blizzard gave us these functions to use mouse detection, it doesn't seem they really cared to finsh the code, because you can not retrieve a triggering player from a trackable event. Nor can a trackable be owned by a player.
The usage of trackables is very limited, because you can not manipulate anything about a trackable once you create it, or before. This means you can not move, scale, color, or make any other kind of modification. You just create it, and that's it.
Also, one of the reasons not many people know of trackables, is because they require JASS to fully use. You can create and manipulate trackables through the Custom Script action, but there is no event in GUI that uses trackables.
Fortunately, the functions are not very hard to understand and require little, if any, JASS knowledge.


Usage
I wanted to bring these trackables to attention, because even many JASSers seem to not know what they are. Trackables are a powerful tool that can be used to make better interactive systems, and even things like mini-games.

To use trackables, first you must create them. They can not be pre-placed in a map, so you must make them through triggers. They are created somewhat like units are created, only you use a model string to determine the model of the trackable, not an id or name.
This is actually very useful, because you can use any valid model path. This includes units, buildings, doodads...anything with a model path. If you use a unit or buildiing model, the trackable will appear looking like a neutral hostile unit, with no team colors.
Trackables do play animations. If you want a trackable to be invisible, you just insert a void string argument (""). Here is the function to create a trackable:

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CreateTrackable(string modelpath, real x, real y, real facing)

modelpath is the path of the model you would like to use. Use "" for an invisable trackable. Remember to use \\ instead of \.
real x and real y are the coordinates of the location to create the trackable
facing is the angle that the trackable faces (remember this cannot be changed after creation)

The events for trackables are as follows:

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TriggerRegisterTrackableHitEvent(trigger whichTrigger, trackable t)
TriggerRegisterTrackableTrackEvent(trigger whichTrigger, trackable t)

trackable is a handle that you use like any other handle (unit, location...).

TriggerRegisterTrackableHitEvent registers when a player clicks on a trackable. TriggerRegisterTrackableTrackEvent registers when a player moves his mouse across a trackable.
You may notice that this same system is in place with normal units in Warcraft III. When you click a unit, you select it. When you pass over a unit with your mouse, a bar shows it's health.
Trackable events work like any other event, but you also need to specify a trackable for the event to register.

A Trigger:
This trigger will create a trackable, and when someone passes over it, a message will be sent.

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function Massage takes nothing returns nothing
    call DisplayTextToForce(GetPlayersAll(),"Peasant: OOh, that feels nice.") //Displays the pleasure of the peasant when we rub him with our mouse
endfunction

//===========================================================================
function InitTrig_zomg takes nothing returns nothing
 local trigger t=CreateTrigger() //Creates the trigger
 local trackable tr=CreateTrackable("units\\human\\Peasant\\Peasant.mdl",0,0,-90) //Creates our trackable, with the peasant model
    call TriggerRegisterTrackableTrackEvent(t,tr) //Registers when someone passes over tr with their mouse
    call TriggerAddAction(t,function Massage) //Calls our actions function
endfunction

You may notice I display the message to all players. This is because there is no 'GetTriggeringPlayer' for a trackable event, which is probably the biggest limitation of trackables. But, there is a 'GetTriggeringTrackable'. Which opens up possibilites to fix the missing TriggeringPlayer problem. (With 'GetTriggeringTrackable', you may be able to stimulate a Triggering Player, maybe by using the Handle Vars or another system)

The Result:




ADD: Trackable Workarounds (credits to KaTTana)
Using Handle Vars With Trackables
KaTTana wrote this part better than I can, so here it is.
You can find KaTTana's Trackables tutorial here: Link
You can find KaTTana's Handle Var turorial here: Link

A Part of KaTTana's Tutorial:
"We don't have any natives for getting the (x,y) coordinates of a trackable, but we can handle that ourselves with the Local Handle Variables.
Here is a custom API for extended use of trackables.

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// ===========================
//   Trackable API

function GetTrackableX takes trackable tc returns real
    return GetHandleReal(tc, "x")
endfunction
function GetTrackableY takes trackable tc returns real
    return GetHandleReal(tc, "y")
endfunction
function GetTrackableFacing takes trackable tc returns real
    return GetHandleReal(tc, "facing")
endfunction
function GetTrackablePath takes trackable tc returns string
    return GetHandleString(tc, "path")
endfunction

function NewTrackable takes string path, real x, real y, real facing returns trackable
    local trackable tc = CreateTrackable(path, x, y, facing)
    call SetHandleReal(tc, "x", x)
    call SetHandleReal(tc, "y", y)
    call SetHandleReal(tc, "facing", facing)
    call SetHandleString(tc, "path", path)
    return tc
endfunction

Trackables in Multiplayer
Previously, the tutorial stated that trackables didn't work in multiplayer, but that was wrong. They work fine, and they don't desynchronize the game.
However, there is no way to determine which player triggered the event on a trackable. We can work around this by creating a trackable for each player - each can only be triggered by one player.

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// t1 and t2 are visually the same trackable, but in fact they only work for one player each
    local trackable t1 // Player 1's trackable
    local trackable t2 // Player 2's trackable
    local string peasant = "units\\human\\Peasant\\Peasant.mdl"
    local string invisible = ""
    local string path = invisible

    if ( GetLocalPlayer() == Player(0) ) then
        set path = peasant
    endif
    set t1 = CreateTrackable(path, -500, 0, 0)

    set path = invisible
    if ( GetLocalPlayer() == Player(1) ) then
        set path = peasant
    endif
    set t2 = CreateTrackable(path, -500, 0, 0)

    call SetHandleInt(t1, "player", 0) // Store which player "owns" this trackable
    call SetHandleInt(t2, "player", 1) // Same for player 2

    // Add events to register track/hit on t1 and t2...

After this, you can determine the player triggering a trackable by reading the local integer named "player" on the triggering trackable.

We can extend to NewTrackable if you like:

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function GetTrackableOwner takes trackable t returns player
    return Player(GetHandleInt(t, "player"))
endfunction

function NewTrackable takes string path, real x, real y, real facing, player owner returns trackable
    local trackable tc
    local string invisible = ""
    if GetLocalPlayer() != owner then
        set path = invisible
    endif
    set tc = CreateTrackable(path, x, y, facing)
    call SetHandleReal(tc, "x", x)
    call SetHandleReal(tc, "y", y)
    call SetHandleReal(tc, "facing", facing)
    call SetHandleString(tc, "path", path)
    call SetHandleInt(tc, "player", GetPlayerId(owner))
    return tc
endfunction

Giving height to Trackables
Although the natives do not allow it, a simple workaround enables us to create trackables at a given height above ground.

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function CreateTrackableZ takes string path, real x, real y, real z, real face returns trackable
    local destructable d = CreateDestructableZ( 'OTip', x, y, z, 0.00, 1, 0 )
    local trackable tr = CreateTrackable( path, x, y, face )
    call RemoveDestructable( d )
    set d = null
    return tr
endfunction

It works by creating an Invisible Platform at the given height, and then creating the trackable on top of that. After removing the platform, the trackable stays in place."
_________________________________________________________________

Once again, that was part of KaTTana's trackable tutorial.

[Risen]

This should be in the JASS Section, And If you wish, Make all of your (copy and pasted tutorials, Don't worry, I've seen most of the tutorials on the intarwebs sometime ago) in one post, And use a spoiler for each topic.. E.G.

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Learning Jass tutorial;
[spoiler]Jass stuff[/spoiler]
Learning how to have sex tutorial;
[spoiler]Find a hot girl.[/spoiler]

Can't use spoilers inside [codes] :[

[Senethior459]

If you want to make all of them into one thread, then after you do so, tell someone on Staff, and we'll delete the old topics for you.

[storyyeller]

I never knew about trackables. It sounds really cool. I'll have to try them sometime.