3. Premier pas dans les entrailles de WME [WME Resource Center]

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
====== 3. Premier tour dans les entrailles de WME ======

Nous avons découvert les outils et nous avons appris les bases du script, il maintenant temps de voir comment ces connaissances s'applique à la conception d'un jeu. Avant de commencer ce tour nous allons d'abord faire un bref survol des types de fichiers que vous allez utiliser dans WME (et je recommande fortement d'utiliser cette convention de nomination):

***.script** – sont les fichiers qui contiennent le programme proprement dit.
***.inc** – sont les fichiers Include qui peuvent être intégré dans les fichiers de script. Leur but est de vous faire économiser des centaines de lignes de code, qui serait autrement répéter dans plusieurs fichiers. Le parfait exemple de ceci est le fichier data\scripts\base.inc. Vous intégrerez ce fichier dans presque tous les scripts.
***.scene** – est le fichier qui contient la définition de la scène tel que défini dans l'éditeur de scène. Bien que vous puissiez définir ce fichier à la main, c'est beaucoup plus confortable d'utiliser sceneEdit pour faire le sale boulot.
***.sprite** – produit de l'éditeur de sprite
***.actor** – est le fichier qui définit l'acteur et ses animations.
***.entity** – est le fichier qui stocke la définition des éléments sprite.
***.font** – est le fichier de définition de police. C'est une interface entre la police effective et celle de WME. Actuellement, il existe deux types de polices pris en charge - de type bitmap et true-type.
***.window** – est un fichier de définition des éléments de fenêtre GUI.
***.image** – s'agit d'un fichier spécial pour stocker une image (avec la possibilité de tiling, etc.) Ceci est utile pour les éléments de l'interface graphique.
***.button** – est un fichier contenant la définitions des boutons.

De plus WME a quelques fichiers spéciaux prédéfinis que vous pouvez également changer, mais ceux-ci sont par défaut:

**default.game** et **startup.settings** sont des fichiers créés par le Gestionnaire de projet et stockés dans le Package (principal) du jeu.
**string.tab** situé au même endroit contient la table de localisation pour les textes. **(TRADUCTION A REVOIR)**
**items.items** contient la définition des objets de l'inventaire utilisé dans le jeu (data\items)
**responses.def** est le fichier qui définit la manière dont la fenêtre de dialogue devrait ressembler.
**inventory.def** est le fichier qui définit à quoi ressemble la boite de l'inventaire (data\interface)

Mais assez parlé de cela et nous allons commencer avec la chose la plus simple - les ajustements de scène. Si nous explorons le contenu de l'une des scènes créées dans l'explorateur, nous allons voir qu'il y a toujours un fichier de scène et un dossier **scr** qui contient le fichier **scene_init.script**

WME lit le fichier de scène de la scène courante, prépare tous les //nœuds// tel que défini dans le fichier de scène, joint tous les scripts qui sont présents dans le fichier de scène et exécute le fichier appelé **scene_init.script**. C'est le fichier que nous allons examiner maintenant et je vais y ajouter mes commentaires:

<code script>
#include "scripts\base.inc"

// voici les trucs qui initialise la scène
actor.SkipTo(733, 562); 		// On positionne l'acteur a une certaine position
actor.Direction = DI_DOWN;	// On définit la direction vers laquelle il fait face
actor.Active = true;			// On fait qu'il soit visible pour cette scène

////////////////////////////////////////////////////////////////////////////////
// état de la scène
global Statewarehouse; 	// On créé une variable globale qui a le même nom que
// la scène précédé du mot State

// default values
if(Statewarehouse==null)  	//Nous lançons le jeu pour la première fois donc la valeur 
{				// n'a pas été encore initialisée
  Statewarehouse.Visited = false;  //Nous n'avons jamais été dans la scène encore
}

////////////////////////////////////////////////////////////////////////////////
// scène de configuration en fonction des variables d'état
////////////////////////////////////////////////////////////////////////////////
if(!Statewarehouse.Visited) //Si nous n'avons jamais été dans la scène
{
  Statewarehouse.Visited = true; //Définir que nous sommes venu ici

  // ceci est notre première visite dans cette scène ...
}
</code>

Maintenant cela peut vous paraitre débile comme script qui ne fait rien d'autre que de vérifier si nous somme aller dans une scène ou pas, mais croyez-moi, il y a plus qu'il n'y parait. Ceci est un script vraiment très astucieux qui compte avec beaucoup de possibilités différentes. il compte pour le jeu qui a été récemment lancé, il compte pour une scène revisitée, il compte du fait que vous pouvez avoir un événement spécial à l'entré de la scène. Rappelez-vous ces moments cinématographiques quand vous avez joué à une aventure, marchant dans une scène seulement pour voir le pont s'effondrer? Vous ne voudriez pas le voir s'effondrer à chaque fois que vous visitez cette scène? C'est sûr une fois suffit.

Alors maintenant, que nous avons découvert ce qui se passe dans ce script, c'est vraiment très simple. Comme il y a des milliers de méthodes différentes, j'ai décidé de choisir la manière douce façon de les présenter si besoin, même si Max étaient très malheureux avec moi la dernière fois, j'ai consulté des approches non-violentes.

Regardons un exemple du début du script.

<code script>
actor.SkipTo(733, 562);
</code>

**EN COURS DE TRADUCTION**

We know that objects have their **methods** which are identified by .name(); notation. So plain and simple we’re calling method SkipTo() of our actor object. “actor” is a global variable which contains an actor object and is declared in different script. Now someone stands up and shouts at me: “You liar, you told us, that every global variable must be declared explicitly in the script by a keyword global.” Ha, I would reply, but it’s of course true. It’s there, but neatly hidden in the included file base.inc See the power of includes? You don’t have to declare an actor, whom you would use for almost every script. You simply put it in the include file and that’s it. Template does the rest.

So let’s get back to our actor object and look at the very first methods we saw + add two more very useful methods:

//**Actor object methods and attributes**//
**actor.SkipTo(x,y);**  - places an actor to a specified screen position. Always double check, that this position is inside of a region.
**actor.Direction = ?;** - is an attribute which sets the direction actor is looking. We have 8 constants (DI_UP, DI_DOWN, DI_LEFT, DI_RIGHT, DI_UPRIGHT, DI_UPLEFT,  DI_DOWNRIGHT, DI_DOWNLEFT)
**actor.Active = true / false;** - is an attribute common to all nodes and actors which makes them active or inactive (visible or invisible).
**actor.GoTo(x,y);** - instead of direct placing of the actor, actor walks to specified coordinates
**actor.Talk(string);** - actor says a text line.

So I bet you’re eager to try the new methods in action. Let’s work on our **scene_init.script** then! Open the scene_init.script file located in //data->scenes->warehouse->scr// folder. Note that from now on, when I’ll refer to the scene_init.script you’ll find it easily without my assistance. Locate the line **actor.Active = true;** and add some more lines behind this one so you’ll get the following result:

<code script>
actor.Active = true;
actor.GoTo(365,561);
actor.Direction = DI_DOWN;
actor.Talk("What a beautiful warehouse!");
</code>

Save your script and run the game from the Project Manager. Before we go on, let’s speak about one of the most important aspects of the game programming in WME. **WME produces a file called wme.log which is placed in the project root directory.** This is a critical file where all problems / script errors etc. are stored. So if you for example make a typo in the script, the game just simply states Script compiler error, but this file tells you what file and on which line contains this error. So learn to open it often or your work will be very slow.

Oh-key. Let’s move on and try some interaction with the Scene. Open the warehouse scene in the scene edit again and select the door region entity we’ve created earlier. Click on the **scripts** button. And here click on **“New script”** button.

{{wmebook:c5_1.jpg|}}

In the next dialogue select template “empty.script” on the left side and press ok.


{{wmebook:c5_2.jpg|}}

This operation will create an empty file called **door.script** and place it in the scr folder. It also attaches the file to the entity so from now on you’re able to catch interaction with our door. Press OK again and **save your scene**. Now open the newly created file which contains the following:

<code script>
#include "scripts\base.inc"

////////////////////////////////////////////////////////////////////////////////
//on "event"
//{
//  ...
//}
</code>

As you can see it’s not very useful. It has include of our old friend **base.inc** but apart from that it doesn’t do anything. We need to expand it a bit. I was briefly explaining **events** in the script chapter and now it’s time to use them. Change the script so it will read:

<code script>
#include "scripts\base.inc"
on "LeftClick"
{
	actor.Talk("I've clicked on the door");	
}
</code>

Save the script, run the game and click left mouse button on the door. Voila! We’ve defined our first interaction with the game world. We’ll expand more on that but before I’ll offer you a set of most useful events which are available from the WME side. 

**on "LeftClick"** – Left mouse button was clicked over the node.
**on "RightClick"** – Right mouse button was clicked over the node.
**on "MiddleClick"** – Middle mouse button was clicked over the node.
**on "LeftDoubleClick"** – Left mouse button was double-clicked over the node.
**on "RightDoubleClick"** – Right mouse button was double-clicked over the node.
There are more events to use, but for the start we’ll be ok with these.

The scripts attached to the node have another interesting feature, they are parts of the object so you can access their properties by the identifier **this**. Let’s experiment with this concept a bit. Change the actor.Talk to read:

<code script>
actor.Talk(this.Name);
</code>

If you save the script and run the game, upon clicking on the door actor says “Door”. Does it ring a bell? But of course, it’s a **Name** we’ve set in the scene edit. As you can see, what we set in the Scene Editor is easily accessible from the script which brings us to yet another actor method: 

**actor.GoToObject(Node);** - Goes to coordinates specified in the Scene Editor under “Walk to” and then turns to the direction specified in the same place.

But we also know that the entity is represented by a keyword this. Can’t it be simpler than that? Try to rewrite your event handler to:

<code script>
on "LeftClick"
{
	actor.GoToObject(this);
	actor.Talk(this.Name);	
}
</code>

Provided you’ve set correctly the coordinates in the scene editor, actor should go to the door and says the word “Door”.

Last experiment with our infamous door for now is setting their **Active** property to false and thus disabling the door hotspot after we click it.

<code script>
on "LeftClick"
{
	actor.GoToObject(this);
	actor.Talk(this.Name);	
	this.Active = false;
}
</code>

We’ve scratched surface of two objects so far. Actor object and Region Entity object, which we referenced by keyword **this** and hid it through setting its attribute **Active** to false.

Let me return back to the image we’ve seen at the beginning and look at this very image from a developers point of view.

{{wmebook:ch1diag.jpg|}}

Now it won’t probably surprise you that the main game object is called **Game**. You can also see that everything in this diagram is derived from the Game object. If we look at our door entity from this point of view to see where it’s hidden, we’d go this way:

Game -> Scene -> Door.

We know, that we can reference Scene as Scene, but don’t let this fool you.((Remember that nested notation problem?)) The scene is in demo actually defined in the **game.script** which is the master brain of the game as follows:
<code script>Scene = Game.Scene;</code> 

In the base.inc our Scene is defined as **global Scene;** and because we include **base.inc** into all our files, we can readily reference Scene object from everywhere. 

As we can guess, Game object would serve for the global purposes of the game while Scene object would be useful for per Scene operations. Let me introduce you to the most used functions which represent very well each object.

**Game.ChangeScene(filename);** is a function which changes the scene. It takes as an argument path to the .scene file 
**Scene.GetNode(NodeName);** is a function which returns the object named NodeName from the scene. 

We’ll do something, which would demonstrate the power of WME now. Return to your warehouse scene in scene edit and let’s tweak it a bit. First we should create a new region and call it Exit. Position it to the left bottom corner as on the following image (you should immediately discover by now that it’s the red shape). Also note the position in the scene tree. If you put it above the floor, the mechanism presented wouldn’t work because the floor region would cover the Exit region and this way the Exit region would never get his voice. Last thing which remains to do is to attach a script to this region. Use an empty template and save the scene. 

{{wmebook:c5_3.jpg|}}

Before we go on, let’s discuss two more events (we already know Mouse related events).  

**on "ActorEntry"** occurs when actor enters the current region. This is the basic logic behind so called trap regions. Trap regions mean that actor triggers an event upon entering certain portion of the screen.

**on "ActorLeave"** occurs when actor leaves the current region.

Last thing we’d need for this example is taking the game out of player’s control. This is the vital part of successful game design. We want to trigger a scene and in the middle player clicks somewhere else, character didn’t finish the whole sequence and you’re stuck in an unsolvable loop. This kind of nightmare met many designers so let’s avoid it while we still can.

**Game.Interactive = true / false;** Takes the game out of players control or returns it back. Always remember to return the game back to Interactive mode or your game will be stuck and players will get angry. So always think of the noninteractive mode as of a block.

We’ll try to combine those ideas into our first more complex game logic.

First we’ll adapt the **door.script** to look like this:

<code script>
on "LeftClick"  
{
	Game.Interactive = false;    // We want our player to make more things at once and we don't want to be interrupted.
	actor.GoToObject(this);
	this.Active = false;  // We disable the door so the hotspot is not visible or active anymore.
	actor.Talk("Oh no. The door is welded shut.");	
	Game.Interactive = true; // Allow player to play some more.
}
</code>

Then we open the **exit.script** and add a new event there. The file should look like this:

<code script>
#include "scripts\base.inc"

on "ActorEntry"  //Actor entered the Exit region
{
	Game.Interactive  = false;
	var door = Scene.GetNode("Door"); //We get the object corresponding to the scene name door into a variable named door
	
	if (door.Active) // If door was not clicked, it was not disabled, so this path will be used
	{
		actor.Talk("I don't want to return to my flat before I am sure I can't enter the warehouse!");
	}	
	else //we know that the door is welded shut so we can leave the scene
	{
		actor.Talk("Oh well, there really is no way how could I enter that damn warehouse");
		Game.ChangeScene("scenes\room\room.scene");
	}
	Game.Interactive = true;
}
</code>

Okay. Time to explain what’s going on in here. Our thought process as a game designer was that player needs to enter the warehouse but the warehouse is welded shut. We for some reason need our player to discover the fact that the door is welded shut so the game could proceed. So we decided to allow him to change the scene only after he discovered that the warehouse was welded shut. 

Code-wise we have the region which would be normally used as an exit region, but we’ve added the condition that until the door region was active (which means that player didn’t click on it because if he did, the door region turns inactive), player can’t leave the screen.

Save all scripts and run the game. Test the game thoroughly so you’re sure that you really understand the coding behind this logic. It’s one of the critical aspects of adventure game designing and if you get this right, you’ll be in no time creating your own adventures.

**Important:**
Critical thing to know is how path in wme works in general. We’ve seen in **Game.ChangeScene("scenes\room\room.scene");** that we didn’t start with the data path. That’s totally correct! Write it thousand times – I’ll never include the root package name in the referenced path. Why? Because this would work only in debug mode, and when you compile your game in the packages and send it around, it won’t work. The same applies to all files (images, sounds etc.). Never reference files outside of packages. They’ll work in debug mode, but they won’t get compiled and you’ll be in it for the worst nightmares. Think of package as of a virtual root directory and all references should be starting from that point. More about that in the chapter about packages.

Let’s move on to the last part of this chapter, which will cover the daemon issue. We’ll start right off with our first daemon. Before we explain how it works, we’ll have to take a look at a few new methods:

**Game.AttachScript(filename);** - Attaches a new script file to the Game object, making it global for the whole game. This script is attached until it’s detached or ends.
**Game.DetachScript(filename);** - Detaches script from the Game object.

**Scene.AttachScript(filename);** - Attaches a new script file to the current scene,  making it active until player doesn’t change the current scene, or script is detached or ends.
**Scene.DetachScript(filename);** - Detaches script from the Scene object.

We can of course attach script to the scene object in the Scene Editor or script to Game object in the Project Manager, but we want our script to be attached in the middle of the gameplay. 

Next command we’d learn is totally necessary for the daemon writing. It’s command Sleep.
**Sleep(time);** - Pauses the script for certain amount of milliseconds. 

Sleep serves two purposes. First - it lets the script wait for certain amount of time and second - it hands the program flow to other threads. Here’s the typical daemon pitfall:

<code script>
var a = 0;
while (1) // infinite loop, the same as while(true)
{
   a = a + 1;
   if (a > 100) a = 0;
}
</code>

**Never do this. It’ll halt your computer. Script takes over the whole processing power and the rest of the game never get control back. This way also Windows never gets control back which results in hung up computer.** So how to fix this?

<code script>
var a = 0;
while (1)
{
   a = a + 1;
   if (a > 100) a = 0;
   Sleep(1);		
}
</code>

This daemon is correct (remember our previous chapter), because it hands over the control from the script. One millisecond is here only formally. The important fact is that you DO hand over the control.

So enough theory and let’s make some daemon fun with the commands, we’ve just learned. Oh wait. We’d need one more command:

**Game.Msg(text);** - although we’ve seen it before let’s recap that it displays an onscreen debug message. Very useful command.

What we’re going to do is a funny little timed sequence, which occurs in our warehouse scene. The scenario is as follows. Player examines the door to discover that there’s a time bomb attached to it. If he can’t exit quickly enough, the Scene is reloaded (it’s the hardcore-adventure-fan-way how to tell the player, that he has died).

First we’ll create the new script in the scr folder (from the empty template) and name it **bomb.script**.

Tip: if you get more skilled, you can add the new files manually by creating a text file with a script extension created in the corresponding folder.
Then we modify the **door.script** so it’ll read the following:

<code script>
#include "scripts\base.inc"

on "LeftClick"  
{
	Game.Interactive = false;    // We want our player to make more things at once and we don't want to be interrupted.
	actor.GoToObject(this);
	this.Active = false;  // We disable the door so the hotspot is not visible or active anymore.
	actor.Talk("Oh no. There's a timed bomb attached to the door! I have to find an exit before it explodes.");	
	Scene.AttachScript("scenes\warehouse\scr\bomb.script");
	Game.Interactive = true; // Allow player to play some more.
}
</code>

I’ve hilighted the line which attaches our new script and thus starting the countdown.
Now let’s look at the **bomb.script** contents.

<code script>
#include "scripts\base.inc"

for (var timer=6;timer>-1;timer = timer -1)  // let's set up a loop which would go down from 6 to 0.
{
	Game.Msg("Countdown: " + timer); //Let's display how much time do we have left.
	Sleep(1000); // Sleep one second (and also hand the game over to other threads)
}

Game.Interactive = false; //Death cutsene
actor.Talk("I've just died. Let's try again");
Game.ChangeScene("scenes\warehouse\warehouse.scene");
var door = Scene.GetNode("Door");
door.Active = true; // If we die, we need to return the door to its active state or we'll never discover the bomb again.
Game.Interactive = true;
</code>

And the last change we’ll make is to the **exit.script**. If we found an exit in time, actor will be able to escape, but what if he arrives there in the nick of time and while talking his line, the time runs away and he dies? So let’s prevent this from happening by detaching the bomb script and letting him say something more reasonable.

So the contents of the **exit.script** would look like this:

<code script>
#include "scripts\base.inc"

on "ActorEntry"
{
	var door = Scene.GetNode("Door");
	Game.Interactive = false;
	if (door.Active)
	{
		actor.Talk("I don't want to return to my flat before I am sure I can't enter the warehouse!");
	}	
	else
	{
		Scene.DetachScript("scenes\warehouse\scr\bomb.script");
		actor.Talk("Phew. That was close");
		Game.ChangeScene("scenes\room\room.scene");
	}
	Game.Interactive = true;
}
</code>

Save everything and test our little scheme to see some more of the effects.

On closing of this chapter I’ll introduce a little change to our scheme. This change is not necessary in our example, but it will be necessary in different case. For now we’re testing, if the entity region Door is Active for another decision. But what if we need to apply the similar logic to more than one scene? If we stand in different scene, we logically can’t use entity this way because it’s not anymore part of the current scene.

So what we can do is using a global variable. Let’s make a change to our scripts then!
Last code listing for this script triplet is then (changes in bold):

**bomb.script**
<code script>
#include "scripts\base.inc"

for (var timer=6;timer>-1;timer = timer -1)  // let's set up a loop which would go down from 6 to 0.
{
	Game.Msg("Countdown: " + timer); //Let's display how much time do we have left.
	Sleep(1000); // Sleep one second (and also hand the game over to other threads)
}

Game.Interactive = false; //Death cutsene
actor.Talk("I've just died. Let's try again");
var door = Scene.GetNode("Door");
door.Active = true; // If we die, we need to return the door to its active state or we'll never discover the bomb again.
global doorClicked = false;
Game.ChangeScene("scenes\warehouse\warehouse.scene");
Game.Interactive = true;
</code>

**door.script**
<code script>
#include "scripts\base.inc"

on "LeftClick"  
{
	Game.Interactive = false;    // We want our player to make more things at once and we don't want to be interrupted.
	global doorClicked = true;
	actor.GoToObject(this);
	this.Active = false;  // We disable the door so the hotspot is not visible or active anymore.
	actor.Talk("Oh no. There's a timed bomb attached to the door! I have to find an exit before it explodes.");	
	Scene.AttachScript("scenes\warehouse\scr\bomb.script");
	Game.Interactive = true; // Allow player to play some more.
}
</code>

**exit.script**
<code script>
#include "scripts\base.inc"

on "ActorEntry"
{
	var door = Scene.GetNode("Door");
	Game.Interactive = false;
	global doorClicked;
	if (!doorClicked)
	{
		actor.Talk("I don't want to return to my flat before I am sure I can't enter the warehouse!");
	}	
	else
	{
		Scene.DetachScript("scenes\warehouse\scr\bomb.script");
		actor.Talk("Phew. That was close");
		Game.ChangeScene("scenes\room\room.scene");
	}
	Game.Interactive = true;
}
</code>

We’ve seen in this chapter some neat tricks with the way how we can handle the game logic. We’ve also learned some of the important concepts for the tying scene to the code and we are able to use a couple of very basic commands and object methods. But for now we all the time used a lot of prebuilt demo code. Next chapter is all about starting the project from scratch. We’ll build upon this blank project until we create a little feature packed game. So stay tuned, we’re getting into it.