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API:Events

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There are several different types of events that you can respond to. In general, each type of object has a corresponding event for changes, additions, and removals. Each event will be triggered once per object that changes. If more than one property on the object changes at the same time, only one "global" event (e.g. change:graphic) is triggered.

Contents

Callback Parameters

When you listen to an event, you create a function known as a callback that is executed anytime the event occurs. The callback function receives several parameters which are objects that tell you information you want to know about the event so you can decide what to do.

Callback parameters for each event will vary, but include:

obj

The object that was changed. Any changes you make to this object will also be saved to the game. So if you want to move a Graphic object to the left, you would modify the left property of obj using set.

  • obj.get("property") returns the current value for the property.
  • obj.set("property", "newvalue") sets a new value for the property. If you're changing several properties at once you can pass an object: obj.set({left: 10, top: 20});


prev

This is an object of the properties of the obj as they were before any changes were made due to this event. Useful for determining "how much" a property has changed.

NOTE: This is a basic object, so you access the properties using bracket-notation: prev["bar1_value"], NOT using set or get functions.

Event Ordering

Events are fired synchronously (meaning each function won't start until the previous one has finished) in order from first-bound to last-bound, and also from specific property to general object. So given the following:

on("change:graphic", function1);
on("change:graphic", function2);
on("change:graphic:left", function3);

If the objects left property changed, then the order would be function3, then function1, then function2.

In addition, if you have multiple scripts in your campaign, the scripts are loaded in the same order they appear on your Campaign Scripts page, from left-to-right.

Note: Events are only triggered by changes made by players/the GM playing the game. Events will not be triggered by API changes. So if a player moves a piece on the tabletop, you would receive a "change:graphic" event. If you modify the same graphic's property in an API script, there will not be a "change:graphic" event triggered.

Campaign Events

ready

This event fires after all the current data for the campaign has been loaded. So if you want to find a list of all objects in a campaign, or a specific object that is already in the Campaign, be sure to only look for it after the ready event fires. In addition, if you bind to add events (such as add:graphic) before the ready event fires, you will receive add events for objects that were already present in the campaign.

on("ready", function() {
  var tokenThatAlreadyExisted = getObj("graphic", "-ABc123");
});

change:campaign:playerpageid

Fired whenever the page that the players are currently on changes.

change:campaign:turnorder

Fired whenever the turn order listing for the campaign changes.

change:campaign:initiativepage

Fired whenever the turn order is hidden or shown for a page. This may not be the same as the ID of the currently active page. If this is set to false (including if an API script sets it to false), it will close the turn order for all GMs/players. Setting it to a valid page ID will open it for all GMs/players.

Object Events

change:graphic

Triggered whenever a Graphic object (which is almost any type of object on the tabletop, including tokens, maps, and cards) changes.

Note: API created Graphic objects will trigger this event on create.

Callback paramters: obj, prev

on("change:graphic", function(obj, prev) {    
  //Do something with "obj" here. "prev" is a list of previous values.
  // Note that "obj" and "prev" are different TYPES of objects. 
  // to work with obj you need to use obj.get("name");
  // to work with prev you can use prev["name"];
});


change:graphic:(property)

You can also bind to an event for each specific property on the object. So if you have a script that you want to run only when the rotation changes, you would do:

on("change:graphic:rotation", function(obj, prev) {    
  //Always set rotation back to 0, so no one can rotate objects.    
  obj.set("rotation", 0);
});

add:graphic

Triggered whenever a graphic object is added to the tabletop for the first time. Will also be called for existing objects when the tabletop starts up if you bind to this event outside of the ready event.

Callback parameters: obj

on("add:graphic", function(obj) {
  //Will be called for all new graphics, including ones that already existed at the start of the play session.
});

var started = false;

on("ready", function() {
  on("add:graphic", function(obj) {
    //Will only be called for new objects that get added, since existing objects have already been loaded before the ready event fires.
  });
  //You could also set a variable and ignore add events until it is true.
  started = true;
});

destroy:graphic

Triggered whenver a graphic object was removed from the tabletop.

Callback parameters: obj

Other Object Types

There are also events for all the other object types, and sub-types, such as:

change:path, add:path, destroy:path, change:text, add:text, destroy:text, change:token, add:token, destroy:token, change:card, add:card, destroy:card

See the Objects reference for a complete list of all object types and sub-types.