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Event Layers

Modified on 2016/06/19 10:39 by Administrator Paths: Tutorial Categorized as Design objects, Main concepts
Element Icon New Element
Category: AddIn: Base Elements
Creator: OkazoLab Team Scope: Parent Event
Owns Snippets: no Usage: Runtime Screen,Snippets


The hierarchical nature of EventIDE means that layers are necessary if more than one event is going to be active at any time during the experiment. Although one event can contain a number of elements (such as images, sounds or button presses) it is often the case that these elements need to act independently of one another. In an experiment containing a simple visual task for example, a component of the stimuli to be used (such as a pair of curves) may rotate independently to another component of the stimuli (such as colored markers that sit on the curves). Creating these events as different layers means that they will all operate together in real time, yet with independent properties and parameters. Layers are essential for creating a smooth running experiment and careful design of the experiment structure means that coding of each event can be minimized.


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Practical Use

In order to edit the experiment layers - navigate to the 'HQ' page and then click on the small arrow in the top right hand corner. The Event Layers and Event Flow Chart sections will now be visible.

Event Layers

Additional Events can easily be added to the current layer or a sub-layer can be added by clicking on the + within an event. There are a number of properties of the layers that need to be considered.

  1. Sub-layers will always obey the parent layer. If a parent event is programmed to last only 1 second, but two sub-events are programmed to last 3 and then 4 seconds respectively, the sub layer will only be activated for 1 second and the sub-events will be cut short.
  2. An element of control such as a button press on a parent event, will also be active for all sub-layer events. It is thus unnecessary to add the button press to each sub layer event.
  3. If sub-events have a transparent background, any images from the parent event will be visible.

Event Flow Chart

The order of events within each layer can be manipulated using the Event Flow Chart. If a layer is selected on the left side of the window (Event Layers), then each event will show up within the Event Flow Chart as a circle with a number inside it.

The flow of events can be changed by clicking on the circle corresponding to the event and whilst holding the mouse button down, dragging the mouse to the next event in the sequence (as represented by a circle). Each event can have multiple inputs and outputs. If an event has more than one possible successive event in the output flow - the specific coding of each event will determine which of these outputs is activated. Figures 2 abd 3 below show different examples of possible event flows.

Figure 2 represents two different experiments: the first one has only one experimental layer with two parent events whereas, the second one has two layers defined: there are four parent events and for the first parent event there are three children events defined, which will be activated as soon as parent event is.


Figure 3: Example of a more complex flow chart - Event 1 will be followed by Event 2 but from this event both Events 3 or 4 could follow (this kind of flow is useful for providing feedback to participants after their response). Both Events 3 and 4 then lead back to the beginning of the sequence.



  1. It is always a good idea to have the top layer of any experiment as an ‘Experiment’ parent event - off this the rest of the experiment will hang as sub layers.
  2. Be careful! If from an event there are two possibilities of flow, by default the order in which you have drawn the flow will be followed. Be careful with this order!
  3. When you want to delete an event if all the children events are collapsed inside a parent event and you delete this parent event all the children events will be deleted with it. Before deleting an event be sure it is not collapsed.

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