---
title: event_ui_triggered
summary: An MD condition for a Lua UI event, with payload read through event.param3.
section: reference
kind: api
status: reference
tags: ["X4","modding","event","ui","triggered"]
sources: ["https://wiki.egosoft.com/X4%20Foundations%20Wiki/Modding%20Support/"]
---
## Return value

| Type | Meaning |
| --- | --- |
| [event data](wiki:type-md-values) | MD condition, not a Lua return. screen/control are matching expressions; event.param3 is the sender-defined payload in the shown bridge. |

[Types and methods](wiki:types)

## Observed form


Layer: Mission Director cue conditions. Insert the cue below inside `cues`. Its screen/control pair matches [AddUITriggeredEvent](wiki:add-ui-triggered-event).




```xml
<cue name="Receive" instantiate="true" namespace="this">
  <conditions>
    <event_ui_triggered screen="'WikiBridge'" control="'ping'" />
  </conditions>
  <actions>
    <set_value name="$Payload" exact="event.param3" />
  </actions>
</cue>
```



**What happens:** On a matching WikiBridge / ping event, $Payload receives its payload. For the paired Lua example it is the string "hello". Without the event, these cue actions do not run.

## Parameters


`screen` and `control` are expressions used to match the event. In the shown project contract, `event.param3` holds the payload.



## Before a mutation


Validate value types, list length, context and rights to the target object. A UI event is not authorization. `instantiate` and `namespace` affect repeated handling and variable scope. A one-time Init uses a different lifecycle: see [cues](wiki:md-cues).