Runtime widget interaction

widget(action="invoke_runtime_function") drives a live UMG widget while Play-In-Editor is running. It covers two shapes:

• A UFUNCTION on the UserWidget. Pass functionName with no childName. The function must take no parameters.
• An interaction on a child widget. Pass childName. The handler writes the new state through the widget's own setter and broadcasts the delegate the real interaction fires, so Blueprint logic bound to that event runs. Setting the property without the broadcast would leave the graph unrun, which is the reason this path exists.

Locate the widget with widgetName (exact instance name) or className (first match). widget(action="list_runtime") lists the live instances.

This is one interaction per call, and it calls the widget's own setter rather than synthesizing an input event. For a timed sequence of interactions, or for real key and axis events at the input layer, use pie(inject_input*) from the PIE Studio plugin. See Widgets for where that line sits.

Supported child widgets

Any other class returns an error naming the class and listing the supported ones, so a UI pass never records a silent no-op as a pass.

Selecting a single delegate

functionName alongside childName narrows the broadcast instead of naming a UFUNCTION on the parent. On a text field, functionName: "OnTextChanged" sets the text and fires only the change event, which is how you exercise live validation without the commit path. A name the child does not expose returns an error listing the delegates it does.

commitMethod picks the commit type for text fields and spin boxes: OnEnter (default), OnUserMovedFocus, OnCleared, Default.

Examples

Toggle a checkbox and run its bound graph:

{ "action": "invoke_runtime_function", "widgetName": "WBP_Settings_C_0", "childName": "CheckBox_0" }

Set a checkbox explicitly, move a slider, type a name, pick a combo entry:

{ "action": "invoke_runtime_function", "className": "WBP_Settings", "childName": "InvertYCheck", "value": true }
{ "action": "invoke_runtime_function", "className": "WBP_Settings", "childName": "MasterVolume", "value": 0.35 }
{ "action": "invoke_runtime_function", "className": "WBP_Settings", "childName": "PlayerName", "value": "Ada" }
{ "action": "invoke_runtime_function", "className": "WBP_Settings", "childName": "QualityCombo", "value": "Epic" }

Response

{
  "success": true,
  "widget": "WBP_Settings_C_0",
  "child": "InvertYCheck",
  "childClass": "CheckBox",
  "interaction": "check",
  "previousValue": "unchecked",
  "value": "checked",
  "isChecked": true,
  "invoked": "OnCheckStateChanged",
  "delegates": ["OnCheckStateChanged"]
}

invoked holds the primary delegate name, delegates every delegate broadcast by the call. Numeric widgets also return requestedValue when clamping changed the applied value, and the combo box returns selectedIndex.

Broadcast accounting

Each delegate fires exactly once per call. Some UMG setters broadcast on their own, so the handler only broadcasts by hand where the setter is silent:

• UCheckBox::SetCheckedState, USpinBox::SetValue and every SetText overload are silent. The handler broadcasts.
• USlider::SetValue broadcasts OnValueChanged, but only when the value actually moves. Driving the slider to the value it already holds is still a request to run the graph, so the handler broadcasts in that case.
• UComboBoxString::SetSelectedOption broadcasts OnSelectionChanged on a real change and no-ops when the option is already selected, where the handler broadcasts with ESelectInfo::Direct.