Lyra Default UI Policy Details

This is part of How Common UI is Setup in LyraStarterGame. Read that as well for more info.

Default UI Policy

The Lyra UI Manager Subsystem implements a single global “UI Policy”, which ultimately is just a widget that defines prioritized widget container “layers”.

Which widget to use is defined via a Blueprint class, as configured in the INI:

• In DefaultGame.ini:
  • Set Default UI Policy = Content/UI/B_LyraUIPolicy

DefaultGame.ini Setting:

[/Script/LyraGame.LyraUIManagerSubsystem]
DefaultUIPolicyClass=/Game/UI/B_LyraUIPolicy.B_LyraUIPolicy_C

Lyra UI Manager Subsystem

LyraUIManagerSubsystem : public GameUIManagerSubsystem from CommonGame

This subsystem manages the creation of the UI Layout widget and adding it to the local player’s viewport. It also supports changing the UI Policy at runtime. See its C++ code if you need to do that.

Lyra UI Policy

B_LyraUIPolicy : public GameUIPolicy from CommonGame

UCLASS(Abstract, Blueprintable, Within = GameUIManagerSubsystem)
class COMMONGAME_API UGameUIPolicy : public UObject

This BP specifies a single global UI Layout Widget:

• In B_LyraUIPolicy:
  • Set Game UI Policy / LayoutClass = Content/UI/W_OverallUILayout

Set Overall UI Layout = W_OverallUILayout

Overall UI Layout

W_OverallUILayout : public PrimaryGameLayout from CommonGame

/**
 * The primary game UI layout of your game.  This widget class represents how to layout, push and display all layers
 * of the UI for a single player.  Each player in a split-screen game will receive their own primary game layout.
 */
UCLASS(Abstract, meta = (DisableNativeTick))
class COMMONGAME_API UPrimaryGameLayout : public UCommonUserWidget

Lyra UI Layers

The W_OverallUILayout widget defines 4 widget layer stacks:

• UI.Layer.Game - Things like the HUD.
• UI.Layer.GameMenu - “Menus” specifically related to gameplay, like maybe an in game inventory UI.
• UI.Layer.Menu - Things like the settings screen.
• UI.Layer.Modal - Confirmation dialogs, error dialogs.

Common Activatable Widget Containers

CommonUI ships with both Stack and Queue containers, and Lyra only uses Stack by default.

If you need something more complex than a Stack or Queue, you can derive your own layer type by deriving from CommonUI UCommonActivatableWidgetContainerBase.

Common Activatable Widget Stack

CommonActivatableWidgetStack : public UCommonActivatableWidgetContainerBase from CommonUI

/** 
 * A display stack of ActivatableWidget elements. 
 * 
 * - Only the widget at the top of the stack is displayed and activated. All others are deactivated.
 * - When that top-most displayed widget deactivates, it's automatically removed and the preceding entry is displayed/activated.
 * - If RootContent is provided, it can never be removed regardless of activation state
 */
UCLASS()
class COMMONUI_API UCommonActivatableWidgetStack : public UCommonActivatableWidgetContainerBase

You can create your own, more complex Layer type by sub-classing CommonActivatableWidgetContainerBase.

All other widgets are CommonActivatableWidget derivatives, and rather than getting added directly to the viewport, they get pushed onto one of the UI layer stacks.

Common Activatable Widget Queue

CommonActivatableWidgetQueue : public UCommonActivatableWidgetContainerBase from CommonUI

/** 
 * A display queue of ActivatableWidget elements. 
 *
 * - Only one widget is active/displayed at a time, all others in the queue are deactivated.
 * - When the active widget deactivates, it is automatically removed from the widget, 
 *		released back to the pool, and the next widget in the queue (if any) is displayed
 */
UCLASS()
class COMMONUI_API UCommonActivatableWidgetQueue : public UCommonActivatableWidgetContainerBase