ProjectDialogueUI

Dialogue panel widget and ViewModel for the ALIS dialogue system.

Architecture

IDialogueService -> DialogueViewModel -> W_DialoguePanel
                    (auto_visibility)    (JSON layout)

• DialogueViewModel: Subscribes to IDialogueService via FProjectServiceLocator. Exposes bIsActive, SpeakerName, DialogueText, Options as VIEWMODEL_PROPERTY fields.
• W_DialoguePanel: Inherits UProjectUserWidget. Visual layout loaded from Data/DialoguePanel.json. Widget children resolved by FProjectUIWidgetBinder.
• ui_definitions.json: Registers panel with vm_creation: "Global", auto_visibility: "bIsActive", layout_json: "DialoguePanel.json".

Option state rendering:

• FDialogueOptionView.bLocked=true -> option button disabled + greyed text ((Unavailable) suffix).
• FDialogueOptionView.bConditionSatisfied=true -> subtle green highlight for conditional choices that are currently available.

Why UProjectUserWidget (not UUserWidget)

The original implementation inherited UUserWidget directly and used BindWidgetOptional + manual SetDialogueViewModel(). This broke in two ways:

1. ViewModel injection failed silently - ProjectUIFactorySubsystem::InjectViewModel() checks three paths: IProjectViewModelConsumer, UProjectActivatableWidget, UProjectUserWidget. Plain UUserWidget matches none, so DialogueVM stayed null and the panel collapsed itself.

2. No visual content - BindWidgetOptional requires a Blueprint subclass to populate widget references. Without one, SpeakerText, DialogueText, OptionsContainer, ContinueButton were all null.

The fix aligns with the project-wide data-driven UI pattern (same as W_InventoryPanel):

• UProjectUserWidget provides JSON layout loading, ViewModel lifecycle, and theme support
• DialoguePanel.json defines the widget tree declaratively
• FProjectUIWidgetBinder resolves children by name (type-safe, logged)
• No Blueprint widget needed

See Plugins/UI/ProjectUI/Source/ProjectUI/Public/Widgets/ProjectUserWidget.h for the base class contract.

Files

File	Purpose
Data/ui_definitions.json	Panel registration (layer, VM, auto_visibility, layout)
Data/DialoguePanel.json	Visual layout (JSON widget tree)
Source/.../MVVM/DialogueViewModel.h/.cpp	ViewModel (service subscription, property notification)
Source/.../Widgets/W_DialoguePanel.h/.cpp	Widget (layout binding, option buttons, continue)

Modifying the Layout

Edit Data/DialoguePanel.json. The JSON format supports:

• Widget types: CanvasPanel, VerticalBox, HorizontalBox, Border, TextBlock, Button, SizeBox, etc.
• Anchors: Fill, BottomCenter, Center, TopLeft, etc.
• Theme refs: font: "HeadingSmall", color: "Text", background: "Background"
• Hot reload in editor (file watcher rebuilds layout on save)

See Plugins/UI/ProjectInventoryUI/Data/InventoryPanel.json for a complex layout example.