ue5-ui-umg-slate

Quick Start

• Identify whether feature belongs to UMG, Slate, or hybrid bridge.
• Define data source component/subsystem and UI binding point.
• Output widget tree intent and runtime binding sequence.

API Anchors (UE5.6-UE5.8)

• UMG lifecycle and viewport anchors:
  • UUserWidget::NativeConstruct(), UUserWidget::NativeDestruct()
  • UUserWidget::AddToViewport(...)
  • UWidget::RemoveFromParent()
  • UWidget::SetVisibility(...)
  • UWidget::SetKeyboardFocus()
• UMG input mode anchors:
  • UWidgetBlueprintLibrary::SetInputMode_UIOnlyEx(...)
  • UWidgetBlueprintLibrary::SetInputMode_GameAndUIEx(...)
  • UWidgetBlueprintLibrary::SetInputMode_GameOnly(...)
• UMG/Slate bridge anchors:
  • UWidget::TakeWidget() for Slate bridge hand-off
  • SCompoundWidget, SLATE_BEGIN_ARGS(...)
  • FSlateApplication::SetKeyboardFocus(...), SetUserFocus(...)
• Viewport geometry anchor:
  • UGameViewportClient::GetViewportSize(...)

UI Stage Contract

• Every UI task must define:
  • UI layer ownership (UMG-only, Slate-only, or hybrid bridge)
  • data source and update trigger (pull, push, event, or mixed)
  • focus and input ownership transition
  • viewport-safe placement behavior for tooltip/popup
  • teardown/cleanup path for unbinds and widget removal
• If any item is missing, the UI implementation is incomplete.

Workflow

1) UI Architecture Decision

• Select UMG for standard game HUD/menu work.
• Select Slate for custom rendering/input behavior that UMG cannot express cleanly.
• Select hybrid when a UWidget host needs to embed custom Slate content.

2) Construct and Lifetime

• Initialize widget bindings in construct/init path.
• Register event listeners once and store handles when required.
• Define destruct/unregister logic explicitly to avoid stale bindings.

3) Data Binding and Refresh

• Bind runtime data from one authoritative source (subsystem/component/view model).
• Use event-driven refresh for high-frequency data where possible.
• Keep display widgets read-only for gameplay state mutation.

4) Input and Focus Ownership

• Set input mode deliberately when opening/closing UI contexts.
• Set keyboard/user focus to intended root widget.
• Ensure focus return path back to gameplay on close.

5) Tooltip/Popup Viewport Clamp

• Compute desired tooltip position from anchor and cursor/widget geometry.
• Clamp final placement to viewport bounds to avoid off-screen rendering.
• Debounce high-frequency hover updates to avoid flicker.

6) Remove and Cleanup

• Remove widget from parent or viewport on close.
• Clear timers/delegates and transient references.
• Confirm no duplicate instances persist after reopen.

Constraints

• Keep UI rendering and gameplay state mutation separated.
• Avoid direct gameplay writes from passive display widgets.
• Clamp tooltip and popup placement to viewport bounds.
• Prefer deterministic input ownership and focus transitions.
• Keep Slate-only code isolated behind clear bridge boundaries.
• Do not rely on per-frame polling if event-driven updates are available.

Failure Handling

• Symptom: widget appears but never refreshes.
  • Locate: construct timing, binding registration, source event firing.
  • Fix: bind after source readiness and verify event subscription path.
• Symptom: widget refreshes once then stops.
  • Locate: lost delegate handle or widget recreated without rebind.
  • Fix: rebind on construct and unbind on destruct; prevent duplicate create/destroy churn.
• Symptom: input is swallowed by UI unexpectedly.
  • Locate: current input mode and focused widget path.
  • Fix: enforce intended input mode and set explicit focus target.
• Symptom: keyboard/controller navigation breaks after popup open.
  • Locate: focus transfer and return path.
  • Fix: store previous focus owner and restore on popup close.
• Symptom: tooltip flickers near screen edges.
  • Locate: oscillating clamp output and hover source jitter.
  • Fix: debounce hover updates and clamp with stable viewport metrics.
• Symptom: memory growth after repeated open/close.
  • Locate: stale delegate/timer/reference retention.
  • Fix: clear bindings and transient refs in teardown.

UE5.6-UE5.8 Compatibility Notes

• UMG lifecycle, input mode, and Slate focus APIs listed above are stable in UE5.6-UE5.8.
• Prefer Enhanced Input + explicit UI input mode ownership across all supported versions.

Escalation

• Escalate when behavior requires engine-level Slate customization beyond project scope.
• Escalate when UI architecture conflicts with existing CommonUI framework decisions.