Lots of work on focus management

Source/Integration/LuprexViewportClient.cpp

@@ -0,0 +1,62 @@
+////////////////////////////////////////////////////////////
+//
+// LuprexViewportClient.cpp
+//
+////////////////////////////////////////////////////////////
+
+#include "LuprexViewportClient.h"
+#include "Common.h"
+#include "PlayerControllerBase.h"
+#include "Engine/GameInstance.h"
+#include "Framework/Application/SlateApplication.h"
+#include "Layout/WidgetPath.h"
+#include "Widgets/SViewport.h"
+
+UlxViewportClient::UlxViewportClient(const FObjectInitializer &ObjectInitializer)
+	: Super(ObjectInitializer)
+{
+	UE_LOG(LogLuprexIntegration, Display, TEXT("UlxViewportClient constructed"));
+}
+
+bool UlxViewportClient::InputKey(const FInputKeyEventArgs &EventArgs)
+{
+	UE_LOG(LogLuprexIntegration, Display, TEXT("UlxViewportClient::InputKey key=%s event=%d"),
+		*EventArgs.Key.ToString(), (int32)EventArgs.Event);
+
+	// Only act on left mouse button presses that bubbled up to the
+	// viewport unhandled.  Walk the widget path under the cursor and
+	// find the nearest focusable ancestor of whatever was hit.  If it
+	// isn't the game viewport itself, hand it to the player controller
+	// to apply on its next UpdateInputMode pass; that's the point in
+	// the frame where we can override SViewport's own click-focus
+	// behaviour without fighting it.
+	if ((EventArgs.Event == IE_Pressed) && (EventArgs.Key == EKeys::LeftMouseButton))
+	{
+		FSlateApplication &Slate = FSlateApplication::Get();
+		FVector2D MousePos = Slate.GetCursorPos();
+		FWidgetPath Path = Slate.LocateWindowUnderMouse(
+			MousePos, Slate.GetInteractiveTopLevelWindows());
+
+		if (Path.IsValid())
+		{
+			TSharedPtr<SViewport> ViewportWidget = GetGameViewportWidget();
+			for (int32 Idx = Path.Widgets.Num() - 1; Idx >= 0; --Idx)
+			{
+				TSharedRef<SWidget> Widget = Path.Widgets[Idx].Widget;
+				if (!Widget->SupportsKeyboardFocus()) continue;
+				if (ViewportWidget.IsValid() && Widget == ViewportWidget) break;
+				if (UGameInstance *GI = GetGameInstance())
+				{
+					if (AlxPlayerControllerBase *PC = Cast<AlxPlayerControllerBase>(
+						GI->GetFirstLocalPlayerController(GetWorld())))
+					{
+						PC->ClickToFocus(Widget);
+					}
+				}
+				break;
+			}
+		}
+	}
+
+	return Super::InputKey(EventArgs);
+}