From f7816ee1fd7cdd7fe3f01f13dcaa57205ce78c80 Mon Sep 17 00:00:00 2001
From: Sebastian <sebastian.e.gross@gmail.com>
Date: Sat, 2 Sep 2017 18:42:41 +0100
Subject: [PATCH] Added ImGui.InputEnabled console variable to control when
 ImGui should receive inputs.

---
 Source/ImGui/Private/SImGuiWidget.cpp | 56 +++++++++++++++++++++++++++
 Source/ImGui/Private/SImGuiWidget.h   | 13 ++++++-
 2 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/Source/ImGui/Private/SImGuiWidget.cpp b/Source/ImGui/Private/SImGuiWidget.cpp
index 476b648..7043714 100644
--- a/Source/ImGui/Private/SImGuiWidget.cpp
+++ b/Source/ImGui/Private/SImGuiWidget.cpp
@@ -12,6 +12,15 @@
 #include "Utilities/ScopeGuards.h"
 
 
+namespace CVars
+{
+	TAutoConsoleVariable<int> InputEnabled(TEXT("ImGui.InputEnabled"), 0,
+		TEXT("Allows to enable or disable ImGui input mode.\n")
+		TEXT("0: disabled (default)\n")
+		TEXT("1: enabled, input is routed to ImGui and with a few exceptions is consumed."),
+		ECVF_Default);
+}
+
 BEGIN_SLATE_FUNCTION_BUILD_OPTIMIZATION
 void SImGuiWidget::Construct(const FArguments& InArgs)
 {
@@ -20,6 +29,9 @@ void SImGuiWidget::Construct(const FArguments& InArgs)
 	ContextIndex = InArgs._ContextIndex;
 
 	ModuleManager->OnPostImGuiUpdate().AddRaw(this, &SImGuiWidget::OnPostImGuiUpdate);
+
+	// Sync visibility with default input enabled state.
+	SetVisibilityFromInputEnabled();
 }
 END_SLATE_FUNCTION_BUILD_OPTIMIZATION
 
@@ -28,6 +40,15 @@ SImGuiWidget::~SImGuiWidget()
 	ModuleManager->OnPostImGuiUpdate().RemoveAll(this);
 }
 
+void SImGuiWidget::Tick(const FGeometry& AllottedGeometry, const double InCurrentTime, const float InDeltaTime)
+{
+	Super::Tick(AllottedGeometry, InCurrentTime, InDeltaTime);
+
+	// Note: Moving that update to console variable sink or callback might seem like a better alternative but input
+	// setup in this function is better handled here.
+	UpdateInputEnabled();
+}
+
 FReply SImGuiWidget::OnKeyChar(const FGeometry& MyGeometry, const FCharacterEvent& CharacterEvent)
 {
 	InputState.AddCharacter(CharacterEvent.GetCharacter());
@@ -154,6 +175,41 @@ void SImGuiWidget::CopyModifierKeys(const FPointerEvent& MouseEvent)
 	}
 }
 
+void SImGuiWidget::SetVisibilityFromInputEnabled()
+{
+	// If we don't use input disable hit test to make this widget invisible for cursors hit detection.
+	SetVisibility(bInputEnabled ? EVisibility::Visible : EVisibility::HitTestInvisible);
+}
+
+void SImGuiWidget::UpdateInputEnabled()
+{
+	const bool bEnabled = CVars::InputEnabled.GetValueOnGameThread() > 0;
+	if (bInputEnabled != bEnabled)
+	{
+		bInputEnabled = bEnabled;
+
+		SetVisibilityFromInputEnabled();
+
+		// Setup input to show cursor and take focus when we use input or clear state and pass focus back to viewport
+		// when we don't.
+		auto& Slate = FSlateApplication::Get();
+		if (bInputEnabled)
+		{
+			Slate.ResetToDefaultPointerInputSettings();
+			Slate.SetKeyboardFocus(SharedThis(this));
+		}
+		else
+		{
+			if (Slate.GetKeyboardFocusedWidget().Get() == this)
+			{
+				Slate.SetUserFocusToGameViewport(Slate.GetUserIndexForKeyboard());
+			}
+
+			UpdateInputMode(false, false);
+		}
+	}
+}
+
 void SImGuiWidget::UpdateInputMode(bool bNeedKeyboard, bool bNeedMouse)
 {
 	const EInputMode NewInputMode =
diff --git a/Source/ImGui/Private/SImGuiWidget.h b/Source/ImGui/Private/SImGuiWidget.h
index 27bb843..10861e9 100644
--- a/Source/ImGui/Private/SImGuiWidget.h
+++ b/Source/ImGui/Private/SImGuiWidget.h
@@ -36,7 +36,9 @@ public:
 	// SWidget overrides
 	//----------------------------------------------------------------------------------------------------
 
-	virtual bool SupportsKeyboardFocus() const override { return true; }
+	virtual void Tick(const FGeometry& AllottedGeometry, const double InCurrentTime, const float InDeltaTime) override;
+
+	virtual bool SupportsKeyboardFocus() const override { return bInputEnabled; }
 
 	virtual FReply OnKeyChar(const FGeometry& MyGeometry, const FCharacterEvent& CharacterEvent) override;
 
@@ -64,7 +66,7 @@ public:
 
 private:
 
-	enum class EInputMode
+	enum class EInputMode : uint8
 	{
 		None,
 		MouseOnly,
@@ -74,6 +76,12 @@ private:
 	FORCEINLINE void CopyModifierKeys(const FInputEvent& InputEvent);
 	FORCEINLINE void CopyModifierKeys(const FPointerEvent& MouseEvent);
 
+	// Update visibility based on input enabled state.
+	void SetVisibilityFromInputEnabled();
+
+	// Update input enabled state from console variable.
+	void UpdateInputEnabled();
+
 	// Determine new input mode based on requirement hints.
 	void UpdateInputMode(bool bNeedKeyboard, bool bNeedMouse);
 
@@ -91,6 +99,7 @@ private:
 	int32 ContextIndex = 0;
 
 	EInputMode InputMode = EInputMode::None;
+	bool bInputEnabled = false;
 
 	FImGuiInputState InputState;
 };