Changed modifier keys handling and cleaned ImGui Input State:

- Separate modifier keys interface and data from generic keys.
- Cleaned interface to better differentiate between full reset and clearing update data.
- Fixed bug in code clearing characters.

Source/ImGui/Private/ImGuiInputState.cpp

@@ -7,7 +7,7 @@
 
 FImGuiInputState::FImGuiInputState()
 {
-	ClearState();
+	ResetState();
 }
 
 void FImGuiInputState::AddCharacter(TCHAR Char)
@@ -45,22 +45,23 @@ void FImGuiInputState::SetMouseDown(uint32 MouseIndex, bool bIsDown)
 	}
 }
 
-void FImGuiInputState::ClearState()
+void FImGuiInputState::ResetState()
 {
 	ClearCharacters();
+	ClearKeys();
 
-	using std::fill;
-	fill(KeysDown, &KeysDown[Utilities::GetArraySize(KeysDown)], false);
-	fill(MouseButtonsDown, &MouseButtonsDown[Utilities::GetArraySize(MouseButtonsDown)], false);
+	ClearMouseButtons();
+	ClearMouseAnalogue();
 
-	// Fully expanding dirty parts of both arrays, to inform about the change.
-	KeysUpdateRange.SetFull();
-	MouseButtonsUpdateRange.SetFull();
+	ClearModifierKeys();
 }
 
 void FImGuiInputState::ClearUpdateState()
 {
+	if (InputCharactersNum > 0)
+	{
 		ClearCharacters();
+	}
 
 	KeysUpdateRange.SetEmpty();
 	MouseButtonsUpdateRange.SetEmpty();
@@ -70,6 +71,38 @@ void FImGuiInputState::ClearUpdateState()
 
 void FImGuiInputState::ClearCharacters()
 {
+	using std::fill;
+	fill(InputCharacters, &InputCharacters[Utilities::GetArraySize(InputCharacters)], 0);
 	InputCharactersNum = 0;
-	InputCharacters[0];
+}
+
+void FImGuiInputState::ClearKeys()
+{
+	using std::fill;
+	fill(KeysDown, &KeysDown[Utilities::GetArraySize(KeysDown)], false);
+
+	// Expand update range because keys array has been updated.
+	KeysUpdateRange.SetFull();
+}
+
+void FImGuiInputState::ClearMouseButtons()
+{
+	using std::fill;
+	fill(MouseButtonsDown, &MouseButtonsDown[Utilities::GetArraySize(MouseButtonsDown)], false);
+
+	// Expand update range because mouse buttons array has been updated.
+	MouseButtonsUpdateRange.SetFull();
+}
+
+void FImGuiInputState::ClearMouseAnalogue()
+{
+	MousePosition = FVector2D::ZeroVector;
+	MouseWheelDelta = 0.f;
+}
+
+void FImGuiInputState::ClearModifierKeys()
+{
+	bIsControlDown = false;
+	bIsShiftDown = false;
+	bIsAltDown = false;
 }

Source/ImGui/Private/ImGuiInputState.h

@@ -76,8 +76,29 @@ public:
 	// @param Position - New mouse position
 	void SetMousePosition(const FVector2D& Position) { MousePosition = Position; }
 
-	// Clear state and mark as dirty.
-	void ClearState();
+	// Get Control down state.
+	bool IsControlDown() const { return bIsControlDown; }
+
+	// Set Control down state.
+	// @param bIsDown - True, if Control is down
+	void SetControlDown(bool bIsDown) { bIsControlDown = bIsDown; }
+
+	// Get Shift down state.
+	bool IsShiftDown() const { return bIsShiftDown; }
+
+	// Set Shift down state.
+	// @param bIsDown - True, if Shift is down
+	void SetShiftDown(bool bIsDown) { bIsShiftDown = bIsDown; }
+
+	// Get Alt down state.
+	bool IsAltDown() const { return bIsAltDown; }
+
+	// Set Alt down state.
+	// @param bIsDown - True, if Alt is down
+	void SetAltDown(bool bIsDown) { bIsAltDown = bIsDown; }
+
+	// Reset state and mark as dirty.
+	void ResetState();
 
 	// Clear part of the state that is meant to be updated in every frame like: accumulators, buffers and information
 	// about dirty parts of keys or mouse buttons arrays.
@@ -86,6 +107,10 @@ public:
 private:
 
 	void ClearCharacters();
+	void ClearKeys();
+	void ClearMouseButtons();
+	void ClearMouseAnalogue();
+	void ClearModifierKeys();
 
 	FVector2D MousePosition = FVector2D::ZeroVector;
 	float MouseWheelDelta = 0.f;
@@ -98,4 +123,8 @@ private:
 
 	FKeysArray KeysDown;
 	FKeysIndexRange KeysUpdateRange;
+
+	bool bIsControlDown = false;
+	bool bIsShiftDown = false;
+	bool bIsAltDown = false;
 };

Source/ImGui/Private/ImGuiInteroperability.cpp

@@ -154,9 +154,9 @@ namespace ImGuiInterops
 		IO.MouseWheel += InputState.GetMouseWheelDelta();
 
 		// Copy key modifiers.
-		IO.KeyCtrl = InputState.GetKeys()[LeftControl] || InputState.GetKeys()[RightControl];
-		IO.KeyShift = InputState.GetKeys()[LeftShift] || InputState.GetKeys()[RightShift];
-		IO.KeyAlt = InputState.GetKeys()[LeftAlt] || InputState.GetKeys()[RightAlt];
+		IO.KeyCtrl = InputState.IsControlDown();
+		IO.KeyShift = InputState.IsShiftDown();
+		IO.KeyAlt = InputState.IsAltDown();
 		IO.KeySuper = false;
 
 		// Copy buffers.
@@ -172,7 +172,7 @@ namespace ImGuiInterops
 
 		if (InputState.GetCharactersNum() > 0)
 		{
-			Copy(InputState.GetCharacters(), IO.InputCharacters, InputState.GetCharactersNum());
+			Copy(InputState.GetCharacters(), IO.InputCharacters);
 		}
 	}
 }

Source/ImGui/Private/SImGuiWidget.cpp

@@ -29,12 +29,14 @@ SImGuiWidget::~SImGuiWidget()
 FReply SImGuiWidget::OnKeyChar(const FGeometry& MyGeometry, const FCharacterEvent& CharacterEvent)
 {
 	InputState.AddCharacter(CharacterEvent.GetCharacter());
+
 	return FReply::Handled();
 }
 
 FReply SImGuiWidget::OnKeyDown(const FGeometry& MyGeometry, const FKeyEvent& KeyEvent)
 {
 	InputState.SetKeyDown(ImGuiInterops::GetKeyIndex(KeyEvent), true);
+	CopyModifierKeys(KeyEvent);
 
 	// If this is tilde key then let input through and release the focus to allow console to process it.
 	if (KeyEvent.GetKey() == EKeys::Tilde)
@@ -48,39 +50,58 @@ FReply SImGuiWidget::OnKeyDown(const FGeometry& MyGeometry, const FKeyEvent& Key
 FReply SImGuiWidget::OnKeyUp(const FGeometry& MyGeometry, const FKeyEvent& KeyEvent)
 {
 	InputState.SetKeyDown(ImGuiInterops::GetKeyIndex(KeyEvent), false);
+	CopyModifierKeys(KeyEvent);
+
 	return FReply::Handled();
 }
 
 FReply SImGuiWidget::OnMouseButtonDown(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
 {
 	InputState.SetMouseDown(ImGuiInterops::GetMouseIndex(MouseEvent), true);
+	CopyModifierKeys(MouseEvent);
+
 	return FReply::Handled();
 }
 
 FReply SImGuiWidget::OnMouseButtonDoubleClick(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
 {
 	InputState.SetMouseDown(ImGuiInterops::GetMouseIndex(MouseEvent), true);
+	CopyModifierKeys(MouseEvent);
+
 	return FReply::Handled();
 }
 
 FReply SImGuiWidget::OnMouseButtonUp(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
 {
 	InputState.SetMouseDown(ImGuiInterops::GetMouseIndex(MouseEvent), false);
+	CopyModifierKeys(MouseEvent);
+
 	return FReply::Handled();
 }
 
 FReply SImGuiWidget::OnMouseWheel(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
 {
 	InputState.AddMouseWheelDelta(MouseEvent.GetWheelDelta());
+	CopyModifierKeys(MouseEvent);
+
 	return FReply::Handled();
 }
 
 FReply SImGuiWidget::OnMouseMove(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
 {
 	InputState.SetMousePosition(MouseEvent.GetScreenSpacePosition() - MyGeometry.AbsolutePosition);
+	CopyModifierKeys(MouseEvent);
+
 	return FReply::Handled();
 }
 
+void SImGuiWidget::CopyModifierKeys(const FInputEvent& InputEvent)
+{
+	InputState.SetControlDown(InputEvent.IsControlDown());
+	InputState.SetShiftDown(InputEvent.IsShiftDown());
+	InputState.SetAltDown(InputEvent.IsAltDown());
+}
+
 void SImGuiWidget::OnPostImGuiUpdate()
 {
 	InputState.ClearUpdateState();

Source/ImGui/Private/SImGuiWidget.h

@@ -12,6 +12,8 @@ class FImGuiModuleManager;
 // Slate widget for rendering ImGui output and storing Slate inputs.
 class SImGuiWidget : public SLeafWidget
 {
+	typedef SLeafWidget Super;
+
 public:
 
 	SLATE_BEGIN_ARGS(SImGuiWidget)
@@ -49,6 +51,8 @@ public:
 
 private:
 
+	FORCEINLINE void CopyModifierKeys(const FInputEvent& InputEvent);
+
 	void OnPostImGuiUpdate();
 
 	virtual int32 OnPaint(const FPaintArgs& Args, const FGeometry& AllottedGeometry, const FSlateRect& MyClippingRect, FSlateWindowElementList& OutDrawElements, int32 LayerId, const FWidgetStyle& WidgetStyle, bool bParentEnabled) const override;