Retake the focus when loosing it while ImGui has the input

Plugins/Cog/Source/CogEngine/Private/CogEngineWindow_Slate.cpp

@@ -52,7 +52,7 @@ void FCogEngineWindow_Slate::RenderContent()
 void FCogEngineWindow_Slate::RenderUser(FSlateUser& User)
 {
 
-    if (ImGui::BeginTable("SlateUser", 2, ImGuiTableFlags_Borders))
+    if (ImGui::BeginTable("SlateUser", 2, ImGuiTableFlags_Borders | ImGuiTableFlags_Resizable))
     {
 	    constexpr ImVec4 LabelColor(1.0f, 1.0f, 1.0f, 0.5f);
 

Plugins/Cog/Source/CogImgui/Private/CogImguiContext.cpp

@@ -206,6 +206,17 @@ void FCogImguiContext::Shutdown()
     }
 }
 
+//--------------------------------------------------------------------------------------------------------------------------
+void FCogImguiContext::OnImGuiWidgetFocusLost()
+{
+    FCogImGuiContextScope ImGuiContextScope(Context, PlotContext);
+
+    if (bEnableInput && GameViewport->GetGameViewportWidget()->HasUserFocus(0))
+    {
+        bRetakeFocus = true;
+    }
+}
+
 //--------------------------------------------------------------------------------------------------------------------------
 void FCogImguiContext::OnDisplayMetricsChanged(const FDisplayMetrics& DisplayMetrics) const
 {
@@ -238,7 +249,7 @@ void FCogImguiContext::OnDisplayMetricsChanged(const FDisplayMetrics& DisplayMet
 bool FCogImguiContext::BeginFrame(float InDeltaTime)
 {
     FCogImGuiContextScope ImGuiContextScope(Context, PlotContext);
-
+    
     //-------------------------------------------------------------------------------------------------------
     // Skip the first frame, to let the main widget update its TickSpaceGeometry which is returned by the 
     // platform callback ImGui_GetWindowPos. When using viewports Imgui needs to know the main viewport 
@@ -250,6 +261,16 @@ bool FCogImguiContext::BeginFrame(float InDeltaTime)
         return false;
     }
 
+    //-------------------------------------------------------------------------------------------------------
+    // Sometime the game can retake unaware that ImGui want to keep the focus and mouse unlock.
+    // This typically happens when switching level.  
+    //-------------------------------------------------------------------------------------------------------
+    if (bRetakeFocus)
+    {
+        SetEnableInput(true);
+        bRetakeFocus = false;
+    }
+
     ImGuiIO& IO = ImGui::GetIO();
     IO.DeltaTime = InDeltaTime;
 
@@ -696,16 +717,14 @@ static APlayerController* GetLocalPlayerController(const UWorld* World)
 }
 
 //--------------------------------------------------------------------------------------------------------------------------
-void FCogImguiContext::SetEnableInput(bool Value)
+void FCogImguiContext::SetEnableInput(const bool InValue)
 {
     FCogImGuiContextScope ImGuiContextScope(Context, PlotContext);
 
-    bEnableInput = Value; 
+    bEnableInput = InValue; 
 
     if (FSlateApplication::IsInitialized() == false)
-    {
-        return; 
-    }
+    { return; }
 
     if (bEnableInput)
     {

Plugins/Cog/Source/CogImgui/Private/CogImguiWidget.cpp

@@ -277,6 +277,17 @@ FReply SCogImguiWidget::OnFocusReceived(const FGeometry& MyGeometry, const FFocu
     return Super::OnFocusReceived(MyGeometry, FocusEvent);
 }
 
+//--------------------------------------------------------------------------------------------------------------------------
+void SCogImguiWidget::OnFocusLost(const FFocusEvent& InFocusEvent)
+{
+    SLeafWidget::OnFocusLost(InFocusEvent);
+
+    if (Context != nullptr)
+    {
+        Context->OnImGuiWidgetFocusLost();
+    }
+}
+
 //--------------------------------------------------------------------------------------------------------------------------
 void SCogImguiWidget::RefreshVisibility()
 {

Plugins/Cog/Source/CogImgui/Public/CogImguiContext.h

@@ -47,7 +47,7 @@ public:
 
 	bool GetEnableInput() const { return bEnableInput; }
 
-	void SetEnableInput(bool Value);
+	void SetEnableInput(bool InValue);
 
 	bool GetWantCaptureMouse() const { return bWantCaptureMouse; }
 
@@ -81,6 +81,8 @@ public:
 
 	TSharedPtr<const SCogImguiWidget> GetMainWidget() const { return MainWidget; }
 
+	void OnImGuiWidgetFocusLost();
+
 	static bool GetIsNetImguiInitialized() { return bIsNetImGuiInitialized; }
 
 private:
@@ -179,6 +181,8 @@ private:
 
 	bool bSkipRendering = false;
 
+	bool bRetakeFocus = false;
+
 	static bool bIsNetImGuiInitialized;
 
 };

Plugins/Cog/Source/CogImgui/Public/CogImguiWidget.h

@@ -51,6 +51,8 @@ public:
     virtual FReply OnMouseMove(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent) override;
 
     virtual FReply OnFocusReceived(const FGeometry& MyGeometry, const FFocusEvent& FocusEvent) override;
+    
+    virtual void OnFocusLost(const FFocusEvent& InFocusEvent) override;
 
     void SetDrawData(const ImDrawData* InDrawData);