Fixed potential for initialization fiasco when using delegates container. Fixed bug in code protecting redirecting handles from self-referencing. Updated project version and status.

CHANGES.md

@@ -5,6 +5,10 @@ Versions marked as 'unofficial' are labelled only for the needs of this changelo
 Change History
 --------------
 
+Version: 1.22 (2021/04)
+- Fixed potential for initialization fiasco when using delegates container.
+- Fixed bug in code protecting redirecting handles from self-referencing.
+
 Version: 1.21 (2020/07-09)
 Improving stability
 - Fixed a crash in the input handler caused by invalidated by hot-reload instance trying to unregister a delegate.

ImGui.uplugin

@@ -1,7 +1,7 @@
 {
 	"FileVersion": 3,
 	"Version": 1,
-	"VersionName": "1.21",
+	"VersionName": "1.22",
 	"FriendlyName": "ImGui",
 	"Description": "",
 	"Category": "Debug",

README.md

@@ -9,14 +9,24 @@ Dear ImGui is an immediate-mode graphical user interface library that is very li
 
 Status
 ------
-Version: 1.21
+Version: 1.22
 
 ImGui version: 1.74
 
-Supported engine version: 4.25*
+Supported engine version: 4.26*
 
 \* *Plugin has been tested and if necessary updated to compile and work with this engine version. As long as possible I will try to maintain backward compatibility of existing features and possibly but not necessarily when adding new features. When it comes to bare-bone ImGui version it should be at least backward compatible with the engine version 4.15. For NetImgui it needs to be determined.*
 
+Current work
+------------
+
+Currently, I'm a little busy outside of this project so changes come slowly. But here is what to expect in the reasonably near future:
+- Stability first, so fixes for more critical issues like an invalidation of handles after reloading texture resources will be pushed first. The same goes for merges.
+- There are a few smaller issues that I'm aware of and that might be not reported but which I want to fix.
+- ImGui needs to be updated.
+- Smaller features might be slowly pushed but bigger ones will need to wait. The same goes for merges.
+- There is a branch with NetImgui which is really good, and which will be eventually merged to master, but first I want to fix a few issues that I know about (some are discussed in thread #28). In the meantime, the NetImgui branch is pretty much ready to use.
+
 
 About
 -----

Source/ImGui/Private/ImGuiDelegatesContainer.cpp

@@ -11,11 +11,10 @@
 // Non-editor version without container redirection
 //
 
-static FImGuiDelegatesContainer DelegatesContainer;
-
 FImGuiDelegatesContainer& FImGuiDelegatesContainer::Get()
 {
-	return DelegatesContainer;
+	static FImGuiDelegatesContainer* Container = new FImGuiDelegatesContainer();
+	return *Container;
 }
 
 #endif // !WITH_EDITOR
@@ -36,14 +35,11 @@ struct FImGuiDelegatesContainerHandle : Utilities::TRedirectingHandle<FImGuiDele
 	{
 		if (FImGuiModule* Module = FModuleManager::GetModulePtr<FImGuiModule>("ImGui"))
 		{
-			SetParent(&Module->GetDelegatesContainerHandle());
+			SetParent(Module->DelegatesContainerHandle);
 		}
 	}
 };
 
-static FImGuiDelegatesContainer DelegatesContainer;
-static FImGuiDelegatesContainerHandle DelegatesHandle(DelegatesContainer);
-
 FImGuiDelegatesContainer& FImGuiDelegatesContainer::Get()
 {
 	return GetHandle().Get();
@@ -51,7 +47,14 @@ FImGuiDelegatesContainer& FImGuiDelegatesContainer::Get()
 
 FImGuiDelegatesContainerHandle& FImGuiDelegatesContainer::GetHandle()
 {
-	return DelegatesHandle;
+	struct FContainerInstance
+	{
+		FContainerInstance() : Container(), Handle(Container) {}
+		FImGuiDelegatesContainer Container;
+		FImGuiDelegatesContainerHandle Handle;
+	};
+	static FContainerInstance* Instance = new FContainerInstance();
+	return Instance->Handle;
 }
 
 void FImGuiDelegatesContainer::MoveContainer(FImGuiDelegatesContainerHandle& OtherContainerHandle)

Source/ImGui/Private/ImGuiImplementation.cpp

@@ -30,7 +30,7 @@ struct FImGuiContextHandle : public Utilities::TRedirectingHandle<ImGuiContext*>
 	{
 		if (FImGuiModule* Module = FModuleManager::GetModulePtr<FImGuiModule>("ImGui"))
 		{
-			SetParent(&Module->GetImGuiContextHandle());
+			SetParent(Module->ImGuiContextHandle);
 		}
 	}
 };

Source/ImGui/Private/ImGuiModule.cpp

@@ -100,6 +100,18 @@ void FImGuiModule::ReleaseTexture(const FImGuiTextureHandle& Handle)
 
 void FImGuiModule::StartupModule()
 {
+	// Initialize handles to allow cross-module redirections. Other handles will always look for parents in the active
+	// module, which means that we can only redirect to started modules. We don't have to worry about self-referencing
+	// as local handles are guaranteed to be constructed before initializing pointers.
+	// This supports in-editor recompilation and hot-reloading after compiling from the command line. The latter method
+	// theoretically doesn't support plug-ins and will not load re-compiled module, but its handles will still redirect
+	// to the active one.
+
+#if WITH_EDITOR
+	ImGuiContextHandle = &ImGuiImplementation::GetContextHandle();
+	DelegatesContainerHandle = &FImGuiDelegatesContainer::GetHandle();
+#endif
+
 	// Create managers that implements module logic.
 
 	checkf(!ImGuiModuleManager, TEXT("Instance of the ImGui Module Manager already exists. Instance should be created only during module startup."));
@@ -148,10 +160,17 @@ void FImGuiModule::ShutdownModule()
 			FImGuiModule& LoadedModule = FImGuiModule::Get();
 			if (&LoadedModule != this)
 			{
-				// Statically bound functions will be still made to the obsolete module so we need to  
-				ImGuiImplementation::SetParentContextHandle(LoadedModule.GetImGuiContextHandle());
+				// Statically bound functions can be bound to the obsolete module, so we need to manually redirect.
 
-				FImGuiDelegatesContainer::MoveContainer(LoadedModule.GetDelegatesContainerHandle());
+				if (LoadedModule.ImGuiContextHandle)
+				{
+					ImGuiImplementation::SetParentContextHandle(*LoadedModule.ImGuiContextHandle);
+				}
+
+				if (LoadedModule.DelegatesContainerHandle)
+				{
+					FImGuiDelegatesContainer::MoveContainer(*LoadedModule.DelegatesContainerHandle);
+				}
 
 				if (bMoveProperties)
 				{
@@ -169,16 +188,6 @@ void FImGuiModule::SetProperties(const FImGuiModuleProperties& Properties)
 {
 	ImGuiModuleManager->GetProperties() = Properties;
 }
-
-FImGuiContextHandle& FImGuiModule::GetImGuiContextHandle()
-{
-	return ImGuiImplementation::GetContextHandle();
-}
-
-FImGuiDelegatesContainerHandle& FImGuiModule::GetDelegatesContainerHandle()
-{
-	return FImGuiDelegatesContainer::GetHandle();
-}
 #endif
 
 FImGuiModuleProperties& FImGuiModule::GetProperties()

Source/ImGui/Private/Utilities/RedirectingHandle.h

@@ -8,8 +8,8 @@
 
 namespace Utilities
 {
-	// Handle initialized as a pointer to a default value, but once attached it will follow the parent handle.
-	// When detached it will revert back to the default value. Intended for cross-module redirections.
+	// Handle initialized as a pointer to a default value, but can be redirected to follow other handles.
+	// When detached, it will revert to the default value. Intended for cross-module redirections.
 	template<typename T>
 	struct TRedirectingHandle
 	{
@@ -49,7 +49,7 @@ namespace Utilities
 				}
 
 				// Protecting from setting itself as a parent.
-				Parent = (Parent != this) ? InParent : nullptr;
+				Parent = (InParent != this) ? InParent : nullptr;
 
 				if (Parent)
 				{

Source/ImGui/Public/ImGuiModule.h

@@ -168,8 +168,8 @@ private:
 
 #if WITH_EDITOR
 	virtual void SetProperties(const FImGuiModuleProperties& Properties);
-	virtual struct FImGuiContextHandle& GetImGuiContextHandle();
-	virtual struct FImGuiDelegatesContainerHandle& GetDelegatesContainerHandle();
+	struct FImGuiContextHandle* ImGuiContextHandle = nullptr;
+	struct FImGuiDelegatesContainerHandle* DelegatesContainerHandle = nullptr;
 	friend struct FImGuiContextHandle;
 	friend struct FImGuiDelegatesContainerHandle;
 #endif