Removed dependency on headers included in the PCH and fixed any non-unity issues.

CHANGES.md

@@ -8,6 +8,7 @@ Change History
 Version: 1.20 (2020/06)
 Transition to IWYU and maintenence:
 - Replaced includes of monolithic headers.
+- Removed dependency on core, engine and ImGui module headers includes in the PCH.
 
 Version: 1.19 (2020/03-06)
 - Integrated fix for issue with ImGui popup/modal windows not being able to be closed in transparent mouse input mode. 

Source/ImGui/Private/Editor/ImGuiEditor.cpp

@@ -11,6 +11,7 @@
 #include "ImGuiModuleSettings.h"
 
 #include <ISettingsModule.h>
+#include <Modules/ModuleManager.h>
 
 
 #define LOCTEXT_NAMESPACE "ImGuiEditor"

Source/ImGui/Private/Editor/ImGuiEditor.h

@@ -4,6 +4,9 @@
 
 #if WITH_EDITOR
 
+#include <Delegates/IDelegateInstance.h>
+
+
 // Registers module's settings in editor (due to a small size of this code we don't use a separate editor module).
 class FImGuiEditor
 {

Source/ImGui/Private/ImGuiContextProxy.cpp

@@ -9,7 +9,8 @@
 #include "ImGuiInteroperability.h"
 #include "Utilities/Arrays.h"
 
-#include <Runtime/Launch/Resources/Version.h>
+#include <GenericPlatform/GenericPlatformFile.h>
+#include <Misc/Paths.h>
 
 
 static constexpr float DEFAULT_CANVAS_WIDTH = 3840.f;

Source/ImGui/Private/ImGuiDelegates.cpp

@@ -5,6 +5,8 @@
 #include "ImGuiDelegates.h"
 #include "ImGuiDelegatesContainer.h"
 
+#include <Engine/World.h>
+
 
 FSimpleMulticastDelegate& FImGuiDelegates::OnWorldEarlyDebug()
 {

Source/ImGui/Private/ImGuiDemo.cpp

@@ -3,9 +3,10 @@
 #include "ImGuiPrivatePCH.h"
 
 #include "ImGuiDemo.h"
-
 #include "ImGuiModuleProperties.h"
 
+#include <CoreGlobals.h>
+
 
 // Demo copied (with minor modifications) from ImGui examples. See https://github.com/ocornut/imgui.
 void FImGuiDemo::DrawControls(int32 ContextIndex)

Source/ImGui/Private/ImGuiImplementation.cpp

@@ -15,7 +15,13 @@
 #define IMGUI_DISABLE_WIN32_DEFAULT_IME_FUNCTIONS
 #endif // PLATFORM_XBOXONE
 
+#if PLATFORM_WINDOWS
+#include <Windows/AllowWindowsPlatformTypes.h>
+#endif // PLATFORM_WINDOWS
+
 #if WITH_EDITOR
+#include "imgui.h"
+
 // Global ImGui context pointer.
 ImGuiContext* GImGuiContextPtr = nullptr;
 // Handle to the global ImGui context pointer.
@@ -24,10 +30,6 @@ ImGuiContext** GImGuiContextPtrHandle = &GImGuiContextPtr;
 #define GImGui (*GImGuiContextPtrHandle)
 #endif // WITH_EDITOR
 
-#if PLATFORM_WINDOWS
-#include <Windows/AllowWindowsPlatformTypes.h>
-#endif // PLATFORM_WINDOWS
-
 #include "imgui.cpp"
 #include "imgui_demo.cpp"
 #include "imgui_draw.cpp"

Source/ImGui/Private/ImGuiInputHandler.cpp

@@ -10,6 +10,7 @@
 #include "ImGuiModuleSettings.h"
 
 #include <Engine/Console.h>
+#include <Framework/Application/SlateApplication.h>
 #include <GameFramework/InputSettings.h>
 #include <Input/Events.h>
 

Source/ImGui/Private/ImGuiInputHandlerFactory.cpp

@@ -3,9 +3,10 @@
 #include "ImGuiPrivatePCH.h"
 
 #include "ImGuiInputHandlerFactory.h"
-
 #include "ImGuiInputHandler.h"
 
+#include <Engine/GameViewportClient.h>
+
 
 UImGuiInputHandler* FImGuiInputHandlerFactory::NewHandler(const FStringClassReference& HandlerClassReference, FImGuiModuleManager* ModuleManager, UGameViewportClient* GameViewport, int32 ContextIndex)
 {

Source/ImGui/Private/ImGuiInputHandlerFactory.h

@@ -2,6 +2,9 @@
 
 #pragma once
 
+#include "ImGuiModuleSettings.h"
+
+
 class FImGuiModuleManager;
 class UGameViewportClient;
 class UImGuiInputHandler;

Source/ImGui/Private/ImGuiInteroperability.h

@@ -5,6 +5,7 @@
 #include "TextureManager.h"
 
 #include <GenericPlatform/ICursor.h>
+#include <Input/Events.h>
 
 #include <imgui.h>
 

Source/ImGui/Private/ImGuiModule.cpp

@@ -2,10 +2,10 @@
 
 #include "ImGuiPrivatePCH.h"
 
-#include "ImGuiModuleManager.h"
+#include "ImGuiModule.h"
 
 #include "ImGuiDelegatesContainer.h"
-#include "ImGuiTextureHandle.h"
+#include "ImGuiModuleManager.h"
 #include "TextureManager.h"
 #include "Utilities/WorldContext.h"
 #include "Utilities/WorldContextIndex.h"

Source/ImGui/Private/ImGuiModuleCommands.cpp

@@ -3,6 +3,7 @@
 #include "ImGuiPrivatePCH.h"
 
 #include "ImGuiModuleCommands.h"
+#include "ImGuiModuleProperties.h"
 
 #include "Utilities/DebugExecBindings.h"
 

Source/ImGui/Private/ImGuiModuleManager.cpp

@@ -7,6 +7,7 @@
 #include "ImGuiInteroperability.h"
 #include "Utilities/WorldContextIndex.h"
 
+#include <Framework/Application/SlateApplication.h>
 #include <Modules/ModuleManager.h>
 
 #include <imgui.h>

Source/ImGui/Private/ImGuiModuleSettings.cpp

@@ -7,6 +7,8 @@
 #include "ImGuiModuleCommands.h"
 #include "ImGuiModuleProperties.h"
 
+#include <ConfigCacheIni.h>
+#include <Engine/Engine.h>
 #include <GameFramework/GameUserSettings.h>
 
 

Source/ImGui/Private/ImGuiModuleSettings.h

@@ -2,11 +2,21 @@
 
 #pragma once
 
+#include "VersionCompatibility.h"
+
 #include <SlateTypes.h>
 #include <Curves/CurveFloat.h>
 #include <Delegates/Delegate.h>
 #include <UObject/Object.h>
 
+// We use FStringClassReference, which is supported by older and newer engine versions. Starting from 4.18, it is
+// a typedef of FSoftClassPath, which is also recognized by UHT.
+#if ENGINE_COMPATIBILITY_LEGACY_STRING_CLASS_REF
+#include <StringClassReference.h>
+#else
+#include <UObject/SoftObjectPath.h>
+#endif
+
 #include "ImGuiModuleSettings.generated.h"
 
 

Source/ImGui/Private/ImGuiPrivatePCH.h

@@ -11,13 +11,5 @@
 #include <CoreMinimal.h>
 #include <Engine/Engine.h>
 
-// For backward compatibility we will use FStringClassReference which in newer engine versions is a typedef for
-// FSoftClassPath. Include right soft class reference header to avoid warnings in newer engine version.
-#if ENGINE_COMPATIBILITY_LEGACY_STRING_CLASS_REF
-#include <StringClassReference.h>
-#else
-#include <UObject/SoftObjectPath.h>
-#endif
-
 // You should place include statements to your module's private header files here.  You only need to
 // add includes for headers that are used in most of your module's source files though.

Source/ImGui/Private/TextureManager.cpp

@@ -4,6 +4,9 @@
 
 #include "TextureManager.h"
 
+#include <Engine/Texture2D.h>
+#include <Framework/Application/SlateApplication.h>
+
 #include <algorithm>
 
 

Source/ImGui/Private/TextureManager.h

@@ -6,6 +6,8 @@
 #include <Textures/SlateShaderResource.h>
 
 
+class UTexture2D;
+
 // Index type to be used as a texture handle.
 using TextureIndex = int32;
 

Source/ImGui/Private/Widgets/SImGuiCanvasControl.cpp

@@ -4,6 +4,7 @@
 
 #include "SImGuiCanvasControl.h"
 
+#include <Rendering/DrawElements.h>
 #include <SlateOptMacros.h>
 
 

Source/ImGui/Private/Widgets/SImGuiWidget.cpp

@@ -19,6 +19,7 @@
 #include <Engine/Console.h>
 #include <Engine/GameViewportClient.h>
 #include <Engine/LocalPlayer.h>
+#include <Framework/Application/SlateApplication.h>
 #include <GameFramework/GameUserSettings.h>
 #include <SlateOptMacros.h>
 #include <Widgets/SViewport.h>

Source/ImGui/Private/Widgets/SImGuiWidget.h

@@ -5,6 +5,7 @@
 #include "ImGuiModuleDebug.h"
 #include "ImGuiModuleSettings.h"
 
+#include <Rendering/RenderingCommon.h>
 #include <Widgets/DeclarativeSyntaxSupport.h>
 #include <Widgets/SCompoundWidget.h>
 
@@ -16,6 +17,9 @@ class FImGuiModuleManager;
 class SImGuiCanvasControl;
 class UImGuiInputHandler;
 
+class UGameViewportClient;
+class ULocalPlayer;
+
 // Slate widget for rendering ImGui output and storing Slate inputs.
 class SImGuiWidget : public SCompoundWidget
 {

Source/ImGui/Public/ImGuiInputHandler.h

@@ -3,6 +3,7 @@
 #pragma once
 
 #include <CoreMinimal.h>
+#include <Input/Reply.h>
 #include <UObject/Object.h>
 #include <UObject/WeakObjectPtr.h>