#lockdown Nick.Penwarden
#rb none
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MAJOR FEATURES + CHANGES
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Change 3209340 on 2016/11/23 by Ben.Marsh
Convert UE4 codebase to an "include what you use" model - where every header just includes the dependencies it needs, rather than every source file including large monolithic headers like Engine.h and UnrealEd.h.
Measured full rebuild times around 2x faster using XGE on Windows, and improvements of 25% or more for incremental builds and full rebuilds on most other platforms.
* Every header now includes everything it needs to compile.
* There's a CoreMinimal.h header that gets you a set of ubiquitous types from Core (eg. FString, FName, TArray, FVector, etc...). Most headers now include this first.
* There's a CoreTypes.h header that sets up primitive UE4 types and build macros (int32, PLATFORM_WIN64, etc...). All headers in Core include this first, as does CoreMinimal.h.
* Every .cpp file includes its matching .h file first.
* This helps validate that each header is including everything it needs to compile.
* No engine code includes a monolithic header such as Engine.h or UnrealEd.h any more.
* You will get a warning if you try to include one of these from the engine. They still exist for compatibility with game projects and do not produce warnings when included there.
* There have only been minor changes to our internal games down to accommodate these changes. The intent is for this to be as seamless as possible.
* No engine code explicitly includes a precompiled header any more.
* We still use PCHs, but they're force-included on the compiler command line by UnrealBuildTool instead. This lets us tune what they contain without breaking any existing include dependencies.
* PCHs are generated by a tool to get a statistical amount of coverage for the source files using it, and I've seeded the new shared PCHs to contain any header included by > 15% of source files.
Tool used to generate this transform is at Engine\Source\Programs\IncludeTool.
[CL 3209342 by Ben Marsh in Main branch]
Cocoa isn't an event-polling API as UE4 expects, so previously we were subverting the NSApplication's event handling to pretend that it was. When the engine wasn't running the event loop fast enough, such as when loading where it isn't processed at all, this resulted in unresponsive windows and Spinning-Beachball-Of-Death. That isn't very satisfactory & to some users appears as if the application has crashed. To address these deficiencies without further attempts to subvert Cocoa, the game is now punted onto a separate thread where it can run its own tight-loop, leaving the main thread to handle the Cocoa event run-loop. Events are captured by delegate objects, as Cocoa requires, but dispatched and handled on the game thread which makes Cocoa appear more like other platform APIs to the higher-level UE4 code.
This can all be disabled using the MAC_SEPARATE_GAME_THREAD define in CocoaThread.cpp.
#codereview michael.trepka
[CL 2262543 by Mark Satterthwaite in Main branch]
#summary Replaced instances of DragDrop::IsTypeMatch with FDragDropEvent::GetOperationAs()
#note Please change any instances of DragDrop::IsTypeMatch for the templated FDragDropEvent::GetOperationAs<>() or FDragDropOperation::IsOfType<>() where necessary
#proj Editor
#branch UE4
#reviewedby Nick.Atamas
[CL 2042222 by Andrew Rodham in Main branch]
