#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]
TTP# 337136 - SETTINGS: Target Platform settings polish
TTP# 337652 - EDITOR: Limit Project supported Android icons down to 1
TTP# 337650 - EDITOR: There is only 1 icon for Apple for Project Supported Platforms
DesktopPlatform now contains a static array of FPlatformInfo. This can be used to query UE4 about its available platforms, even when they're not available as a target platform.
FPlatformInfo contains the information required by the editor (such as a localized display name and icon), as well as whether a platform is a variation ("flavor") of another, and if so, whether the flavor affects the build output (eg, Win32 or Win64), or the cook output (eg, Android_XYZ). This lets the editor build up nested menus for the "Package Project" and "Cook Project" options, rather than just showing everything as a flat list.
ReviewedBy Thomas.Sarkanen, Max.Preussner
[CL 2095796 by Jamie Dale in Main branch]
