UnrealScript中的Cpptext{}段落

http://wiki.beyondunreal.com/Cpptext

在UScript发现了Cpptext{}的段落,很神奇,还以为是类似查了Wiki,这是一种脚本中的CPP预声明,

引用如下

Unreal Script可以内嵌汇编的,但是只能用在cpptext里面做为C++生成函数的一部分。
如果是其它地方,目前尚不支持,因为支持也没有意义,因为就算能内嵌汇编,你也只能内嵌UnrealScript虚拟机的虚拟指令,然而这些指令是很危险的。
况且内嵌虚拟机的指令并不能带来效率上的优势。

Cpptext

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Starting with Unreal Engine 2 UnrealScript classes/structs support cpptext(prefix for C++text) block declarations. The cpptext is a block declaration where programmers can implement C++ functions it also can only be declared in native classes, any text within this block will then be exported to the corresponding native class prefixClasses.h file when compiled.

Note: structs use cppstruct instead and starting with Unreal Engine 3 it was renamed to structcpptext.

Example

Taken from Canvas.uc.

cpptext
{
    //...
    void DrawTile(UTexture* Tex, FLOAT X, FLOAT Y, FLOAT XL, FLOAT YL, FLOAT U, FLOAT V, FLOAT UL, FLOAT VL, const FLinearColor& Color);
    //...
}

This exports DrawTile into class UCanvas in file EngineClasses.h e.g.

class UCanvas : public UObject
{
    //...
    void DrawTile(UTexture* Tex, FLOAT X, FLOAT Y, FLOAT XL, FLOAT YL, FLOAT U, FLOAT V, FLOAT UL, FLOAT VL, const FLinearColor& Color);
    //...
};

Why use cpptext over native functions

Even though you can just make a native UnrealScript function that will also get exported the same way but then translated to C++, it doesn't support all formats thus in that case the native coder can implement functions that cannot be declared in UnrealScript but also because the native coder might not want you to be able to call a function from within UnrealScript.

See also

posted @ 2012-02-20 17:27  Zephyroal  阅读(1073)  评论(0编辑  收藏  举报