config.md 3.3 KB
Crash Course: configuration
Table of Contents
Introduction
EnTT doesn't offer many hooks for customization but it certainly offers
some.
In the vast majority of cases, users will have no interest in changing the
default parameters. For all other cases, the list of possible configurations
with which it's possible to adjust the behavior of the library at runtime can be
found below.
Definitions
All options are intended as parameters to the compiler (or user-defined macros
within the compilation units, if preferred).
Each parameter can result in internal library definitions. It's not recommended
to try to also modify these definitions, since there is no guarantee that they
will remain stable over time unlike the options below.
ENTT_NOEXCEPT
The purpose of this parameter is to suppress the use of noexcept by this
library.
To do this, simply define the variable without assigning any value to it.
ENTT_USE_ATOMIC
In general, EnTT doesn't offer primitives to support multi-threading. Many of
the features can be split over multiple threads without any explicit control and
the user is the only one who knows if and when a synchronization point is
required.
However, some features aren't easily accessible to users and can be made
thread-safe by means of this definition.
ENTT_ID_TYPE
entt::id_type is directly controlled by this definition and widely used within
the library.
By default, its type is std::uint32_t. However, users can define a different
default type if necessary.
ENTT_PAGE_SIZE
As is known, the ECS module of EnTT is based on sparse sets. What is less
known perhaps is that these are paged to reduce memory consumption in some
corner cases.
The default size of a page is 32kB but users can adjust it if appropriate. In
all case, the chosen value must be a power of 2.
ENTT_ASSERT
For performance reasons, EnTT doesn't use exceptions or any other control
structures. In fact, it offers many features that result in undefined behavior
if not used correctly.
To get around this, the library relies on a lot of asserts for the purpose of
detecting errors in debug builds. However, these assertions may in turn affect
performance to an extent.
This option is meant to disable all controls.
ENTT_NO_ETO
In order to reduce memory consumption and increase performance, empty types are
never stored by the ECS module of EnTT.
Use this variable to treat these types like all others and therefore to create a
dedicated storage for them.
ENTT_STANDARD_CPP
EnTT mixes non-standard language features with others that are perfectly
compliant to offer some of its functionalities.
This definition will prevent the library from using non-standard techniques,
that is, functionalities that aren't fully compliant with the standard C++.
While there are no known portability issues at the time of this writing, this
should make the library fully portable anyway if needed.