Coding Guidelines

1. Naming Conventions

1.1 Variable Names

1.1.1 Global Variable naming

All global variables must start with the ACE prefix followed by the component, separated by underscores. Global variables may not contain the fnc_ prefix if the value is not callable code.

Example: ace_component_myVariableName

For ACE this is done automatically through the usage of the GVAR macro family.

1.1.2 Private Variable naming

To make code as readable as possible, try to use self explanatory variable names and avoid using single character variable names.

Example: _velocity instead of _v

1.1.3 Function naming

All functions shall use ACE and the component name as a prefix, as well as the fnc_ prefix behind the component name.

Example: PREFIX_COMPONENT_fnc_functionName

For ACE this is done automatically through the usage of the PREP macro.

1.2 Files & Config

1.2.1 SQF files

Files containing SQF scripts shall have a file name extension of .sqf.

1.2.2 Header files

All header files shall have the file name extension of .hpp.

1.2.3 Own SQF File

All functions shall be put in their own .sqf file.

1.2.4 Config elements

Config files shall be split up into different header files, each with the name of the config and be included in the config.cpp of the component.

Example:

#include "ACE_Settings.hpp"

And in ACE_Settings.hpp:

class ACE_Settings {
    // Content
};

1.2.5 Addon template

Addon template is at extras/blank repo directory.

1.3 Stringtable

All text that shall be displayed to a user shall be defined in a stringtable.xml file for multi-language support.

• There shall be no empty stringtable language values.
• All stringtables shall follow the format as specified by Tabler and the translation guidelines form.

2. Macro Usage

2.1 Module/PBO specific Macro Usage

The family of GVAR macros define global variable strings or constants for use within a module. Please use these to make sure we follow naming conventions across all modules and also prevent duplicate/overwriting between variables in different modules. The macro family expands as follows, for the example of the module ‘balls’:

There also exists the FUNC family of Macros:

The FUNC and EFUNC macros shall NOT be used inside QUOTE macros if the intention is to get the function name or assumed to be the function variable due to call tracing (see below). If you need to 100% always be sure that you are getting the function name or variable use the DFUNC or DEFUNC macros. For example QUOTE(FUNC(face)) == "ace_balls_fnc_face" would be an illegal use of FUNC inside QUOTE.

Using FUNC or EFUNC inside a QUOTE macro is fine if the intention is for it to be executed as a function.

LINKFUNC macro allows to recompile function used in event handler code when function cache is disabled. E.G. player addEventHandler ["Fired", LINKFUNC(firedEH)]; will run updated code after each recompile.

2.1.1 FUNC Macros, Call Tracing, and Non-ACE3/Anonymous Functions

ACE3 implements a basic call tracing system that can dump the call stack on errors or wherever you want. To do this the FUNC macros in debug mode will expand out to include metadata about the call including line numbers and files. This functionality is automatic with the use of calls via FUNC and EFUNC, but any calls to other functions need to use the following macros:

These macros will call these functions with the appropriate wrappers and enable call logging into them (but to no further calls inside obviously).

2.2 General Purpose Macros

CBA script_macros_common.hpp

QUOTE() is utilized within configuration files for bypassing the quote issues in configuration macros. So, all code segments inside a given config should utilize wrapping in the QUOTE() macro instead of direct strings. This allows us to use our macros inside the string segments, such as QUOTE(_this call FUNC(balls))

2.2.1 setVariable, getVariable family macros

These macros are allowed but are not enforced.

2.2.2 STRING family macros

Note that you need the strings in module stringtable.xml in the correct format: STR_ACE_<module>_<string>

Example: STR_ACE_Balls_Banana

Script strings:

Config Strings (require $ as first character):

2.2.3 Path family macros

The family of path macros define global paths to files for use within a module. Please use these to reference files in the ACE3 project. The macro family expands as follows, for the example of the module ‘balls’:

3. Functions

Functions shall be created in the functions\ subdirectory, named fnc_functionName.sqf They shall then be indexed via the PREP(functionName) macro in the XEH_preInit.sqf file.

The PREP macro allows for CBA function caching, which drastically speeds up load times. Beware though that function caching is enabled by default and as such to disable it you need to #define DISABLE_COMPILE_CACHE above your #include "script_component.hpp" include!

3.1 Includes

Every function includes the script_component.hpp file on the first line. Any additional includes or defines must be below this include.

All code written must be below this include and any potential additional includes or defines.

3.1.1 Reasoning

This ensures every function starts off in an uniform way and enforces function documentation. The include appears before the header to avoid incorrect line numbers in script errors.

3.2 Headers

Every function should have a header of the following format appear before any code:

/*
 * Author: [Name of Author(s)]
 * [Description]
 *
 * Arguments:
 * 0: The first argument <STRING>
 * 1: The second argument which contains sub values <ARRAY>
 * - 0: Number of bannanas <NUMBER>
 * - 1: Bannana Color <STRING>
 * 2: Multiple input types <STRING|ARRAY|CODE>
 * 3: Optional input <BOOL> (default: true)
 * 4: Optional input with multiple types <CODE|STRING> (default: {true})
 * 5: Not mandatory input <STRING> (default: nil)
 *
 * Return Value:
 * The return value <BOOL>
 *
 * Example:
 * ["something", player] call ace_common_fnc_imanexample
 *
 * Public: [Yes/No]
 */

This is not the case for inline functions or functions not contained in their own file.

4. Global Variables

All Global Variables are defined in the XEH_preInit.sqf file of the component they will be used in with an initial default value.

Exceptions:

• Dynamically generated global variables.
• Variables that do not origin from the ACE3 project, such as BI global variables or third party such as CBA.

5. Code Style

To help with some of the coding style we recommend you get the plugin EditorConfig for your editor. It will help with correct indentations and deleting trailing spaces.

5.1 Braces placement

Braces { } which enclose a code block will have the first bracket placed behind the statement in case of if, switch statements or while, waitUntil & for loops. The second brace will be placed on the same column as the statement but on a separate line.

• Opening brace on the same line as keyword
• Closing brace in own line, same level of indentation as keyword

Yes:

class Something: Or {
    class Other {
        foo = "bar";
    };
};

No:

class Something : Or
{
    class Other
    {
        foo = "bar";
    };
};

Also no:

class Something : Or {
    class Other {
        foo = "bar";
        };
    };

When using if/else, it is encouraged to put else on the same line as the closing brace to save space:

if (alive player) then {
    player setDamage 1;
} else {
    hint ":(";
};

In cases where there are a lot of one-liner classes, it is allowed to use something like this to save space:

class One {foo = 1;};
class Two {foo = 2;};
class Three {foo = 3;};

5.1.1 Reasoning

Putting the opening brace in its own line wastes a lot of space, and keeping the closing brace on the same level as the keyword makes it easier to recognize what exactly the brace closes.

5.2 Indents

Every new scope should be on a new indent. This will make the code easier to understand and read. Indentations consist of 4 spaces. Tabs are not allowed. Tabs or spaces are not allowed to trail on a line, last character needs to be non blank.

Good:

call {
    call {
        if (/* condition */) then {
            /* code */
        };
    };
};

Bad:

call {
        call {
        if (/* condition */) then {
            /* code */
        };
        };
};

5.3 Inline comments

Inline comments should use //. Usage of /* */ is allowed for larger comment blocks.

Example:

//// Comment   // < incorrect
// Comment     // < correct
/* Comment */  // < correct

5.4 Comments in code

All code shall be documented by comments that describe what is being done. This can be done through the function header and/or inline comments.

Comments within the code shall be used when they are describing a complex and critical section of code or if the subject code does something a certain way because of a specific reason. Unnecessary comments in the code are not allowed.

Good:

// find the object with the most blood loss
_highestObj = objNull;
_highestLoss = -1;
{
    if ([_x] call EFUNC(medical,getBloodLoss) > _highestLoss) then {
        _highestLoss = [_x] call EFUNC(medical,getbloodloss);
        _highestObj = _x;
    };
} foreach _units;

Good:

// Check if the unit is an engineer
(_obj getvariable [QGVAR(engineerSkill), 0] >= 1);

Bad:

// Get the engineer skill and check if it is above 1
(_obj getvariable [QGVAR(engineerSkill), 0] >= 1);

Bad:

// Get the variable myValue from the object
_myValue = _obj getvariable [QGVAR(myValue), 0];

Bad:

// Loop through all units to increase the myvalue variable
{
    _x setvariable [QGVAR(myValue), (_x getvariable [QGVAR(myValue), 0]) + 1];
} forEach _units;

5.5 Brackets around code

When making use of brackets ( ), use as few as possible, unless doing so decreases readability of the code. Avoid statements such as:

if (!(_value)) then { };

However the following is allowed:

_value = (_array select 0) select 1;

Any conditions in statements shall always be wrapped around brackets. Both uses of the ! operator below are allowed.

if (_value) then {};
if (!_value) then {};
if !(_value) then {};

Use of the ! operator on the lefthand-side of brackets can be more readable, particularly for more complex conditions or macros:

if !(_value && _otherValue && {_thirdValue call _something}) then {};
if !(GETEGVAR(addon,globalVariableName,defaultValue)) then {};

5.6 Magic Numbers

There shall be no magic numbers. Any magic number shall be put in a define either on top of the .sqf file (below the header), or in the script_component.hpp file in the root directory of the component (recommended) in case it is used in multiple locations.

Magic numbers are any of the following:

• A constant numerical or text value used to identify a file format or protocol
• Distinctive unique values that are unlikely to be mistaken for other meanings
• Unique values with unexplained meaning or multiple occurrences which could (preferably) be replaced with named constants

Source

5.7 Spaces between array elements

When using array notation [], always use a space between elements to improve code readability.

Good:

params ["_unit", "_vehicle"];
private _pos = [0, 0, 0];

Bad:

params ["_unit","_vehicle"];
private _pos = [0,0,0];

6. Code Standards

6.1 Error testing

If a function returns error information, then that error information will be tested.

6.2 Unreachable Code

There shall be no unreachable code.

6.3 Function Parameters

Parameters of functions must be retrieved through the usage of the param or params commands. If the function is part of the public API, parameters must be checked on allowed data types and values through the usage of the param and params commands.

Usage of the CBA Macro PARAM_x or BIS_fnc_param is deprecated and not allowed within the ACE project.

6.4 Return Values

Functions and code blocks that specific a return a value must have a meaningful return value. If no meaningful return value, the function should return nil.

6.5 Private Variables

All private variables shall make use of the private keyword on initialization. When declaring a private variable before initialization, usage of the private ARRAY syntax is allowed. All private variables must be either initialized using the private keyword, or declared using the private ARRAY syntax. Exceptions to this rule are variables obtained from an array, which shall be done with usage of the params command family, which ensures the variable is declared as private.

Good:

private _myVariable = "hello world";

Good:

_myArray params ["_elementOne", "_elementTwo"];

Bad:

_elementOne = _myArray select 0;
_elementTwo = _myArray select 1;

6.6 Lines of Code

Any one function shall contain no more than 250 lines of code, excluding the function header and any includes.

6.7 Variable declarations

Declarations should be at the smallest feasible scope.

Good:

if (call FUNC(myCondition)) then {
    private _areAllAboveTen = true; // <- smallest feasable scope

    {
        if (_x >= 10) then {
            _areAllAboveTen = false;
        };
    } forEach _anArray;

    if (_areAllAboveTen) then {
        hint "all values are above ten!";
    };
}

Bad:

private _areAllAboveTen = true; // <- this is bad, because it can be initialized in the if statement
if (call FUNC(myCondition)) then {
    {
        if (_x >= 10) then {
            _areAllAboveTen = false;
        };
    } forEach _anArray;

    if (_areAllAboveTen) then {
        hint "all values are above ten!";
    };
};

6.8 Variable initialization

Private variables will not be introduced until they can be initialized with meaningful values.

Good:

private _myVariable = 0; // good because the value will be used
{
    _x params ["_value", "_amount"];
    if (_value > 0) then {
        _myVariable = _myVariable + _amount;
    };
} forEach _array;

Bad:

private _myvariable = 0; // Bad because it is initialized with a zero, but this value does not mean anything
if (_condition) then {
    _myVariable = 1;
} else {
    _myvariable = 2;
};

Good:

private _myvariable = [1, 2] select _condition;

6.9 Initialization expression in for loops

The initialization expression in a for loop shall perform no actions other than to initialize the value of a single for loop parameter.

6.10. Increment expression in for loops

The increment expression in a for loop shall perform no action other than to change a single loop parameter to the next value for the loop.

6.11. getVariable

When using getVariable, there shall either be a default value given in the statement or the return value shall be checked for correct data type as well as return value. A default value may not be given after a nil check.

Bad:

_return = obj getvariable "varName";
if (isnil "_return") then { _return = 0 };

Good:

_return = obj getvariable ["varName", 0];

Good:

_return = obj getvariable "varName";
if (isnil "_return") exitwith {};

6.12. Global Variables

Global variables should not be used to pass along information from one function to another. Use arguments instead.

Bad:

fnc_example = {
    hint GVAR(myVariable);
};

GVAR(myVariable) = "hello my variable";
call fnc_example;

Good:

fnc_example = {
    params ["_content"];
    hint _content;
};

["hello my variable"] call fnc_example;

6.13. Temporary Objects & Variables

Unnecessary temporary objects or variables should be avoided.

6.14. Commented out Code

Code that is not used (commented out) shall be deleted.

6.15. Constant Global Variables

There shall be no constant global variables, constants shall be put in a #define.

6.16. Logging

Functions shall whenever possible and logical, make use of logging functionality through the logging and debugging macros from CBA and ACE3.

6.17. Constant Private Variables

Constant private variables that are used more as once shall be put in a #define.

6.18. Code used more than once

Any piece of code that could/is used more than once, shall be put in a function and it’s separate .sqf file, unless this code is less as 5 lines and used only in a per-frame handler.

7. Design considerations

7.1 Readability vs Performance

This is a large open source project that will get many different maintainers in its lifespan. When writing code, keep in mind that other developers also need to be able to understand your code. Balancing readability and performance of code is a non black and white subject. The rule of thumb is:

• When improving performance of code that sacrifices readability (or visa-versa), first see if the design of the implementation is done in the best way possible.
• Document that change with the reasoning in the code.

7.2 Scheduled vs Unscheduled

Avoid the usage of scheduled space as much as possible and stay in unscheduled. This is to provide a smooth experience to the user by guaranteeing code to run when we want it. See Performance considerations, spawn & execVM for more information.

This also helps avoid various bugs as a result of unguaranteed execution sequences when running multiple scripts.

7.3 Event driven

All ACE3 components shall be implemented in an event driven fashion. This is done to ensure code only runs when it is required and allows for modularity through low coupling components.

Event handlers in ACE3 are implemented through the CBA event system (ACE3’s own event system is deprecated since 3.6.0). They should be used to trigger or allow triggering of specific functionality.

More information on the CBA Events System and CBA Player Events pages.

Warning about BIS event handlers: BIS’s event handlers (addEventHandler, addMissionEventHandler) are slow when passing a large code variable. Use a short code block that calls the function you want.

player addEventHandler ["Fired", FUNC(handleFired)]; // bad
player addEventHandler ["Fired", {call FUNC(handleFired)}]; // good

8. Performance Considerations

8.1 Adding Elements to Arrays

When adding new elements to an array, pushBack shall be used instead of the binary addition or set. When adding multiple elements to an array append may be used instead.

Good:

_a pushBack _value;

Also good:

_a append [1, 2, 3];

Bad:

_a set [ count _a, _value];
_a = a + _[value];

When adding an new element to a dynamic location in an array or when the index is pre-calculated, set may be used.

When adding multiple elements to an array, the binary addition may be used for the entire addition.

8.2 createVehicle

createVehicle array shall be used.

8.3 createVehicle(Local) position

createVehicle(Local) used with a non-[0, 0, 0] position performs search for empty space to prevent collisions on spawn. Where possible [0, 0, 0] position shall be used, except on # objects (e.g. #lightsource, #soundsource) where empty position search is not performed.

This code requires ~1.00ms and will be higher with more objects near wanted position:

_vehicle = _type createVehicleLocal _posATL;
_vehicle setposATL _posATL;

While this one requires ~0.04ms:

_vehicle = _type createVehicleLocal [0, 0, 0];
_vehicle setposATL _posATL;

8.4 Unscheduled vs Scheduled

All code that has a visible effect for the user or requires time specific guaranteed execution shall be written in unscheduled space.

8.5 Avoid spawn & execVM

execVM and spawn are to be avoided wherever possible.

8.6 Empty Arrays

When checking if an array is empty isEqualTo shall be used.

8.7 for Loops

for "_y" from # to # step # do { ... }

shall be used instead of

for [{ ... },{ ... },{ ... }] do { ... };

whenever possible.

8.8 while Loops

While is only allowed when used to perform a unknown finite amount of steps with unknown or variable increments. Infinite while loops are not allowed.

Good:

_original = _obj getvariable [QGVAR(value), 0];
while {_original < _weaponThreshold} do {
    _original = [_original, _weaponClass] call FUNC(getNewValue);
}

Bad:

while {true} do {
    // anything
};

8.9 waitUntil

The waitUntil command shall not be used. Instead, make use of CBA’s CBA_fnc_waitUntilAndExecute

[{
    params ["_unit"];
    _unit getVariable [QGVAR(myVariable), false]
},
{
    params ["_unit"];
    // Execute any code
}, [_unit]] call CBA_fnc_waitUntilAndExecute;