aseprite/docs/CODING_STYLE.md

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2018-06-13 20:22:46 +00:00
# Code Style Guidelines
Some general rules to write code: Try to follow the same style/format
of the file that you are editing (naming, indentation, etc.) or the
style of the module (some [submodules](https://github.com/aseprite/aseprite/blob/main/.gitmodules),
created by us, or by third-parties, have their own style).
There is a [.clang-format](https://github.com/aseprite/aseprite/blob/main/.clang-format)
file available but we are not using it at the moment, probably we
should start using some
[clang-format-diff.py](https://clang.llvm.org/docs/ClangFormat.html#script-for-patch-reformatting)
for patches, but this wasn't yet adopted in the development process.
There is a [.clang-tidy](https://github.com/aseprite/aseprite/blob/main/.clang-tidy)
file used [in the GitHub actions](https://github.com/aseprite/aseprite/blob/main/.github/workflows/clang_tidy.yml)
executed on each PR. These rules are adopted progressively on patches
because are only executed in the diff, and if some rule is violated a
comment by [aseprite-bot](https://github.com/aseprite-bot) is made.
## Basics
Basic statements:
```c++
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void global_function(int arg1,
const int arg2, // You can use "const" preferably
const int arg3, ...)
{
int value;
const int constValue = 0;
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// We prefer to use "var = (condition ? ...: ...)" instead of
// "var = condition ? ...: ...;" to make clear about the
// ternary operator limits.
int conditionalValue1 = (condition ? 1: 2);
int conditionalValue2 = (condition ? longVarName:
otherLongVarName);
// If a condition will return, we prefer the "return"
// statement in its own line to avoid missing the "return"
// keyword when we read code.
if (condition)
return;
// You can use braces {} if the condition has multiple lines
// or the if-body has multiple lines.
if (condition1 ||
condition2) {
return;
}
if (condition) {
...
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...
...
}
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// We prefer to avoid whitespaces between "var=initial_value"
// or "var<limit" to see better the "; " separation. Anyway it
// can depend on the specific condition/case, etc.
for (int i=0; i<10; ++i) {
...
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// Same case as in if-return.
if (condition)
break;
...
}
while (condition) {
...
}
do {
...
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} while (condition);
switch (condition) {
case 1:
...
break;
case 2: {
int varInsideCase;
...
break;
}
default:
break;
}
}
```
## Namespaces
Define namespaces with lower case:
```c++
namespace app {
...
} // namespace app
```
## Classes
Define classes with `CapitalCase` and member functions with `camelCase`:
```c++
class ClassName {
public:
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ClassName()
: m_memberVarA(1),
m_memberVarB(2),
m_memberVarC(3) {
...
}
virtual ~ClassName();
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// We can return in the same line for getter-like functions
int memberVar() const { return m_memberVar; }
void setMemberVar();
protected:
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virtual void onEvent1() { } // Do nothing functions can be defined as "{ }"
virtual void onEvent2() = 0;
private:
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int m_memberVarA;
int m_memberVarB;
int m_memberVarC;
int m_memberVarD = 4; // We can initialize variables here too
};
class Special : public ClassName {
public:
Special();
protected:
void onEvent2() override { // No need to repeat virtual in overridden methods
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...
}
};
```
## Const
We use the const-west notation:
* [NL.26: Use conventional const notation](https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#nl26-use-conventional-const-notation)
There is a problem with `clang-tidy` that will make comments using
East const notation: [#4361](https://github.com/aseprite/aseprite/issues/4361)
## C++17
We are using C++17 standard. Some things cannot be used because we're
targetting macOS 10.9, some notes are added about this:
* Use `nullptr` instead of `NULL` macro
* Use `auto`/`auto*` for complex types/pointers, iterators, or when
the variable type is obvious (e.g. `auto* s = new Sprite;`)
* Use range-based for loops (`for (const auto& item : values) { ... }`)
* Use template alias (`template<typename T> alias = orig<T>;`)
* Use generic lambda functions
* Use `std::shared_ptr`, `std::unique_ptr`, or `base::Ref`, but
generally we'd prefer value semantics instead of smart pointers
* Use `std::min`/`std::max`/`std::clamp`
* Use `std::optional` but taking care of some limitations from macOS 10.9:
* Use `std::optional::has_value()` instead of `std::optional::operator bool()` ([example](https://github.com/aseprite/laf/commit/81622fcbb9e4a0edc14a02250c387bd6fa878708))
* Use `std::optional::operator*()` instead of `std::optional::value()` ([example](https://github.com/aseprite/aseprite/commit/4471dab289cdd45762155ce0b16472e95a7f8642))
* Use `std::variant` but taking care of some limitations from macOS 10.9:
* Use `T* p = std::get_if<T>(&value)` instead of `T v = std::get<T>(value)` or
create an auxiliary `get_value()` using `std::get_if` function ([example](https://github.com/aseprite/aseprite/commit/dc0e57728ae2b10cd8365ff0a50263daa8fcc9ac#diff-a59e14240d83bffc2ea917d7ddd7b2762576b0e9ab49bf823ba1a89c653ff978R98))
* Don't use `std::visit()`, use some alternative with switch-case and the `std::variant::index()` ([example](https://github.com/aseprite/aseprite/commit/574f58375332bb80ce5572fdedb1028617786e45))
* Use `std::any` but taking care of some limitations from macOS 10.9:
* Use `T* p = std::any_cast<T>(&value)` instead of `T v = std::any_cast<T>(value)` ([example](https://github.com/aseprite/aseprite/commit/c8d4c60f07df27590381ef28001a40f8f785f50e))
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* Use `static constexpr T v = ...;`
* You can use `<atomic>`, `<thread>`, `<mutex>`, and `<condition_variable>`
* Prefer `using T = ...;` instead of `typedef ... T`
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* Use `[[fallthrough]]` if needed
* Use `= {}` only to specify a default argument value of an
user-defined type in a function declaration, e.g.
`void func(const std::string& s = {}) { ... }`.
In other cases (e.g. a member variable of an user-defined type)
it's not required or we prefer to use the explicit value
for built-in types (`int m_var = 0;`).
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* We use gcc 9.2 or clang 9.0 on Linux, so check the features available in
https://en.cppreference.com/w/cpp/compiler_support