[olympic] Remove Ox from developer-handbook.md
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@ -1,4 +1,4 @@
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# Nostalgia Developer Handbook
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# Olympic Developer Handbook
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## About
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@ -47,7 +47,7 @@ All components have a platform indicator next to them:
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* Ox - Library of things useful for portable bare metal and userland code. Not really that external...
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* clargs - Command Line Args processing (PG)
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* claw - Reads and writes Metal or Organic Claw with header to indicate which
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* event - Qt-like signal system
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* event - Qt-like signal system (PG)
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* fs - file system (PG)
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* logconn - connects logging to Bullock (P-)
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* mc - Metal Claw serialization, builds on model (PG)
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@ -59,6 +59,10 @@ All components have a platform indicator next to them:
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* teagba - GBA assembly startup code (mostly pulled from devkitPro under MPL
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2.0), and custom GBA hardware interop code (-G)
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Most GBA code is built on PC because it is small and helps to work on both
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projects with the same CMake build dir, but GBA code is never linked with any
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executables on PC.
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## Platform Notes
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### GBA
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@ -88,6 +92,7 @@ The GBA has two major resources for learning about its hardware:
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* Pointer and reference designators should be bound to the identifier name and
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not the type, unless there is not identifier name, in which case it should be
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bound to the type.
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* East const
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### Write C++, Not C
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@ -160,479 +165,29 @@ classes in question.
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## Project Systems
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### Error Handling
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The GBA build has exceptions disabled.
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Instead of throwing exceptions, all engine code must return ```ox::Error```s.
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For the sake of consistency, try to stick to ```ox::Error``` in non-engine code
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as well, but non-engine code is free to use exceptions when they make sense.
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Nostalgia and Ox both use ```ox::Error``` to report errors. ```ox::Error``` is
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a struct that has overloaded operators to behave like an integer error code,
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plus some extra fields to enhance debuggability.
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If instantiated through the ```OxError(x)``` macro, it will also include the
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file and line of the error.
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The ```OxError(x)``` macro should only be used for the initial instantiation of
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an ```ox::Error```.
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In addition to ```ox::Error``` there is also the template ```ox::Result<T>```.
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```ox::Result``` simply wraps the type T value in a struct that also includes
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error information, which allows the returning of a value and an error without
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resorting to output parameters.
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If a function returns an ```ox::Error``` or ```ox::Result``` it should be
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declared as ```noexcept``` and all exceptions should be translated to an
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```ox::Error```.
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```ox::Result``` can be used as follows:
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```cpp
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ox::Result<int> foo(int i) noexcept {
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if (i < 10) {
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return i + 1; // implicitly calls ox::Result<T>::Result(T)
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}
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return OxError(1); // implicitly calls ox::Result<T>::Result(ox::Error)
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}
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int caller1() {
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auto v = foo(argc);
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if (v.error) {
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return 1;
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}
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std::cout << v.value << '\n';
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return 0;
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}
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int caller2() {
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// it is also possible to capture the value and error in their own variables
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auto [val, err] = foo(argc);
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if (err) {
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return 1;
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}
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std::cout << val << '\n';
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return 0;
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}
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ox::Error caller3(int &i) {
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return foo(i).moveTo(i);
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}
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ox::Error caller4(int &i) {
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return foo(i).copyTo(i);
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}
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int caller5(int i) {
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return foo(i).unwrap(); // unwrap will kill the program if there is an error
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}
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int caller6(int i) {
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return foo(i).unwrapThrow(); // unwrap will throw if there is an error
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}
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int caller7(int i) {
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return foo(i).or_value(0); // will return 0 if foo returned an error
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}
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ox::Result<uint64_t> caller8(int i) {
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return foo(i).to<uint64_t>(); // will convert the result of foo to uint64_t
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}
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```
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Lastly, there are a few macros available to help in passing ```ox::Error```s
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back up the call stack, ```oxReturnError```, ```oxThrowError```, and
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```oxRequire```.
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```oxReturnError``` is by far the more helpful of the two.
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```oxReturnError``` will return an ```ox::Error``` if it is not 0 and
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```oxThrowError``` will throw an ```ox::Error``` if it is not 0.
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Because exceptions are disabled for GBA builds and thus cannot be used in the
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engine, ```oxThrowError``` is only really useful at the boundary between
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engine libraries and Nostalgia Studio.
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Since ```ox::Error``` is always nodiscard, you must do something with them.
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In rare cases, you may not have anything you can do with them or you may know
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the code will never fail in that particular instance.
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This should be used sparingly.
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```cpp
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void studioCode() {
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auto [val, err] = foo(1);
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oxThrowError(err);
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doStuff(val);
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}
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ox::Error engineCode() noexcept {
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auto [val, err] = foo(1);
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oxReturnError(err);
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doStuff(val);
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return {};
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}
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void anyCode() {
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auto [val, err] = foo(1);
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std::ignore = err;
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doStuff(val);
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}
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```
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Both macros will also take the ```ox::Result``` directly:
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```cpp
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void studioCode() {
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auto valerr = foo(1);
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oxThrowError(valerr);
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doStuff(valerr.value);
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}
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ox::Error engineCode() noexcept {
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auto valerr = foo(1);
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oxReturnError(valerr);
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doStuff(valerr.value);
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return {};
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}
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```
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Ox also has the ```oxRequire``` macro, which will initialize a value if there is no error, and return if there is.
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It aims to somewhat emulate the ```?``` operator in Rust and Swift.
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Rust ```?``` operator:
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```rust
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fn f() -> Result<i32, i32> {
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// do stuff
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}
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fn f2() -> Result<i32, i32> {
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let i = f()?;
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Ok(i + 4)
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}
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```
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```oxRequire```:
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```cpp
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ox::Result<int> f() noexcept {
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// do stuff
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}
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ox::Result<int> f2() noexcept {
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oxRequire(i, f()); // const auto [out, oxConcat(oxRequire_err_, __LINE__)] = x; oxReturnError(oxConcat(oxRequire_err_, __LINE__))
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return i + 4;
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}
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```
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```oxRequire``` is not quite as versatile, but it should still cleanup a lot of otherwise less ideal code.
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```oxRequire``` also has variants for throwing the error and for making to value non-const:
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* ```oxRequireM``` - oxRequire Mutable
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* ```oxRequireT``` - oxRequire Throw
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* ```oxRequireMT``` - oxRequire Mutable Throw
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The throw variants of ```oxRequire``` are generally legacy code.
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```ox::Result::unwrapThrow``` is generally preferred now.
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### Logging and Output
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Ox provides for logging and debug prints via the ```oxTrace```, ```oxDebug```, and ```oxError``` macros.
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Each of these also provides a format variation.
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Ox also provide ```oxOut``` and ```oxErr``` for printing to stdout and stderr.
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These are intended for permanent messages and always go to stdout and stderr.
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Tracing functions do not go to stdout unless the OXTRACE environment variable is set.
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They also print with the channel that they are on, along with file and line.
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Debug statements go to stdout and go to the logger on the "debug" channel.
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Where trace statements are intended to be written with thoughtfulness,
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debug statements are intended to be quick and temporary insertions.
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Debug statements trigger compilation failures if OX_NODEBUG is enabled when CMake is run,
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as it is on Jenkins builds, so ```oxDebug``` statements should never be checked in.
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This makes ```oxDebug``` preferable to other forms of logging, as temporary prints should
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never be checked in.
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```oxError``` always prints.
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It includes file and line, and is prefixed with a red "ERROR:".
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It should generally be used conservatively.
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It shuld be used only when there is an error that is not technically fatal, but
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the user almost certainly wants to know about it.
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```oxTrace``` and ```oxTracef```:
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```cpp
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void f(int x, int y) { // x = 9, y = 4
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oxTrace("nostalgia.core.sdl.gfx") << "f:" << x << y; // Output: "f: 9 4"
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oxTracef("nostalgia.core.sdl.gfx", "f: {}, {}", x, y); // Output: "f: 9, 4"
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}
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```
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```oxDebug``` and ```oxDebugf```:
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```cpp
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void f(int x, int y) { // x = 9, y = 4
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oxDebug() << "f:" << x << y; // Output: "f: 9 4"
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oxDebugf("f: {}, {}", x, y); // Output: "f: 9, 4"
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}
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```
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```oxError``` and ```oxErrorf```:
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```cpp
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void f(int x, int y) { // x = 9, y = 4
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oxError() << "f:" << x << y; // Output: "ERROR: (<file>:<line>): f: 9 4"
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oxErrorf("f: {}, {}", x, y); // Output: "ERROR: (<file>:<line>): f: 9, 4"
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}
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```
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Olympic builds on Ox as its standard-ish library.
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Please read the [Ox documentation](deps/ox/ox-docs.md).
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The Ox way of doing things is the Olympic way of doing things.
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### File I/O
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All engine file I/O should go through nostalgia::core::Context, which should go
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through ox::FileSystem. Similarly, all studio file I/O should go thorough
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nostalgia::studio::Project, which should go through ox::FileSystem.
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All engine file I/O should go through Keel, which should go through
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```ox::FileSystem```.
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Similarly, all studio file I/O should go thorough
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```nostalgia::studio::Project```, which should go through ```ox::FileSystem```.
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ox::FileSystem abstracts away differences between conventional storage devices
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and ROM.
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```ox::FileSystem``` abstracts away differences between conventional storage
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devices and ROM.
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### Model System
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Olympic files are generally just [Claw objects](deps/ox/ox-docs.md#serialization).
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Ox has a model system that provides a sort of manual reflection mechanism.
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#### Keel
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Models require a model function for the type that you want to model.
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It is also good to provide a type name and type version number, though that is not required.
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Keel, as its name implies, is a foundational component of Olympic.
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Keel is the asset management system.
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The model function takes an instance of the type it is modelling and a template
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parameter type.
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The template parameter type must implement the API used in the models, but it
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can do anything with the data provided to it.
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Keel provides for the following needs:
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Here is an example from the Nostalgia/Core package:
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```cpp
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struct NostalgiaPalette {
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static constexpr auto TypeName = "net.drinkingtea.nostalgia.core.NostalgiaPalette";
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static constexpr auto TypeVersion = 1;
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ox::Vector<Color16> colors;
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};
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struct NostalgiaGraphic {
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static constexpr auto TypeName = "net.drinkingtea.nostalgia.core.NostalgiaGraphic";
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static constexpr auto TypeVersion = 1;
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int8_t bpp = 0;
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// rows and columns are really only used by TileSheetEditor
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int rows = 1;
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int columns = 1;
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ox::FileAddress defaultPalette;
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NostalgiaPalette pal;
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ox::Vector<uint8_t> pixels;
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};
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template<typename T>
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constexpr ox::Error model(T *h, ox::CommonPtrWith<NostalgiaPalette> auto *pal) noexcept {
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h->template setTypeInfo<NostalgiaPalette>();
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// it is also possible to provide the type name and type version as function arguments
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//h->setTypeInfo("net.drinkingtea.nostalgia.core.NostalgiaPalette", 1);
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oxReturnError(h->field("colors", &pal->colors));
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return {};
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}
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template<typename T>
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constexpr ox::Error model(T *h, ox::CommonPtrWith<NostalgiaGraphic> auto *ng) noexcept {
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h->template setTypeInfo<NostalgiaGraphic>();
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oxReturnError(h->field("bpp", &ng->bpp));
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oxReturnError(h->field("rows", &ng->rows));
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oxReturnError(h->field("columns", &ng->columns));
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oxReturnError(h->field("defaultPalette", &ng->defaultPalette));
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oxReturnError(h->field("pal", &ng->pal));
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oxReturnError(h->field("pixels", &ng->pixels));
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return {};
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}
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```
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The model system also provides for unions:
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```cpp
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#include <ox/model/types.hpp>
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class FileAddress {
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template<typename T>
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friend constexpr Error model(T*, ox::CommonPtrWith<FileAddress> auto*) noexcept;
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public:
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static constexpr auto TypeName = "net.drinkingtea.ox.FileAddress";
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union Data {
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static constexpr auto TypeName = "net.drinkingtea.ox.FileAddress.Data";
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char *path;
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const char *constPath;
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uint64_t inode;
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};
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protected:
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FileAddressType m_type = FileAddressType::None;
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Data m_data;
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};
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template<typename T>
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constexpr Error model(T *h, ox::CommonPtrWith<FileAddress::Data> auto *obj) noexcept {
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h->template setTypeInfo<FileAddress::Data>();
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oxReturnError(h->fieldCString("path", &obj->path));
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oxReturnError(h->fieldCString("constPath", &obj->path));
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oxReturnError(h->field("inode", &obj->inode));
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return {};
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}
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template<typename T>
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constexpr Error model(T *io, ox::CommonPtrWith<FileAddress> auto *fa) noexcept {
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io->template setTypeInfo<FileAddress>();
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// cannot read from object in Reflect operation
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if constexpr(ox_strcmp(T::opType(), OpType::Reflect) == 0) {
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int8_t type = 0;
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oxReturnError(io->field("type", &type));
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oxReturnError(io->field("data", UnionView(&fa->m_data, 0)));
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} else {
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auto type = static_cast<int8_t>(fa->m_type);
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oxReturnError(io->field("type", &type));
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fa->m_type = static_cast<FileAddressType>(type);
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oxReturnError(io->field("data", UnionView(&fa->m_data, static_cast<int>(fa->m_type))));
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}
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return {};
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}
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```
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There are also macros in ```<ox/model/def.hpp>``` for simplifying the declaration of models:
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```cpp
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oxModelBegin(NostalgiaGraphic)
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oxModelField(bpp)
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oxModelField(rows)
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oxModelField(columns)
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oxModelField(defaultPalette)
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oxModelField(pal)
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oxModelField(pixels)
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oxModelEnd()
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```
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### Serialization
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Using the model system, Ox provides for serialization.
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Ox has MetalClaw and OrganicClaw as its serialization format options.
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MetalClaw is a custom binary format designed for minimal size.
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OrganicClaw is a wrapper around JsonCpp, chosen because it technically
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implements a superset of JSON.
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OrganicClaw requires support for 64 bit integers, whereas normal JSON
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technically does not.
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These formats do not currently support floats.
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There is also a wrapper format called Claw that provides a header at the
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beginning of the file and can dynamically switch between the two depending on
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what the header says is present.
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The Claw header also includes information about the type and type version of
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the data.
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Claw header: ```M1;net.drinkingtea.nostalgia.core.NostalgiaPalette;1;```
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That reads:
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* Format is Metal Claw, version 1
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* Type ID is net.drinkingtea.nostalgia.core.NostalgiaPalette
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* Type version is 1
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Except when the data is exported for loading on the GBA, Claw is always used as
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a wrapper around the bare formats.
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#### Metal Claw Example
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##### Read
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```cpp
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#include <ox/mc/read.hpp>
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ox::Result<NostalgiaPalette> loadPalette1(ox::BufferView const&buff) noexcept {
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return ox::readMC<NostalgiaPalette>(buff);
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}
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ox::Result<NostalgiaPalette> loadPalette2(ox::BufferView const&buff) noexcept {
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NostalgiaPalette pal;
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oxReturnError(ox::readMC(buff, pal));
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return pal;
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}
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```
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##### Write
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```cpp
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#include <ox/mc/write.hpp>
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ox::Result<ox::Buffer> writeSpritePalette1(NostalgiaPalette const&pal) noexcept {
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ox::Buffer buffer(ox::units::MB);
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std::size_t sz = 0;
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oxReturnError(ox::writeMC(buffer.data(), buffer.size(), pal, &sz));
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buffer.resize(sz);
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return buffer;
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}
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ox::Result<ox::Buffer> writeSpritePalette2(NostalgiaPalette const&pal) noexcept {
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return ox::writeMC(pal);
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}
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```
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#### Organic Claw Example
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##### Read
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```cpp
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#include <ox/oc/read.hpp>
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ox::Result<NostalgiaPalette> loadPalette1(ox::BufferView const&buff) noexcept {
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return ox::readOC<NostalgiaPalette>(buff);
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}
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ox::Result<NostalgiaPalette> loadPalette2(ox::BufferView const&buff) noexcept {
|
||||
NostalgiaPalette pal;
|
||||
oxReturnError(ox::readOC(buff, &pal));
|
||||
return pal;
|
||||
}
|
||||
```
|
||||
|
||||
##### Write
|
||||
|
||||
```cpp
|
||||
#include <ox/oc/write.hpp>
|
||||
|
||||
ox::Result<ox::Buffer> writeSpritePalette1(NostalgiaPalette const&pal) noexcept {
|
||||
ox::Buffer buffer(ox::units::MB);
|
||||
oxReturnError(ox::writeOC(buffer.data(), buffer.size(), pal));
|
||||
return buffer;
|
||||
}
|
||||
|
||||
ox::Result<ox::Buffer> writeSpritePalette2(NostalgiaPalette const&pal) noexcept {
|
||||
return ox::writeOC(pal);
|
||||
}
|
||||
```
|
||||
|
||||
#### Claw Example
|
||||
|
||||
##### Read
|
||||
|
||||
```cpp
|
||||
#include <ox/claw/read.hpp>
|
||||
|
||||
ox::Result<NostalgiaPalette> loadPalette1(ox::BufferView const&buff) noexcept {
|
||||
return ox::readClaw<NostalgiaPalette>(buff);
|
||||
}
|
||||
|
||||
ox::Result<NostalgiaPalette> loadPalette2(ox::BufferView const&buff) noexcept {
|
||||
NostalgiaPalette pal;
|
||||
oxReturnError(ox::readClaw(buff, pal));
|
||||
return pal;
|
||||
}
|
||||
```
|
||||
|
||||
##### Write
|
||||
|
||||
```cpp
|
||||
#include <ox/claw/write.hpp>
|
||||
|
||||
ox::Result<ox::Buffer> writeSpritePalette(NostalgiaPalette const&pal) noexcept {
|
||||
return ox::writeClaw(pal);
|
||||
}
|
||||
```
|
||||
* Type conversion
|
||||
* Asset bundling
|
||||
* Asset loading (including flyweighting on PC and preloading to ROM on the GBA)
|
||||
|
||||
Loading…
Reference in New Issue
Block a user