A Rust crate that implements a frame-rate-independent game loop. The code is based on "Fix Your Timestep!", it's extremely lightweight and supports both native execution and compilation to wasm.
```rust use gameloop::gameloop;
fn main() { let game = YourGame::new();
game_loop(game, 240, 0.1, |g| {
g.game.your_update_function();
}, |g| {
g.game.your_render_function();
});
} ```
The value 240 is the number of updates per second. It is not the frame rate.
In web environments, the frame rate is controlled by
requestAnimationFrame,
otherwise render is called as quickly as possible, though you can slow it down
with std::thread::sleep
if you wish. This may be useful if vsync is enabled or to save power on mobile
devices.
The value 0.1 is the maximum frame time which serves as an escape hatch if
your functions can't keep up with 240 updates per second. Otherwise, your game
would 'death spiral' falling further and further behind. For example, if your
render function takes 0.5 seconds, only 24 updates would occur instead of 120.
This slows your game down but that's better than crashing.
The g closure argument lets you access your game state which can be anything
you like. You can also access the game loop's running time, how many updates
there have been, etc. It also provides a blending_factor that you may use in
your render function to interpolate frames and produce smoother animations. See
the article above for more explanation.
By default, the amount of accumulated time since the last frame is measured
immediately before your render function is called. However, you can call
g.re_accumulate() right before you need to access g.blending_factor() for
more precise timings. This is useful if your render function does work before
it gets round to drawing, such as computing lighting.
In web environments, requestAnimationFrame only runs when the browser tab is
active. Setting a maximum frame time ensures your game doesn't fall far behind
on its updates and is effectively paused. Also, game_loop is asynchronous and
returns immediately rather than blocking until g.exit() is called. Other than
that, the interface is exactly the same.
The crate now supports running a frame-rate independent game loop inside a winit window. You can enable this feature in your Cargo.toml:
toml
[dependencies]
game_loop = { version = "*", features = ["window"] }
With this feature enabled, the interface is a little bit different:
```rust use gameloop::gameloop;
use gameloop::winit::event::{Event, WindowEvent}; use gameloop::winit::eventloop::EventLoop; use gameloop::winit::window::{Window, WindowBuilder};
fn main() { let eventloop = EventLoop::new(); let window = WindowBuilder::new().build(&eventloop).unwrap();
let game = YourGame::new();
game_loop(event_loop, window, game, 240, 0.1, |g| {
g.game.your_update_function();
}, |g| {
g.game.your_render_function(&g.window);
}, |g, event| {
g.game.your_window_handler(event);
});
} ```
Notably, the game_loop function now takes a winit
EventLoop
and Window and
an additional closure to handle window events such as resizing the window or
closing it. The window can be accessed through the g closure argument. This is
so you can bind a graphics context to it or set its title, etc.
Winit also supports wasm so in theory it should Just Work, but I haven't tested it yet. Please refer to winit documentation for more information.
There's a Game of Life example that shows how to use the crate in its basic form, without wasm or windowing. You can run it with:
sh
cargo run --example game_of_life
There's a windowing example that shows how to use the crate alongside a winit window. You can run it with:
sh
cargo run --example using_a_window --features window
MIT