如何解决 SDL2 的这个锈蚀生命周期问题? [英] How to solve this rust lifetime bound issue of SDL2?

问题描述

我正在尝试使用 sdl2 ttf 渲染一些字体.sdl2 中 Font 类型的类型对使用 PhantomData 的上下文具有生命周期依赖性.我觉得很难使用.这是我尝试使用的最少代码.

I'm trying to render some font using sdl2 ttf. The type of Font type in sdl2 has a lifetime dependency on the context using PhantomData. I find it very difficult to use. Here's the the minimal code I'm trying to use.

main.rs

extern crate sdl2;

use sdl2::ttf::{self, Font};
use sdl2::ttf::Sdl2TtfContext;

struct App<'ttf> {
    ctx: Sdl2TtfContext,
    glyph_renderer: GlyphRenderer<'ttf>,
}

impl<'ttf> App<'ttf> {
    fn render(&self) {}
}

struct GlyphRenderer<'ttf> {
    font: Font<'ttf, 'static>,
}

fn main() {
    let ttf_context = ttf::init().unwrap();

    let font = ttf_context.load_font("./assets/Supermercado-Regular.ttf", 50).unwrap();
    let glyph_renderer = GlyphRenderer { font };

    let app = App {
        ctx: ttf_context,
        glyph_renderer,
    };

    app.render();
}

Cargo.toml

[package]
name = "demo-rust"
version = "0.1.0"
authors = ["clojure"]

[dependencies.sdl2]
version = "0.31.0"
default-features = false
features = ["ttf"]

1. ttf_context 已移动.我可以解决这个问题，但要以一种丑陋的方式更改代码.
2. 字体在上下文中具有生命周期限制.无法修复此问题.

本文档包含 Sdl2TtfContext 和 Font 的声明，如果您觉得有用的话.文档

This documentation contains the declaration of Sdl2TtfContext and Font, should you find it useful. DOC

推荐答案

好的，我可以通过将上下文创建移到外部作用域来解决这个问题.它不能放在结构上.

Alright, I am able to fix this issue by moving context creation to the outer scope. It cannot be put on a struct.

fn start(ttf_context: &Sdl2TtfContext) {
    let font = ttf_context.load_font("./assets/Supermercado-Regular.ttf", 50).unwrap();
    let glyph_renderer = GlyphRenderer { font };

    let app = App {
        glyph_renderer,
    };

    app.render();
}

fn main() {
    let ttf_context = ttf::init().unwrap();
    start(&ttf_context);
}

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