How to solve this rust lifetime bound issue of SDL2?

Question

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"]

ttf_context is moved. I can solve this one, but by changing code in a ugly way.
Font has lifetime bound on context. Cannot fix this one.

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

Questions seeking debugging help ("**why isn't this code working?**") must include the desired behavior, a specific problem or error and the shortest code necessary to reproduce it **in the question itself**. Questions without a **clear problem statement** are not useful to other readers. See: [How to create a Minimal, Complete, and Verifiable example](https://stackoverflow.com/help/mcve). — Tim Diekmann, Apr 10 '18 at 08:02
Tim, I updated the code. Now it includes a shortest code example. — osamu, Apr 10 '18 at 21:16

score 0 · Answer 1 · answered Apr 11 '18 at 01:16

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);
}

How to solve this rust lifetime bound issue of SDL2?

1 Answers1

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