> 开发分支文档 — commit c5a119d39ba4c149dc90ed5711c4e76759080b41
> 包版本: @zenfg/webgpu 0.2.0, @zenfg/snapshot 0.1.1, @zenfg/inspector 0.2.0, zenfg 0.2.0, zenfg-snapshot 0.1.1
> Source: https://github.com/uinosoft/zenfg/blob/c5a119d39ba4c149dc90ed5711c4e76759080b41/crates/zenfg/examples/persistent_state.rs

# zenfg: persistent-state

此页展示完整、经过编译检查的包内示例。设备和应用状态由调用方管理。代码保留英文。

```rust
use zenfg::{
    BufferDesc, BufferRange, CompileOptions, FrameGraph, ImportBufferOptions, InitialContents,
    RootReason,
};

fn main() -> Result<(), zenfg::FrameGraphError> {
    let (device, queue) = wgpu::Device::noop(&wgpu::DeviceDescriptor::default());
    let native_state = device.create_buffer(&wgpu::BufferDescriptor {
        label: Some("caller-owned persistent state"),
        size: 64,
        usage: wgpu::BufferUsages::COPY_DST,
        mapped_at_creation: false,
    });
    let mut graph = FrameGraph::with_device(&device);

    // Persistent state is re-imported in every frame; the native resource stays
    // caller-owned. The first clear defines it, so later imports may promise
    // `Defined` initial contents.
    for frame_index in 0..2 {
        let mut frame = graph.begin_frame();
        let state = frame.import_buffer(
            BufferDesc::new("state", 64),
            ImportBufferOptions {
                initial_contents: if frame_index == 0 {
                    InitialContents::Undefined
                } else {
                    InitialContents::Defined
                },
                exposed_usage: Some(wgpu::BufferUsages::COPY_DST),
            },
        )?;
        frame.bind_imported_buffer(state, &native_state)?;

        frame.clear_buffer(
            format!("write persistent state {frame_index}"),
            state,
            BufferRange::whole(),
        )?;
        frame.mark_buffer_root(state, BufferRange::whole(), RootReason::PersistentState)?;
        frame.compile(CompileOptions::default())?.execute(&queue)?;
    }
    Ok(())
}

```