Suspended backend not supported for WgpuTextureBackend (requ

Error message

Suspended backend not supported for WgpuTextureBackend (requires device/queue)

What it means

Error "Suspended backend not supported for WgpuTextureBackend (requires device/queue)" thrown in slint-ui/slint.

Source

Thrown at internal/renderers/femtovg/wgpu.rs:443

    fn render_output(&self) -> impl Into<femtovg::renderer::WGPURenderOutput> {
        self.render_output.clone()
    }
}

struct WgpuTextureBackend {
    instance: wgpu::Instance,
    device: wgpu::Device,
    queue: wgpu::Queue,
    render_output: RefCell<Option<femtovg::renderer::WGPURenderOutput>>,
}

impl GraphicsBackend for WgpuTextureBackend {
    type Renderer = femtovg::renderer::WGPURenderer;
    type WindowSurface = TextureWindowSurface;
    const NAME: &'static str = "WGPU Texture";

    fn new_suspended() -> Self {
        panic!("Suspended backend not supported for WgpuTextureBackend (requires device/queue)");
    }

    fn clear_graphics_context(&self) {
        // Nothing to clear here, we don't own the device/queue/texture
    }

    fn begin_surface_rendering(
        &self,
    ) -> Result<BeginRendering<Self::WindowSurface>, Box<dyn std::error::Error + Send + Sync>> {
        let render_output =
            self.render_output.borrow().clone().ok_or("No texture set for rendering")?;
        Ok(BeginRendering::Acquired(TextureWindowSurface { render_output }))
    }

    fn submit_commands(&self, commands: <Self::Renderer as femtovg::Renderer>::CommandBuffer) {
        self.queue.submit(commands);
    }

View on GitHub (pinned to 3fd8f2ec03)

Solutions

Do not suspend the application while using the WGPU texture backend without device/queue access.
Keep the device and queue alive for the duration of the suspension.

When it happens

Trigger: Thrown at internal/renderers/femtovg/wgpu.rs:443 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of slint-ui/slint@3fd8f2ec03 (2026-08-19). Data as JSON: /api/errors/6a57b858a80d73c6. Report an issue: GitHub.