Allow iced_wgpu to render to any TextureView

wgpu/src/window/backend.rs

@@ -0,0 +1,99 @@
+use crate::{window::SwapChain, Renderer, Settings, Target};
+
+use iced_native::MouseCursor;
+use raw_window_handle::HasRawWindowHandle;
+
+#[derive(Debug)]
+pub struct Backend {
+    device: wgpu::Device,
+    queue: wgpu::Queue,
+}
+
+impl iced_native::window::Backend for Backend {
+    type Settings = Settings;
+    type Renderer = Renderer;
+    type Surface = wgpu::Surface;
+    type SwapChain = SwapChain;
+
+    fn new(settings: Self::Settings) -> (Backend, Renderer) {
+        let adapter = wgpu::Adapter::request(&wgpu::RequestAdapterOptions {
+            power_preference: wgpu::PowerPreference::Default,
+            backends: wgpu::BackendBit::all(),
+        })
+        .expect("Request adapter");
+
+        let (mut device, queue) =
+            adapter.request_device(&wgpu::DeviceDescriptor {
+                extensions: wgpu::Extensions {
+                    anisotropic_filtering: false,
+                },
+                limits: wgpu::Limits { max_bind_groups: 2 },
+            });
+
+        let renderer = Renderer::new(settings, &mut device);
+
+        (Backend { device, queue }, renderer)
+    }
+
+    fn create_surface<W: HasRawWindowHandle>(
+        &mut self,
+        window: &W,
+    ) -> wgpu::Surface {
+        wgpu::Surface::create(window)
+    }
+
+    fn create_swap_chain(
+        &mut self,
+        surface: &Self::Surface,
+        width: u32,
+        height: u32,
+        scale_factor: f64,
+    ) -> SwapChain {
+        SwapChain::new(&self.device, surface, width, height, scale_factor)
+    }
+
+    fn draw<T: AsRef<str>>(
+        &mut self,
+        renderer: &mut Self::Renderer,
+        swap_chain: &mut SwapChain,
+        output: &<Self::Renderer as iced_native::Renderer>::Output,
+        overlay: &[T],
+    ) -> MouseCursor {
+        let (frame, viewport) = swap_chain.next_frame();
+
+        let mut encoder = self.device.create_command_encoder(
+            &wgpu::CommandEncoderDescriptor { todo: 0 },
+        );
+
+        let _ = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
+            color_attachments: &[wgpu::RenderPassColorAttachmentDescriptor {
+                attachment: &frame.view,
+                resolve_target: None,
+                load_op: wgpu::LoadOp::Clear,
+                store_op: wgpu::StoreOp::Store,
+                clear_color: wgpu::Color {
+                    r: 1.0,
+                    g: 1.0,
+                    b: 1.0,
+                    a: 1.0,
+                },
+            }],
+            depth_stencil_attachment: None,
+        });
+
+        let mouse_cursor = renderer.draw(
+            &mut self.device,
+            &mut encoder,
+            Target {
+                texture: &frame.view,
+                viewport,
+            },
+            output,
+            overlay,
+        );
+
+        self.queue.submit(&[encoder.finish()]);
+
+        mouse_cursor
+    }
+}

wgpu/src/window/swap_chain.rs

@@ -0,0 +1,49 @@
+use crate::Viewport;
+
+/// The rendering target of a window.
+///
+/// It represents a series of virtual framebuffers with a scale factor.
+#[derive(Debug)]
+pub struct SwapChain {
+    raw: wgpu::SwapChain,
+    viewport: Viewport,
+}
+
+impl SwapChain {}
+
+impl SwapChain {
+    pub fn new(
+        device: &wgpu::Device,
+        surface: &wgpu::Surface,
+        width: u32,
+        height: u32,
+        scale_factor: f64,
+    ) -> SwapChain {
+        SwapChain {
+            raw: new_swap_chain(surface, width, height, device),
+            viewport: Viewport::new(width, height, scale_factor),
+        }
+    }
+
+    pub fn next_frame(&mut self) -> (wgpu::SwapChainOutput<'_>, &Viewport) {
+        (self.raw.get_next_texture(), &self.viewport)
+    }
+}
+
+fn new_swap_chain(
+    surface: &wgpu::Surface,
+    width: u32,
+    height: u32,
+    device: &wgpu::Device,
+) -> wgpu::SwapChain {
+    device.create_swap_chain(
+        &surface,
+        &wgpu::SwapChainDescriptor {
+            usage: wgpu::TextureUsage::OUTPUT_ATTACHMENT,
+            format: wgpu::TextureFormat::Bgra8UnormSrgb,
+            width,
+            height,
+            present_mode: wgpu::PresentMode::Vsync,
+        },
+    )
+}