examples: Add sctk_subsurface_img

Test scrolling. Single color buffers in `sctk_subsurface` aren't good
for comparing it, and `sctk_subsurface_gst` isn't working on latest gst
with explicit sync (and AppSync isn't accepting the dmabuf when I try to
modify it.)

examples/sctk_subsurface_img/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "sctk_subsurface_img"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+iced = { path = "../..", default-features = false, features = [
+    "tokio",
+    "wayland",
+    "winit",
+    "debug",
+    "tiny-skia",
+    "image",
+] }
+iced_runtime = { path = "../../runtime" }
+env_logger = "0.10"
+futures-channel = "0.3.29"
+calloop = "0.13"
+rustix = { version = "0.38.30", features = ["fs", "shm"] }
+cctk.workspace = true
+image = { workspace = true, features = ["png"] }

examples/sctk_subsurface_img/src/main.rs

@@ -0,0 +1,135 @@
+use cctk::sctk::reexports::client::protocol::wl_shm;
+use iced::{
+    platform_specific::shell::subsurface_widget::{
+        self, Shmbuf, SubsurfaceBuffer,
+    },
+    window::{self, Id, Settings},
+    Element, Length, Subscription, Task,
+};
+use image::{ImageReader, Pixel};
+use rustix::{io::Errno, shm::ShmOFlags};
+use std::{
+    env,
+    os::fd::OwnedFd,
+    path::Path,
+    sync::Arc,
+    time::{SystemTime, UNIX_EPOCH},
+};
+
+fn main() -> iced::Result {
+    let args = env::args();
+    if args.len() != 2 {
+        eprintln!("usage: sctk_subsurface_img [image path]");
+        return Ok(());
+    }
+    let path = args.skip(1).next().unwrap();
+    if !Path::new(&path).exists() {
+        eprintln!("File `{path}` not found.");
+        return Ok(());
+    }
+
+    iced::daemon(
+        SubsurfaceApp::title,
+        SubsurfaceApp::update,
+        SubsurfaceApp::view,
+    )
+    .subscription(SubsurfaceApp::subscription)
+    .run_with(|| SubsurfaceApp::new(path))
+}
+
+#[derive(Debug, Clone)]
+struct SubsurfaceApp {
+    path: String,
+    buffer: SubsurfaceBuffer,
+}
+
+#[derive(Debug, Clone)]
+pub enum Message {
+    Id(Id),
+}
+
+impl SubsurfaceApp {
+    fn new(path: String) -> (SubsurfaceApp, Task<Message>) {
+        let img = ImageReader::open(&path)
+            .unwrap()
+            .decode()
+            .unwrap()
+            .to_rgba8();
+        let fd = create_memfile().unwrap();
+        for pixel in img.pixels() {
+            let [r, g, b, a] = <[u8; 4]>::try_from(pixel.channels()).unwrap();
+            rustix::io::write(&fd, &[b, g, r, a]).unwrap();
+        }
+        let shmbuf = Shmbuf {
+            fd,
+            offset: 0,
+            width: img.width() as i32,
+            height: img.height() as i32,
+            stride: img.width() as i32 * 4,
+            format: wl_shm::Format::Xrgb8888,
+        };
+        let buffer = SubsurfaceBuffer::new(Arc::new(shmbuf.into())).0;
+
+        (
+            SubsurfaceApp { path, buffer },
+            iced::window::open(Settings {
+                ..Default::default()
+            })
+            .1
+            .map(Message::Id),
+        )
+    }
+
+    fn title(&self, _id: window::Id) -> String {
+        String::from("SubsurfaceApp")
+    }
+
+    fn update(&mut self, message: Message) -> Task<Message> {
+        match message {
+            Message::Id(_) => {}
+        }
+        Task::none()
+    }
+
+    fn view(&self, _id: window::Id) -> Element<Message> {
+        // TODO compare side-by-side with image widget; key bind to toggle?
+        let image = subsurface_widget::Subsurface::new(self.buffer.clone())
+            .content_fit(iced::ContentFit::None);
+        /*
+        let image = iced::widget::image::Image::new(&self.path)
+            .content_fit(iced::ContentFit::None);
+        */
+        iced::widget::scrollable(image).into()
+    }
+
+    fn subscription(&self) -> Subscription<Message> {
+        Subscription::none()
+    }
+}
+
+fn create_memfile() -> rustix::io::Result<OwnedFd> {
+    loop {
+        let flags = ShmOFlags::CREATE | ShmOFlags::EXCL | ShmOFlags::RDWR;
+
+        let time = SystemTime::now();
+        let name = format!(
+            "/iced-sctk-{}",
+            time.duration_since(UNIX_EPOCH).unwrap().subsec_nanos()
+        );
+
+        match rustix::io::retry_on_intr(|| {
+            rustix::shm::shm_open(&name, flags, 0600.into())
+        }) {
+            Ok(fd) => match rustix::shm::shm_unlink(&name) {
+                Ok(_) => return Ok(fd),
+                Err(errno) => {
+                    return Err(errno.into());
+                }
+            },
+            Err(Errno::EXIST) => {
+                continue;
+            }
+            Err(err) => return Err(err.into()),
+        }
+    }
+}