Xilem example for http cats API, requiring workers and image component

masonry/src/widget/image.rs

@@ -22,6 +22,8 @@ use crate::{
 /// A widget that renders a bitmap Image.
 ///
 /// The underlying image uses `Arc` for buffer data, making it cheap to clone.
+///
+/// This currently uses bilinear interpolation, which falls down when the image is larger than the
 pub struct Image {
     image_data: ImageBuf,
     fill: FillStrat,
@@ -87,7 +89,7 @@ impl Widget for Image {
             trace!("Computed size: {}", size);
             return size;
         }
-        // This size logic has NOT been carefully considered
+        // This size logic has NOT been carefully considered, in particular with regards to self.fill.
         // TODO: Carefully consider it
         let size =
             bc.constrain_aspect_ratio(image_size.height / image_size.width, image_size.width);

xilem/examples/http_cats.rs

@@ -32,7 +32,7 @@ struct Status {
 }
 
 #[derive(Debug)]
-/// What operations have happened on a fetching image.
+/// The state of the download of an image from a URL
 enum ImageState {
     NotRequested,
     Pending,
@@ -144,7 +144,6 @@ impl HttpCats {
 
 /// Load a [`vello::peniko::Image`] from the given url.
 async fn image_from_url(url: &str) -> anyhow::Result<Image> {
-    // TODO: Error handling
     let response = reqwest::get(url).await?;
     let bytes = response.bytes().await?;
     let image = image::load_from_memory(&bytes)?.into_rgba8();
@@ -185,7 +184,7 @@ impl Status {
             ),
             ImageState::Pending => OneOf3::B(sized_box(spinner()).width(80.).height(80.)),
             // TODO: Alt text?
-            ImageState::Available(image_data) => OneOf3::C(image(image_data.clone())),
+            ImageState::Available(image_data) => OneOf3::C(image(image_data)),
         };
         flex((
             prose(format!("HTTP Status Code: {}", self.code)).alignment(TextAlignment::Middle),

xilem/src/view/image.rs

@@ -1,18 +1,29 @@
 // Copyright 2024 the Xilem Authors
 // SPDX-License-Identifier: Apache-2.0
 
+//! The bitmap image widget.
+
 use masonry::widget::{self, FillStrat};
 use xilem_core::{Mut, ViewMarker};
 
 use crate::{MessageResult, Pod, View, ViewCtx, ViewId};
 
-/// Displays a bitmap Image.
+/// Displays the bitmap `image`.
 ///
 /// By default, the Image will scale to fit its box constraints ([`FillStrat::Fill`]).
 /// To configure this, call [`fill`](Image::fill) on the returned value.
-pub fn image(image: vello::peniko::Image) -> Image {
+///
+/// Corresponds to the [`Image`](widget::Image) widget.
+///
+/// It is not currently supported to use a GPU-resident [texture](vello::wgpu::Texture) in this widget.
+/// See [#gpu>vello adding wgpu texture buffers to scene](https://xi.zulipchat.com/#narrow/stream/197075-gpu/topic/vello.20adding.20wgpu.20texture.20buffers.20to.20scene)
+/// for discussion.
+pub fn image(image: &vello::peniko::Image) -> Image {
     Image {
-        image,
+        // Image only contains a `Blob` and Copy fields, and so is cheap to clone.
+        // We take by reference as we expect all users of this API will need to clone, and it's
+        // easier than documenting that cloning is cheap.
+        image: image.clone(),
         fill: FillStrat::default(),
     }
 }
@@ -39,7 +50,6 @@ impl<State, Action> View<State, Action, ViewCtx> for Image {
     type ViewState = ();
 
     fn build(&self, _: &mut ViewCtx) -> (Self::Element, Self::ViewState) {
-        // Image's clone is cheap, so it's ok for this to be a view.
         (Pod::new(widget::Image::new(self.image.clone())), ())
     }