Auto merge of #23661 - julientregoat:i-21289, r=jdm

Refactor ImageCache::find_image_or_metadata -> ImageCache::{get_image, track_image}

<!-- Please describe your changes on the following line: -->
Updated the `ImageCache` trait to replace `find_image_or_metadata` with two new functions `track_image` and `get_image`, as well as a new enum (`ImageCacheResult`).

As a result, I was able to refactor the functions that previously called `find_image_or_metadata` pretty cleanly. For a list of these functions, please see the commit information.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #21289  (GitHub issue number if applicable)

<!-- Either: -->
- [ ] There are tests for these changes OR
- [x] These changes do not require tests because tests already exist for these components. I ran `cargo test` in `net`, `net_traits`, `layout`, and `script` successfully.

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

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5 files changed, 102 insertions, 139 deletions

diff --git a/components/script/canvas_state.rs b/components/script/canvas_state.rs
index d0dca9b2d15..2376d6f8d85 100644
--- a/components/script/canvas_state.rs
+++ b/components/script/canvas_state.rs
@@ -38,12 +38,7 @@ use euclid::{
     vec2,
 };
 use ipc_channel::ipc::{self, IpcSender};
-use net_traits::image_cache::CanRequestImages;
-use net_traits::image_cache::ImageCache;
-use net_traits::image_cache::ImageOrMetadataAvailable;
-use net_traits::image_cache::ImageResponse;
-use net_traits::image_cache::ImageState;
-use net_traits::image_cache::UsePlaceholder;
+use net_traits::image_cache::{ImageCache, ImageResponse};
 use net_traits::request::CorsSettings;
 use pixels::PixelFormat;
 use profile_traits::ipc as profiled_ipc;
@@ -261,19 +256,12 @@ impl CanvasState {
         url: ServoUrl,
         cors_setting: Option<CorsSettings>,
     ) -> ImageResponse {
-        let response = self.image_cache.find_image_or_metadata(
-            url.clone(),
-            self.origin.clone(),
-            cors_setting,
-            UsePlaceholder::No,
-            CanRequestImages::No,
-        );
-        match response {
-            Ok(ImageOrMetadataAvailable::ImageAvailable(image, url)) => {
-                ImageResponse::Loaded(image, url)
-            },
-            Err(ImageState::Pending(_)) => ImageResponse::None,
-            _ => {
+        match self
+            .image_cache
+            .get_image(url.clone(), self.origin.clone(), cors_setting)
+        {
+            Some(image) => ImageResponse::Loaded(image, url),
+            None => {
                 // Rather annoyingly, we get the same response back from
                 // A load which really failed and from a load which hasn't started yet.
                 self.missing_image_urls.borrow_mut().push(url);
diff --git a/components/script/dom/htmlcanvaselement.rs b/components/script/dom/htmlcanvaselement.rs
index d5327e27dea..9e04585168c 100644
--- a/components/script/dom/htmlcanvaselement.rs
+++ b/components/script/dom/htmlcanvaselement.rs
@@ -432,8 +432,7 @@ impl<'a> From<&'a WebGLContextAttributes> for GLContextAttributes {
 
 pub mod utils {
     use crate::dom::window::Window;
-    use net_traits::image_cache::CanRequestImages;
-    use net_traits::image_cache::{ImageOrMetadataAvailable, ImageResponse, UsePlaceholder};
+    use net_traits::image_cache::ImageResponse;
     use net_traits::request::CorsSettings;
     use servo_url::ServoUrl;
 
@@ -443,18 +442,15 @@ pub mod utils {
         cors_setting: Option<CorsSettings>,
     ) -> ImageResponse {
         let image_cache = window.image_cache();
-        let response = image_cache.find_image_or_metadata(
-            url.into(),
+        let result = image_cache.get_image(
+            url.clone(),
             window.origin().immutable().clone(),
             cors_setting,
-            UsePlaceholder::No,
-            CanRequestImages::No,
         );
-        match response {
-            Ok(ImageOrMetadataAvailable::ImageAvailable(image, url)) => {
-                ImageResponse::Loaded(image, url)
-            },
-            _ => ImageResponse::None,
+
+        match result {
+            Some(image) => ImageResponse::Loaded(image, url),
+            None => ImageResponse::None,
         }
     }
 }
diff --git a/components/script/dom/htmlimageelement.rs b/components/script/dom/htmlimageelement.rs
index b5f20784c8e..052b622bb9f 100644
--- a/components/script/dom/htmlimageelement.rs
+++ b/components/script/dom/htmlimageelement.rs
@@ -43,7 +43,7 @@ use crate::dom::values::UNSIGNED_LONG_MAX;
 use crate::dom::virtualmethods::VirtualMethods;
 use crate::dom::window::Window;
 use crate::fetch::create_a_potential_cors_request;
-use crate::image_listener::{add_cache_listener_for_element, ImageCacheListener};
+use crate::image_listener::{generate_cache_listener_for_element, ImageCacheListener};
 use crate::microtask::{Microtask, MicrotaskRunnable};
 use crate::network_listener::{self, NetworkListener, PreInvoke, ResourceTimingListener};
 use crate::script_thread::ScriptThread;
@@ -54,13 +54,15 @@ use dom_struct::dom_struct;
 use euclid::Point2D;
 use html5ever::{LocalName, Prefix, QualName};
 use ipc_channel::ipc;
+use ipc_channel::ipc::IpcSender;
 use ipc_channel::router::ROUTER;
 use mime::{self, Mime};
 use msg::constellation_msg::PipelineId;
 use net_traits::image::base::{Image, ImageMetadata};
-use net_traits::image_cache::UsePlaceholder;
-use net_traits::image_cache::{CanRequestImages, CorsStatus, ImageCache, ImageOrMetadataAvailable};
-use net_traits::image_cache::{ImageResponder, ImageResponse, ImageState, PendingImageId};
+use net_traits::image_cache::{
+    CanRequestImages, CorsStatus, ImageCache, ImageCacheResult, ImageOrMetadataAvailable,
+    ImageResponse, PendingImageId, PendingImageResponse, UsePlaceholder,
+};
 use net_traits::request::{CorsSettings, Destination, Initiator, RequestBuilder};
 use net_traits::{FetchMetadata, FetchResponseListener, FetchResponseMsg, NetworkError};
 use net_traits::{ReferrerPolicy, ResourceFetchTiming, ResourceTimingType};
@@ -317,35 +319,27 @@ impl HTMLImageElement {
     fn fetch_image(&self, img_url: &ServoUrl) {
         let window = window_from_node(self);
         let image_cache = window.image_cache();
-        let response = image_cache.find_image_or_metadata(
-            img_url.clone().into(),
+        let sender = generate_cache_listener_for_element(self);
+        let cache_result = image_cache.track_image(
+            img_url.clone(),
             window.origin().immutable().clone(),
             cors_setting_for_element(self.upcast()),
+            sender,
             UsePlaceholder::Yes,
             CanRequestImages::Yes,
         );
-        match response {
-            Ok(ImageOrMetadataAvailable::ImageAvailable(image, url)) => {
-                self.process_image_response(ImageResponse::Loaded(image, url));
-            },
 
-            Ok(ImageOrMetadataAvailable::MetadataAvailable(m)) => {
-                self.process_image_response(ImageResponse::MetadataLoaded(m));
+        match cache_result {
+            ImageCacheResult::Available(ImageOrMetadataAvailable::ImageAvailable(image, url)) => {
+                self.process_image_response(ImageResponse::Loaded(image, url))
             },
-
-            Err(ImageState::Pending(id)) => {
-                add_cache_listener_for_element(image_cache, id, self);
+            ImageCacheResult::Available(ImageOrMetadataAvailable::MetadataAvailable(m)) => {
+                self.process_image_response(ImageResponse::MetadataLoaded(m))
             },
-
-            Err(ImageState::LoadError) => {
-                self.process_image_response(ImageResponse::None);
-            },
-
-            Err(ImageState::NotRequested(id)) => {
-                add_cache_listener_for_element(image_cache, id, self);
-                self.fetch_request(img_url, id);
-            },
-        }
+            ImageCacheResult::Pending(_) => (),
+            ImageCacheResult::ReadyForRequest(id) => self.fetch_request(img_url, id),
+            ImageCacheResult::LoadError => self.process_image_response(ImageResponse::None),
+        };
     }
 
     fn fetch_request(&self, img_url: &ServoUrl, id: PendingImageId) {
@@ -943,14 +937,13 @@ impl HTMLImageElement {
         if let Some(src) = selected_source {
             if let Ok(img_url) = base_url.join(&src) {
                 let image_cache = window.image_cache();
-                let response = image_cache.find_image_or_metadata(
-                    img_url.clone().into(),
+                let response = image_cache.get_image(
+                    img_url.clone(),
                     window.origin().immutable().clone(),
                     cors_setting_for_element(self.upcast()),
-                    UsePlaceholder::No,
-                    CanRequestImages::No,
                 );
-                if let Ok(ImageOrMetadataAvailable::ImageAvailable(image, url)) = response {
+
+                if let Some(image) = response {
                     // Cancel any outstanding tasks that were queued before the src was
                     // set on this element.
                     self.generation.set(self.generation.get() + 1);
@@ -963,7 +956,7 @@ impl HTMLImageElement {
                     self.abort_request(State::CompletelyAvailable, ImageRequestPhase::Current);
                     self.abort_request(State::Unavailable, ImageRequestPhase::Pending);
                     let mut current_request = self.current_request.borrow_mut();
-                    current_request.final_url = Some(url);
+                    current_request.final_url = Some(img_url.clone());
                     current_request.image = Some(image.clone());
                     current_request.metadata = Some(metadata);
                     // Step 6.3.6
@@ -1010,13 +1003,12 @@ impl HTMLImageElement {
     /// Step 2-12 of https://html.spec.whatwg.org/multipage/#img-environment-changes
     fn react_to_environment_changes_sync_steps(&self, generation: u32) {
         // TODO reduce duplicacy of this code
-        fn add_cache_listener_for_element(
-            image_cache: Arc<dyn ImageCache>,
-            id: PendingImageId,
+
+        fn generate_cache_listener_for_element(
             elem: &HTMLImageElement,
             selected_source: String,
             selected_pixel_density: f64,
-        ) {
+        ) -> IpcSender<PendingImageResponse> {
             let trusted_node = Trusted::new(elem);
             let (responder_sender, responder_receiver) = ipc::channel().unwrap();
 
@@ -1025,27 +1017,30 @@ impl HTMLImageElement {
                 .task_manager()
                 .networking_task_source_with_canceller();
             let generation = elem.generation.get();
-            ROUTER.add_route(responder_receiver.to_opaque(), Box::new(move |message| {
-                debug!("Got image {:?}", message);
-                // Return the image via a message to the script thread, which marks
-                // the element as dirty and triggers a reflow.
-                let element = trusted_node.clone();
-                let image = message.to().unwrap();
-                let selected_source_clone = selected_source.clone();
-                let _ = task_source.queue_with_canceller(
-                    task!(process_image_response_for_environment_change: move || {
-                        let element = element.root();
-                        // Ignore any image response for a previous request that has been discarded.
-                        if generation == element.generation.get() {
-                            element.process_image_response_for_environment_change(image,
-                                USVString::from(selected_source_clone), generation, selected_pixel_density);
-                        }
-                    }),
-                    &canceller,
-                );
-            }));
+            ROUTER.add_route(
+                responder_receiver.to_opaque(),
+                Box::new(move |message| {
+                    debug!("Got image {:?}", message);
+                    // Return the image via a message to the script thread, which marks
+                    // the element as dirty and triggers a reflow.
+                    let element = trusted_node.clone();
+                    let image = message.to().unwrap();
+                    let selected_source_clone = selected_source.clone();
+                    let _ = task_source.queue_with_canceller(
+                        task!(process_image_response_for_environment_change: move || {
+                            let element = element.root();
+                            // Ignore any image response for a previous request that has been discarded.
+                            if generation == element.generation.get() {
+                                element.process_image_response_for_environment_change(image,
+                                    USVString::from(selected_source_clone), generation, selected_pixel_density);
+                            }
+                        }),
+                        &canceller,
+                    );
+                }),
+            );
 
-            image_cache.add_listener(id, ImageResponder::new(responder_sender, id));
+            responder_sender
         }
 
         let elem = self.upcast::<Element>();
@@ -1099,25 +1094,32 @@ impl HTMLImageElement {
 
         let window = window_from_node(self);
         let image_cache = window.image_cache();
+
         // Step 14
-        let response = image_cache.find_image_or_metadata(
-            img_url.clone().into(),
+        let sender = generate_cache_listener_for_element(
+            self,
+            selected_source.0.clone(),
+            selected_pixel_density,
+        );
+        let cache_result = image_cache.track_image(
+            img_url.clone(),
             window.origin().immutable().clone(),
             cors_setting_for_element(self.upcast()),
+            sender,
             UsePlaceholder::No,
             CanRequestImages::Yes,
         );
-        match response {
-            Ok(ImageOrMetadataAvailable::ImageAvailable(_image, _url)) => {
+
+        match cache_result {
+            ImageCacheResult::Available(ImageOrMetadataAvailable::ImageAvailable(_image, _url)) => {
                 // Step 15
                 self.finish_reacting_to_environment_change(
                     selected_source,
                     generation,
                     selected_pixel_density,
-                );
+                )
             },
-
-            Ok(ImageOrMetadataAvailable::MetadataAvailable(m)) => {
+            ImageCacheResult::Available(ImageOrMetadataAvailable::MetadataAvailable(m)) => {
                 self.process_image_response_for_environment_change(
                     ImageResponse::MetadataLoaded(m),
                     selected_source,
@@ -1125,18 +1127,7 @@ impl HTMLImageElement {
                     selected_pixel_density,
                 );
             },
-
-            Err(ImageState::Pending(id)) => {
-                add_cache_listener_for_element(
-                    image_cache.clone(),
-                    id,
-                    self,
-                    selected_source.0,
-                    selected_pixel_density,
-                );
-            },
-
-            Err(ImageState::LoadError) => {
+            ImageCacheResult::LoadError => {
                 self.process_image_response_for_environment_change(
                     ImageResponse::None,
                     selected_source,
@@ -1144,17 +1135,8 @@ impl HTMLImageElement {
                     selected_pixel_density,
                 );
             },
-
-            Err(ImageState::NotRequested(id)) => {
-                add_cache_listener_for_element(
-                    image_cache,
-                    id,
-                    self,
-                    selected_source.0,
-                    selected_pixel_density,
-                );
-                self.fetch_request(&img_url, id);
-            },
+            ImageCacheResult::ReadyForRequest(id) => self.fetch_request(&img_url, id),
+            ImageCacheResult::Pending(_) => (),
         }
     }
 
diff --git a/components/script/dom/htmlvideoelement.rs b/components/script/dom/htmlvideoelement.rs
index f83c05bbe0a..a890b49af72 100644
--- a/components/script/dom/htmlvideoelement.rs
+++ b/components/script/dom/htmlvideoelement.rs
@@ -19,16 +19,17 @@ use crate::dom::node::{document_from_node, window_from_node, Node};
 use crate::dom::performanceresourcetiming::InitiatorType;
 use crate::dom::virtualmethods::VirtualMethods;
 use crate::fetch::FetchCanceller;
-use crate::image_listener::{add_cache_listener_for_element, ImageCacheListener};
+use crate::image_listener::{generate_cache_listener_for_element, ImageCacheListener};
 use crate::network_listener::{self, NetworkListener, PreInvoke, ResourceTimingListener};
 use dom_struct::dom_struct;
 use euclid::default::Size2D;
 use html5ever::{LocalName, Prefix};
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
-use net_traits::image_cache::UsePlaceholder;
-use net_traits::image_cache::{CanRequestImages, ImageCache, ImageOrMetadataAvailable};
-use net_traits::image_cache::{ImageResponse, ImageState, PendingImageId};
+use net_traits::image_cache::{
+    CanRequestImages, ImageCache, ImageCacheResult, ImageOrMetadataAvailable, ImageResponse,
+    PendingImageId, UsePlaceholder,
+};
 use net_traits::request::{CredentialsMode, Destination, RequestBuilder};
 use net_traits::{
     CoreResourceMsg, FetchChannels, FetchMetadata, FetchResponseListener, FetchResponseMsg,
@@ -155,27 +156,23 @@ impl HTMLVideoElement {
         // network activity as possible.
         let window = window_from_node(self);
         let image_cache = window.image_cache();
-        let response = image_cache.find_image_or_metadata(
-            poster_url.clone().into(),
+        let sender = generate_cache_listener_for_element(self);
+        let cache_result = image_cache.track_image(
+            poster_url.clone(),
             window.origin().immutable().clone(),
             None,
+            sender,
             UsePlaceholder::No,
             CanRequestImages::Yes,
         );
-        match response {
-            Ok(ImageOrMetadataAvailable::ImageAvailable(image, url)) => {
-                self.process_image_response(ImageResponse::Loaded(image, url));
-            },
 
-            Err(ImageState::Pending(id)) => {
-                add_cache_listener_for_element(image_cache, id, self);
+        match cache_result {
+            ImageCacheResult::Available(ImageOrMetadataAvailable::ImageAvailable(img, url)) => {
+                self.process_image_response(ImageResponse::Loaded(img, url));
             },
-
-            Err(ImageState::NotRequested(id)) => {
-                add_cache_listener_for_element(image_cache, id, self);
-                self.do_fetch_poster_frame(poster_url, id, cancel_receiver);
+            ImageCacheResult::ReadyForRequest(id) => {
+                self.do_fetch_poster_frame(poster_url, id, cancel_receiver)
             },
-
             _ => (),
         }
     }
diff --git a/components/script/image_listener.rs b/components/script/image_listener.rs
index fffaf3acc03..7bf81c80d76 100644
--- a/components/script/image_listener.rs
+++ b/components/script/image_listener.rs
@@ -8,20 +8,20 @@ use crate::dom::bindings::reflector::DomObject;
 use crate::dom::node::{window_from_node, Node};
 use crate::task_source::TaskSource;
 use ipc_channel::ipc;
+use ipc_channel::ipc::IpcSender;
 use ipc_channel::router::ROUTER;
-use net_traits::image_cache::{ImageCache, ImageResponder, ImageResponse, PendingImageId};
-use std::sync::Arc;
+use net_traits::image_cache::{ImageResponse, PendingImageResponse};
 
 pub trait ImageCacheListener {
     fn generation_id(&self) -> u32;
     fn process_image_response(&self, response: ImageResponse);
 }
 
-pub fn add_cache_listener_for_element<T: ImageCacheListener + DerivedFrom<Node> + DomObject>(
-    image_cache: Arc<dyn ImageCache>,
-    id: PendingImageId,
+pub fn generate_cache_listener_for_element<
+    T: ImageCacheListener + DerivedFrom<Node> + DomObject,
+>(
     elem: &T,
-) {
+) -> IpcSender<PendingImageResponse> {
     let trusted_node = Trusted::new(elem);
     let (responder_sender, responder_receiver) = ipc::channel().unwrap();
 
@@ -49,5 +49,5 @@ pub fn add_cache_listener_for_element<T: ImageCacheListener + DerivedFrom<Node>
         }),
     );
 
-    image_cache.add_listener(id, ImageResponder::new(responder_sender, id));
+    responder_sender
 }