Honor standard image source selection

crates/obscura-js/js/bootstrap.js

@@ -4216,8 +4216,7 @@ class HTMLImageElement extends Element {
   setAttribute(name, value) {
     const normalized = String(name).toLowerCase();
     super.setAttribute(name, value);
-    if (normalized === "src" || normalized === "srcset" || normalized === "sizes"
-        || normalized === "data-src" || normalized === "data-srcset") {
+    if (normalized === "src" || normalized === "srcset" || normalized === "sizes") {
       this._imageSourceChanged();
     }
     else if ((normalized === "onload" || normalized === "onerror")
@@ -4227,8 +4226,7 @@ class HTMLImageElement extends Element {
   removeAttribute(name) {
     const normalized = String(name).toLowerCase();
     super.removeAttribute(name);
-    if (normalized === "src" || normalized === "srcset" || normalized === "sizes"
-        || normalized === "data-src" || normalized === "data-srcset") {
+    if (normalized === "src" || normalized === "srcset" || normalized === "sizes") {
       this._imageSourceChanged();
     }
   }

crates/obscura-js/src/runtime.rs

@@ -2683,7 +2683,7 @@ mod tests {
                 "1px", "2px", "3px", "4px",
                 "5px", "2px", "rgb(70, 80, 90)",
                 "column", "wrap", "center",
-                "space-between", "6px", "9px", "translate(3px, 4px)"
+                "space-between", "6px", "9px", "matrix(1, 0, 0, 1, 3, 4)"
             ])
         );
 
@@ -5600,6 +5600,125 @@ mod tests {
             .unwrap()
     }
 
+    #[cfg(feature = "render")]
+    #[tokio::test(flavor = "current_thread")]
+    async fn parser_image_data_src_mutation_does_not_restart_lifecycle() {
+        let requests = std::sync::Arc::new(std::sync::Mutex::new(Vec::new()));
+        let seen = requests.clone();
+        let png = two_by_three_png();
+        let mut rt = parser_image_runtime(
+            r#"<img id="image" src="real.png" data-src="deferred.png">"#,
+            move |url: &str| {
+                seen.lock().unwrap().push(url.to_string());
+                Some(png.clone())
+            },
+        );
+        rt.execute_script(
+            "observe-data-src-mutation",
+            r#"
+                globalThis.__dataSrcEvents = [];
+                const image = document.getElementById("image");
+                image.addEventListener("load", () => __dataSrcEvents.push(image.currentSrc));
+                void image.complete;
+            "#,
+        )
+        .unwrap();
+        rt.run_event_loop_bounded(100).await.unwrap();
+        assert_eq!(
+            rt.evaluate("[image.complete, image.currentSrc, __dataSrcEvents]")
+                .unwrap(),
+            serde_json::json!([
+                true,
+                "http://example.com/page/real.png",
+                ["http://example.com/page/real.png"]
+            ])
+        );
+
+        rt.execute_script(
+            "mutate-non-source-data-attribute",
+            r#"
+                image.dataset.src = "ignored.png";
+                globalThis.__afterDataSrcMutation = [image.complete, image.currentSrc];
+            "#,
+        )
+        .unwrap();
+        rt.run_event_loop_bounded(100).await.unwrap();
+        assert_eq!(
+            rt.evaluate("[__afterDataSrcMutation, __dataSrcEvents]")
+                .unwrap(),
+            serde_json::json!([
+                [true, "http://example.com/page/real.png"],
+                ["http://example.com/page/real.png"]
+            ])
+        );
+        assert_eq!(
+            *requests.lock().unwrap(),
+            vec!["http://example.com/page/real.png".to_string()]
+        );
+    }
+
+    #[cfg(feature = "render")]
+    #[tokio::test(flavor = "current_thread")]
+    async fn parser_image_data_src_is_inert_until_script_assigns_src() {
+        let requests = std::sync::Arc::new(std::sync::Mutex::new(Vec::new()));
+        let seen = requests.clone();
+        let png = two_by_three_png();
+        let mut rt = parser_image_runtime(
+            r#"<img id="image" data-src="promoted.png">"#,
+            move |url: &str| {
+                seen.lock().unwrap().push(url.to_string());
+                Some(png.clone())
+            },
+        );
+        assert_eq!(
+            rt.evaluate(
+                r#"(() => {
+                    globalThis.image = document.getElementById("image");
+                    globalThis.__promotedEvents = [];
+                    image.addEventListener("load", () => __promotedEvents.push(image.currentSrc));
+                    return [image.src, image.currentSrc, image.complete,
+                            image.naturalWidth, image.naturalHeight];
+                })()"#,
+            )
+            .unwrap(),
+            serde_json::json!(["", "", true, 0, 0])
+        );
+        rt.run_event_loop_bounded(100).await.unwrap();
+        assert!(requests.lock().unwrap().is_empty());
+
+        rt.execute_script(
+            "promote-data-src-through-page-script",
+            r#"
+                image.src = image.dataset.src;
+                globalThis.__afterSrcPromotion = [image.complete, image.currentSrc];
+            "#,
+        )
+        .unwrap();
+        assert_eq!(
+            rt.evaluate("__afterSrcPromotion").unwrap(),
+            serde_json::json!([false, "http://example.com/page/promoted.png"])
+        );
+        rt.run_event_loop_bounded(100).await.unwrap();
+        assert_eq!(
+            rt.evaluate(
+                "[image.complete, image.naturalWidth, image.naturalHeight, \
+                  image.currentSrc, __promotedEvents]"
+            )
+            .unwrap(),
+            serde_json::json!([
+                true,
+                2,
+                3,
+                "http://example.com/page/promoted.png",
+                ["http://example.com/page/promoted.png"]
+            ])
+        );
+        assert_eq!(
+            *requests.lock().unwrap(),
+            vec!["http://example.com/page/promoted.png".to_string()]
+        );
+    }
+
     #[cfg(feature = "render")]
     #[tokio::test(flavor = "current_thread")]
     async fn parser_image_lifecycle_uses_shared_render_resource() {

crates/obscura-render/src/paint.rs

@@ -5166,12 +5166,10 @@ fn collect_content_image_intrinsics(
 
 /// Choose the URL to paint for an `<img>`. Browsers do not use `src` alone:
 /// a wrapping `<picture>`'s `<source>`s, `srcset`, and `sizes` select by
-/// type/media/viewport/density, and lazy-loaded images keep the real URL in
-/// `data-src`/`data-srcset` with `src` holding a 1x1 placeholder until script
-/// swaps it in. Since obscura may not have run the site's lazy-load script,
-/// resolve the same URL the browser would end up with: a matching `<picture>`
-/// source first, then a real candidate from `srcset`/`data-srcset`, then a
-/// non-inline `src`/`data-*` URL, then any `src` (an inlined data: image).
+/// type/media/viewport/density. Non-standard lazy-loader attributes such as
+/// `data-src` are deliberately ignored until page script copies them into the
+/// real `src`/`srcset`; promoting them here changes `currentSrc`, lifecycle
+/// events, and resource timing relative to browsers.
 fn resolve_img_url(
     tree: &DomTree,
     nid: obscura_dom::tree::NodeId,
@@ -5184,32 +5182,17 @@ fn resolve_img_url(
         return Some(pick);
     }
     let sizes = node.get_attribute("sizes");
-    for a in ["srcset", "data-srcset"] {
-        if let Some(v) = node.get_attribute(a) {
+    if let Some(v) = node.get_attribute("srcset") {
         if let Some(pick) = best_srcset_candidate(v, sizes, viewport) {
             return Some(pick);
         }
     }
-    }
-    let url_attrs = ["src", "data-src", "data-lazy-src", "data-original", "data-fallback-src", "data-lazy"];
-    // A non-inline URL first (a data: src is usually the lazy-load placeholder).
-    for a in url_attrs {
-        if let Some(v) = node.get_attribute(a) {
-            let v = v.trim();
-            if !v.is_empty() && !v.starts_with("data:") {
-                return Some((v.to_string(), 1.0));
-            }
-        }
-    }
-    // Otherwise fall back to whatever is there (an inlined data: image).
-    for a in url_attrs {
-        if let Some(v) = node.get_attribute(a) {
+    if let Some(v) = node.get_attribute("src") {
         let v = v.trim();
         if !v.is_empty() {
             return Some((v.to_string(), 1.0));
         }
     }
-    }
     None
 }
 
@@ -6538,6 +6521,65 @@ mod tests {
         );
     }
 
+    #[test]
+    fn data_source_attributes_are_not_image_candidates_or_fetches() {
+        let tree = parse_html(
+            r#"<img id="lazy" data-src="real.png"
+                     data-srcset="small.png 1x, large.png 2x"
+                     data-lazy-src="other.png" data-original="original.png">"#,
+        );
+        let lazy = tree.get_element_by_id("lazy").expect("lazy image");
+        let calls = std::sync::Arc::new(std::sync::atomic::AtomicUsize::new(0));
+        let loader_calls = calls.clone();
+        let mut resources = RenderResourceCache::with_loader(move |_url: &str| {
+            loader_calls.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+            None
+        });
+
+        assert_eq!(resolve_img_url(&tree, lazy, (800.0, 600.0)), None);
+        assert_eq!(
+            resources.image_element_metadata(
+                &tree,
+                lazy,
+                (800.0, 600.0),
+                Some("https://example.test/page"),
+            ),
+            None
+        );
+        assert_eq!(calls.load(std::sync::atomic::Ordering::SeqCst), 0);
+    }
+
+    #[test]
+    fn data_uri_src_remains_selected_when_data_src_is_present() {
+        const PLACEHOLDER: &str = "data:image/svg+xml,%3Csvg%20xmlns=%22http://www.w3.org/2000/svg%22%20width=%221%22%20height=%221%22/%3E";
+        let tree = parse_html(&format!(
+            r#"<img id="lazy" src="{PLACEHOLDER}" data-src="real.png">"#
+        ));
+        let lazy = tree.get_element_by_id("lazy").expect("lazy image");
+        let calls = std::sync::Arc::new(std::sync::atomic::AtomicUsize::new(0));
+        let loader_calls = calls.clone();
+        let mut resources = RenderResourceCache::with_loader(move |_url: &str| {
+            loader_calls.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+            None
+        });
+
+        assert_eq!(
+            resolve_img_url(&tree, lazy, (800.0, 600.0)),
+            Some((PLACEHOLDER.to_string(), 1.0))
+        );
+        let metadata = resources
+            .image_element_metadata(
+                &tree,
+                lazy,
+                (800.0, 600.0),
+                Some("https://example.test/page"),
+            )
+            .expect("selected placeholder");
+        assert_eq!(metadata.0, PLACEHOLDER);
+        assert_eq!(metadata.2, Some((1.0, 1.0)));
+        assert_eq!(calls.load(std::sync::atomic::Ordering::SeqCst), 0);
+    }
+
     #[test]
     fn enabled_bmp_and_ico_formats_have_metadata_and_full_raster_decode() {
         use std::io::Cursor;