Match image file extensions case-insensitively (#8430)

`image.PNG` and `cat.SVG` were not recognized as images.

Adds `egui::load::has_extension(uri, extension)`, which ignores ASCII
case and any `#fragment`, and uses it for the `.svg`, `.gif`, `.webp`
and `.png` checks.

Note: gif/webp URIs like `a#b.gif` no longer match, since the fragment
is now excluded.

* [x] I have followed the instructions in the PR template

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

crates/eframe/src/native/glow_integration.rs

@@ -1720,7 +1720,7 @@ fn save_screenshot_and_exit(
     screen_size_in_pixels: [u32; 2],
 ) {
     assert!(
-        path.ends_with(".png"),
+        egui::load::has_extension(path, "png"),
         "Expected EFRAME_SCREENSHOT_TO to end with '.png', got {path:?}"
     );
     let screenshot = painter.read_screen_rgba(screen_size_in_pixels);

crates/egui/src/load.rs

@@ -306,6 +306,19 @@ macro_rules! generate_loader_id {
 }
 pub use crate::generate_loader_id;
 
+/// Does the given URI end with the given file extension?
+///
+/// The comparison ignores ASCII case and any `#fragment` at the end of the URI,
+/// so `has_extension("cat.GIF#frame=2", "gif")` is `true`.
+///
+/// This is useful when implementing an [`ImageLoader`].
+pub fn has_extension(uri: &str, extension: &str) -> bool {
+    let path = uri.split('#').next().unwrap_or(uri);
+    std::path::Path::new(path)
+        .extension()
+        .is_some_and(|found| found.eq_ignore_ascii_case(extension))
+}
+
 pub type BytesLoadResult = Result<BytesPoll>;
 
 /// Represents a loader capable of loading raw unstructured bytes from somewhere,
@@ -639,3 +652,14 @@ impl Loaders {
         }
     }
 }
+
+#[test]
+fn test_has_extension() {
+    assert!(has_extension("cat.svg", "svg"));
+    assert!(has_extension("cat.SVG", "svg"));
+    assert!(has_extension("http://example.com/cat.gif#frame=2", "gif"));
+    assert!(!has_extension("cat.svg.png", "svg"));
+    assert!(!has_extension("svg", "svg"));
+    assert!(!has_extension("cat.jpeg", "jpg"));
+    assert!(!has_extension("cat.svg?v=1", "svg"));
+}

crates/egui/src/load/texture_loader.rs

@@ -150,5 +150,5 @@ impl TextureLoader for DefaultTextureLoader {
 }
 
 fn is_svg(uri: &str) -> bool {
-    uri.ends_with(".svg")
+    super::has_extension(uri, "svg")
 }

crates/egui/src/widgets/image.rs

@@ -934,7 +934,7 @@ fn animated_image_frame_index(ctx: &Context, uri: &str) -> usize {
 
 /// Checks if uri is a gif file
 fn is_gif_uri(uri: &str) -> bool {
-    uri.ends_with(".gif") || uri.contains(".gif#")
+    crate::load::has_extension(uri, "gif")
 }
 
 /// Checks if bytes are gifs
@@ -944,7 +944,7 @@ pub fn has_gif_magic_header(bytes: &[u8]) -> bool {
 
 /// Checks if uri is a webp file
 fn is_webp_uri(uri: &str) -> bool {
-    uri.ends_with(".webp") || uri.contains(".webp#")
+    crate::load::has_extension(uri, "webp")
 }
 
 /// Checks if bytes are webp

crates/egui_extras/src/loaders/svg_loader.rs

@@ -29,7 +29,7 @@ impl SvgLoader {
 }
 
 fn is_supported(uri: &str) -> bool {
-    uri.ends_with(".svg")
+    egui::load::has_extension(uri, "svg")
 }
 
 impl Default for SvgLoader {