Markdown pictures: freed with their elements, glyphs whole, failures keep the source, file URLs parsed, Mermaid labels in Ely's ink

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/primitives/held.rs

@@ -0,0 +1,53 @@
+use std::sync::Arc;
+
+use gpui::{App, Asset, ElementId, RenderImage, Window};
+
+/// An element's asset; freed on change or when it leaves.
+pub(crate) struct Held<A: Asset> {
+    source: Option<A::Source>,
+    image: Option<Arc<RenderImage>>,
+}
+
+impl<A: Asset> Held<A> {
+    fn free(&mut self, cx: &mut App) {
+        if let Some(source) = self.source.take() {
+            cx.remove_asset::<A>(&source);
+        }
+        if let Some(image) = self.image.take() {
+            // The window may be drawing; free after it.
+            cx.defer(move |cx| cx.drop_image(image, None));
+        }
+    }
+}
+
+/// `source` as `A` for element `id`; the previous one freed.
+pub(crate) fn hold<A: Asset>(
+    id: impl Into<ElementId>,
+    source: &A::Source,
+    image: impl Fn(&A::Output) -> Option<Arc<RenderImage>>,
+    window: &mut Window,
+    cx: &mut App,
+) -> Option<A::Output>
+where
+    A::Source: PartialEq,
+{
+    let held = window.use_keyed_state(id, cx, |_, cx| {
+        cx.on_release(|held: &mut Held<A>, cx| held.free(cx))
+            .detach();
+        Held {
+            source: None,
+            image: None,
+        }
+    });
+    let loaded = window.use_asset::<A>(source, cx);
+    held.update(cx, |held, cx| {
+        if held.source.as_ref() != Some(source) {
+            held.free(cx);
+            held.source = Some(source.clone());
+        }
+        if let Some(loaded) = &loaded {
+            held.image = image(loaded);
+        }
+    });
+    loaded
+}

src/primitives/mod.rs

@@ -5,6 +5,7 @@ mod divider;
 mod files;
 mod focus;
 mod ghost;
+mod held;
 mod icon;
 mod image;
 mod layer;
@@ -28,6 +29,7 @@ pub(crate) use focus::{
 };
 pub use focus::{FocusNext, FocusPrev, FocusRing, FocusScope};
 pub use ghost::DragGhost;
+pub(crate) use held::hold;
 pub use icon::{Icon, IconName};
 pub use image::Image;
 pub(crate) use image::{checked_ratio, framed};