From 8333615072318b02cd846259a794cf28558b9e86 Mon Sep 17 00:00:00 2001
From: Vanadiae <vanadiae35@gmail.com>
Date: Tue, 5 Aug 2025 14:41:32 +0200
Subject: [PATCH] Fix memory leak when `forget_image` is called while loading
 (#7380)

This is the same issue that was fixed for the http bytes loader in
239ade9a59692f23a6b1d779a9c2631cf774896a

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

----------------

Funnily, [this
comment](https://github.com/emilk/egui/issues/3747#issuecomment-1872192997)
describes exactly how I encountered this issue:

> That assert is wrong if something calls forget between the start of
the request and the end of it.

I'm displaying lots of images in a scrolling grid (20 or so visible at a
time). It seems like image textures are never freed up automatically so
it stacks up a lot meaning I have to unload the image textures manually
with `egui::Context::forget_image()` in each `eframe::App::update()`
call for the images that are no longer shown when scrolling.

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
---
 crates/egui_extras/src/loaders/ehttp_loader.rs | 16 +++++++++++++---
 crates/egui_extras/src/loaders/image_loader.rs | 16 +++++++++-------
 2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/crates/egui_extras/src/loaders/ehttp_loader.rs b/crates/egui_extras/src/loaders/ehttp_loader.rs
index abe5d96f..7310cc6e 100644
--- a/crates/egui_extras/src/loaders/ehttp_loader.rs
+++ b/crates/egui_extras/src/loaders/ehttp_loader.rs
@@ -94,9 +94,19 @@ impl BytesLoader for EhttpLoader {
                             Err(format!("Failed to load {uri:?}"))
                         }
                     };
-                    log::trace!("finished loading {uri:?}");
-                    cache.lock().insert(uri, Poll::Ready(result));
-                    ctx.request_repaint();
+                    let mut cache = cache.lock();
+                    if let std::collections::hash_map::Entry::Occupied(mut entry) =
+                        cache.entry(uri.clone())
+                    {
+                        let entry = entry.get_mut();
+                        *entry = Poll::Ready(result);
+                        ctx.request_repaint();
+                        log::trace!("Finished loading {uri:?}");
+                    } else {
+                        log::trace!(
+                            "Canceled loading {uri:?}\nNote: This can happen if `forget_image` is called while the image is still loading."
+                        );
+                    }
                 }
             });
 
diff --git a/crates/egui_extras/src/loaders/image_loader.rs b/crates/egui_extras/src/loaders/image_loader.rs
index 18e1e483..82df87b3 100644
--- a/crates/egui_extras/src/loaders/image_loader.rs
+++ b/crates/egui_extras/src/loaders/image_loader.rs
@@ -100,14 +100,16 @@ impl ImageLoader for ImageCrateLoader {
                         let result = crate::image::load_image_bytes(&bytes)
                             .map(Arc::new)
                             .map_err(|err| err.to_string());
-                        log::trace!("ImageLoader - finished loading {uri:?}");
-                        let prev = cache.lock().insert(uri, Poll::Ready(result));
-                        debug_assert!(
-                            matches!(prev, Some(Poll::Pending)),
-                            "Expected previous state to be Pending"
-                        );
+                        let mut cache = cache.lock();
 
-                        ctx.request_repaint();
+                        if let std::collections::hash_map::Entry::Occupied(mut entry) = cache.entry(uri.clone()) {
+                            let entry = entry.get_mut();
+                            *entry = Poll::Ready(result);
+                            ctx.request_repaint();
+                            log::trace!("ImageLoader - finished loading {uri:?}");
+                        } else {
+                            log::trace!("ImageLoader - canceled loading {uri:?}\nNote: This can happen if `forget_image` is called while the image is still loading.");
+                        }
                     }
                 })
                 .expect("failed to spawn thread");