pub fn handles(&self) -> impl Iterator<Item = (EguiTextureId, AssetId<Image>)> + '_ {
        self.egui_textures
            .0
            .iter()
            .map(|(&(window, texture_id), managed_tex)| {
                (
                    EguiTextureId::Managed(MainEntity::from(window), texture_id),
                    managed_tex.id(),
                )
            })
            .chain(
                self.user_textures
                    .textures
                    .iter()
                    .map(|(handle, id)| (EguiTextureId::User(*id), handle.id())),
            )
    }
Returns an iterator over all textures (both Egui and Bevy managed).
src/render_systems.rs