solitaire_data/src/theme_store_client.rs

@@ -19,6 +19,10 @@ use thiserror::Error;
 /// so downloading it is pure waste.
 pub const MAX_THEME_DOWNLOAD_BYTES: u64 = 20 * 1024 * 1024;
 
+/// Hard cap on a preview PNG download — previews are small decorative
+/// thumbnails; anything past this is a misconfigured server.
+pub const MAX_PREVIEW_BYTES: u64 = 512 * 1024;
+
 /// Errors surfaced by [`ThemeStoreClient`].
 #[derive(Debug, Error)]
 pub enum ThemeStoreError {
@@ -110,6 +114,42 @@ impl ThemeStoreClient {
         verify_archive(&bytes, entry)?;
         Ok(bytes.to_vec())
     }
+
+    /// Fetch the preview PNG the catalog advertises for `entry`.
+    ///
+    /// Returns `Http(404)` when the entry carries no `preview_url` —
+    /// the same shape the server answers with when the file is absent,
+    /// so callers only handle one "no preview" case. Previews are
+    /// decorative; unlike archives they carry no checksum, only the
+    /// [`MAX_PREVIEW_BYTES`] size cap.
+    pub async fn fetch_preview(
+        &self,
+        entry: &ThemeCatalogEntry,
+    ) -> Result<Vec<u8>, ThemeStoreError> {
+        let Some(path) = entry.preview_url.as_deref() else {
+            return Err(ThemeStoreError::Http(404));
+        };
+        let resp = self
+            .client
+            .get(format!("{}{}", self.base_url, path))
+            .send()
+            .await
+            .map_err(|e| ThemeStoreError::Network(e.to_string()))?;
+        if !resp.status().is_success() {
+            return Err(ThemeStoreError::Http(resp.status().as_u16()));
+        }
+        let bytes = resp
+            .bytes()
+            .await
+            .map_err(|e| ThemeStoreError::Network(e.to_string()))?;
+        if bytes.len() as u64 > MAX_PREVIEW_BYTES {
+            return Err(ThemeStoreError::Oversized {
+                expected: MAX_PREVIEW_BYTES,
+                got: bytes.len() as u64,
+            });
+        }
+        Ok(bytes.to_vec())
+    }
 }
 
 /// Checks downloaded `bytes` against the catalog `entry`'s declared

solitaire_engine/src/theme_store_plugin.rs

@@ -14,6 +14,9 @@
 //! filesystem-based; the plugin is gated out on wasm32 alongside
 //! `SyncPlugin`.
 
+use std::collections::HashMap;
+
+use bevy::asset::RenderAssetUsages;
 use bevy::prelude::*;
 use bevy::tasks::{AsyncComputeTaskPool, Task, futures_lite::future};
 use thiserror::Error;
@@ -105,6 +108,21 @@ struct InstallTask(Option<(String, Task<InstallResult>)>);
 #[derive(Resource, Default)]
 struct StoreBaseUrl(Option<String>);
 
+/// Decoded preview thumbnails by theme id (Phase H). Session-lifetime:
+/// previews survive closing and reopening the store, so a revisit
+/// renders instantly without refetching.
+#[derive(Resource, Default)]
+struct PreviewCache(HashMap<String, Handle<Image>>);
+
+/// One in-flight preview download: raw PNG bytes or the fetch error.
+type PreviewFetch = Task<Result<Vec<u8>, ThemeStoreError>>;
+
+/// In-flight preview downloads, one per catalog entry that advertises
+/// a `preview_url` not already in [`PreviewCache`]. `String` is the
+/// theme id the bytes belong to.
+#[derive(Resource, Default)]
+struct PreviewTasks(Vec<(String, PreviewFetch)>);
+
 // ---------------------------------------------------------------------------
 // Plugin
 // ---------------------------------------------------------------------------
@@ -118,6 +136,8 @@ impl Plugin for ThemeStorePlugin {
             .init_resource::<CatalogTask>()
             .init_resource::<InstallTask>()
             .init_resource::<StoreBaseUrl>()
+            .init_resource::<PreviewCache>()
+            .init_resource::<PreviewTasks>()
             // Esc-close reads keyboard input; register defensively so
             // the plugin works under MinimalPlugins in tests.
             .init_resource::<ButtonInput<KeyCode>>()
@@ -129,6 +149,7 @@ impl Plugin for ThemeStorePlugin {
                 (
                     handle_open_request,
                     poll_catalog_task,
+                    poll_preview_tasks,
                     handle_install_buttons,
                     poll_install_task,
                     handle_close_button,
@@ -176,6 +197,7 @@ fn handle_open_request(
     mut catalog_task: ResMut<CatalogTask>,
     mut store_base: ResMut<StoreBaseUrl>,
     mut warning_toast: MessageWriter<WarningToastEvent>,
+    previews: Res<PreviewCache>,
     mut commands: Commands,
     font_res: Option<Res<FontResource>>,
 ) {
@@ -207,16 +229,28 @@ fn handle_open_request(
         rt.block_on(async { ThemeStoreClient::new(base_url).fetch_catalog().await })
     }));
 
-    spawn_store_modal(&mut commands, &catalog_state, None, font_res.as_deref());
+    spawn_store_modal(
+        &mut commands,
+        &catalog_state,
+        None,
+        &previews,
+        font_res.as_deref(),
+    );
 }
 
-/// Polls the catalog fetch; on completion updates [`CatalogState`] and
+/// Polls the catalog fetch; on completion updates [`CatalogState`],
+/// kicks off preview downloads for entries not yet in the cache, and
 /// rebuilds the modal if it is still open.
+#[allow(clippy::too_many_arguments)]
 fn poll_catalog_task(
     mut catalog_task: ResMut<CatalogTask>,
     mut catalog_state: ResMut<CatalogState>,
     screens: Query<Entity, With<ThemeStoreScreen>>,
     registry: Option<Res<ThemeRegistry>>,
+    rt: Option<Res<TokioRuntimeResource>>,
+    store_base: Res<StoreBaseUrl>,
+    previews: Res<PreviewCache>,
+    mut preview_tasks: ResMut<PreviewTasks>,
     mut commands: Commands,
     font_res: Option<Res<FontResource>>,
 ) {
@@ -229,7 +263,29 @@ fn poll_catalog_task(
     catalog_task.0 = None;
 
     *catalog_state = match result {
-        Ok(entries) => CatalogState::Loaded(entries),
+        Ok(entries) => {
+            // Fetch previews for anything new. Decorative — failures
+            // just leave the row text-only, so errors only log.
+            if let (Some(rt), Some(base_url)) = (rt.as_ref(), store_base.0.as_deref()) {
+                for entry in entries
+                    .iter()
+                    .filter(|e| e.preview_url.is_some() && !previews.0.contains_key(&e.id))
+                {
+                    let rt = rt.0.clone();
+                    let base_url = base_url.to_owned();
+                    let entry = entry.clone();
+                    preview_tasks.0.push((
+                        entry.id.clone(),
+                        AsyncComputeTaskPool::get().spawn(async move {
+                            rt.block_on(async {
+                                ThemeStoreClient::new(base_url).fetch_preview(&entry).await
+                            })
+                        }),
+                    ));
+                }
+            }
+            CatalogState::Loaded(entries)
+        }
         Err(e) => {
             warn!("theme store: catalog fetch failed: {e}");
             CatalogState::Error(e.to_string())
@@ -241,10 +297,69 @@ fn poll_catalog_task(
         &mut commands,
         &catalog_state,
         registry.as_deref(),
+        &previews,
         font_res.as_deref(),
     );
 }
 
+/// Polls in-flight preview downloads. Each finished PNG is decoded into
+/// an [`Image`] asset and cached by theme id; the open modal rebuilds
+/// once per frame that added at least one preview, so thumbnails pop in
+/// as they arrive. Failures log and leave the row text-only. Skipped
+/// entirely when `Assets<Image>` is absent (`MinimalPlugins` tests).
+#[allow(clippy::too_many_arguments)]
+fn poll_preview_tasks(
+    mut preview_tasks: ResMut<PreviewTasks>,
+    mut previews: ResMut<PreviewCache>,
+    images: Option<ResMut<Assets<Image>>>,
+    catalog_state: Res<CatalogState>,
+    screens: Query<Entity, With<ThemeStoreScreen>>,
+    registry: Option<Res<ThemeRegistry>>,
+    mut commands: Commands,
+    font_res: Option<Res<FontResource>>,
+) {
+    if preview_tasks.0.is_empty() {
+        return;
+    }
+    let Some(mut images) = images else {
+        return;
+    };
+
+    let mut added = false;
+    preview_tasks.0.retain_mut(|(id, task)| {
+        let Some(result) = future::block_on(future::poll_once(task)) else {
+            return true; // still downloading
+        };
+        match result {
+            Ok(bytes) => match image::load_from_memory(&bytes) {
+                Ok(dyn_img) => {
+                    let handle = images.add(Image::from_dynamic(
+                        dyn_img,
+                        true,
+                        RenderAssetUsages::RENDER_WORLD,
+                    ));
+                    previews.0.insert(id.clone(), handle);
+                    added = true;
+                }
+                Err(e) => warn!("theme store: preview for '{id}' failed to decode: {e}"),
+            },
+            Err(e) => warn!("theme store: preview fetch for '{id}' failed: {e}"),
+        }
+        false
+    });
+
+    if added {
+        rebuild_open_modal(
+            &screens,
+            &mut commands,
+            &catalog_state,
+            registry.as_deref(),
+            &previews,
+            font_res.as_deref(),
+        );
+    }
+}
+
 /// Starts a download + import task when an Install button is pressed.
 /// One install at a time; repeat clicks while busy are ignored.
 fn handle_install_buttons(
@@ -308,6 +423,7 @@ fn poll_install_task(
     screens: Query<Entity, With<ThemeStoreScreen>>,
     mut info_toast: MessageWriter<InfoToastEvent>,
     mut warning_toast: MessageWriter<WarningToastEvent>,
+    previews: Res<PreviewCache>,
     mut commands: Commands,
     font_res: Option<Res<FontResource>>,
 ) {
@@ -343,6 +459,7 @@ fn poll_install_task(
         &mut commands,
         &catalog_state,
         registry.as_deref(),
+        &previews,
         font_res.as_deref(),
     );
 }
@@ -378,11 +495,12 @@ fn rebuild_open_modal(
     commands: &mut Commands,
     catalog_state: &CatalogState,
     registry: Option<&ThemeRegistry>,
+    previews: &PreviewCache,
     font_res: Option<&FontResource>,
 ) {
     for entity in screens {
         commands.entity(entity).despawn();
-        spawn_store_modal(commands, catalog_state, registry, font_res);
+        spawn_store_modal(commands, catalog_state, registry, previews, font_res);
     }
 }
 
@@ -391,6 +509,7 @@ fn spawn_store_modal(
     commands: &mut Commands,
     catalog_state: &CatalogState,
     registry: Option<&ThemeRegistry>,
+    previews: &PreviewCache,
     font_res: Option<&FontResource>,
 ) {
     let body_font = TextFont {
@@ -433,7 +552,15 @@ fn spawn_store_modal(
                 for entry in entries {
                     let installed =
                         registry.is_some_and(|registry| registry.find(&entry.id).is_some());
-                    spawn_store_row(card, entry, installed, &body_font, &caption_font, font_res);
+                    spawn_store_row(
+                        card,
+                        entry,
+                        installed,
+                        previews.0.get(&entry.id),
+                        &body_font,
+                        &caption_font,
+                        font_res,
+                    );
                 }
             }
         }
@@ -452,12 +579,20 @@ fn spawn_store_modal(
     commands.entity(scrim).insert(ScrimDismissible);
 }
 
-/// One catalog row: name + author/size caption on the left, Install
-/// button (or "Installed" caption) on the right.
+/// Height of a row's preview thumbnail in logical pixels; the width
+/// follows the theme's own `card_aspect` so a preview is never
+/// stretched.
+const PREVIEW_THUMB_HEIGHT_PX: f32 = 72.0;
+
+/// One catalog row: preview thumbnail (when downloaded) + name +
+/// author/size caption on the left, Install button (or "Installed"
+/// caption) on the right.
+#[allow(clippy::too_many_arguments)]
 fn spawn_store_row(
     parent: &mut ChildSpawnerCommands,
     entry: &ThemeCatalogEntry,
     installed: bool,
+    preview: Option<&Handle<Image>>,
     body_font: &TextFont,
     caption_font: &TextFont,
     font_res: Option<&FontResource>,
@@ -477,25 +612,45 @@ fn spawn_store_row(
         ))
         .with_children(|row| {
             row.spawn(Node {
-                flex_direction: FlexDirection::Column,
-                row_gap: VAL_SPACE_2,
+                flex_direction: FlexDirection::Row,
+                align_items: AlignItems::Center,
+                column_gap: VAL_SPACE_3,
                 ..default()
             })
-            .with_children(|col| {
-                col.spawn((
-                    Text::new(entry.name.clone()),
-                    body_font.clone(),
-                    TextColor(TEXT_PRIMARY),
-                ));
-                col.spawn((
-                    Text::new(format!(
-                        "by {} — {} KB",
-                        entry.author,
-                        entry.size_bytes.div_ceil(1024)
-                    )),
-                    caption_font.clone(),
-                    TextColor(TEXT_SECONDARY),
-                ));
+            .with_children(|left| {
+                if let Some(handle) = preview {
+                    let (aw, ah) = entry.card_aspect;
+                    let width = PREVIEW_THUMB_HEIGHT_PX * aw.max(1) as f32 / ah.max(1) as f32;
+                    left.spawn((
+                        ImageNode::new(handle.clone()),
+                        Node {
+                            width: Val::Px(width),
+                            height: Val::Px(PREVIEW_THUMB_HEIGHT_PX),
+                            ..default()
+                        },
+                    ));
+                }
+                left.spawn(Node {
+                    flex_direction: FlexDirection::Column,
+                    row_gap: VAL_SPACE_2,
+                    ..default()
+                })
+                .with_children(|col| {
+                    col.spawn((
+                        Text::new(entry.name.clone()),
+                        body_font.clone(),
+                        TextColor(TEXT_PRIMARY),
+                    ));
+                    col.spawn((
+                        Text::new(format!(
+                            "by {} — {} KB",
+                            entry.author,
+                            entry.size_bytes.div_ceil(1024)
+                        )),
+                        caption_font.clone(),
+                        TextColor(TEXT_SECONDARY),
+                    ));
+                });
             });
             if installed {
                 row.spawn((
@@ -661,4 +816,85 @@ mod tests {
         ));
         assert_eq!(screen_count(&mut app), 1);
     }
+
+    // -----------------------------------------------------------------------
+    // Phase H part 2: preview thumbnails
+    // -----------------------------------------------------------------------
+
+    fn catalog_entry(id: &str, preview: bool) -> ThemeCatalogEntry {
+        ThemeCatalogEntry {
+            id: id.into(),
+            name: id.into(),
+            author: "Test".into(),
+            version: "1.0.0".into(),
+            card_aspect: (2, 3),
+            size_bytes: 1024,
+            sha256: "00".into(),
+            download_url: format!("/api/themes/{id}/download"),
+            preview_url: preview.then(|| format!("/api/themes/{id}/preview")),
+        }
+    }
+
+    /// A row whose theme id is in the [`PreviewCache`] renders an
+    /// `ImageNode` thumbnail; a row without one stays text-only.
+    #[test]
+    fn loaded_row_shows_preview_thumbnail_only_when_cached() {
+        let mut app = headless_app();
+        let cached = catalog_entry("with-preview", true);
+        let uncached = catalog_entry("without-preview", false);
+
+        let mut cache = PreviewCache::default();
+        cache
+            .0
+            .insert(cached.id.clone(), Handle::<Image>::default());
+        let state = CatalogState::Loaded(vec![cached, uncached]);
+
+        {
+            let world = app.world_mut();
+            let mut commands = world.commands();
+            spawn_store_modal(&mut commands, &state, None, &cache, None);
+        }
+        app.update();
+
+        let thumbs = app
+            .world_mut()
+            .query::<&ImageNode>()
+            .iter(app.world())
+            .count();
+        assert_eq!(
+            thumbs, 1,
+            "exactly the cached entry must render a preview thumbnail"
+        );
+    }
+
+    /// The thumbnail width follows the theme's own card aspect so a
+    /// preview never renders stretched.
+    #[test]
+    fn preview_thumbnail_width_follows_card_aspect() {
+        let mut app = headless_app();
+        let mut entry = catalog_entry("wide", true);
+        entry.card_aspect = (1, 1); // square theme art
+        let mut cache = PreviewCache::default();
+        cache.0.insert(entry.id.clone(), Handle::<Image>::default());
+        let state = CatalogState::Loaded(vec![entry]);
+
+        {
+            let world = app.world_mut();
+            let mut commands = world.commands();
+            spawn_store_modal(&mut commands, &state, None, &cache, None);
+        }
+        app.update();
+
+        let node = app
+            .world_mut()
+            .query_filtered::<&Node, With<ImageNode>>()
+            .single(app.world())
+            .expect("thumbnail node must exist");
+        assert_eq!(node.height, Val::Px(PREVIEW_THUMB_HEIGHT_PX));
+        assert_eq!(
+            node.width,
+            Val::Px(PREVIEW_THUMB_HEIGHT_PX),
+            "a 1:1 aspect must yield a square thumbnail"
+        );
+    }
 }