🐛 Fix client-side wasm export encoding jpeg and webp as png

frontend/src/app/main/data/exports/wasm.cljs

@@ -13,7 +13,10 @@
 
 (defn export-image-uri
   [{:keys [type scale object-id]}]
-  (let [bytes (wasm.api/render-shape-pixels object-id scale)
+  ;; The export type doubles as the encoder format, so the bytes always match
+  ;; the mtype we wrap them in. `:svg` never reaches here — it needs vector
+  ;; markup and `exports.assets/wasm-export-types` keeps it off this path.
+  (let [bytes (wasm.api/render-shape-pixels object-id scale type)
         mtype (format->mtype type)
         blob (wapi/create-blob bytes mtype)]
     (wapi/create-uri blob)))

frontend/src/app/main/data/workspace/thumbnails_wasm.cljs

@@ -68,7 +68,9 @@
                           {sel-w :width sel-h :height} (:selrect frame)
                           max-size (mth/max (or ext-w sel-w) (or ext-h sel-h))
                           scale (mth/max 1 (/ target-size max-size))
-                          png-bytes (wasm.api/render-shape-pixels frame-id scale)]
+                          ;; Thumbnails are always PNG: they need the alpha
+                          ;; channel and are consumed as a `image/png` data uri.
+                          png-bytes (wasm.api/render-shape-pixels frame-id scale :png)]
                       (if (or (nil? png-bytes) (zero? (.-length png-bytes)))
                         (do
                           (l/error :hint "render-shape-pixels returned empty" :frame-id (str frame-id))

frontend/src/app/render_wasm/api.cljs

@@ -2629,7 +2629,10 @@
         (reset! transition-image* snapshot)))))
 
 (defn render-shape-pixels
-  [shape-id scale]
+  "Renders a shape subtree to encoded image bytes. `format` is :png, :jpeg or
+  :webp; jpeg is flattened onto white on the Rust side, since it has no alpha
+  channel."
+  [shape-id scale format]
   (let [buffer (uuid/get-u32 shape-id)
 
         offset
@@ -2638,7 +2641,8 @@
                 (aget buffer 1)
                 (aget buffer 2)
                 (aget buffer 3)
-                scale)
+                scale
+                (sr/translate-raster-format format))
 
         heap (mem/get-heap-u8)
         heapu32 (mem/get-heap-u32)

render-wasm/src/main.rs

@@ -976,6 +976,9 @@ pub extern "C" fn get_shape_extrect(a: u32, b: u32, c: u32, d: u32) -> Result<*m
     })
 }
 
+/// Raster image via the GPU surface. Returns `[len][width][height][bytes]`
+/// (LE). `format` selects the encoder: 0 = PNG, 1 = JPEG, 2 = WEBP (see
+/// `RasterFormat`).
 #[no_mangle]
 #[wasm_error]
 pub extern "C" fn render_shape_pixels(
@@ -984,6 +987,7 @@ pub extern "C" fn render_shape_pixels(
     c: u32,
     d: u32,
     scale: f32,
+    format: u32,
 ) -> Result<*mut u8> {
     let id = uuid_from_u32_quartet(a, b, c, d);
 
@@ -991,9 +995,11 @@ pub extern "C" fn render_shape_pixels(
         return Err(Error::CriticalError("Scale is not finite".to_string()));
     }
 
+    let format = RasterFormat::from_u32(format)?;
+
     with_state!(state, {
         let (data, width, height) =
-            state.render_shape_pixels(&id, scale, performance::get_time())?;
+            state.render_shape_pixels(&id, scale, performance::get_time(), format)?;
 
         let len = data.len() as u32;
         let mut buf = Vec::with_capacity(4 + data.len());

render-wasm/src/render.rs

@@ -2429,6 +2429,7 @@ impl RenderState {
         tree: ShapesPoolRef,
         scale: f32,
         timestamp: i32,
+        format: raster::RasterFormat,
     ) -> Result<(Vec<u8>, i32, i32)> {
         let target_surface = SurfaceId::Export;
 
@@ -2459,7 +2460,7 @@ impl RenderState {
 
         self.surfaces
             .canvas(target_surface)
-            .clear(skia::Color::TRANSPARENT);
+            .clear(format.clear_color());
 
         if tree.len() != 0 {
             let Some(shape) = tree.get(id) else {
@@ -2476,6 +2477,14 @@ impl RenderState {
             self.render_area_with_margins = extrect;
             self.surfaces.update_render_context(extrect, scale);
 
+            // `resize_export_surface` swaps in a brand-new (zeroed, i.e.
+            // transparent) surface whenever the dimensions change, discarding
+            // the clear above — so an opaque backdrop has to be laid down again
+            // here, after the resize.
+            if let Some(background) = format.opaque_background() {
+                self.surfaces.canvas(target_surface).clear(background);
+            }
+
             self.pending_nodes.push(NodeRenderState {
                 id: *id,
                 visited_children: false,
@@ -2496,10 +2505,10 @@ impl RenderState {
         let data = image
             .encode(
                 Some(&mut get_gpu_state().context),
-                skia::EncodedImageFormat::PNG,
+                format.encoded(),
-                100,
+                format.quality(),
             )
-            .expect("PNG encode failed");
+            .unwrap_or_else(|| panic!("{format:?} encode failed"));
         let skia::ISize { width, height } = image.dimensions();
 
         // Restore the workspace render state.

render-wasm/src/state.rs

@@ -96,8 +96,9 @@ impl State {
         id: &Uuid,
         scale: f32,
         timestamp: i32,
+        format: RasterFormat,
     ) -> Result<(Vec<u8>, i32, i32)> {
-        get_render_state().render_shape_pixels(id, &self.shapes, scale, timestamp)
+        get_render_state().render_shape_pixels(id, &self.shapes, scale, timestamp, format)
     }
 
     pub fn render_shape_pdf(&mut self, id: &Uuid, scale: f32) -> Result<Vec<u8>> {