feat: solid background position in roundRect fallback

src/scene/fancyBackground.ts

@@ -104,6 +104,7 @@ const addContentBackground = (
     const y =
       (normalizedDimensions.height - contentSize.height) / 2 - FANCY_BG_PADDING;
 
+    // fixme: position is no scaled to the center
     if (context.roundRect) {
       context.roundRect(
         x,
@@ -119,10 +120,14 @@ const addContentBackground = (
     } else {
       roundRect(
         context,
-        FANCY_BG_PADDING * exportScale,
-        FANCY_BG_PADDING * exportScale,
-        normalizedDimensions.width - FANCY_BG_PADDING * 2 * exportScale,
-        normalizedDimensions.height - FANCY_BG_PADDING * 2 * exportScale,
+        x,
+        y,
+        (contentSize.width +
+          (DEFAULT_EXPORT_PADDING + FANCY_BG_BORDER_RADIUS) * 2) *
+          exportScale,
+        (contentSize.height * exportScale +
+          (DEFAULT_EXPORT_PADDING + FANCY_BG_BORDER_RADIUS) * 2) *
+          exportScale,
         FANCY_BG_BORDER_RADIUS * exportScale,
       );
     }