Preview: auto-choose base64 embed for small PDFs and file iframe for large; apply to pipeline + all debug previews

app.py

@@ -513,6 +513,19 @@ def _pdf_to_iframe_file(pdf_path: Path, width="100%", height="900px") -> str:
     except Exception:
         return ""
 
+def _pdf_preview_html(pdf_path: Path, width="100%", height="900px") -> str:
+    """Choose base64 embed for small PDFs; served-file iframe for large PDFs.
+    This avoids blank previews for large files while keeping inline render for small ones.
+    """
+    try:
+        size = pdf_path.stat().st_size if isinstance(pdf_path, Path) else 0
+    except Exception:
+        size = 0
+    # 5 MB threshold (tunable)
+    if size and size <= 5 * 1024 * 1024:
+        return _pdf_to_iframe_html(pdf_path, width=width, height=height)
+    return _pdf_to_iframe_file(pdf_path, width=width, height=height)
+
 def preview_image_from_pdf(pdf_file):
     """Render first page of PDF to PNG for image preview. Returns path or None."""
     try:
@@ -773,7 +786,7 @@ def debug_compile_output_zip():
 
     try:
         # Use served file path to avoid data: URI issues
-        html = _pdf_to_iframe_file(pdf_path, height="700px")
+        html = _pdf_preview_html(pdf_path, height="700px")
         _write_logs(LOG_PATH, logs)
         return html
     except Exception as e:
@@ -887,7 +900,7 @@ def debug_compile_last_pipeline_zip():
             + "</pre>"
         )
     try:
-        html = _pdf_to_iframe_file(pdf_path, height="700px")
+        html = _pdf_preview_html(pdf_path, height="700px")
         _write_logs(LOG_PATH, logs)
         return html
     except Exception as e:
@@ -990,7 +1003,7 @@ def debug_compile_uploaded_zip(zip_file):
             + "</pre>"
         )
     try:
-        html = _pdf_to_iframe_file(pdf_path, height="700px")
+        html = _pdf_preview_html(pdf_path, height="700px")
         _write_logs(LOG_PATH, logs)
         return html
     except Exception as e:
@@ -1200,7 +1213,7 @@ def run_pipeline(arxiv_url, pdf_file, openai_key, logo_files, meeting_logo_file,
     try:
         pdf_path = _compile_poster_pdf(OUTPUT_DIR, logs)
         if pdf_path and pdf_path.exists():
-            pdf_html = _pdf_to_iframe_file(pdf_path)
+            pdf_html = _pdf_preview_html(pdf_path)
             compiled_pdf_file = str(pdf_path)
             logs.append("🖨️ PDF ready for preview in UI.")
     except Exception as e: