Improve and externalize debug rendering settings

src/ocrmypdf/_pipeline.py

@@ -35,6 +35,7 @@ from ocrmypdf.exceptions import (
 )
 from ocrmypdf.helpers import IMG2PDF_KWARGS, Resolution, safe_symlink
 from ocrmypdf.hocrtransform import DebugRenderOptions, HocrTransform
+from ocrmypdf.hocrtransform._font import Helvetica
 from ocrmypdf.pdfa import generate_pdfa_ps
 from ocrmypdf.pdfinfo import Colorspace, Encoding, PageInfo, PdfInfo
 from ocrmypdf.pluginspec import OrientationConfidence
@@ -741,24 +742,25 @@ def render_hocr_page(hocr: Path, page_context: PageContext) -> Path:
         return output_file
 
     dpi = get_page_square_dpi(page_context, calculate_image_dpi(page_context))
-    debug = options.pdf_renderer == 'hocrdebug'
-    debug_render_options = None
-    if debug:
-        debug_render_options = DebugRenderOptions(
-            render_baseline=True,
-            render_triangle=True,
-            render_line_bbox=False,
-            render_word_bbox=True,
-            render_paragraph_bbox=False,
-            render_space_bbox=False,
+    debug_kwargs = {}
+    if options.pdf_renderer == 'hocrdebug':
+        debug_kwargs = dict(
+            debug_render_options=DebugRenderOptions(
+                render_baseline=True,
+                render_triangle=True,
+                render_line_bbox=False,
+                render_word_bbox=True,
+                render_paragraph_bbox=False,
+                render_space_bbox=False,
+            ),
+            font=Helvetica(),
         )
     HocrTransform(
-        hocr_filename=hocr,
-        dpi=dpi.to_scalar(),  # square
-        debug_render_options=debug_render_options,
+        hocr_filename=hocr, dpi=dpi.to_scalar(), **debug_kwargs  # square
     ).to_pdf(
         out_filename=output_file,
         image_filename=None,
+        invisible_text=True if not debug_kwargs else False,
     )
     return output_file