pdf: continuous scroll bench harness and per-frame render path

1 files changed, 10 insertions, 2 deletions

diff --git a/src/pdf_bridge.h b/src/pdf_bridge.h
index 40eaa46c..a3d2de89 100644
--- a/src/pdf_bridge.h
+++ b/src/pdf_bridge.h
@@ -198,9 +198,15 @@ int pardes_pdf_measure_render(
 );
 
 /*
- * Rasterize directly into an exactly-sized caller-owned packed RGBA buffer.
+ * Rasterize one horizontal BAND of a page — rows [band_y, band_y+band_height)
+ * of the raster `pardes_pdf_measure_render` describes — directly into an
+ * exactly-sized caller-owned packed RGBA buffer, `stride * band_height` bytes.
+ * A full page is the band `(0, height)`.
+ *
  * MuPDF wraps but never owns or frees samples. Every successful pixel is
  * opaque, including the caller-supplied highlights composited onto the page.
+ * The CTM does not depend on the band, so a band's rows are bit-identical to
+ * the same rows of the whole page: it is a clip, not a different rendering.
  */
 int pardes_pdf_render_into(
     pardes_pdf_document *document,
@@ -215,7 +221,9 @@ int pardes_pdf_render_into(
     size_t samples_len,
     int width,
     int height,
-    int stride
+    int stride,
+    int band_y,
+    int band_height
 );
 
 int pardes_pdf_page_text(