add notes about performance improvement for the future

services/bao-video/src/main.rs

@@ -12,6 +12,15 @@ const IMAGE_WIDTH: usize = 256;
 const IMAGE_HEIGHT: usize = 240;
 const BW_THRESH: u8 = 128;
 
+// Next steps for performance improvement:
+//
+// Improve qr::mapping -> point_from_hv_lines such that we're not just deriving the HV
+// lines from the the edges of the finder regions, we're also using the very edge of
+// the whole QR code itself to guide the line. This will improve the intersection point
+// so that we can accurately hit the "fourth corner". At the moment it's sort of a
+// luck of the draw if the interpolation hits exactly right, or if we're roughly a module
+// off from ideal, which causes the data around that point to be interpreted incorrectly.
+
 pub fn blit_to_display(sh1107: &mut Oled128x128, frame: &[u8], display_cleared: bool) {
     for (y, row) in frame.chunks(IMAGE_WIDTH).enumerate() {
         if y & 1 == 0 {