diff --git a/src/guiguts/highlight.py b/src/guiguts/highlight.py
index c859341..40e92eb 100644
--- a/src/guiguts/highlight.py
+++ b/src/guiguts/highlight.py
@@ -236,6 +236,12 @@ def get_screen_window_coordinates() -> tuple[str, str]:
     Find start and end coordinates for viewport (with a margin of
     offscreen text added for padding).
     """
+    # TODO: check if peer exists (see PrefKey.SPLIT_TEXT_WINDOW)
+    # TODO: if it does, can get peer's coords with maintext().peer.yview()
+    # maybe refactor this method to take a text widget as an arg
+    # (are maintext() and maintext().peer the same kind of thing??)
+    # and then in some places we can get only main input's coords and in others we can get peer's?
+
     # A magic number cribbed from Tk.pm's TextEdit.pm.
     # This is how many rows to explore beyond the visible viewport.
     offscreen_rows = 80