A click that takes no text tells the event reader nothing, and click records are tested for their offsets

Dogfooding saw a body right-click reported as ML0 0 2 3 qty. On file panes
the offsets were right in every case tried here (a scratch made over 9P and
clicked while another pane is active, after a hover, scrolled, soft-wrapped,
tab-indented, inside parentheses); the test now holds them. The 0 0 form
is a terminal's body, which has no offsets to give (its body is a history
snapshot); since the event file now takes a record back whole, such a record
can still be written back and done, and the docs say so. What the test did
find: a click on whitespace sent an empty record, where acme's look3 and
execute return without a word on an empty expansion (look.c:37, exec.c:141).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 4 insertions, 1 deletions

diff --git a/docs/fs.md b/docs/fs.md
index ccf06dd1..65b987d8 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -251,7 +251,10 @@ at `0 0` carrying the line (the root's `look` and `exec` still act at once);
 writing a record back performs the action. acme takes back only `<origin>
 <action><q0> <q1>`, the text of that range; pardes takes the record whole as
 it was read too, and for an empty range acts on its text, which is how such
-a line is done. `ctl` reads acme's window status line — serial, tag length, body
+a line is done. A click in a file's body carries the offsets of the text it
+took; one in a terminal's body cannot, since that body is a history
+snapshot, and is also at `0 0` with its text. A click that takes no text
+sends nothing, as in acme. `ctl` reads acme's window status line — serial, tag length, body
 length, a reserved zero, the dirty flag, the width in cells, the font and the
 tab width — followed by rio's `current` or `notcurrent` (rio(4), `wctl`):
 whether the pane has the keyboard. It takes the pane's builtins (below),