warnings and window-point

[Juanma Barranquero <lekktu@gmail.com>]

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Not sure if that's a bug or a feature, because it's been so since the
beginning (it already happens in 22.1, where warnings.el was introduced).
But it is definitely weird.

Warnings are added at the end of the *Warnings* buffer, and the buffer is
displayed, but the window-point does not move. So if you write a lot of
warnings, like

(dotimes (i 40) (lwarn 'emacs :warning "i = %d" i))

only the beginning of the buffer is shown, and the window-point is stuck at
the beginning of the *second* warning in the buffer. Basically, if you have
the *Warnings* buffer open in some window, but you don't scroll it, once
the window is full, you're unaware that new warnings are appearing.

Perhaps the idea is to keep past warnings visible until the user scrolls
the buffer themself, but if warning-series is set, display-warning calls
set-window-start and sets the origin of the window at the first warning of
the series (and weirdly, the window-point is not reset to the first visible
position in the window).

(dotimes (i 100)
  (when (= i 50) (setq warning-series t))
  (lwarn 'emacs :warning "i = %d" i))

What I would've expected is something like this:

diff --git i/lisp/emacs-lisp/warnings.el w/lisp/emacs-lisp/warnings.el
index e5c1d9cec4..c9d7aff529 100644
--- i/lisp/emacs-lisp/warnings.el
+++ w/lisp/emacs-lisp/warnings.el
@@ -316,7 +316,8 @@ display-warning
                     (warning-suppress-p type warning-suppress-types)
                     (let ((window (display-buffer buffer)))
-                      (when (and (markerp warning-series)
-                                 (eq (marker-buffer warning-series)
buffer))
-                        (set-window-start window warning-series))
+                      (if (and (markerp warning-series)
+                               (eq (marker-buffer warning-series) buffer))
+                          (set-window-start window warning-series)
+                        (set-window-point window end))
                       (sit-for 0)))))))))

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