* src/xdisp.c (syms_of_xdisp) <"scroll-minibuffer-conservatively">: New var

Fix bug#44070, which causes the minibuffer display to jump upon minor edit

(redisplay_window): Obey it.
* lisp/simple.el (end-of-buffer): Obey it.

* test/src/xdisp-tests.el (xdisp-tests--in-minibuffer): New macro,
extracted from `xdisp-tests--minibuffer-resizing`.
(xdisp-tests--minibuffer-resizing): Use it.
(xdisp-tests--minibuffer-scroll): New test.

1 files changed, 46 insertions, 25 deletions

diff --git a/test/src/xdisp-tests.el b/test/src/xdisp-tests.el
index 95c39dacc3e..fad90fad531 100644
--- a/test/src/xdisp-tests.el
+++ b/test/src/xdisp-tests.el
@@ -21,34 +21,55 @@
 
 (require 'ert)
 
+(defmacro xdisp-tests--in-minibuffer (&rest body)
+  (declare (debug t) (indent 0))
+  `(catch 'result
+     (minibuffer-with-setup-hook
+         (lambda ()
+           (let ((redisplay-skip-initial-frame nil)
+                 (executing-kbd-macro nil)) ;Don't skip redisplay
+             (throw 'result (progn . ,body))))
+       (let ((executing-kbd-macro t)) ;Force real minibuffer in `read-string'.
+         (read-string "toto: ")))))
+
 (ert-deftest xdisp-tests--minibuffer-resizing () ;; bug#43519
-  ;; FIXME: This test returns success when run in batch but
-  ;; it's only a lucky accident: it also returned success
-  ;; when bug#43519 was not fixed.
   (should
    (equal
     t
-    (catch 'result
-      (minibuffer-with-setup-hook
-          (lambda ()
-            (insert "hello")
-            (let ((ol (make-overlay (point) (point)))
-                  (redisplay-skip-initial-frame nil)
-                  (max-mini-window-height 1)
-                  (text "askdjfhaklsjdfhlkasjdfhklasdhflkasdhflkajsdhflkashdfkljahsdlfkjahsdlfkjhasldkfhalskdjfhalskdfhlaksdhfklasdhflkasdhflkasdhflkajsdhklajsdgh"))
-              ;; (save-excursion (insert text))
-              ;; (sit-for 2)
-              ;; (delete-region (point) (point-max))
-              (put-text-property 0 1 'cursor t text)
-              (overlay-put ol 'after-string text)
-              (let ((executing-kbd-macro nil)) ;Don't skip redisplay
-                (redisplay 'force))
-              (throw 'result
-                     ;; Make sure we do the see "hello" text.
-                     (prog1 (equal (window-start) (point-min))
-                       ;; (list (window-start) (window-end) (window-width))
-                       (delete-overlay ol)))))
-        (let ((executing-kbd-macro t)) ;Force real minibuffer in `read-string'.
-          (read-string "toto: ")))))))
+    (xdisp-tests--in-minibuffer
+      (insert "hello")
+      (let ((ol (make-overlay (point) (point)))
+            (max-mini-window-height 1)
+            (text "askdjfhaklsjdfhlkasjdfhklasdhflkasdhflkajsdhflkashdfkljahsdlfkjahsdlfkjhasldkfhalskdjfhalskdfhlaksdhfklasdhflkasdhflkasdhflkajsdhklajsdgh"))
+        ;; (save-excursion (insert text))
+        ;; (sit-for 2)
+        ;; (delete-region (point) (point-max))
+        (put-text-property 0 1 'cursor t text)
+        (overlay-put ol 'after-string text)
+        (redisplay 'force)
+        ;; Make sure we do the see "hello" text.
+        (prog1 (equal (window-start) (point-min))
+          ;; (list (window-start) (window-end) (window-width))
+          (delete-overlay ol)))))))
+
+(ert-deftest xdisp-tests--minibuffer-scroll () ;; bug#44070
+  (let ((posns
+         (xdisp-tests--in-minibuffer
+           (let ((max-mini-window-height 4))
+             (dotimes (_ 80) (insert "\nhello"))
+             (beginning-of-buffer)
+             (redisplay 'force)
+             (end-of-buffer)
+             ;; A simple edit like removing the last `o' shouldn't cause
+             ;; the rest of the minibuffer's text to move.
+             (list
+              (progn (redisplay 'force) (window-start))
+              (progn (delete-char -1)
+                     (redisplay 'force) (window-start))
+              (progn (goto-char (point-min)) (redisplay 'force)
+                     (goto-char (point-max)) (redisplay 'force)
+                     (window-start)))))))
+    (should (equal (nth 0 posns) (nth 1 posns)))
+    (should (equal (nth 1 posns) (nth 2 posns)))))
 
 ;;; xdisp-tests.el ends here