bug#54800: 28.1; calc: Cursor positioned at weird position in calc stack

[Christoph Arenz]

    When the content of the calc stack inclusive top-of-stack symbol `.'
    
    gets larger in height than the calc window, the cursor is positioned
    at
    
    a weird position in the upper half of the stack window. When
    
    line-numbering is on, the cursor is positioned at the beginning of
    the
    
    line at the line number. Calling `calc-realign' does not change the
    
    cursor postion.
    
    
    How to reproduce:
    
    1. emacs -Q
    
    2. C-x * * (to start calc)
    
    3. enter a number and RET
    
    4. repeat No. 3 until the stacks grows and the symptom appears
    
    
    Expected behavior for the cursor is to be placed on the `.' symbol,
    
    representing the top of the stack.
    
    
    5. After pressing `o' [calc-realign], the expected behavior would
    also
    
    be for the cursor to be positioned at the top of the calc stack.
    
    
    Debugging the function calc-align-stack-window with edebug, the
    symptom
    
    goes away when placing a breakpoint at the line
    
    (calc-cursor-stack-index 0) just after the set-window-start call,
    and
    
    then continuing from there.
    
    
    The following patch fixes the problem for me, but I do not fully
    
    understand the NOFORCE option of the set-window-start function.

Thanks, Christoph

1 file changed, 1 insertion(+), 1 deletion(-)
lisp/calc/calc.el | 2 +-

modified   lisp/calc/calc.el
@@ -1816,7 +1816,7 @@ calc-align-stack-window
           (progn
         (calc-cursor-stack-index 0)
         (vertical-motion (- 2 (window-height win)))
-        (set-window-start win (point)))))
+        (set-window-start win (point) 'noforce))))
     (calc-cursor-stack-index 0)
     (if (looking-at " *\\.$")
         (goto-char (1- (match-end 0)))))

    In GNU Emacs 28.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version
    3.22.30, cairo version 1.15.10)
    
    of 2022-04-05 built on M92p
    
    Repository revision: 5a223c7f2ef4c31abbd46367b6ea83cd19d30aa7
    
    Repository branch: HEAD
    
    Windowing system distributor 'The X.Org Foundation', version
    11.0.11906000
    
    System Description: Ubuntu 18.04.6 LTS
    
    
    Configured features:
    
    ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ
    JPEG
    
    LCMS2 LIBOTF LIBSELINUX LIBXML2 M17N_FLT MODULES NOTIFY INOTIFY
    PDUMPER
    
    PNG RSVG SECCOMP SOUND THREADS TIFF TOOLKIT_SCROLL_BARS X11 XDBE XIM
    XPM
    
    GTK3 ZLIB
    
    
    Important settings:
    
    value of $LC_MONETARY: de_DE.UTF-8
    
    value of $LC_NUMERIC: de_DE.UTF-8
    
    value of $LC_TIME: de_DE.UTF-8
    
    value of $LANG: en_US.UTF-8
    
    value of $XMODIFIERS: @im=ibus
    
    locale-coding-system: utf-8-unix