Allow precision-scrolling nonselected windows when the minibuffer is resized

* doc/lispref/windows.texi (Vertical Scrolling): Document new
`preserve-vscroll-p' parameter of `set-window-vscroll'.
* etc/NEWS: Announce new parameter.

* lisp/pixel-scroll.el (pixel-scroll-precision-scroll-down-page)
(pixel-scroll-precision-scroll-up-page): Use that parameter when
setting the vscroll.

* src/window.c (window_scroll_pixel_based, Fset_window_vscroll):
Adjust for new parameter.
* src/window.h (struct window): New flag `preserve_vscroll_p'.

* src/xdisp.c (redisplay_window): Preserve the vscroll inside
force_start on frozen windows with that flag set.  (bug#55312)

1 files changed, 7 insertions, 1 deletions

diff --git a/doc/lispref/windows.texi b/doc/lispref/windows.texi
index 97908bea001..57763c146da 100644
--- a/doc/lispref/windows.texi
+++ b/doc/lispref/windows.texi
@@ -5508,7 +5508,7 @@ pixels, rather than in units of the normal line height.
 @end example
 @end defun
 
-@defun set-window-vscroll window lines &optional pixels-p
+@defun set-window-vscroll window lines &optional pixels-p preserve-vscroll-p
 This function sets @var{window}'s vertical scroll position to
 @var{lines}.  If @var{window} is @code{nil}, the selected window is
 used.  The argument @var{lines} should be zero or positive; if not, it
@@ -5530,6 +5530,12 @@ The return value is the result of this rounding.
 
 If @var{pixels-p} is non-@code{nil}, @var{lines} specifies a number of
 pixels.  In this case, the return value is @var{lines}.
+
+Normally, the vscroll does not take effect on windows that aren't the
+@code{minibuffer-scroll-window} or the selected window when the
+mini-window is resized (@pxref{Minibuffer Windows}).  This ``frozen''
+behavior is disabled when the @var{preserve-vscroll-p} parameter is
+non-@code{nil}, which means to set the vscroll as usual.
 @end defun
 
 @defvar auto-window-vscroll