From 98d0722d1e6e5d9d5b877f7df7e8ccd624ca9bd5 Mon Sep 17 00:00:00 2001 From: Eshel Yaron Date: Sun, 4 Jun 2023 19:41:20 +0300 Subject: [PATCH v3] Avoid header line with some empty non-nil formats Allow the value of 'header-line-format' to indicate that no header line should be displayed when it trivially yields 'nil', even if it is not plain 'nil'. Previously, any non-nil 'header-line-format' resulted in a (possibly empty) header line. This change adds some flexibility by also taking a non-nil value of 'header-line-format' to mean that no header line should be displayed if it's a list whose 'car' is a symbol and either that symbol is ':eval' and the second list element evaluates to 'nil', or the symbol's value as a variable is 'nil' or void. (Bug#63825) * src/xdisp.c (safe_eval_inhibit_quit): New function. * src/lisp.h (safe_eval_inhibit_quit): Declare it. * src/window.c (null_header_line_format): New function. (window_wants_header_line): Use it. * doc/lispref/modes.texi (Header Line): Update to reflect new conditions for displaying a window's header line. * etc/NEWS: Announce updated treatment of 'header-line-format'. --- doc/lispref/modes.texi | 9 ++++++++ etc/NEWS | 8 +++++++ src/lisp.h | 1 + src/window.c | 50 ++++++++++++++++++++++++++++++++++++++++-- src/xdisp.c | 6 +++++ 5 files changed, 72 insertions(+), 2 deletions(-) diff --git a/doc/lispref/modes.texi b/doc/lispref/modes.texi index c2698da6d99..d2a05fe29e4 100644 --- a/doc/lispref/modes.texi +++ b/doc/lispref/modes.texi @@ -2597,6 +2597,15 @@ Header Lines line. @end defvar +Emacs displays the header line for a window unless +@code{header-line-format} is either @code{nil}, or it's a list whose +@sc{car} is a symbol, and either that symbol is @code{:eval} and the +second list element evaluates to @code{nil} or the symbol's value as a +variable is @code{nil} or void. Note that there are other possible +values @code{header-line-format} that result in an empty header line +(for example, @code{""}), but all other values tell Emacs to display a +header line, whether or not it is empty. + If @code{display-line-numbers-mode} is turned on in a buffer (@pxref{Display Custom, display-line-numbers-mode,, emacs, The GNU Emacs Manual}), the buffer text is indented on display by the amount diff --git a/etc/NEWS b/etc/NEWS index 9529282f047..f09e8972bc6 100644 --- a/etc/NEWS +++ b/etc/NEWS @@ -451,6 +451,14 @@ hooks named after the feature name, like 'esh-mode-unload-hook'. +++ ** 'copy-tree' now copies records when its optional 2nd argument is non-nil. ++++ +** Certain values of 'header-line-format' now inhibit empty header line. +Emacs now avoids displaying a header line, instead of displaying an +empty one, when 'header-line-format' is a list whose 'car' is a +symbol, and either that symbol is ':eval' and the second element of +the list evaluates to 'nil' or the symbol's value as a variable is +'nil' or void. + * Lisp Changes in Emacs 30.1 diff --git a/src/lisp.h b/src/lisp.h index 2bfcd1a1983..2978de962d9 100644 --- a/src/lisp.h +++ b/src/lisp.h @@ -4174,6 +4174,7 @@ verify (FLT_RADIX == 2 || FLT_RADIX == 16); extern void syms_of_xdisp (void); extern void init_xdisp (void); extern Lisp_Object safe_eval (Lisp_Object); +extern Lisp_Object safe_eval_inhibit_quit (Lisp_Object); extern bool pos_visible_p (struct window *, ptrdiff_t, int *, int *, int *, int *, int *, int *); diff --git a/src/window.c b/src/window.c index f4e09f49eae..9429679061e 100644 --- a/src/window.c +++ b/src/window.c @@ -5471,6 +5471,48 @@ window_wants_mode_line (struct window *w) } +/** + * null_header_line_format: + * + * Return non-zero when header line format FMT indicates that the + * header line should not be displayed at all. + * + * This is when FMT is nil, or if FMT is a cons cell and either its + * car is a symbol whose value as a variable is nil or void, or its + * car is the symbol ':eval' and its cadr evaluates to nil. + */ +static bool +null_header_line_format (Lisp_Object fmt, struct frame * f) +{ + Lisp_Object car; + Lisp_Object val; + + if (NILP (fmt)) + return true; + + if (CONSP (fmt)) + { + car = XCAR (fmt); + if (SYMBOLP (car)) + { + if (EQ (car, QCeval)) + { + val = safe_eval_inhibit_quit (XCAR (XCDR (fmt))); + if (!FRAME_LIVE_P (f)) + signal_error (":eval deleted the frame being displayed", fmt); + return NILP (val); + } + val = find_symbol_value (car); + return (SYMBOLP (car) + && (EQ (val, Qunbound) + || NILP (val))); + } + } + + return false; +} + + /** * window_wants_header_line: * @@ -5491,12 +5533,16 @@ window_wants_header_line (struct window *w) Lisp_Object window_header_line_format = window_parameter (w, Qheader_line_format); + struct frame * f = WINDOW_XFRAME(w); + return (WINDOW_LEAF_P (w) && !MINI_WINDOW_P (w) && !WINDOW_PSEUDO_P (w) && !EQ (window_header_line_format, Qnone) - && (!NILP (window_header_line_format) - || !NILP (BVAR (XBUFFER (WINDOW_BUFFER (w)), header_line_format))) + && (!null_header_line_format (window_header_line_format, f) + || !null_header_line_format (BVAR (XBUFFER (WINDOW_BUFFER (w)), + header_line_format), + f)) && (WINDOW_PIXEL_HEIGHT (w) > (window_wants_mode_line (w) ? 2 * WINDOW_FRAME_LINE_HEIGHT (w) diff --git a/src/xdisp.c b/src/xdisp.c index a6ec966ea3c..5e25857322f 100644 --- a/src/xdisp.c +++ b/src/xdisp.c @@ -3074,6 +3074,12 @@ safe__eval (bool inhibit_quit, Lisp_Object sexpr) return safe__call1 (inhibit_quit, Qeval, sexpr); } +Lisp_Object +safe_eval_inhibit_quit (Lisp_Object sexpr) +{ + return safe__eval (true, sexpr); +} + /* Call function FN with two arguments ARG1 and ARG2. Return the result, or nil if something went wrong. */ -- 2.39.2 (Apple Git-143)