7 files changed, 64 insertions, 10 deletions

diff --git a/doc/lispref/debugging.texi b/doc/lispref/debugging.texi
index 058c9319544..9ae40949d1e 100644
--- a/doc/lispref/debugging.texi
+++ b/doc/lispref/debugging.texi
@@ -77,6 +77,7 @@ debugger recursively.  @xref{Recursive Editing}.
 
 @menu
 * Error Debugging::       Entering the debugger when an error happens.
+* Debugging Redisplay::   Getting backtraces from redisplay errors.
 * Infinite Loops::        Stopping and debugging a program that doesn't exit.
 * Function Debugging::    Entering it when a certain function is called.
 * Variable Debugging::    Entering it when a variable is modified.
@@ -105,6 +106,10 @@ debugger, set the variable @code{debug-on-error} to non-@code{nil}.
 (The command @code{toggle-debug-on-error} provides an easy way to do
 this.)
 
+Note that, for technical reasons, you cannot use the facilities
+defined in this subsection to debug errors in Lisp that the redisplay
+code has invoked.  @xref{Debugging Redisplay}, for help with these.
+
 @defopt debug-on-error
 This variable determines whether the debugger is called when an error
 is signaled and not handled.  If @code{debug-on-error} is @code{t},
@@ -213,6 +218,45 @@ file, use the option @samp{--debug-init}.  This binds
 bypasses the @code{condition-case} which normally catches errors in the
 init file.
 
+@node Debugging Redisplay
+@subsection Debugging Redisplay Errors
+@cindex redisplay errors
+@cindex debugging redisplay errors
+
+When an error occurs in Lisp code which redisplay has invoked, Emacs's
+usual debugging mechanisms are unusable, for technical reasons.  This
+subsection describes how to get a backtrace from such an error, which
+should be helpful in debugging it.
+
+These directions apply to Lisp forms used, for example, in
+@code{:eval} mode line constructs (@pxref{Mode Line Data}), and in all
+hooks invoked from redisplay, such as:
+
+@itemize
+@item
+@code{fontification-functions} (@pxref{Auto Faces}).
+@item
+@code{window-scroll-functions} (@pxref{Window Hooks}).
+@end itemize
+
+Note that if you have had an error in a hook function called from
+redisplay, the error handling might have removed this function from
+the hook.  You will thus need to reinitialize that hook somehow,
+perhaps with @code{add-hook}, to be able to replay the bug.
+
+To generate a backtrace in these circumstances, set the variable
+@code{backtrace-on-redisplay-error} to non-@code{nil}.  When the error
+occurs, Emacs will dump the backtrace to the buffer
+@file{*Redisplay-trace*}, but won't automatically display it in a
+window.  This is to avoid needlessly corrupting the redisplay you are
+debugging.  You will thus need to display the buffer yourself, with a
+command such as @code{switch-to-buffer-other-frame} @key{C-x 5 b}.
+
+@defvar backtrace-on-redisplay-error
+Set this variable to non-@code{nil} to enable the generation of a
+backtrace when an error occurs in any Lisp called from redisplay.
+@end defvar
+
 @node Infinite Loops
 @subsection Debugging Infinite Loops
 @cindex infinite loops
diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index ace67fbedb7..96079dc106a 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -8596,9 +8596,9 @@ Characters of Unicode General Category [Cf], such as U+200E
 images, such as U+00AD @sc{soft hyphen}.
 
 @item variation-selectors
-Unicode VS-1 through VS-16 (U+FE00 through U+FE0F), which are used to
-select between different glyphs for the same codepoints (typically
-emojis).
+Unicode VS-1 through VS-256 (U+FE00 through U+FE0F and U+E0100 through
+U+E01EF), which are used to select between different glyphs for the same
+codepoints (typically emojis).
 
 @item no-font
 Characters for which there is no suitable font, or which cannot be
diff --git a/doc/lispref/functions.texi b/doc/lispref/functions.texi
index 8265e58210e..ddf7cff6c2e 100644
--- a/doc/lispref/functions.texi
+++ b/doc/lispref/functions.texi
@@ -217,6 +217,14 @@ function.  For example:
 @end example
 @end defun
 
+@defun compiled-function-p object
+This function returns @code{t} if @var{object} is a function object
+that was either built-in (a.k.a.@: ``primitive'', @pxref{What Is a
+Function}), or byte-compiled (@pxref{Byte Compilation}), or
+natively-compiled (@pxref{Native Compilation}), or a function loaded
+from a dynamic module (@pxref{Dynamic Modules}).
+@end defun
+
 @defun subr-arity subr
 This works like @code{func-arity}, but only for built-in functions and
 without symbol indirection.  It signals an error for non-built-in
diff --git a/doc/lispref/loading.texi b/doc/lispref/loading.texi
index 0972a7a123c..4e4f12dc324 100644
--- a/doc/lispref/loading.texi
+++ b/doc/lispref/loading.texi
@@ -440,7 +440,7 @@ similarly-named file in a directory earlier on @code{load-path}.
 For instance, suppose @code{load-path} is set to
 
 @example
-  ("/opt/emacs/site-lisp" "/usr/share/emacs/23.3/lisp")
+  ("/opt/emacs/site-lisp" "/usr/share/emacs/29.1/lisp")
 @end example
 
 @noindent
diff --git a/doc/lispref/objects.texi b/doc/lispref/objects.texi
index 1bae1924557..7b5e9adee29 100644
--- a/doc/lispref/objects.texi
+++ b/doc/lispref/objects.texi
@@ -2022,6 +2022,9 @@ with references to further information.
 @item byte-code-function-p
 @xref{Byte-Code Type, byte-code-function-p}.
 
+@item compiled-function-p
+@xref{Byte-Code Type, compiled-function-p}.
+
 @item case-table-p
 @xref{Case Tables, case-table-p}.
 
diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi
index d591b219cd0..35828018417 100644
--- a/doc/lispref/os.texi
+++ b/doc/lispref/os.texi
@@ -1544,11 +1544,11 @@ as traditional Gregorian years do; for example, the year number
 @defun time-convert time form
 This function converts a time value into a Lisp timestamp.
 
-The optional @var{form} argument specifies the timestamp form to be
-returned.  If @var{form} is the symbol @code{integer}, this function
-returns an integer count of seconds.  If @var{form} is a positive
-integer, it specifies a clock frequency and this function returns an
-integer-pair timestamp @code{(@var{ticks} . @var{form})}.  If @var{form} is
+The @var{form} argument specifies the timestamp form to be returned.
+If @var{form} is the symbol @code{integer}, this function returns an
+integer count of seconds.  If @var{form} is a positive integer, it
+specifies a clock frequency and this function returns an integer-pair
+timestamp @code{(@var{ticks} . @var{form})}.  If @var{form} is
 @code{t}, this function treats it as a positive integer suitable for
 representing the timestamp; for example, it is treated as 1000000000
 if @var{time} is @code{nil} and the platform timestamp has nanosecond
diff --git a/doc/lispref/processes.texi b/doc/lispref/processes.texi
index 382053ab24a..db6b4c35ef7 100644
--- a/doc/lispref/processes.texi
+++ b/doc/lispref/processes.texi
@@ -1960,7 +1960,6 @@ because @var{seconds} can be floating point to specify
 waiting a fractional number of seconds.  If @var{seconds} is 0, the
 function accepts whatever output is pending but does not wait.
 
-@c Emacs 22.1 feature
 If @var{process} is a process, and the argument @var{just-this-one} is
 non-@code{nil}, only output from that process is handled, suspending output
 from other processes until some output has been received from that