* lisp/emacs-lisp/trace.el: Rewrite, use nadvice and lexical-binding.

(trace-buffer): Don't purecopy.
(trace-entry-message, trace-exit-message): Add `context' arg.
(trace--timer): New var.
(trace-make-advice): Adjust for use in nadvice.
Add `context' argument.  Delay `display-buffer' via a timer.
(trace-function-internal): Use advice-add.
(trace--read-args): New function.
(trace-function-foreground, trace-function-background): Use it.
(trace-function): Rename to trace-function-foreground and redefine as
an alias to that new name.
(untrace-function, untrace-all): Adjust to the use of nadvice.

1 files changed, 9 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index b63d3f8d538..6ef093991ae 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -32,6 +32,15 @@ so we will look at it and add it to the manual.
 +++
 ** New function `ses-rename-cell' to give SES cells arbitrary names.
 
+** trace-function was largely rewritten.
+New features include:
+- no prompting for the destination buffer, unless a prefix-arg was used.
+- additionally to prompting for a destination buffer, when a prefix-arg is
+  used, the user can enter a "context", i.e. Lisp expression whose value at the
+  time the function is entered/exited will be printed along with the function
+  name and arguments.  Useful to trace the value of (current-buffer) or
+  (point) when the function is invoked.
+
 
 * New Modes and Packages in Emacs 24.4
 ** New nadvice.el package offering lighter-weight advice facilities.