How can I debug a function that performs most work in a temporary buffer?

Question

I've been able to do this before, but I can't remember the 'recipe' of sorts.

Say I've got the following function:

(defun fancy-stuff ()
  (with-current-buffer (get-crazy-process-output)
    (do-crazy-post-process)))

I want to debug the crazy post-processing and be able to see where/when it moves point in that buffer.

I've of course instrumented do-crazy-post-process with edebug-defun, but when I step through the code, I have no visual indication of how point is moving in the temporary buffer.

Answer 1

True to form, I found the answer while asking the question. For anyone else who finds this useful:

(view-buffer-other-window (current-buffer))

If you place this form anywhere in the form that's being instrumented, you'll see point move in real-time as you step through the code. For example,

(defun fancy-stuff ()
  (with-current-buffer (get-crazy-process-output)
    (view-buffer-other-window (current-buffer))
    (do-crazy-post-process)))

Answer 2

I found this question because I was having trouble debugging a function that used with-temp-buffer. Using edebug one can press p to temporarily switch to where point is, but this isn't much good because the temp buffer will be gone once edebug is finished.

The easy way in this case is to replace

(with-temp-buffer
  stuff)

with

(with-current-buffer (get-buffer-create "temp-buffer")
  stuff)

And then use the trick above, so:

(with-current-buffer (get-buffer-create "temp-buffer")
  (view-buffer-other-window (current-buffer))
  stuff)

Now the temp buffer will still be around afterwards for inspection.