Customising helm-mini to have filterd buffers

Question

In my current setup, not having customised it, helm-mini shows me all the buffers in a single list, it then shows the recent files and a section to "Create buffer".

I am wondering if it's possible to have multiple lists of buffers with different filters. Namely, I would like to have a section showing normal buffers, a section showing temporary buffers (normally starting and ending with *), and a section for orphan buffers (not connected to a file).

Answer 1

Based on @jagrg answer, I managed to come up with this

  (defclass tohiko/helm-source-file-buffers (helm-source-buffers)
  ((candidate-transformer :initform (lambda (buffers)
                                     (cl-loop for buf in buffers
                                              when (with-current-buffer
                                                         buf buffer-file-name)
                                              collect buf))))
  )

  (defclass tohiko/helm-source-nonfile-buffers (helm-source-buffers)
  ((candidate-transformer :initform (lambda (buffers)
                                     (cl-loop for buf in buffers
                                              unless (with-current-buffer
                                                         buf buffer-file-name)
                                              collect buf))))
  )

  (setq tohiko/helm-source-file-buffers-list
        (helm-make-source "File Buffers" 'tohiko/helm-source-file-buffers))
  (setq tohiko/helm-source-nonfile-buffers-list
        (helm-make-source "Non-file Buffers" 'tohiko/helm-source-nonfile-buffers))

(setq helm-mini-default-sources '(tohiko/helm-source-file-buffers-list
                                  tohiko/helm-source-nonfile-buffers-list
                                  helm-source-recentf 
                                  helm-source-buffer-not-found))

Although I am a beginner, so I am not sure if I am defining the class correctly. Also, I am using helm-make-source rather than helm-build-in-buffer-source, as @jagrg suggested, I am not sure what the difference is.

Finally, while this view does show new buffers that are not saved, I haven't figured out how to separate them into their own list.

Answer 2

I think you would have to write your own sections, which in helm terms is called sources, and either add them to the helm-mini-default-sources variable or create your own custom command. Filtering is usually done in the candidate-transformer or filtered-candidate-transformer slots. See helm-source-in-buffer for more information.

I'm not sure I understand how you're distinguishing temporary from orphan buffers, maybe you can explain in the comments, but for file buffers and non-file buffers you could try:

(setq tohiko/helm-source-file-buffers
      (helm-build-in-buffer-source "File Buffers"
    :data 'helm-buffer-list
    :candidate-transformer (lambda (buffers)
                 (cl-loop for buf in buffers
                      when (with-current-buffer
                           buf buffer-file-name)
                      collect buf))
    :action (lambda (buffer)
          (switch-to-buffer buffer))))

(setq tohiko/helm-source-nonfile-buffers
      (helm-build-in-buffer-source "Non-file Buffers"
    :data 'helm-buffer-list
    :candidate-transformer (lambda (buffers)
                 (cl-loop for buf in buffers
                      unless (with-current-buffer
                             buf buffer-file-name)
                      collect buf))
    :filtered-candidate-transformer 'helm-skip-boring-buffers
    :action (lambda (buffer)
          (switch-to-buffer buffer))))

(setq helm-mini-default-sources '(tohiko/helm-source-file-buffers
                  tohiko/helm-source-nonfile-buffers
                  helm-source-buffer-not-found))