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Looking into it.

I can't reproduce the problem. What does your config look like? What do you see when you describe-key TAB on a button?

@Alexander-Miller Thank you for looking into this issue.

I can confirm that this issue still exist with the latest version available on Melpa, reproducible with a minimal setup.

I tested with a minimal setup this time so here are some clarification of the symptoms:
Please note that this issue only exists on terminal.
The issue only exist for top level buttons (i.e. project buttons) when cursor is NOT at end of line.
That is:

• doing C-e first, tab triggers treemacs-TAB-action as expected.
• for folders of a project, pressing tab works as expected.

Here is the output of describe-key on a terminal:

TAB runs the command forward-button (found in button-map), which is an
interactive byte-compiled Lisp function in ‘button.el’.

It is bound to TAB.

--> Note that this is TAB but NOT <tab>

For GUI, pressing tab key (the physical action) always triggers treemacs-TAB-action, output of describe-key

<tab> runs the command treemacs-TAB-action (found in
treemacs-mode-map), which is an interactive byte-compiled Lisp
function in ‘treemacs-interface.el’.

--> This is <tab>, NOT TAB. I am not familiar with the code so I am not sure if this can be any clue.

Minimal setup

My Emacs is: GNU Emacs 29.1

I can reproduce this issue with this minimal setup:

1. Create a new directory and cd into it
2. Two options:
   a. Do mkdir elpa and symlink relavent packages into it.
   b. Do M-x package-install then type treemacs, needs Melpa. I used this method.
3. Use this init.el:

(package-initialize)
;; uncomment these if you do `M-x package-install`
;; (require 'package)
;; (add-to-list
;;  'package-archives '("melpa" . "http://melpa.org/packages/"))

(global-set-key (kbd "C-c t") 'treemacs-select-window) ; this is NOT needed to reproduce the error.

(custom-set-variables
   '(package-selected-packages
     '(treemacs))
)

Here are the version numbers from melpa that I used for the dependencies for treemacs:

• treemacs-20231016.2107
• ace-window-20220911.358
• avy-20230420.404
• cfrs-20220129.1149
• dash-20230714.723
• ht-20230703.558
• hydra-20220910.1206
• lv-20200507.1518
• pfuture-20220913.1401
• posframe-20230714.227
• s-20220902.1511

Other (possibly irrelevant) environment informations:

system-configuration-features is:

system-configuration-features is a variable defined in ‘C source code’.

Its value is
"ACL GLIB GMP GNUTLS JPEG JSON LIBXML2 MODULES NOTIFY KQUEUE NS PDUMPER PNG RSVG THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER ZLIB"

--> I do NOT have NATIVE-COMP so should the problem should be fairly reproducible.

system info:

OS: macOS Big Sur 11.4 20F71 x86_64
Shell: zsh 5.8
Terminal: kitty 0.30.0
CPU: Intel(R) Core(TM) i5-1038NG7 (8) @ 2 GHz

--> I do NOT think these are relevant

Please tell me if you need more info.
I can sent you an archive of the said minimal setup if you need it.

I have reproduced the problem now, but I've been unable to come up with a fix that's limited to treemacs. I don't know what's different about projects vs other nodes, but this tab misbind is really persistent.

However I do have a solution you can use. I've the following like in my config: (define-key input-decode-map "\C-i" [C-i]). It's supposed to differentiate between tab vs C-i in the terminal, but it should also fix your particular problem.

@Alexander-Miller Your work around is better than mine as mines involves more keypresses with my pinky. Thank you from my future self.

As a summary:

My understanding of the culprit (cause) of this issue:

1. button-buffer-map (button.el) binds TAB as a minor mode key map, which take precedence over buffer local ones
2. The "tab keyboard press" sends TAB in (most) terminal emulator
3. The "tab keyboard press" sends <tab> in Emacs GUI

1 + 3 -> symptom: tab still works in GUI
1 + 2 -> symptom: tab does NOT works only in terminal

With the above understanding there are only a few possible fixes:

• [addresses 1.] remove the TAB binding from button-buffer-map (e.g. at init.el)

• [addresses 1.] use a smaller button (e.g. only the icon)

• [addresses 1.] use keymap for mouse instead of button

• [addresses 2.] send a different key

  • via Emacs <-- your suggestion
  • via your terminal emulator

  --> Is your understanding same as mine?

I had another go at debugging this, and this time I have found how the button-map is actually injected into treemacs (despite it mostly using its own stripped down version of buttons for a very long time). Long story short: a proper solution is possible after all, the latest treemacs should fix your problem now.

Thanks for the fix, I would not have known that the keymap is actually bind at the text properties instead of minor mode.
May I ask how you debug this? Do you bisect or use any other tools or tricks?