bug#38354: 27.0.50; Implement display action display-buffer-in-tab

[Juri Linkov <juri@linkov.net>]

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> With "moving" I really meant "copying" or "cloning" with the
> additional possibility of deleting the original.  So there should be
> only one question: Can we simply make a copy of a tab using its window
> state (window configurations can't be used because we cannot clone
> windows).  If not, what is the problem?

Implemented in the patch below that deletes the window-configuration
from the copied tab, but leaves its window-state.

>> An additional question to consider is how to interactively select
>> an another frame: by frame name, or using other-frame with a numeric
>> prefix argument?
>
> How is this question related to tabs?

Easier to implement than to explain :)  The same patch uses its ARG
the same way as it's used in 'other-frame' to find ARGth frame
where to copy the tab.

>> (push '("test1" .
>>           (display-buffer-reuse-window
>>            (reusable-frames  . visible)
>>            (use-tabs . t)))
>>         display-buffer-alist)
>
> There is one thing I apparently do not understand yet: When you enable
> 'tab-bar-mode' it is global

Do you think we should have 'global-tab-bar-mode' for all frames,
and 'tab-bar-mode' to enable/disable the tab-bar in every frame
separately?

> - that is any window ever shown on any frame is also in at least one
> of that frame's tabs.  Is that right?  So what would 'use-tabs' mean
> here when every window is in a tab already?

These windows in tabs are in window-configurations and window-states.
Now I installed tab-bar-get-buffer-tab that can be used
in display-buffer-reuse-window to search the buffer
in window-states of tabs when use-tabs is non-nil.

>>>    By default, a new tab starts with the current buffer that was current
>>>    before calling the command that adds a new tab.
>>>
>>> That's confusing, at least.
>>
>> Maybe this is better?
>>
>>    By default, a new tab starts with the buffer that was current
>>    before calling the command that adds a new tab.
>
> The current buffer is IMHO a much too obscure object to consider here.
> Don't you mean the buffer of the selected window?

The manual refers to the default value of tab-bar-new-tab-choice
with its docstring:

  If t, start a new tab with the current buffer, i.e. the buffer
  that was current before calling the command that adds a new tab
  (this is the same what `make-frame' does by default).


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diff --git a/lisp/tab-bar.el b/lisp/tab-bar.el
index a36be13e37..340f012247 100644
--- a/lisp/tab-bar.el
+++ b/lisp/tab-bar.el
@@ -645,6 +645,33 @@ tab-bar-move-tab
          (to-index (mod (+ from-index arg) (length tabs))))
     (tab-bar-move-tab-to (1+ to-index) (1+ from-index))))
 
+(defun tab-bar-move-tab-to-frame (arg &optional from-frame from-index to-frame to-index)
+  "Move tab from FROM-INDEX position to new position at TO-INDEX.
+FROM-INDEX defaults to the current tab index.
+FROM-INDEX and TO-INDEX count from 1.
+FROM-FRAME specifies the source frame and defaults to the selected frame.
+TO-FRAME specifies the target frame and defaults the next frame.
+Interactively, ARG selects the ARGth different frame to move to."
+  (interactive "P")
+  (unless from-frame
+    (setq from-frame (selected-frame)))
+  (unless to-frame
+    (dotimes (_ (prefix-numeric-value arg))
+      (setq to-frame (next-frame to-frame))))
+  (unless (eq from-frame to-frame)
+    (let* ((from-tabs (with-selected-frame from-frame
+                        (funcall tab-bar-tabs-function)))
+           (from-index (or from-index (1+ (tab-bar--current-tab-index from-tabs))))
+           (from-tab (nth (1- from-index) from-tabs))
+           (to-tabs (with-selected-frame to-frame
+                      (funcall tab-bar-tabs-function)))
+           (to-index (max 0 (min (1- (or to-index 1)) (1- (length to-tabs))))))
+      (setq from-tabs (delq from-tab from-tabs))
+      (cl-pushnew (assq-delete-all 'wc from-tab) (nthcdr to-index to-tabs))
+      (set-frame-parameter from-frame 'tabs from-tabs)
+      (set-frame-parameter to-frame 'tabs to-tabs)
+      (force-mode-line-update t))))
+
 \f
 (defcustom tab-bar-new-tab-to 'right
   "Defines where to create a new tab.