Re: Q: child frames on ttys

["Gerd Möllmann" <gerd.moellmann@gmail.com>]

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Gerd Möllmann <gerd.moellmann@gmail.com> writes:

> Gerd Möllmann <gerd.moellmann@gmail.com> writes:
>
>> Gerd Möllmann <gerd.moellmann@gmail.com> writes:
>
>> * What we have
>>
>> Child frames are created with the =parent-frame= frame parameter on
>> GUIs. This parameter can be changed at any time to create a hierarchy
>> of child fremes. It can be reset to make a frame a non-child frame.
>>
>> A terminal's =tty_display_info= contains a =top_frame= member which is the
>> topmost frame in z-order, where z-order is a bit misleading because
>> all frames currently occupy the whole terminal screen. IOW making a
>> frame the topmost frame obsures all other frames.
>>
>> Redisplay considers topmost frames only (more than one for multiple
>> terminals).
>>
>> The function =frame-restack= can be used to change the z-order of
>> frames. It currently does not handle tty frames.
>>
>> =frame-list= contains child frames.
>>
>> * Terminology
>>
>> A =root frame= is a frame with no parent frame. It always occupies the
>> whole terminal.
>>
>> * Steps
>>
>> 1. Let frames have arbitrary ~(x, y, w, h)~ except for root frames,
>>    which have ~(0, 0, terminal-width, terminal-height)~. Change
>>    =frame-geometry=.
>>
>> 2. Give root frames a =child_frames= list which is in z-order, topmost
>>    last. Add a =tty-frame-restack= which acts on this list.
>>
>> 3. In =redisplay_internal=, act only on root frames. Generating desired
>>    glyphs generates glyphs for the root frame, then child frames in
>>    z-order, topmost last, i.e. in the order of =frame::child_frames=.
>>
>> 4. Making a frame visible means making all children frames visible.
>>
>> 5. Do not clear the terminal, unless switching to another root frame.
>>
>> 6. Update: Build frame matrices for all windows visible on a terminal.
>>    Copy visible parts of child fraem desired glyphs to root frame
>>    desired glyphs. Then write to the screen.
>>
>> 7. After writing to the screen, copy visble parts of root frame
>>    current glyphs to current glyphs of children.
>
> Changed this to:
>
> 7. After writing to the screen, for all child frames that were
>    displayed, update current matrices from desired matrices. There is
>    no need to copy glyphs from the root frame since we have them already in
>    the desired matrix.
>
>> 8. Add something like =ns-frame-list-z-order= for ttys.
>>
>> * Don't
>>
>> 1. Allocate child frame glyphs from a common pool. Reason is clipping.
>>    Don't want to change glyph generation in redisplay to take clipping
>>    into account. It's not worth the effort.

So, this seems to work, at least in principle. Where in principle means
I didn't try much yet, but it looks like I can at least display
overlapping child frames.


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I have a question regarding the child frame feature in general though.

As I said before, I want to use them for Corfu and Posframe, the latter
with Vertico and Transient. But the child frame feature looks like
something much more general, more like a general MDI feature, as opposed
to SDI. And my question is: Is that actually used somewhere? In some
package, or in Emacs itself? If it is, I'd be grateful for a pointer.

(Background is of course that I'm trying to assess how much work is
ahead, and if I want to do it :-).