[konsole] [Bug 403729] New: Proper BiDi support

[Egmont Koblinger]

https://bugs.kde.org/show_bug.cgi?id=403729

            Bug ID: 403729
           Summary: Proper BiDi support
           Product: konsole
           Version: unspecified
          Platform: Other
                OS: Linux
            Status: REPORTED
          Severity: wishlist
          Priority: NOR
         Component: emulation
          Assignee: konsole-devel at kde.org
          Reporter: egmont at gmail.com
  Target Milestone: ---

Konsole's BiDi suffers from several problems. (Apparently all it does is passes
continuous runs of identical attributes to some BiDi-aware font rendering.
There's much more to BiDi than this.)

Here's some of the problems (the list is not complete):

- It unconditionally applies the BiDi algorithm on the contents. This makes it
literally, mathematically provably impossible to have proper BiDi-aware text
viewers/editors on top of such a platform. (You can disable BiDi in the
settings, but having to do so every time one enters or leaves a text editor is
an unacceptable user experience.)

- It applies BiDi on lines of text, rather than paragraphs as the BiDi
algorithm specifies.

- Upon every change of text attributes, it starts over the BiDi algorithm. That
is, e.g. the output of a "grep" which colors the match doesn't show up
properly.

- Also a side effect of the latter: text highlighting experience is terrible,
the characters move around as you highlight with the mouse.

- There's no support for overall right alignment (bug 401185).

I've spent a couple of months studying the topic, and came up with a first
draft proposal for the desired behavior, available at
https://terminal-wg.pages.freedesktop.org/bidi/ .

I'm inviting you to join the discussion of the proposal if you have any
comments, and asking you to implement BiDi according to that proposal.

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