Re: Broken commandline

[Hans-Peter Sorge]

    Hi Jürgen,
    
    thank you for comment.
    
    I am quite sure it's not an APL-character problem.
    
    The characters in question are defined within the APL-keyboard
    layout as normal UTF-8 characters.
    
    The "overlay" I experience is different from APL-Character over
    strike:
    An APL over strike is   character-backspace-character
    
    The UTF-8 character display problem is: 
      - enter APL-character,   see  half-space-left-half-character
      - enter [SPACE],         see right-half-character-half-space
      - in effect having one character displayed in two consecutive
    positions.
      - Entering a third character. It will not display. 'Covered' by
    [SPACE] 
              
    
    The following code (run in Konsole 21.04.1)

• KDE Frameworks 5.82.0
• Qt 5.15.2 (kompiliert gegen 5.15.2)
• Das xcb Fenstersystem

    displays
    a couple of UTF characters (many non APL).
    
    Then selecting a line the selection will show that selected
    characters move to the left.
    
    for ((a=128;a<192;a=a+1)); do 
          for ((n=128;n<190;n=n+1));do 
               printf -vh '\\x%2x\\x%2x\\x%2x' 226 $a $n;
               echo -en "$h";
               done;
          echo;
          done
    
    It seems to me, that eg. Chinese characters take twice the space
    compared with simple UTF characters.
    When the Chinese characters get selected, they do not 'shrink'. 
    
    However, there are "graphically oriented" UTF characters (including
    ⍝⊖⍟⍱), that take two character positions when being displayed
    and take one character position when being selected.   
    
    So it's not an APL character / font handling problem. It Just
    happened to be the first popup.
    
    I'll open a bug report with Fedora.
    
    Best Regards
    
    Hans-Peter

Am 03.06.21 um 11:49 schrieb Dr. Jürgen Sauermann:

> Hi
>       Hans-Peter,
>       
>       
>       the behaviour that you describe looks like somewhere in your
>       platform there
>       
>       is some character-backspace-character detector active that
>       replaces the
>       
>       characters displayed when they are being overstruck.
>       
>       
>       I wrote such character-backspace-character detectors myself in the
>       1980s
>       
>       as part of (APL-) terminal drivers and my experience from that
>       time is that they
>       
>       were somewhat unreliable (for example, you had to consider the
>       time between the
>       
>       different keystrokes to distinguish between a valid overstrike
>       sequence and the
>       
>       same sequence with backspace meaning to delete (the first
>       character) rather than
>       
>       overstrike, auto-line feed of the terminal at the end of a long
>       line, etc.).
>       
>       
>       For that reason i took care not to implement overstrike sequences
>       in GNU
>       
>       APL but to maintain a strict 1:1 relation between keystrokes and
>       APL
>       
>       characters (which was not possible in the 1980s due to the lack of
>       Unicode).
>       
>       
>       As a consequence, your platform should not become aware of APL
>       
>       in the first place but rather behave like a standard Unicode
>       terminal.
>       
>       Note that Unicode has its own overstrike-like mechanism which is
>       
>       entirely incompatible with the old APL overstrikes (and this
>       mechanism
>       
>       should not be used either with GNU APL).
>       
>       
>       I believe the other applications follow suit here (in not
>       supporting overstrikes)
>       
>       while firefox (or maybe X) tries to.
>       
>       
>       Again, GNU APL was specifically designed to not not need APL fonts
>       in the first
>       
>       place and using them nevertheless will therefore cause more
>       trouble then help.
>       
>       
>       Best Regards,
>       
>       Jürgen
>       
>       
>       
>       On 6/2/21 11:23 AM, Hans-Peter Sorge wrote:
>       
> > Hi,
> >         
> >         
> >         I am on Fedora 34 now (apl SVN: 1198:1472M)
> >         
> >         
> >         The apl font partially fails to work with keyboard layout apl.
> >         
> >         
> >         The "over strike characters" ⌽⍉⍟⍝⍱⍲ ,when entered in a terminal,
> >         appear in half....
> >         
> >         The left half of the character is being displayed when entered.
> >         
> >         The right half appears when space bar is being pressed.
> >         
> >         Anny further character entered is being offset by one.
> >         
> >         
> >         That is  ⌽[space]ABC  -> ends up as ⌽BC where space bar
> >         "overlays" character A!
> >         
> >         The Apl-Session, terminal, emacs, vi are affected too. slikedid,
> >         Firefox are OK.
> >         
> >         
> >         If changing the layout via *setxkbmap -layout "apl"* I get ����
> >         instead of ⌽⍉⍟⍝.
> >         
> >         The � are being displayed the same way as described above: Left
> >         half character, [SPACEBAR] right half of the character.
> >         
> >         
> >         I installed apl from the repository to verify the behavior -
> >         that segfaults.
> >         
> >         
> >         The font-manager shows
> >         
> >         ⍝  APL FUNCTIONAL SYMBOL UP SHOE JOT   U+235D
> >         
> >         So there is nothing special about this and 'normal' UTF-8
> >         characters.
> >         
> >         
> >         The terminal font is set to *latarcyrheb-sun16* in
> >         */etc/voconsole.conf.*
> >         
> >         
> >         Changing the terminal font to either Unifont-APL8x16-12.1.02 or
> >         NotoSansMono did not help.
> >         
> >         
> >         Emacs:
> >         
> >         After some 'fiddling around' font changes with emacs *M-x
> >         menu-set-font* will display ⍝ in one go,
> >         
> >         Char ⍝ will be displayed for different fonts - even if the
> >         font-manager does not show it.
> >         
> >         Char ⍝ with font NotoSansMono selected will be displayed in one
> >         shot but with additional spacing to the left and right.
> >         
> >         Char ⍝ with Unifont selected will be displayed w/o spacing.
> >         
> >         ( The console fonts and the content of *menu-set-font* are
> >         different...)
> >         
> >         
> >         Hopefully some one has an idea where / how to dig deeper into
> >         the problem.
> >         
> >         
> >         Best Regards
> >         
> >         Hans-Peter
> >         
> >         
> >         
> >         
> >         Is there / some where an experiment going on to 'improve'
> >         character composition?
> >         
> >         
> >         
> >         
> >       
>       
>