Fix removing multibyte characters in prompt, fixes #974

[necauqua]

This change does what i've said in #974, works well for me.

[actionless]

bit32 is available only in lua 5.2

in lua 5.3 you can do rshift with >>, but idk how to handle that for lua 5.1

[necauqua]

Oh, i see
I know about operators, but bit32 is still in 5.3 (which i have) so i thought this is good enough to be universally compatible.

I've just realized that you can just compare if byte is in range [128;192) instead, huh

[codecov]

Codecov Report

Merging #2383 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2383      +/-   ##
==========================================
+ Coverage   83.97%   83.98%   +0.01%     
==========================================
  Files         477      477              
  Lines       32750    32746       -4     
==========================================
+ Hits        27502    27503       +1     
+ Misses       5248     5243       -5

Flag	Coverage Δ
#c_code	72.58% <ø> (+0.01%)	⬆️
#functionaltests	71.93% <0%> (+0.01%)	⬆️
#lua53	87.14% <100%> (+0.01%)	⬆️
#samples	71.73% <0%> (+0.01%)	⬆️
#unittests	58.33% <100%> (+0.02%)	⬆️

Impacted Files	Coverage Δ
lib/awful/prompt.lua	48.58% <100%> (+0.49%)	⬆️
property.c	77.67% <0%> (+0.46%)	⬆️

[actionless]

but bit32 is still in 5.3 (which i have)

mb you got installed it from luarocks as dep for some other app?

[necauqua]

luarocks said that it is installed and provided by VM or rocks_provided, idk what it means, but i guess there is really no deprecated bit32 module in Lua 5.3, yeah.
Anyway, fixed it with range check

[actionless]

https://travis-ci.org/awesomeWM/awesome/jobs/425915324#L3404

[necauqua]

There is always that one thing that I miss (multiple times), ugh

[necauqua]

I've realized that there is also an unfixed delete
Just no cursor movement allowed (for me at least) in desktop icons prompt to notice
For delete you can also remove one byte and then remove continuation bytes in a loop, but utf-8 has the prefix code, so delete could work a bit quicker, i guess:

if byte < 128 => remove 1 byte
elseif byte < 192 => continuation byte, shoulnt get there normally, remove it(with a loop so no broken utf left)?
elseif byte < 224 => remove 2 bytes
elseif byte < 240 => remove 3 bytes
elseif byte < 248 => remove 4 bytes
else => definitely invalid utf

May i commit such a fix when i get back to my PC?

above comment

[actionless]

idk, mb to add some helper to gears for working with utf8 strings?

[necauqua]

Update:

• laptop broke, had to finally buy a good new one (and except that i am busy with university and so on)
• offset calculation function works, i only have some minor problems with surrogates
• in process of redoing that ugly if-elseif 300 or so lines in awful.prompt to be more abstract (e.g. there are duplicates and i upgraded to utf-8 only ctlr+backspace but there is still ctrl+w and so on).

And yeah, awful.prompt's cursor variable counts bytes and not codepoints (as it did) to make string.sub function useful (and not to redo awful.prompt completely) and cursor moves by calculated delta of bytes.

[actionless]

@necauqua any update on this?

[necauqua]

Uh, completely forgot about this, I'm sorry.
I've moved to full-time job in october and since I am also a student, I did no code for joy at home in like a month (not counting small and simple labworks for the university).
I'll try to finish this on weekend maybe

[actionless]

no worries, take your time; i was just checking up for stalled PRs