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curses.addch('a', curses.color_pair(1)) ignores the color information #81919

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mgedmin mannequin opened this issue Aug 1, 2019 · 8 comments
Closed

curses.addch('a', curses.color_pair(1)) ignores the color information #81919

mgedmin mannequin opened this issue Aug 1, 2019 · 8 comments
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3.7 (EOL) end of life 3.8 only security fixes 3.9 only security fixes stdlib Python modules in the Lib dir

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@mgedmin
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mgedmin mannequin commented Aug 1, 2019

BPO 37738
Nosy @mgedmin, @vstinner, @miss-islington
PRs
  • bpo-37738: Fix curses addch(str, color_pair) #15071
  • [3.8] bpo-37738: Fix curses addch(str, color_pair) (GH-15071) #15272
  • [3.7] bpo-37738: Fix curses addch(str, color_pair) (GH-15071) #15273
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    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = None
closed_at = <Date 2019-08-14.11:01:28.955>
created_at = <Date 2019-08-01.13:45:15.175>
labels = ['3.8', '3.7', 'library', '3.9']
title = "curses.addch('a', curses.color_pair(1)) ignores the color information"
updated_at = <Date 2019-08-14.11:01:28.954>
user = 'https://github.com/mgedmin'

    bugs.python.org fields:

    activity = <Date 2019-08-14.11:01:28.954>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2019-08-14.11:01:28.955>
closer = 'vstinner'
components = ['Library (Lib)']
creation = <Date 2019-08-01.13:45:15.175>
creator = 'mgedmin'
dependencies = []
files = []
hgrepos = []
issue_num = 37738
keywords = ['patch']
message_count = 8.0
messages = ['348855', '348862', '348863', '349672', '349673', '349674', '349676', '349677']
nosy_count = 3.0
nosy_names = ['mgedmin', 'vstinner', 'miss-islington']
pr_nums = ['15071', '15272', '15273']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue37738'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']
    @mgedmin
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    mgedmin mannequin commented Aug 1, 2019

    curses.addch() ignores color information if I pass it a string of length one. Color works fine if I pass it a byte string or an int. Here's a reproducer:

    ### start of example ###
import curses                                                                                                                               
                                                                                                                                            
                                                                                                                                            
def main(stdscr):                                                                                                                           
    curses.start_color()                                                                                                                    
    curses.use_default_colors()                                                                                                             
    curses.init_pair(1, curses.COLOR_RED, -1)                                                                                               
    curses.init_pair(2, curses.COLOR_GREEN, -1)                                                                                             
    curses.curs_set(0)                                                                                                                      
                                                                                                                                            
    stdscr.addch("a", curses.color_pair(1))                                                                                                 
    stdscr.addch("b", curses.color_pair(2) | curses.A_BOLD)                                                                                 
    stdscr.addch(b"c", curses.color_pair(1))                                                                                                
    stdscr.addch(b"d", curses.color_pair(2) | curses.A_BOLD)                                                                                
    stdscr.addch(ord("e"), curses.color_pair(1))                                                                                            
    stdscr.addch(ord("f"), curses.color_pair(2) | curses.A_BOLD)                                                                            
    stdscr.refresh()                                                                                                                        
                                                                                                                                            
    stdscr.getch()                                                                                                                          
                                                                                                                                            
                                                                                                                                            
curses.wrapper(main)                                                                                                                        
### end of example ###

    On Python 2.7 this prints 'abcdef' in alternating red and green. On Python 3.5 through 3.8 this prints 'ab' in white and the rest in red/green.

    Note that only color pair information is lost -- the bold attribute is correctly set on the 'b'.

    @mgedmin mgedmin mannequin added 3.7 (EOL) end of life 3.8 only security fixes stdlib Python modules in the Lib dir labels Aug 1, 2019
    @vstinner
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    vstinner commented Aug 1, 2019

    stdscr.addch(str, color_pair) is implemented with:

    setcchar(&wcval, wstr, attr, 0, NULL);
    rtn = wadd_wch(self->win, &wcval);

    whereas stdscr.addch(bytes, color_pair) is implemented with:

       rtn = waddch(self->win, cch | (attr_t) attr);

    The 4th argument of setcchar() is "short color_pair": Python always pass 0. It seems to be your bug.

    Attached PR 15071 fix this bug.

    Note: Python 3.5 and 3.6 don't accept bugfixes anymore, only security fixes.

    @vstinner
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    vstinner commented Aug 1, 2019

    I'm able to reproduce the issue on Fedora 30: Python 3.7.4 with ncurses-libs-6.1-10.20180923.fc30.x86_64.

    vstinner@apu$ cat /etc/fedora-release
    Fedora release 30 (Thirty)
    vstinner@apu$ python3 -VV
    Python 3.7.4 (default, Jul 9 2019, 16:32:37)
    [GCC 9.1.1 20190503 (Red Hat 9.1.1-1)]
    vstinner@apu$ python3 -c 'import _curses; print(curses.__file_)'
    /usr/lib64/python3.7/lib-dynload/curses.cpython-37m-x86_64-linux-gnu.so
    vstinner@apu$ ldd $(python3 -c 'import _curses; print(curses.__file    )')
    linux-vdso.so.1 (0x00007ffe6f1b4000)
    libncursesw.so.6 => /lib64/libncursesw.so.6 (0x00007f1acf456000)
    libtinfo.so.6 => /lib64/libtinfo.so.6 (0x00007f1acf427000)
    libpython3.7m.so.1.0 => /lib64/libpython3.7m.so.1.0 (0x00007f1acf0de000)
    libc.so.6 => /lib64/libc.so.6 (0x00007f1acef18000)
    libdl.so.2 => /lib64/libdl.so.2 (0x00007f1acef12000)
    libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f1aceef1000)
    libutil.so.1 => /lib64/libutil.so.1 (0x00007f1aceeea000)
    libm.so.6 => /lib64/libm.so.6 (0x00007f1aceda4000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f1acf4dc000)
    vstinner@apu$ rpm -qf /lib64/libncursesw.so.6
    ncurses-libs-6.1-10.20180923.fc30.x86_64

    @vstinner vstinner added the 3.9 only security fixes label Aug 1, 2019
    @vstinner
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    New changeset 077af8c by Victor Stinner in branch 'master':
    bpo-37738: Fix curses addch(str, color_pair) (GH-15071)
    077af8c

    @vstinner
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    On my Fedora 30 with libncursesw, A_COLOR = 0xff00.

    After my change, _curses uses:

    static inline short
attr_to_color_pair(int attr)
{
    return (short)((attr & A_COLOR) >> 8);
}

...
setcchar(&wcval, wstr, attr, attr_to_color_pair(attr), NULL);
...

    If someone gets troubles with attr passed "directly" as the 3rd argument of setcchar(), we can try to pass (attr & ~A_COLOR) instead. On my Linux, it would mean: only pass the low 8 bits of attr.

    But since it "just" works on my Linux, I prefer to only make minimum changes to fix this issue on Linux.

    @miss-islington
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    New changeset 9842269 by Miss Islington (bot) in branch '3.8':
    bpo-37738: Fix curses addch(str, color_pair) (GH-15071)
    9842269

    @vstinner
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    New changeset 7eef81e by Victor Stinner in branch '3.7':
    bpo-37738: Fix curses addch(str, color_pair) (GH-15071) (GH-15273)
    7eef81e

    @vstinner
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    I fixed the bug in 3.7, 3.8 and master (future 3.9) branches. Thanks Marius Gedminas for the bug report. In the meanwhile, you have to pass bytes strings to addch() :-(

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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