Unable to use delete key or backspace

[jhilker98]

Describe the bug
Hitting the backspace or delete keys appends '^?' to the text I enter instead of deleting it.

To Reproduce
Steps to reproduce the behavior:

1. Write some text in any widget
2. Press delete or backspace

Expected behavior
If I hit delete, the character the cursor is on should be deleted, but if I hit backspace, the previous character should be deleted.

Screenshots
Will update tomorrow with screenshots

Environment:

• OS: Ubuntu 18.04
• Terminal: Alacritty
• Version: 0.1.2

[jwlodek]

I will try and reproduce this tomorrow. Do you have this bug only in Alacritty, or in other terminal emulators on your system as well? There have been some inconsistencies in behavior of py_cui in different terminals, though mostly on windows, I haven't seen something like this on linux.

[jhilker98]

I just tested in Gnome Terminal and had the same issue.

[jwlodek]

Which widget/popup specifically is seeing this behavior?

[jhilker98]

It is on the text box widgets and pop-ups.

…

On Mon, Jan 4, 2021, 12:36 PM Jakub Wlodek ***@***.***> wrote: Which widget/popup specifically is seeing this behavior? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#74 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACY54OGWFZUVANAJGR2JKSDSYH4DDANCNFSM4VRSU6TQ> .

[JeremyBYU]

I have the same exact issue as well. Ubuntu 18.04 gnome terminal.

EDIT:

It seems that the backspace key is not being set right from the ncurses library. My backspace is giving '127' vs ncurses showing '263'. I had to change this code in keys.py in py-cui:

# Pressing backspace returns 8 on windows?
if platform == 'win32':
    KEY_BACKSPACE   = 8
# Adds support for 'delete/backspace' key on OSX
elif platform == 'darwin':
    KEY_BACKSPACE   = 127
else:
    KEY_BACKSPACE   = 127 # curses.KEY_BACKSPACE # CHANGE HERE

[ghost]

Same issue although Jeremy's solution fixes it.

[jwlodek]

This is odd, because I tried to reproduce the issue on my Ubuntu 18.04 machine with gnome-terminal, but I couldn't get that kind of behavior. I wonder what this could possibly be caused by?

[ghost]

I was using alacritty. Maybe alacritty uses different terminfo.

[jwlodek]

I haven't tried alacritty, but @jhilker1 mentioned he tried gnome-terminal and saw the same behavior. It seems that the curses pre-defined backspace key code is not robust, we may need to consider some logic for checking if a key is one of the several possible backspace codes

[JeremyBYU]

Yeah, I think you may need to check for a few possible values:

https://stackoverflow.com/a/54303430

[lenormf]

I could reproduce the issue on Kitty.

[voryzen]

+1 this issue, using konsole, zsh

[jwlodek]

@voryzen could you run the following curses program on your system and let me know what value of keypress you get when pressing backspace/delete?

import sys,os
import curses

def draw_menu(stdscr):
    k = 0
    cursor_x = 0
    cursor_y = 0

    # Clear and refresh the screen for a blank canvas
    stdscr.clear()
    stdscr.refresh()

    # Start colors in curses
    curses.start_color()
    curses.init_pair(1, curses.COLOR_CYAN, curses.COLOR_BLACK)
    curses.init_pair(2, curses.COLOR_RED, curses.COLOR_BLACK)
    curses.init_pair(3, curses.COLOR_BLACK, curses.COLOR_WHITE)

    # Loop where k is the last character pressed
    while (k != ord('q')):

        # Initialization
        stdscr.clear()
        height, width = stdscr.getmaxyx()

        if k == curses.KEY_DOWN:
            cursor_y = cursor_y + 1
        elif k == curses.KEY_UP:
            cursor_y = cursor_y - 1
        elif k == curses.KEY_RIGHT:
            cursor_x = cursor_x + 1
        elif k == curses.KEY_LEFT:
            cursor_x = cursor_x - 1

        cursor_x = max(0, cursor_x)
        cursor_x = min(width-1, cursor_x)

        cursor_y = max(0, cursor_y)
        cursor_y = min(height-1, cursor_y)

        # Declaration of strings
        title = "Curses example"[:width-1]
        subtitle = "Written by Clay McLeod"[:width-1]
        keystr = "Last key pressed: {}".format(k)[:width-1]
        statusbarstr = "Press 'q' to exit | STATUS BAR | Pos: {}, {}".format(cursor_x, cursor_y)
        if k == 0:
            keystr = "No key press detected..."[:width-1]

        # Centering calculations
        start_x_title = int((width // 2) - (len(title) // 2) - len(title) % 2)
        start_x_subtitle = int((width // 2) - (len(subtitle) // 2) - len(subtitle) % 2)
        start_x_keystr = int((width // 2) - (len(keystr) // 2) - len(keystr) % 2)
        start_y = int((height // 2) - 2)

        # Rendering some text
        whstr = "Width: {}, Height: {}".format(width, height)
        stdscr.addstr(0, 0, whstr, curses.color_pair(1))

        # Render status bar
        stdscr.attron(curses.color_pair(3))
        stdscr.addstr(height-1, 0, statusbarstr)
        stdscr.addstr(height-1, len(statusbarstr), " " * (width - len(statusbarstr) - 1))
        stdscr.attroff(curses.color_pair(3))

        # Turning on attributes for title
        stdscr.attron(curses.color_pair(2))
        stdscr.attron(curses.A_BOLD)

        # Rendering title
        stdscr.addstr(start_y, start_x_title, title)

        # Turning off attributes for title
        stdscr.attroff(curses.color_pair(2))
        stdscr.attroff(curses.A_BOLD)

        # Print rest of text
        stdscr.addstr(start_y + 1, start_x_subtitle, subtitle)
        stdscr.addstr(start_y + 3, (width // 2) - 2, '-' * 4)
        stdscr.addstr(start_y + 5, start_x_keystr, keystr)
        stdscr.move(cursor_y, cursor_x)

        # Refresh the screen
        stdscr.refresh()

        # Wait for next input
        k = stdscr.getch()

def main():
    curses.wrapper(draw_menu)

if __name__ == "__main__":
    main()

[voryzen]

Hi @jwlodek,

127

I used both konsole and gnome-terminal

[voryzen]

@jwlodek if it helps at all, these are the changes that I've made to my py_cui keys.py

# Pressing backspace returns 8 on windows?
if platform == 'win32':
    KEY_BACKSPACE   = 8
# Adds support for 'delete/backspace' key on OSX/linux
elif platform == 'darwin' or platform == 'linux':
    KEY_BACKSPACE   = 127
else:
    KEY_BACKSPACE   = curses.KEY_BACKSPACE

[PabloLec]

This issue has been reported on RecoverPy as you can see with the link above.

A simple condition with platform as in:

elif platform == 'darwin' or platform == 'linux':
    KEY_BACKSPACE   = 127

Won't to the job. I've always run PyCui apps on Linux and never had this issue.

For reference, when running @jwlodek testing script, I get 263 for backspace.

OS: Kubuntu 21.04 x86_64
Shell: zsh 5.8
Terminal: terminator

This is most likely caused by xterm. I guess we should catch all three values for backspace.

[PabloLec]

I just published a PR trying to resolve this.
It would be great if someone encountering the initial issue could try it.

• git clone https://github.com/PabloLec/py_cui.git (clone my fork)
• git checkout fix-backspace (go to branch fix-backspace)
• Make sure to be in a virtual env or just uninstall py_cui
• pip install -e . (Install py_cui from branch fix-backspace)
• And try an example, e.g python examples/simple_todo_list.py

[voryzen]

HI @PabloLec,
After installing your backspace fix.

  File "/home/voryzen/Downloads/py_cui/py_cui/widgets.py", line 102, in add_key_command
    self._keybindings[key] = command
AttributeError: 'ScrollMenu' object has no attribute '_keybindings'

[PabloLec]

Hi!

Yes this is fixed by #159 .