Small bug on "CodeInput" and "get_color_from_hex" with solve sollution.

[kmcasi]

Software Versions

• Python: 3.10.4
• OS: Windows 10 Pro N 21H2
• Kivy: 2.1.0
• Kivy installation method: pip

Describe the bug On CodeInput class (kivy\uix\codeinput.py) the background_color value is not self update it via pygments styles. Your on_style_name definition from line 116 is not call it by default and is a bit annoying because I end it up by editing your original code.

Expected behavior As expectation will be to replace if not kwargs.get('background_color'): logic from line 114 with the below one witch fix all of this, or to make a new smarter one but with same result please.

        if not kwargs.get('background_color'):
            try: self.background_color = get_color_from_hex(style.background_color)
            except Exception: self.background_color = [.9, .92, .92, 1]
        else: self.background_color = kwargs.get("background_color")

Additional bug/future The get_color_from_hex definition from line 113 (kivy\utils.py) also have a small room for improve. This one accept just 6-8 characters as value. Pygments style allow also 3 and 6 like #FF0000 == #F00. Again I end it up by editing your original code by doubling each character if len(color) is less then 5 to allow and alpha value just for the sick of the consisting API as in get_hex_from_color. Bellow is the entire get_color_from_hex logic.

def get_color_from_hex(s):
    '''Transform a hex string color to a kivy
    :class:`~kivy.graphics.Color`.
    '''
    if s.startswith('#'):
        return get_color_from_hex(s[1:])
    
    if len(s) < 5:
        tmp = ""
        for i in range(len(s)):
            tmp += s[i] * 2
        s = tmp

    value = [int(x, 16) / 255.
             for x in split('([0-9a-f]{2})', s.lower()) if x != '']
    if len(value) == 3:
        value.append(1.0)
    return value

# First attempt was to work on that regex (like bellow code) but #F00 got me an wrong color like a very dark red/brown
# So just the above code works for me. May by you can get it smarter then me, but with same result?
value = [int(x, 16) / 255.
             for x in split('([0-9a-f]%s)' % "{2}" if len(s) > 4 else "", s.lower()) if x != '']