Window borders are not drawn when "background_opacity" option is set to 0

[syedadeed]

Describe the bug
Window borders are either not visible or just not drawn at all when background_opacity is set to 0

To Reproduce
Steps to reproduce the behavior:

1. Set background_opacity to 0
2. press ctr+shift+enter to create a new window
3. Youll see that there is no window border

Screenshots

Environment details

kitty 0.36.1 (8eb0b556b7) created by Kovid Goyal
Linux arch 6.10.9-arch1-1 #1 SMP PREEMPT_DYNAMIC Mon, 09 Sep 2024 02:38:45 +0000 x86_64
Arch Linux 6.10.9-arch1-1 (/dev/tty)

Running under: Wayland (Hyprland v0.43.0,) missing: single_pixel_buffer
OpenGL: '4.2 (Core Profile) Mesa 24.2.2-arch1.1' Detected version: 4.2
Frozen: False
Fonts:
  medium: MonaspaceXenon-Regular: /home/adeed/.local/share/fonts/Monospace/MonaspaceXenon-Regular.otf:0
          Features: ('calt', 'liga', 'ss01', 'ss02', 'ss03', 'ss04', 'ss05', 'ss07', 'ss08', 'ss09')
    bold: MonaspaceKrypton-Regular: /home/adeed/.local/share/fonts/Monospace/MonaspaceKrypton-Regular.otf:0
          Features: ('calt', 'liga', 'ss01', 'ss02', 'ss03', 'ss04', 'ss05', 'ss07', 'ss08', 'ss09')
  italic: MonaspaceRadon-Regular: /home/adeed/.local/share/fonts/Monospace/MonaspaceRadon-Regular.otf:0
          Features: ('calt', 'liga', 'ss01', 'ss02', 'ss03', 'ss04', 'ss05', 'ss07', 'ss08', 'ss09')
      bi: MonaspaceXenon-SemiBoldItalic: /home/adeed/.local/share/fonts/Monospace/MonaspaceXenon-SemiBoldItalic.otf:0
          Features: ('calt', 'liga', 'ss01', 'ss02', 'ss03', 'ss04', 'ss05', 'ss07', 'ss08', 'ss09')
Paths:
  kitty: /usr/bin/kitty
  base dir: /usr/lib/kitty
  extensions dir: /usr/lib/kitty/kitty
  system shell: /usr/bin/bash
Loaded config files:
  /home/adeed/.config/kitty/kitty.conf

Config options different from defaults:
background_opacity            0
bell_on_tab                   
bold_font                     family='Monaspace Krypton'  style='Regular' features='+calt +liga +ss01 +ss02 +ss03 +ss04 +ss05 +ss07 +ss08 +ss09'
confirm_os_window_close       0
copy_on_select                clipboard
cursor                        None
cursor_blink_interval         (-1.0, kitty.options.utils.EasingFunction(type='cubic-bezier', cubic_bezier_points=(0.42, 0.0, 0.58, 1.0)), kitty.options.utils.EasingFunction())
cursor_shape_unfocused        0
cursor_stop_blinking_after    5.0
enable_audio_bell             False
enabled_layouts               ['grid']
focus_follows_mouse           True
font_family                   family='Monaspace Xenon'    style='Regular' features='+calt +liga +ss01 +ss02 +ss03 +ss04 +ss05 +ss07 +ss08 +ss09'
font_size                     14.0
italic_font                   family='Monaspace Radon'    style='Regular' features='+calt +liga +ss01 +ss02 +ss03 +ss04 +ss05 +ss07 +ss08 +ss09'
modify_font:
    baseline -80%
    cell_height 1
    cell_width 1
    underline_position -115%
mouse_hide_wait               -1.0
notify_on_cmd_finish          NotifyOnCmdFinish(when='always', duration=10.0, action='notify', cmdline=())
scrollback_indicator_opacity  0
scrollback_pager              ['bat', '--wrap=never']
scrollback_pager_history_size 524288000
select_by_word_characters     @-./_~?&=%+*#
strip_trailing_spaces         smart
tab_bar_style                 hidden
touch_scroll_multiplier       2.0
url_style                     5
window_alert_on_bell          False
Colors:
	selection_background          #729491   
	selection_foreground          #ffffff   
	url_color                     #522a70   

Important environment variables seen by the kitty process:
	PATH                                /usr/local/sbin:/usr/local/bin:/usr/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl
	LANG                                C.UTF-8
	EDITOR                              nvim
	SHELL                               /usr/bin/bash
	DISPLAY                             :0
	WAYLAND_DISPLAY                     wayland-1
	USER                                adeed
	XCURSOR_SIZE                        23
	XDG_BACKEND                         wayland
	XDG_SEAT                            seat0
	XDG_SESSION_TYPE                    wayland
	XDG_CURRENT_DESKTOP                 Hyprland
	XDG_SESSION_CLASS                   user
	XDG_VTNR                            1
	XDG_SESSION_ID                      1
	XDG_RUNTIME_DIR                     /run/user/1000

``
Moreover window borders are directly linked to the value of background_opacity option, for example if you set background_opacity to 0.1, the borders are visible but looks kinda faded