Displaying text in larger size causes certain characters to always have larger size

[mfontanini]

Describe the bug
I'm introducing #8226 to presenterm using the latest nightly and I can't say exactly what is it that causes this but I can consistently reproduce this: after printing some text using s=3 I end up getting certain characters always showing up with a larger font size

To Reproduce
I can't say exactly. I'm not doing anything crazy, namely, enter alternate screen, clear screen, using synchronized updates, printing some text with a larger size, some without, using colors + s=3, etc. I tried to simply do some printfs printing text using s=N and colors but it doesn't reproduce the issue.

You can see the WIP code I have for this here https://github.com/mfontanini/presenterm/compare/feat/font-size?expand=1. This part is where the string to be printed is created.

Screenshots

See in this screenshot how certain characters are now always shown in a larger font.

Environment details

kitty 0.39.1 (ea5db4ec09) created by Kovid Goyal
Linux fontarebook 6.8.0-52-generic #53-Ubuntu SMP PREEMPT_DYNAMIC Sat Jan 11 00:06:25 UTC 2025 x86_64
Linux Mint 22.1 Xia fontarebook /dev/tty

DISTRIB_ID=LinuxMint
DISTRIB_RELEASE=22.1
DISTRIB_CODENAME=xia
DISTRIB_DESCRIPTION="Linux Mint 22.1 Xia"
Running under: X11
OpenGL: '3.1.0 NVIDIA 550.120' Detected version: 3.1
Frozen: True
Fonts:
  medium: DejaVuSansMNFM: /home/matias/.fonts/DejaVuSansMono/DejaVuSansMNerdFontMono-Regular.ttf:0
          Features: ()
    bold: DejaVuSansMNFM-Bold: /home/matias/.fonts/DejaVuSansMono/DejaVuSansMNerdFontMono-Bold.ttf:0
          Features: ()
  italic: DejaVuSansMNFM-Oblique: /home/matias/.fonts/DejaVuSansMono/DejaVuSansMNerdFontMono-Oblique.ttf:0
          Features: ()
      bi: DejaVuSansMNFM-ObliqueBold: /home/matias/.fonts/DejaVuSansMono/DejaVuSansMNerdFontMono-BoldOblique.ttf:0
          Features: ()
Paths:
  kitty: /home/matias/.local/kitty.app/bin/kitty
  base dir: /home/matias/.local/kitty.app/lib/kitty
  extensions dir: /home/matias/.local/kitty.app/lib/kitty-extensions
  system shell: /usr/bin/fish
System color scheme: no_preference. Applied color theme type: none
Loaded config files:
  /home/matias/.config/kitty/kitty.conf

Config options different from defaults:
click_interval            0.5
cursor_blink_interval     (0.5, kitty.options.utils.EasingFunction(), kitty.options.utils.EasingFunction())
editor                    lvim
enable_audio_bell         False
font_family               DejaVuSansM Nerd Font Mono
font_size                 12.0
initial_window_height     (1800, 'px')
initial_window_width      (3200, 'px')
mouse_hide_wait           0.0
remember_window_size      False
scrollback_lines          10000
scrollback_pager          ['less', '+G', '-R']
select_by_word_characters :@-./_~?&=%+#
shell_integration         frozenset({'no-cursor'})
tab_bar_style             slant
tab_title_max_length      40
update_check_interval     0.0
window_border_width       (0, 'pt')
Added mouse actions:
	ctrl+left click ungrabbed →  mouse_click_url
Removed mouse actions:
	left click ungrabbed →  mouse_handle_click selection link prompt
Added shortcuts:
	alt+h →  previous_tab
	alt+j →  scroll_page_down
	alt+k →  scroll_page_up
	alt+l →  next_tab
	ctrl+- →  decrease_font_size
	ctrl+= →  increase_font_size
	ctrl+page_down →  next_tab
	ctrl+page_up →  previous_tab
	shift+page_down →  scroll_page_down
	shift+page_up →  scroll_page_up
Changed shortcuts:
	kitty_mod+backspace →  restore_font_size
	kitty_mod+page_down →  move_tab_forward
	kitty_mod+page_up →  move_tab_backward
	kitty_mod+t →  launch --cwd last_reported --type tab
Colors:
	active_border_color       #ffffff   
	active_tab_background     #7aa2f7   
	active_tab_foreground     #1f2335   
	background                #24283b   
	color0                    #1d202f   
	color1                    #f7768e   
	color10                   #9ece6a   
	color11                   #e0af68   
	color12                   #7aa2f7   
	color13                   #bb9af7   
	color14                   #7dcfff   
	color15                   #c0caf5   
	color16                   #ff9e64   
	color17                   #db4b4b   
	color2                    #9ece6a   
	color3                    #e0af68   
	color4                    #7aa2f7   
	color5                    #bb9af7   
	color6                    #7dcfff   
	color7                    #a9b1d6   
	color8                    #414868   
	color9                    #f7768e   
	cursor                    #c0caf5   
	foreground                #c0caf5   
	inactive_tab_background   #292e42   
	inactive_tab_foreground   #545c7e   
	selection_background      #364a82   
	selection_foreground      #c0caf5   
	url_color                 #73daca   

Important environment variables seen by the kitty process:
	PATH                                <redacted>
	LANG                                en_US.UTF-8
	EDITOR                              nvim
	SHELL                               /usr/bin/fish
	DISPLAY                             :0.0
	USER                                matias
	XDG_GREETER_DATA_DIR                /var/lib/lightdm-data/matias
	XDG_RUNTIME_DIR                     /run/user/1000
	XDG_SESSION_DESKTOP                 mate
	XDG_DATA_DIRS                       <redacted>
	XDG_CURRENT_DESKTOP                 MATE
	XDG_SESSION_ID                      c2
	XDG_VTNR                            7
	XDG_SEAT                            seat0
	XDG_SESSION_TYPE                    x11
	XDG_SESSION_PATH                    /org/freedesktop/DisplayManager/Session0
	XDG_CONFIG_DIRS                     /etc/xdg/xdg-mate:/etc/xdg
	XDG_SEAT_PATH                       /org/freedesktop/DisplayManager/Seat0
	XDG_SESSION_CLASS                   user

Additional context
I can reproduce this with kitty --config NONE.

[kovidgoyal]

Run kitty with --dump-bytes. Do the minimum needed to repro the issue and post the dump. I will ttry to reproduce with that.

[mfontanini]

Do the minimum needed to repro the issue

Sure!

1. Run

git clone https://github.com/mfontanini/presenterm
cd presenterm
git checkout feat/font-size
cargo run examples/demo.md

2. Once it starts, press q.
3. Type capital letters, they'll surely look almost all broken

[kovidgoyal]

OK, I can repro with that, I will take a look.

[kovidgoyal]

Yes, the issue is caused by using bold, this is a bug in kitty.

[kovidgoyal]

Minimal reproducer

kitty sh -c 'printf "\e[1m\e]66;s=2;ABCD\a\e[m\n\nABCDEF"; read'