Terminal size reporting appears wrong on hyprland

[alba4k]

Describe the bug The terminal size appears to be more related to what the previous window was than the current one when a program is launched immediatly.

To Reproduce

1. I have albafetch (more on this under additional context) in config.fish (same happens with .bashrc)
2. Open some kitty instances
3. See error

Screenshots

https://github.com/kovidgoyal/kitty/assets/84153269/3bcb0637-b61f-4c9c-be2d-d181b5840338

Environment details

debug info

``` kitty 0.29.2 created by Kovid Goyal Linux dell-xps 6.4.8-zen1-1-zen #1 ZEN SMP PREEMPT_DYNAMIC Thu, 03 Aug 2023 16:01:52 +0000 x86_64 ]P01E1E2E]P8585B70]P7BAC2DE]PFA6ADC8]P1F38BA8]P9F38BA8]P2A6E3A1]PAA6E3A1]P3F9E2AF]PBF9E2AF]P489B4FA]PC89B4FA]P5F5C2E7]PDF5C2E7]P694E2D5]PE94E2D5 Arch Linux 6.4.8-zen1-1-zen (/dev/tty) DISTRIB_ID="Arch" DISTRIB_RELEASE="rolling" DISTRIB_DESCRIPTION="Arch Linux" Running under: Wayland Frozen: False Paths: kitty: /usr/bin/kitty base dir: /usr/lib/kitty extensions dir: /usr/lib/kitty/kitty system shell: /bin/bash Loaded config files: /home/alba4k/.config/kitty/kitty.conf Config options different from defaults: background_opacity 0.85 clipboard_control ('write-clipboard', 'write-primary') confirm_os_window_close 0 cursor_blink_interval 0.6 cursor_shape 2 cursor_stop_blinking_after 10.0 dim_opacity 0.75 editor /usr/bin/nvim font_size 12.0 input_delay 5 modify_font: baseline 0 cell_height 0 cell_width 0 mouse_hide_wait 2.0 repaint_delay 12 shell /bin/fish show_hyperlink_targets True tab_bar_edge 1 tab_bar_style powerline tab_powerline_style round tab_title_template {title} touch_scroll_multiplier 5.0 url_prefixes ('http', 'https', 'file', 'ftp', 'gemini', 'irc', 'gopher', 'mailto', 'news', 'git') url_style 1 visual_bell_duration 0.05 Changed mouse actions: ctrl+shift+left release grabbed → mouse_click_url ctrl+shift+left release ungrabbed → mouse_click_url left click ungrabbed → mouse_click_url_or_select shift+left click grabbed → mouse_click_url_or_select shift+left click ungrabbed → mouse_click_url_or_select Added shortcuts: ctrl++ → change_font_size all +3 ctrl+- → change_font_size all -3 ctrl+backspace → change_font_size all 0 shift+super+w → close_os_window Changed shortcuts: kitty_mod+1 → change_font_size all +3 Colors: active_tab_background #cba6f7 active_tab_foreground #11111b background #1d1c2c color0 #45475a color1 #e97797 color10 #a6e3a1 color11 #f9e2af color12 #89b4fa color13 #ba72e7 color14 #94e2d5 color15 #bac2de color2 #86d394 color3 #e9c99d color4 #79a4fa color5 #aa62e7 color6 #84d9cc color7 #a6adc8 color8 #585b70 color9 #f38ba8 cursor #dfdef1 cursor_text_color #1e1e2e foreground #dfdef1 inactive_tab_background #181825 inactive_tab_foreground #cdd6f4 mark1_background #b4befe mark1_foreground #1e1e2e mark2_background #cba6f7 mark2_foreground #1e1e2e mark3_background #74c7ec mark3_foreground #1e1e2e selection_background #ddb6f2 selection_foreground #1e1e2e tab_bar_background #11111b url_color #f5e0dc Important environment variables seen by the kitty process: PATH /usr/local/sbin:/usr/local/bin:/usr/bin:/usr/lib/jvm/default/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl:/home/alba4k/.local/bin LANG it_CH.UTF-8 SHELL /bin/bash DISPLAY :0 WAYLAND_DISPLAY wayland-1 USER alba4k XCURSOR_SIZE 24 XDG_SESSION_PATH /org/freedesktop/DisplayManager/Session4 XDG_BACKEND wayland XDG_DATA_HOME /home/alba4k/.local/share XDG_CONFIG_HOME /home/alba4k/.config XDG_SEAT seat0 XDG_SESSION_DESKTOP XDG_SESSION_TYPE wayland XDG_CURRENT_DESKTOP Hyprland XDG_SEAT_PATH /org/freedesktop/DisplayManager/Seat0 XDG_CACHE_HOME /home/alba4k/.cache XDG_SESSION_CLASS user XDG_VTNR 3 XDG_SESSION_ID 6 XDG_RUNTIME_DIR /run/user/1000 ```

Additional context I am testing this in the video using albafetch, a tool I wrote; neofetch works fine (probably because it is much slower and gets the information later). In it, I am using ioctl(STDOUT_FILENO, TIOCGWINSZ, (struct winsize*)w) to get the terminal width (man 2 ioctl), Which is getting executed after probably ~1ms since the program is launched. Getting the terminal width in src/main.c, line 384

Just to confirm that the issue was not related to albafetch itself, I tried running this script on startup:

#include <stdio.h>
#include <sys/ioctl.h>

int main() {
    struct winsize w;
    ioctl(1, TIOCGWINSZ, &w);

    printf("width: %u\n", w.ws_col);
}

Which does indeed fall into the same issue

I do not know if this issue is related to kitty or to hyprland (or maybe, who knows, ioctl itself, but probably not), any advice would be appreciated :)

[kovidgoyal]

You cannot rely on the ioctl alone, you need to also handle SIGWINCH. And note that kitty will debounce resizes so SIGWINCH is not sent for every pixel change in during a "live resize". This is to prevent programs running in kitty from continuously redrawing the screen wasting resources. See the resize_debounce_time option in kitty.conf.

[alba4k]

Is that really relevant for a 1ms runtime?

[kovidgoyal]

Do you believe signals take longer than a millisecond to be delivered?

[neurocyte]

I think the point is that a program that just prints a message and quits runs too fast to be expected to see any signals. Should it wait for a signal? That would be pretty unusual.

[neurocyte]

Btw, if hyprland is creating the window and immediately resizing it, then this should probably be considered a bug in hyprland. Or is it not possible to create a window at a specific size on wayland perhaps? (I doubt that)

[kovidgoyal]

It should install a signal handler when it starts, and handle any signals it receives upto the point it prints and quits. That's pretty basic in a pre-emptive multitasking environment.

[kovidgoyal]

I have no idea, I can tell you that, you will receive SIGWINCH from kitty after a resize. There is no guarantee you will receive it in any fixed time under the value of resize_debounce_time however. This is very easy to test. Just let your program sleep/busy loop for a few seconds and install a SIGWINCH handler.