GTK: split resize keybind flicker

[pktpls]

Issue Description

When using the keybinds to resize splits, there's visible flicker similar to the other split flicker issues that were fixed yesterday. The resize flicker has been present ever since gtk-ng. Resizing with mouse drag works fine.

This is something else than the bouncing reported in #1441 - I tested and reproduced the bouncing separately.

Expected Behavior

Resizing splits with the keybinds is reasonably smooth.

Actual Behavior

It flickers, with the split divider and shell prompts sometimes even flickering back to their original position for a few frames. After the resizing, everything seems fine and nothing is obviously broken.

Looking at the logs, it seems to re-instantiate OpenGL for every resize event.

The video first shows smooth resizing with mouse drag, then flickering resizing with the keybinds.

Screencast.From.2026-03-05.12-36-12.mp4

Reproduction Steps

1. Ghostty with empty configuration, except some split keybindings (see below)
2. Create a split so there's two splits with a divider in between.
3. Resize using the resize_split keybind, either with individual presses or keeping it pressed
4. Observe visual flickering

Ghostty Logs

info: ghostty version=1.3.0-main+46522a877
info: ghostty build optimize=ReleaseFast
info: runtime=.gtk
info: font_backend=.fontconfig_freetype
info: dependency harfbuzz=11.0.0
info: dependency fontconfig=21402
info: renderer=renderer.generic.Renderer(renderer.OpenGL)
info: libxev default backend=io_uring
info(os_locale): setlocale from env result=LC_CTYPE=en_US.UTF-8;LC_NUMERIC=de_DE.UTF-8;LC_TIME=de_DE.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=de_DE.UTF-8;LC_MESSAGES=en_US.UTF-8;LC_PAPER=de_DE.UTF-8;LC_NAME=en_US.UTF-8;LC_ADDRESS=de_DE.UTF-8;LC_TELEPHONE=de_DE.UTF-8;LC_MEASUREMENT=de_DE.UTF-8;LC_IDENTIFICATION=en_US.UTF-8
info(gtk): GTK version build=4.20.3 runtime=4.20.3
info(gtk): libadwaita version build=1.8.4 runtime=1.8.4
info: reading configuration file path=/home/user/.config/ghostty/config
info(config): default shell source=env value=/bin/bash
warning(gtk_ghostty_application): setting GDK_DEBUG=
warning(gtk_ghostty_application): setting GDK_DISABLE=gles-api,vulkan
info(gtk_ghostty_application): libxev manual backend=epoll
info(config): default shell source=env value=/bin/bash
info(opengl): loaded OpenGL 4.6
warning(io_exec): no resources dir set, shell integration disabled
warning(gtk_ghostty_application): unimplemented action=.cell_size
info(io_exec): started subcommand path=/bin/sh pid=717596

info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
warning(io_exec): no resources dir set, shell integration disabled
warning(gtk_ghostty_application): unimplemented action=.cell_size
info(io_exec): started subcommand path=/bin/sh pid=717637
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6
info(opengl): loaded OpenGL 4.6

Ghostty Version

Ghostty 1.3.0-main+46522a877

Version
  - version: 1.3.0-main+46522a877
  - channel: tip
Build Config
  - Zig version   : 0.15.2
  - build mode    : .ReleaseFast
  - app runtime   : .gtk
  - font engine   : .fontconfig_freetype
  - renderer      : renderer.generic.Renderer(renderer.OpenGL)
  - libxev        : io_uring
  - kernel version: 6.18.13-200.fc43.x86_64
  - desktop env   : gnome
  - GTK version   :
    build         : 4.20.3
    runtime       : 4.20.3
  - libadwaita    : enabled
    build         : 1.8.4
    runtime       : 1.8.4
  - libX11        : enabled
  - libwayland    : enabled

OS Version Information

Fedora 43

(Linux only) Display Server

Wayland

(Linux only) Desktop Environment/Window Manager

GNOME 49.4

Minimal Ghostty Configuration

keybind = alt+shift+right=new_split:right
keybind = alt+shift+down=new_split:down
keybind = ctrl+shift+up=resize_split:up,10
keybind = ctrl+shift+right=resize_split:right,10
keybind = ctrl+shift+down=resize_split:down,10
keybind = ctrl+shift+left=resize_split:left,10
keybind = ctrl+shift+enter=toggle_split_zoom

# redefine these, so their original binding keys are free
keybind = super+ctrl+shift+left=previous_tab
keybind = super+ctrl+shift+right=next_tab

Additional Relevant Configuration

No response

I acknowledge that:

• I have reviewed the FAQ and confirm that my issue is NOT among them.
• I have searched the Ghostty repository (both open and closed Discussions and Issues) and confirm this is not a duplicate of an existing issue or discussion.
• I have checked the "Preview" tab on all text fields to ensure that everything looks right, and have wrapped all configuration and code in code blocks with a group of three backticks (```) on separate lines.

[T3sT3ro]

Can confirm for X11 and ubuntu 24.04

[sr-verde]

Happens with Arch and Wayland, too.

[MichaEiler]

On Fedora here. I experience the same issue.
This is my configuration in case it helps with the analysis:

window-decoration = client
gtk-titlebar-style = tabs
gtk-wide-tabs = false


theme = Monokai Pro

bell-features = no-system, no-audio, no-title, border#

window-padding-x = 4
window-padding-y = 4

keybind = performable:ctrl+c=copy_to_clipboard
keybind = shift+alt+f=new_split:right
keybind = shift+alt+e=new_split:up
keybind = shift+alt+x=new_split:down
keybind = shift+alt+s=new_split:left

keybind = alt+up=goto_split:up
keybind = alt+down=goto_split:down
keybind = alt+right=goto_split:right
keybind = alt+left=goto_split:left

keybind = shift+alt+up=resize_split:up,30
keybind = shift+alt+left=resize_split:left,30
keybind = shift+alt+right=resize_split:right,30
keybind = shift+alt+down=resize_split:down,30

keybind = shift+alt+z=toggle_split_zoom
keybind = ctrl+shift+w=close_surface
keybind = ctrl+alt+q=close_surface
keybind = shift+alt+v=equalize_splits

scrollback-limit = 10_000_000

[rileyophus]

Also on Fedora, same problem with a fresh install and empty config. It's like, fifty times a second, the split resizes itself to fill half the window then snaps back. Really obnoxious

[MichaEiler]

Can we provide more information or help out in any other way towards resolving this issue? Thank you!

[pktpls]

With #12698 & #12699 this is a lot better but also a lot worse :D @jcollie @dkinzler

On the one hand, while the original divider is still visible, the movement of the actual divider is pretty smooth now.

On the other hand, if we resize too far to the window edge, we get an explosions of splits.

I have to run now but will record a video later today.