GTK: Blinking/Flashing when creating/equalizing/closing splits

[JacobCallahan]

Issue Description

When creating/equalizing/deleting screen splits, there is a very visible "stutter" in the form of a blink/flash for each action. This doesn't happen when the splits are resized. I first noticed this around when I upgraded to ghostty 1.2, but I don't know the exact release that this first occurred (previously splits were smooth).

Expected Behavior

There are no jarring blinks/flashes seen when creating/equalizing/deleting screen splits.

Actual Behavior

See the attached video. Since I can only record up to 60fps, this doesn't catch every blink/flash, but a decent amount of them. They are also more pronounced in person, with only a biological limit on perceivable fps).
https://github.com/user-attachments/assets/c2742e77-6b8b-48b9-bfbd-e1eae925ba8d

Reproduction Steps

1. Open ghostty
2. create/equalize/delete a split

Ghostty Logs

These logs repeat for each split action.

warning(gtk_ghostty_application): unimplemented action=.key_sequence
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(io_exec): found Ghostty resources dir: /home/jake/.local/share/ghostty
info(io_exec): shell integration automatically injected shell=.bash
warning(gtk_ghostty_application): unimplemented action=.cell_size
info(io_exec): started subcommand path=/bin/bash pid=29576
info(io_exec): subcommand cgroup=/user.slice/user-1000.slice/user@1000.service/app.slice/app-ghostty-transient-29174.scope/surfaces/42BA3730.scope
warning(stream): unimplemented OSC command: prompt_end
warning(stream): unimplemented OSC command: prompt_start
warning(stream): unimplemented OSC command: change_window_title
warning(stream): unimplemented OSC command: prompt_end
warning(stream): unimplemented OSC command: prompt_start
warning(stream): unimplemented OSC command: change_window_title
warning(stream): unimplemented OSC command: change_window_title
warning(stream): unimplemented OSC command: report_pwd
warning(stream): unimplemented OSC command: prompt_start
warning(stream): unimplemented OSC command: prompt_end
warning(stream): unimplemented OSC command: prompt_start
warning(stream): unimplemented OSC command: change_window_title

### Ghostty Version

```text
Ghostty 1.3.0-main+86ec29237

Version
  - version: 1.3.0-main+86ec29237
  - 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: 6.17.4-200.fc42.x86_64
  - desktop env   : gnome
  - GTK version   :
    build         : 4.18.6
    runtime       : 4.18.6
  - libadwaita    : enabled
    build         : 1.7.7
    runtime       : 1.7.7
  - libX11        : enabled
  - libwayland    : enabled

OS Version Information

Fedora 42

(Linux only) Display Server

Wayland

(Linux only) Desktop Environment/Window Manager

Gnome 48

Minimal Ghostty Configuration

I don't think this is really relevant, but here are somewhat related config values.

shell-integration = bash
split-divider-color = #f92672

keybind = ctrl+shift+\=new_split:right
keybind = ctrl+shift+-=new_split:down
keybind = ctrl+shift+equal=equalize_splits
keybind = ctrl+shift+x=close_surface

gtk-titlebar-hide-when-maximized = true
fullscreen = true
window-decoration = none

### Additional Relevant Configuration

_No response_

### I acknowledge that:

- [X] I have reviewed the FAQ and confirm that my issue is NOT among them.
- [X] 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.
- [X] 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.

[jcollie]

Duplicate: #8208