Cursor shader only works with block cursor

[Aaron-212]

Issue Description

Previously discussed in Discord: https://discord.com/channels/1005603569187160125/1392174025077428365

Cursor shader only works with cursor-style = block. It doesn't work with bar, underline or block_hollow.

Kat bisected to a9fc3b6

Example with bar cursor:

2025-07-09.10.59.30.mov

Expected Behavior

Cursor shader works with any cursor style.

Actual Behavior

Cursor shader only works with cursor-style = block.

Reproduction Steps

1. Download a cursor shader
2. Use the shader in the config
3. Set cursor style to block
4. Shader works
5. Set cursor style to any style except block
6. Shader doesn't work

Ghostty Logs

No response

Ghostty Version

Ghostty 1.1.4-main+26522ab8c

Version
  - version: 1.1.4-main+26522ab8c
  - channel: tip
Build Config
  - Zig version   : 0.14.1
  - build mode    : builtin.OptimizeMode.ReleaseFast
  - app runtime   : apprt.Runtime.none
  - font engine   : font.main.Backend.coretext
  - renderer      : renderer.generic.Renderer(renderer.Metal)
  - libxev        : kqueue

OS Version Information

macOS 26b3

(Linux only) Display Server

None

(Linux only) Desktop Environment/Window Manager

No response

Minimal Ghostty Configuration

cursor-style = bar
custom-shader = ~/GitHub/KroneCorylus/ghostty-shader-playground/shaders/cursor_smear.glsl

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.

[qwerasd205]

#7893