Text selection misses first character when clicking in middle and dragging left

[lpsgverrilla]

Issue Description

When selecting text by clicking on a character and dragging left (right-to-left selection), the character under the initial click is not included in the selection if the click occurs in the middle or left portion of the character. This creates an unintuitive user experience where the same click position produces different results depending on drag direction.

Root Cause

In src/Surface.zig (lines 4852-4905), the mouseSelection() function uses an asymmetric 60% threshold for cell inclusion:

• Left-to-right selections: Character included if clicked in left 60% of cell
• Right-to-left selections: Character included if clicked in right 40% of cell

const threshold_point: u32 = @intFromFloat(@round(
    @as(f64, @floatFromInt(size.cell.width)) * 0.6,
));

This creates a directionally-dependent "dead zone" that feels like an off-by-one error to users.

Suggested Fix

Change the threshold from 60% to 50% to make selection behavior symmetric and intuitive:

const threshold_point: u32 = @intFromFloat(@round(
    @as(f64, @floatFromInt(size.cell.width)) * 0.5,
));

This ensures clicking in the middle of a character includes it regardless of drag direction.

Additional Notes

Tested the 50% threshold fix locally and it significantly improves the selection UX imo.

Expected Behavior

When clicking anywhere within a character's bounds, that character should be included in the selection regardless of which direction you drag.

Actual Behavior

The character is only included if you click in the right 40% of the character cell when dragging left. Clicking in the middle (or left 60%) excludes it from the selection.

Reproduction Steps

1. Type some text in Ghostty terminal
2. Click on the middle of the first character you want to select
3. Drag the mouse to the left to select text
4. Observe that the character you initially clicked on is not included in the selection

Ghostty Logs

No response

Ghostty Version

1.2.3
tip/development

OS Version Information

Ubuntu 24.04

(Linux only) Display Server

Wayland

(Linux only) Desktop Environment/Window Manager

GNOME 46

Minimal Ghostty Configuration

I don't know what to put here.

Additional Relevant Configuration

No response

I acknowledge that:

• 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 reviewed the FAQ and confirm that my issue is NOT among them.
• 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.

[lpsgverrilla]

what's the reason for the assymetry? 30+ years using computers and I don't remember having this problem once before.

[rhodes-b]

https://github.com/ghostty-org/ghostty/blob/main/src/Surface.zig#L4831-L4854

there is a big comment explaining why its 60% this is the first complaint I've ever seen about it being asymmetrical

I also don't think other terminals (from what I've used) choose 50% either. They decide that any percentage of that cell will be part of that selection

30+ years using computers and I don't remember having this problem once before

I think that is because most programs are quite different than terminals that have a large grid of cells

[lpsgverrilla]

A threshold of 60% of the cell width was chosen empirically because it felt good

Maybe it felt good because he took 60% for himself and left me 1/3 less.

I think that is because most programs are quite different than terminals that have a large grid of cells

Ubuntu terminal, for what I could test doesn't seem to be 60 - 40.

[mitchellh]

It's been 60% for almost 3 years and this is the first complaint. It'll take a lot more feedback for us to change this.

[lpsgverrilla]

Alright, but just out of curiosity: do you happen to select text always from left to right, or not the case?