Initial window size incorrect with respect to window padding

[lilyball]

A brand new Ghostty window calculates the initial window size wrong with respect to window padding, at least on macOS. The result is a new window has extra padding.

My configuration going into this:

• 2x DPI screen
• window-step-resize = true, decoration and other settings at defaults though I turned off the macos shadow for debugging
• Grid Size of 80 columns
• Cell Size of 16px × 31px
• Note that this means the cell grid is 1280px wide

What I'm seeing:

If I set window-padding-x = 0, the viewport is sized perfectly such that there is no horizontal padding.

Surface Info:

Dimensions	Value
Screen Size	1280px × 350px
Window Padding	T=4 B=4 L=0 R=0 px

Screen width of 1280px matches cell grid, so no extra padding.

Screenshot

---

If I set window-padding-x = 1, the viewport has 2pt/4px extra padding on the right.

Dimensions	Value
Screen Size	1288px × 350px
Window Padding	T=4 B=4 L=2 R=2 px

Expected screen width was 1284px (2px + 1280px + 2px), so at 1288px there's an extra 4px on the right (interesting that Surface Info doesn't report this anywhere)

Screenshot

---

If I set window-padding-x = 2, the viewport has 4pt/8px extra padding on the right.

Dimensions	Value
Screen Size	1296px × 350px
Window Padding	T=4 B=4 L=4 R=4 px

Expected screen width was 1288px (4px + 1280px + 4px), so at 1296px there's an extra 8px on the right.

Screenshot

Additional info

I used the Pixie app (from Apple's additional tools for Xcode download) to verify the pixel layout of the window, so I can confirm that what Surface Info reported for the screen size is accurate.

Subsequent resizes of the window preserve this additional padding (thanks to window-step-resize = true). If I turn that off then I can manually resize the window to remove the additional padding, so it's just an error in the initial viewport sizing.

I do note that this is effectively adding twice as much padding as it should. With window-padding-x = 1 it should have a total of 2pt of padding but it has 4pt. With window-padding-x = 2 it should have a total of 4pt of padding but it has 8pt. I am wondering if this is an issue with high-DPI screens where it does an extra pixel density multiplication somewhere (e.g. it calculates 4pt, converts to 8px, then interprets that as 8pt) but I don't have a low-DPI screen available to test with.

[mitchellh]

I am wondering if this is an issue with high-DPI screens where it does an extra pixel density multiplication somewhere (e.g. it calculates 4pt, converts to 8px, then interprets that as 8pt) but I don't have a low-DPI screen available to test with.

I'm almost certain this is the case.

[mitchellh]

I'm not seeing this on my macOS build with high DPI screen. I'm seeing exactly the pixels it's noting. Is there a configuration I'm missing? I tried both a Pro Display XDR and MacBook Pro built-in display.

[lilyball]

I moved my config aside and tried again and I'm seeing the same issue, an extra 8px. Completely out-of-the-box settings:

Dimensions	Value
Screen Size	1600px × 570px
Grid Size	99c × 16r
Cell Size	16px × 35px
Window Padding	T=4 B=4 L=4 R=4
Font Size (Points)1	0 pt
Font Size (Pixels)	26 px

My main screen is an external LG UltraFine with a base resolution of 5120 × 2880, running at 2x DPI for a UI resolution of 2560 × 1440. If I convince Ghostty to open a window on the built-in screen it has the same metrics though. I also double-checked on my other laptop with no external screen and same problem there. This is macOS Sequoia 15.1 on Apple Silicon MBPs.

Footnotes

1. This always reports 0 pt, I assume that's just a bug though. ↩

[rnmmnen]

I run into something similar on a MacBook Pro with the built-in 16-inch (3456 × 2234) display. The screen is on the default "looks like" setting of 1728 × 1117. I narrowed my problem down to just this config:

window-padding-y = 4
window-step-resize = true

Ghostty opens by default in 99c x 33r and has more padding at the bottom than what I'd expect. When I resize the window with the mouse from the bottom, the following happens:

Size	Bottom padding	Notes
99c x 33r	too much	Initial size
99c x 34r	slightly more padding than 33r
99c x 35r	slightly more padding than 34r
99c x 36r	slightly more padding than 35r
99c x 37r	slightly more padding than 36r
99c x 38r	slightly more padding than 37r
		99c x 39r skipped (!)
99c x 40r	no padding at the bottom

After that, the padding starts to slowly increase again.