Blurry font rendering on Debian based systems (NO fractional scaling).

[virtuallyunknown]

Greeting. This is follow up of #1938 which covered a similar issue but concerned fractional scaling. The thread got closed/resolved so I was advised to create a new one exclusively for similar problems but without any fractional scaling enabled on the system.

Demonstration of the problem:

Linux Mint 22
Gnome Terminal (left) / Ghostty (right):

Ubuntu 24.04 (virtual machine)
Gnome Terminal (left) / Ghostty (right):

Comparison GIF:

As you can see, ghostty renders the text blurry as compared to Gnome Terminal. It might seem a bit subtle at first, but it actually makes a big difference when you read text all day and it's preventing me from using ghostty as my main terminal at the moment.

I'd be happy to provide any necessary details and debugging information if anyone is interested in fixing this problem.

Cheers!

Configuration and other debug info (click to expand)

ghosty +version

Ghostty 1.0.2-main+1baf8928

Version
  - version: 1.0.2-main+1baf8928
  - channel: tip
Build Config
  - Zig version: 0.13.0
  - build mode : builtin.OptimizeMode.ReleaseFast
  - app runtime: apprt.Runtime.gtk
  - font engine: font.main.Backend.fontconfig_freetype
  - renderer   : renderer.OpenGL
  - libxev     : main.Backend.io_uring
  - desktop env: other
  - GTK version:
    build      : 4.14.2
    runtime    : 4.14.2
  - libadwaita : enabled
    build      : 1.5.0
    runtime    : 1.5.0
  - libX11     : enabled

ghostty config:

font-family=JetBrains Mono
font-style=Regular
font-size=11

freetype-load-flags=no-hinting

font-feature=-liga
font-feature=-calt
font-feature=-dlig

gtk-titlebar=true

window-theme=ghostty
window-padding-balance=true
confirm-close-surface=false

system information (some non-relevant stuff omitted for brevity/privacy):

System:
  Kernel: 6.8.0-51-generic arch: x86_64 bits: 64 compiler: gcc v: 13.3.0 clocksource: tsc
  Desktop: Cinnamon v: 6.2.9 tk: GTK v: 3.24.41 wm: Muffin v: 6.2.0 vt: 7 dm: LightDM v: 1.30.0
    Distro: Linux Mint 22 Wilma base: Ubuntu 24.04 noble
Machine:
  Type: Desktop Mobo: Micro-Star model: MAG B650 TOMAHAWK WIFI (MS-7D75) v: 1.0
    serial: <superuser required> uuid: <superuser required> UEFI: American Megatrends LLC. v: 1.K0
    date: 10/08/2024
CPU:
  Info: 12-core model: AMD Ryzen 9 7900 bits: 64 type: MT MCP smt: enabled arch: Zen 4 rev: 2
    cache: L1: 768 KiB L2: 12 MiB L3: 64 MiB
  Speed (MHz): avg: 2469 high: 5478 min/max: 545/5482 cores: 1: 545 2: 5417 3: 3675 4: 3493
    5: 545 6: 545 7: 545 8: 5247 9: 5020 10: 3886 11: 4511 12: 5188 13: 545 14: 5478 15: 545 16: 545
    17: 3432 18: 545 19: 545 20: 3600 21: 545 22: 545 23: 3774 24: 545 bogomips: 177596
  Flags: avx avx2 ht lm nx pae sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3 svm
Graphics:
  Device-1: NVIDIA AD107 [GeForce RTX 4060] vendor: Micro-Star MSI driver: nvidia v: 550.120
    arch: Lovelace pcie: speed: 5 GT/s lanes: 8 ports: active: none off: HDMI-A-1
    empty: DP-1,DP-2,DP-3 bus-ID: 01:00.0 chip-ID: 10de:2882 class-ID: 0300
  Display: x11 server: X.Org v: 21.1.11 with: Xwayland v: 23.2.6 driver: X: loaded: nouveau
    unloaded: fbdev,modesetting,vesa failed: nvidia gpu: nvidia,nvidia-nvswitch display-ID: :0
    screens: 1
  Screen-1: 0 s-res: 1920x1080 s-dpi: 81 s-size: 602x343mm (23.70x13.50") s-diag: 693mm (27.28")
  Monitor-1: HDMI-0 res: 1920x1080 dpi: 82 size: 597x336mm (23.5x13.23") diag: 685mm (26.97")
    modes: N/A
  API: EGL v: 1.5 hw: drv: nvidia platforms: device: 0 drv: nvidia device: 2 drv: swrast gbm:
    drv: kms_swrast surfaceless: drv: nvidia x11: drv: nvidia inactive: wayland,device-1
  API: OpenGL v: 4.6.0 compat-v: 4.5 vendor: nvidia mesa v: 550.120 glx-v: 1.4 direct-render: yes
    renderer: NVIDIA GeForce RTX 4060/PCIe/SSE2
Audio:
  Device-1: NVIDIA vendor: Micro-Star MSI driver: snd_hda_intel v: kernel pcie: speed: 16 GT/s
    lanes: 8 bus-ID: 01:00.1 chip-ID: 10de:22be class-ID: 0403
  Device-2: AMD Family 17h/19h HD Audio vendor: Micro-Star MSI driver: snd_hda_intel v: kernel
    pcie: speed: 16 GT/s lanes: 16 bus-ID: 10:00.6 chip-ID: 1022:15e3 class-ID: 0403
  Device-3: Micro Star USB Audio driver: hid-generic,snd-usb-audio,usbhid type: USB rev: 2.0
    speed: 480 Mb/s lanes: 1 bus-ID: 1-6:5 chip-ID: 0db0:422d class-ID: 0300
  API: ALSA v: k6.8.0-51-generic status: kernel-api
  Server-1: PipeWire v: 1.0.5 status: active with: 1: pipewire-pulse status: active
    2: wireplumber status: active 3: pipewire-alsa type: plugin
Info:
  Memory: total: 32 GiB note: est. available: 30.95 GiB used: 15.23 GiB (49.2%)
  Processes: 489 Power: uptime: 24m states: freeze,mem,disk suspend: deep wakeups: 0
    hibernate: platform Init: systemd v: 255 target: graphical (5) default: graphical
  Compilers: gcc: 13.3.0 Client: Cinnamon v: 6.2.9 inxi: 3.3.34

[mkrieger1]

Does it help if you remove freetype-load-flags = no-hinting?

[virtuallyunknown]

There are other issues related to font rendering detailed in #3515, and having this particular setting fixes them, which is why I have it enabled. But to answer your question, it doesn't really help, here is a screenshot with it disabled:

The text still looks blurry to me.

[veltza]

I have the same problem on XFCE (X11).

Look here how badly the letters a, b, and d are rendered with the built-in font (font-size = 10):

Here is Alacritty for comparison:

It's hard to believe that the foreground color is the same #e5e5e5.

[jcollie]

I'm not the font rendering expert here, but I believe that Ghostty always renders the font in monochrome because a glyph is rendered once at a particular size and then added to an atlas for later re-use. Glyphs are later recolored based on the foreground/background colors required at the time. Using RGB subpixels would mean rendering the glyph again for each unique foreground/background pair which could be considerably less performant.

[virtuallyunknown]

I'm not the font rendering expert here, but I believe that Ghostty always renders the font in monochrome because a glyph is rendered once at a particular size and then added to an atlas for later re-use. Glyphs are later recolored based on the foreground/background colors required at the time. Using RGB subpixels would mean rendering the glyph again for each unique foreground/background pair which could be considerably less performant.

This far exceeds my knowledge, but help me understand, if it always uses monochrome, then why is no-monochrome exposed as an option in the config?

PS: I'm not putting doubts on what you're saying, just trying to make sense of this all.

[jcollie]

The people working on improving font support may have plans to add subpixel hinting in the future, we'll have to wait for them to chime in.

[virtuallyunknown]

All right, I appreciate your input! I linked to your comment and also asked on Discord for more info (hope you don't mind), so let's see if someone replies here or there.

Hopefully it's not a dead end because I like ghostty, but I really can't use it like that.

[virtuallyunknown]

For anyone reading later, the devs told me that subpixel rendering is not supported at the moment, but they plan to experiment with it at some time in the future.