Linux: Font-family fallbacks are not working as expected

[cogwheel]

For my use case, I have a main config which loads a local config. The local config correctly overrides all settings except font-family. If any specified font fails to be loaded, it will "become" noto sans. Then any subsequent fallbacks specified will be ignored.

I have reproduced this issue without the need for local overrides. Put the following in your ghostty config (replacing font names as appropriate)

font-family = Some Font That Doesn't Exist
font-family = Some Valid Font Other Than System Default Monospace

You will find that your terminal loads your system default monospace font anyway.

This happens for me both on arch with hyprland and on Ubuntu 24.04 with Gnome desktop

Full startup log:

info: ghostty version=1.0.1
info: ghostty build optimize=ReleaseFast
info: runtime=apprt.Runtime.gtk
info: font_backend=font.main.Backend.fontconfig_freetype
info: dependency harfbuzz=8.4.0
info: dependency fontconfig=21402
info: renderer=renderer.OpenGL
info: libxev backend=main.Backend.io_uring
info(os): setlocale from env result=en_US.UTF-8
info(gtk): GTK version build=4.14.2 runtime=4.14.2
info: reading configuration file path=/home/MYUSERNAME/.config/ghostty/config
info(config): default shell source=env value=/usr/bin/zsh
info(sentry): sentry envelope does not contain crash, discarding
EGL API version 1.5 found
 - Vendor: NVIDIA
 - Version: 1.5
 - Device: /dev/dri/renderD128, 226 128
 - Client APIs: OpenGL_ES OpenGL
 - Extensions:
	EGL_ANDROID_native_fence_sync
	EGL_EXT_buffer_age
	EGL_EXT_client_sync
	EGL_EXT_create_context_robustness
	EGL_EXT_image_dma_buf_import
	EGL_EXT_image_dma_buf_import_modifiers
	EGL_EXT_output_base
	EGL_EXT_present_opaque
	EGL_EXT_stream_acquire_mode
	EGL_EXT_sync_reuse
	EGL_IMG_context_priority
	EGL_KHR_config_attribs
	EGL_KHR_context_flush_control
	EGL_KHR_create_context
	EGL_KHR_create_context_no_error
	EGL_KHR_fence_sync
	EGL_KHR_get_all_proc_addresses
	EGL_KHR_gl_colorspace
	EGL_KHR_gl_renderbuffer_image
	EGL_KHR_gl_texture_2D_image
	EGL_KHR_gl_texture_3D_image
	EGL_KHR_gl_texture_cubemap_image
	EGL_KHR_image
	EGL_KHR_image_base
	EGL_KHR_image_pixmap
	EGL_KHR_no_config_context
	EGL_KHR_partial_update
	EGL_KHR_reusable_sync
	EGL_KHR_stream
	EGL_KHR_stream_attrib
	EGL_KHR_stream_consumer_gltexture
	EGL_KHR_stream_cross_process_fd
	EGL_KHR_stream_fifo
	EGL_KHR_stream_producer_eglsurface
	EGL_KHR_surfaceless_context
	EGL_KHR_swap_buffers_with_damage
	EGL_KHR_wait_sync
	EGL_MESA_image_dma_buf_export
	EGL_NV_nvrm_fence_sync
	EGL_NV_output_drm_flip_event
	EGL_NV_post_sub_buffer
	EGL_NV_quadruple_buffer
	EGL_NV_robustness_video_memory_purge
	EGL_NV_stream_attrib
	EGL_NV_stream_consumer_eglimage
	EGL_NV_stream_consumer_gltexture_yuv
	EGL_NV_stream_cross_display
	EGL_NV_stream_cross_object
	EGL_NV_stream_cross_process
	EGL_NV_stream_cross_system
	EGL_NV_stream_dma
	EGL_NV_stream_fifo_next
	EGL_NV_stream_fifo_synchronous
	EGL_NV_stream_flush
	EGL_NV_stream_metadata
	EGL_NV_stream_origin
	EGL_NV_stream_remote
	EGL_NV_stream_reset
	EGL_NV_stream_socket
	EGL_NV_stream_socket_inet
	EGL_NV_stream_socket_unix
	EGL_NV_stream_sync
	EGL_NV_system_time
	EGL_NV_triple_buffer
	EGL_WL_bind_wayland_display
	EGL_WL_wayland_eglstream
 - Selected fbconfig: R8G8B8A8, depth 0, stencil 0
          high depth: none
Creating EGL context version 3.2 (debug:no, forward:no, legacy:no, es:no)
Created EGL context[0x202456f1]
Using OpenGL backend EGL
info(gtk): libadwaita version build=1.5.0 runtime=1.5.0
Creating EGL context version 3.2 (debug:no, forward:no, legacy:no, es:no)
Created EGL context[0x20508821]
OpenGL version: 4.6 (core)
* GLSL version: 4.60 NVIDIA
* Max texture size: 32768

Enabled features (use GDK_GL_DISABLE env var to disable):
    debug: YES
    unpack-subimage: YES
    half-float: YES
    sync: YES
    base-instance: YES
    buffer-storage: YES
OpenGL version: 4.6 (core)
* GLSL version: 4.60 NVIDIA
* Max texture size: 32768

Enabled features (use GDK_GL_DISABLE env var to disable):
    debug: YES
    unpack-subimage: YES
    half-float: YES
    sync: YES
    base-instance: YES
    buffer-storage: YES
Creating EGL context version 3.3 (debug:no, forward:no, legacy:no, es:no)
Created EGL context[0x20dd7401]
OpenGL version: 4.6 (core)
* GLSL version: 4.60 NVIDIA
* Max texture size: 32768

Enabled features (use GDK_GL_DISABLE env var to disable):
    debug: YES
    unpack-subimage: YES
    half-float: YES
    sync: YES
    base-instance: YES
    buffer-storage: YES
info(grid): loaded OpenGL 4.6
info(font_shared_grid_set): font regular: DejaVu Sans Mono
info(font_shared_grid_set): font regular: Cogslab2 Nerd Font
info(font_shared_grid_set): font bold: DejaVu Sans Mono Bold
info(font_shared_grid_set): font bold: Cogslab2 Nerd Font Bold
info(font_shared_grid_set): font italic: DejaVu Sans Mono Oblique
info(font_shared_grid_set): font italic: Cogslab2 Nerd Font Italic
info(font_shared_grid_set): font bold_italic: DejaVu Sans Mono Bold Oblique
info(font_shared_grid_set): font bold_italic: Cogslab2 Nerd Font Bold Italic
info(io_exec): found Ghostty resources dir: /home/MYUSERNAME/.local/share/ghostty
info(io_exec): shell integration automatically injected shell=termio.shell_integration.Shell.zsh
warning(gtk): unimplemented action=apprt.action.Action.Key.cell_size
warning(gtk): unimplemented action=apprt.action.Action.Key.size_limit
info(io_exec): started subcommand path=/bin/sh pid=6975
info(io_exec): subcommand cgroup=-
info(grid): reallocating GPU buffer old=0 new=8
Destroying EGL context
Destroying EGL context
info(io_exec): read thread got quit signal
info(surface): surface closed addr=20e0b660
info(sentry): sentry envelope does not contain crash, discarding

[taylrfnt]

I am not able to reproduce this behavior on MacOS, logs below with version info.

Timestamp                       Thread     Type        Activity             PID    TTL
2025-02-03 14:20:45.472586-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:default] ghostty version=1.1.1-main+cdd20990
2025-02-03 14:20:45.472643-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:default] ghostty build optimize=ReleaseFast
2025-02-03 14:20:45.472658-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:default] runtime=apprt.Runtime.none
2025-02-03 14:20:45.472665-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:default] font_backend=font.main.Backend.coretext
2025-02-03 14:20:45.472670-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:default] renderer=renderer.Metal
2025-02-03 14:20:45.472676-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:default] libxev backend=main.Backend.kqueue
2025-02-03 14:20:45.472748-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:os] detected system locale=en_US.UTF-8
2025-02-03 14:20:45.472797-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:os] setlocale from env result=en_US.UTF-8
2025-02-03 14:20:45.473058-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:default] reading configuration file path=/Users/taylor/.config/ghostty/config
2025-02-03 14:20:45.473383-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:config] default shell src=passwd value=/bin/zsh
2025-02-03 14:20:45.473392-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:config] default working directory src=passwd value=/Users/taylor
2025-02-03 14:20:45.475756-0600 0x4c943b   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:sentry] sentry envelope does not contain crash, discarding
2025-02-03 14:20:45.478717-0600 0x4c8268   Debug       0x0                  85833  0    ghostty: [com.mitchellh.ghostty:renderer_thread] mailbox message=renderer.message.Message{ .reset_cursor_blink = void }
2025-02-03 14:20:45.537213-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:ghostty] config reload notification
2025-02-03 14:20:45.537258-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:ghostty] config change notification
2025-02-03 14:20:45.549180-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:ghostty] known but unimplemented action action=32
2025-02-03 14:20:45.549623-0600 0x4c9428   Error       0x0                  86052  0    ghostty: [com.mitchellh.ghostty:font_shared_grid_set] font-family regular not found: Test Font
2025-02-03 14:20:45.553233-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:font_shared_grid_set] font regular: CommitMono Nerd Font
2025-02-03 14:20:45.553488-0600 0x4c9428   Error       0x0                  86052  0    ghostty: [com.mitchellh.ghostty:font_shared_grid_set] font-family bold not found: Test Font
2025-02-03 14:20:45.554027-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:font_shared_grid_set] font bold: CommitMono Nerd Font Bold
2025-02-03 14:20:45.554473-0600 0x4c9428   Error       0x0                  86052  0    ghostty: [com.mitchellh.ghostty:font_shared_grid_set] font-family italic not found: Test Font
2025-02-03 14:20:45.555117-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:font_shared_grid_set] font italic: CommitMono Nerd Font Italic
2025-02-03 14:20:45.555542-0600 0x4c9428   Error       0x0                  86052  0    ghostty: [com.mitchellh.ghostty:font_shared_grid_set] font-family bold_italic not found: Test Font
2025-02-03 14:20:45.556130-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:font_shared_grid_set] font bold_italic: CommitMono Nerd Font Bold Italic
2025-02-03 14:20:45.559401-0600 0x4c9428   Info        0x0                  86052  0    ghostty: [com.mitchellh.ghostty:io_exec] found Ghostty resources dir: /Applications/Ghostty.app/Contents/Resources/ghostty

[cogwheel]

Perhaps it's linux only? I get the same behavior on ubuntu and arch. I'll add my full config & logs to the main post.

Edit: the bug happens when my example is the full config.

[cogwheel]

I notice that your logs say "font-family not found" where mine acts like it was found

[taylrfnt]

It may be easier to focus on the first strange log for now: Ghostty finding your font-family options... can you try to see what the output of ghostty +list-fonts is? If you see anything for DejaVu or Cogslab that may be the answer?

If those do exist, then it might just be a codepoint rendering question. If they don't, then we get to something more interesting :)

[cogwheel]

it's not just a codepoint thing. Something is actually changing the invalid font name to a valid one. Deja Vu Sans is the default monospace font on my Ubuntu system, and Noto Sans is the default monospace font on my Arch system.

What seems to be happening is that ghostty is asking the system for a monospaced font named "Some Font That Doesn't Exist". Instead of saying "no, that doesn't exist", it says "here's a font you can use instead". Then ghostty uses that instead, which now becmomes the first font in the list, so subsequent fonts are not even needed.

[00-kat]

Likely a Fontconfig-specific issue, hence why @taylrfnt couldn't reproduce this on macOS.

[cogwheel]

I've narrowed this down to the Fontconfig.discover() function. When it calls fc_config.substituteWithPat, it gets a list of seemingly every font on the system that fits the style (monospace + regular/bold/italic), claiming to have found a match. This list includes the bogus font name too.

The call to fontSort then always finds a match, because it's now searching for a bunch of fonts that do exist.