Linux (GTK 4)

Tier 2 · Demi-supported

linux-gtk is a Tier 2 desktop target using GTK 4 and libadwaita. It provides a GTK interface for the app code you share with other systems. Install the development libraries required by your distribution and check the backend’s accessibility limitations before choosing it.

Getting started

GTK 4.10+, libadwaita 1.5+, and librsvg 2.52+ development files are required (Ubuntu 24.04 and Fedora 40 satisfy these):

sudo apt install libgtk-4-dev libadwaita-1-dev librsvg2-dev pkg-config   # Debian/Ubuntu
sudo dnf install gtk4-devel libadwaita-devel librsvg2-devel pkgconf     # Fedora

cargo install --git https://github.com/daybrite/day day-cli
day new app my-app --toolkit linux-gtk
cd my-app
day launch -t linux-gtk

Add libwebkitgtk-6.0-dev if you use the web view piece. Sound effects play through libpulse, which a desktop already has (system requirements). day doctor --toolkit gtk probes GTK 4, libadwaita, librsvg, glib-compile-resources, and the packaging tools (flatpak-builder, linuxdeploy, linuxdeploy-plugin-gtk); it does not check WebKitGTK.

day pack -t linux-gtk        # single-file .flatpak AND a portable .appimage

day pack produces both formats by default. The flatpak runtime supplies GTK itself (org.gnome.Platform), so that bundle carries only your app and its assets; A user installs it with flatpak install ./my-app-1.0-linux-gtk-x86_64.flatpak. The AppImage carries its own GTK, so a user marks it executable and runs it.

Caveats

libadwaita is required. The window, navigation, tabs, dialogs and animations are all Adwaita types; a plain-GTK build is not a supported configuration.
GtkVideo needs a GStreamer media backend in the GTK build. Distro packages ship one; Homebrew’s gtk4 does not, so the media piece shows GTK’s own “no media backend” error on macos-gtk.
Lottie and map have no GTK arm; each renders its placeholder. cover() presents as a topmost window-sized child (no transition, programmatic dismissal only).
The combo box uses GtkComboBoxText, deprecated in GTK 4.10 but kept because GTK has no editable replacement yet.
A progress node picks its widget at realize time: progress(f) becomes a GtkProgressBar and spinner() a GtkSpinner. A node that starts indeterminate will not turn into a bar on a later value change; use separate nodes if you need both.
Canvas text uses cairo’s toy text API, not Pango, so complex-script shaping inside a canvas is weaker than in a label.
GTK on macOS and Windows (macos-gtk, windows-gtk) exists for development convenience only (Tier 4); day pack skips them, and the accessibility tree is absent (GTK’s a11y bridge is Linux-only). windows-gtk builds against MSYS2’s GTK 4 with a GNU Rust toolchain (setup); there is no WebKitGTK 6 for Windows, so the web view is a placeholder there, and bundled custom fonts don’t register with Pango.

What each piece becomes

The generated coverage matrix, checked in CI, covers every backend; this table adds links and notes.

Day piece	GTK widget
`column` / `row` / `nav_stack` / `section`	`GtkFixed` (Day owns layout)
`label`	`GtkLabel`
`button`	`GtkButton`
`toggle`	`GtkSwitch`
`slider`	`GtkScale`
`text_field`	`GtkEntry`
`secure_field`	`GtkEntry` with `visibility` off
`text_area`	`GtkTextView` in a `GtkScrolledWindow`
`picker().menu()`	`GtkDropDown`
`picker().segmented()`	linked `GtkToggleButton`s
`picker().inline()`	grouped `GtkCheckButton`s (GTK 4’s radio)
`progress(f)`	`GtkProgressBar`
`spinner()`	`GtkSpinner`
`divider`	`GtkSeparator`
`scroll`	`GtkScrolledWindow`
`list`	`GtkListView` (recycling, signal factory)
`nav` (split)	`GtkPaned`
`nav` (stack)	`AdwNavigationView`
`nav_menu`	`GtkListBox` (`.navigation-sidebar`)
`tabs`	`AdwViewStack` + linked toggle buttons
`image`	`GtkPicture`
`vector`	`GtkPicture` showing the raster cache PNG (`.tint` recolors the pixels)
`cover()`	emulated: a topmost window-sized child (no transition, programmatic dismissal only)
`canvas`	`GtkDrawingArea` (cairo)
dialogs / alerts / prompts	`AdwAlertDialog`
file dialogs	`GtkFileDialog`
menu bar / context menus	`GtkPopoverMenuBar` / `GtkPopoverMenu`
external `activity()`	`GtkSpinner`
external `combobox()`	`GtkComboBoxText` (with entry)
external `search_field()`	`GtkSearchEntry`
external `date_picker()`	`GtkCalendar`, in a `GtkMenuButton` popover when compact
external `time_picker()`	linked `GtkSpinButton`s
external `webview()`	`WebKitWebView` (WebKitGTK 6.0)
external `media()`	`GtkVideo`

Text measurement builds a Pango layout on the label’s styled context rather than calling gtk_widget_measure, because a GtkFixed child’s size request would otherwise ratchet upward and never shrink.