Linux (GTK 4)

linux-gtk renders GTK 4 widgets styled by libadwaita, through gtk4-rs. It is the default recommendation on Linux: it’s the toolkit Ubuntu, Fedora and Debian install by default.

Home

Controls

Canvas & shapes

List

Getting started

GTK 4.10+ and libadwaita 1.5+ are required (Ubuntu 24.04 and Fedora 40 both satisfy this):

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

cargo install day-cli
day new app my-app --toolkit linux-gtk
cd my-app
day launch -p linux-gtk

Add libwebkitgtk-6.0-dev if you use the web view piece. day doctor --toolkit gtk checks the whole set.

day pack -p linux-gtk        # single-file .flatpak

The flatpak runtime supplies GTK itself (org.gnome.Platform), so the bundle carries your app and its assets, not the toolkit. flatpak install ./MyApp-1.0-gtk-x86_64.flatpak is all a user needs.

Caveats and special considerations

libadwaita is not optional. 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.
No Lottie, no map on this backend — 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 deliberately: no editable replacement exists 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 — no packaging, and no accessibility tree (GTK’s a11y bridge is Linux-only).

What each piece becomes

Day piece	GTK widget
`column` / `row` / `stack` / `section`	`GtkFixed` (Day owns layout)
`label`	`GtkLabel`
`button`	`GtkButton`
`toggle`	`GtkSwitch`
`slider`	`GtkScale`
`text_field`	`GtkEntry`
`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`
`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 own styled context rather than calling gtk_widget_measure, because a GtkFixed child’s size request would otherwise ratchet upward and never shrink.