quadraui 0.6.1

//! GDK → `quadraui::UiEvent` translation.
//!
//! Phase B.5 Stage 4. This module is the boundary between GTK's
//! native event types (`gdk::Key`, `gdk::ModifierType`,
//! `GestureClick` button presses, drawing-area resize signals) and
//! quadraui's backend-agnostic [`UiEvent`] enum.
//!
//! GTK is callback-driven: signals fire from inside the GTK main
//! loop via Relm4 widget templates. The architectural pattern (B.5
//! option A — the event-queue adapter) is:
//!
//! 1. Each signal callback closure captures
//!    `events_handle: Rc<RefCell<VecDeque<UiEvent>>>` cloned from
//!    `GtkBackend::events_handle()`.
//! 2. Inside the callback, translate the native event to a `UiEvent`
//!    via the helpers in this module.
//! 3. `events_handle.borrow_mut().push_back(ui_event)`.
//! 4. The driver code (Stage 5+) drains the queue via
//!    `Backend::wait_events` / `poll_events`.
//!
//! Stage 4 ships the translation helpers + unit tests; Stage 5 wires
//! actual signal callbacks to use them. The functions are
//! standalone (no Rc/RefCell), so they're trivially testable.

use gtk4::gdk;
use gtk4::glib;
use gtk4::prelude::*;

use crate::{Key, Modifiers, MouseButton, NamedKey, UiEvent};

/// Translate a GDK key event from `EventControllerKey::connect_key_pressed`
/// into a [`UiEvent::KeyPressed`]. Returns `None` for keysyms that
/// don't map to a `Key` value (modifier-only presses, dead keys, etc.).
///
/// `repeat` should be the value the controller's repeat flag reports —
/// today GTK doesn't surface a stable repeat flag through the
/// gtk4-rs binding, so callers pass `false`. The trait honours the
/// field but vimcode's engine doesn't currently distinguish first-press
/// from repeat at this layer.
pub fn gdk_key_to_uievent(
    key: gdk::Key,
    modifiers: gdk::ModifierType,
    repeat: bool,
) -> Option<UiEvent> {
    let key = gdk_key_to_quadraui_key(key)?;
    let modifiers = gdk_modifiers_to_quadraui(modifiers);
    Some(UiEvent::KeyPressed {
        key,
        modifiers,
        repeat,
    })
}

/// Translate a GDK button press from `GestureClick::connect_pressed`
/// into a [`UiEvent::MouseDown`]. The button index follows GTK's
/// convention (1 = primary / left, 2 = middle, 3 = secondary / right);
/// `n_press` is GTK's click count (used by callers to distinguish
/// double-click via `UiEvent::DoubleClick` if desired). The translator
/// here always emits `MouseDown` — caller handles double-click
/// detection if needed.
pub fn gdk_button_to_mouse_down(
    button: u32,
    x: f64,
    y: f64,
    modifiers: gdk::ModifierType,
) -> UiEvent {
    crate::event::mouse_down(
        gdk_button_to_quadraui(button),
        x as f32,
        y as f32,
        gdk_modifiers_to_quadraui(modifiers),
    )
}

/// Translate a GDK button release into [`UiEvent::MouseUp`].
pub fn gdk_button_to_mouse_up(button: u32, x: f64, y: f64) -> UiEvent {
    crate::event::mouse_up(gdk_button_to_quadraui(button), x as f32, y as f32)
}

/// Translate a GDK motion event into [`UiEvent::MouseMoved`]. GTK
/// doesn't surface which buttons are held in the basic motion
/// signal — callers tracking drag state pass an explicit `buttons`
/// mask (today: filled by `GestureDrag` consumers from gesture state).
pub fn gdk_motion_to_uievent(x: f64, y: f64, buttons: crate::ButtonMask) -> UiEvent {
    crate::event::mouse_moved(x as f32, y as f32, buttons)
}

/// Translate a GDK scroll event into [`UiEvent::Scroll`]. `dx`/`dy`
/// are GTK's `EventControllerScroll` deltas (positive `dy` = down —
/// this is the sign GTK4 apps consume directly when driving a
/// `GtkAdjustment`, e.g. `value += dy`; wheel-down / two-finger-down
/// on a non-natural-scroll touchpad reports positive `dy`). We negate
/// `dy` for `UiEvent::Scroll`'s convention (positive y = up toward
/// the top of content) — same as the TUI translator does for
/// crossterm scroll events, and the same negation `macos::events::ns_scroll`
/// applies to `NSEvent` deltas. Win32 is the one native backend that
/// *doesn't* negate — see `win::events::win_wheel_to_uievent`'s doc
/// for why.
///
/// This is the `natural_scroll = false` case of
/// [`gdk_scroll_to_uievent_with_direction`]; kept as its own function
/// so existing callers (and the GTK runner's default wiring) don't
/// need to thread an extra argument through for the common case.
pub fn gdk_scroll_to_uievent(dx: f64, dy: f64, x: f64, y: f64) -> UiEvent {
    gdk_scroll_to_uievent_with_direction(dx, dy, x, y, false)
}

/// Translate a GDK scroll event into [`UiEvent::Scroll`], with an
/// explicit natural-scroll override.
///
/// `dx`/`dy` carry their real magnitude straight through to
/// `delta.x`/`delta.y` (only sign and the `f64` → `f32` cast change) —
/// they are never reduced to ±1. `gtk4::EventControllerScroll`'s
/// `scroll` signal already unifies discrete wheel notches and smooth
/// trackpad deltas into one continuous `(dx, dy)` pair before this
/// function ever sees it (see `src/gtk/run.rs`'s `setup_scroll_controller`,
/// which doesn't set `EventControllerScrollFlags::DISCRETE`), so a
/// wheel step scaled by an OS "lines per notch" setting and a sub-row
/// trackpad nudge both arrive here as, and leave here as, their real
/// `f32` magnitude.
///
/// `natural_scroll = false` reproduces [`gdk_scroll_to_uievent`]'s
/// traditional-direction behavior exactly: wheel-down (positive raw
/// `dy`) becomes negative `delta.y`, i.e. "not up", so compose
/// controllers (`TreeController`, `SidebarSystem`, `ChatController`,
/// `FormController`) scroll the view toward later content.
///
/// `natural_scroll = true` flips the sign again — content follows the
/// gesture, matching touchscreen/trackpad "natural scrolling"
/// semantics — for apps that want an in-app toggle independent of (or
/// layered on top of) the OS-level libinput natural-scroll setting.
/// [`crate::AppLogic::natural_scroll`] is the trait hook the GTK
/// runner reads to pick the flag; `wire_da_events_with_scroll_direction`
/// is the equivalent for consumers wiring their own `DrawingArea`.
pub fn gdk_scroll_to_uievent_with_direction(
    dx: f64,
    dy: f64,
    x: f64,
    y: f64,
    natural_scroll: bool,
) -> UiEvent {
    // `crate::event::scroll` always negates its `dy_native_down_positive`
    // argument to reach quadraui's convention. The natural-scroll flag
    // needs the *opposite* of that negation, so feed it `-dy` — the
    // shared constructor's negation then cancels back out to `+dy`.
    let dy_native_down_positive = if natural_scroll { -dy } else { dy };
    crate::event::scroll(
        dx as f32,
        dy_native_down_positive as f32,
        x as f32,
        y as f32,
    )
}

/// Translate a `GtkDrawingArea` resize into [`UiEvent::WindowResized`].
/// `scale` is the surface scale factor (HiDPI multiplier) — typically
/// `widget.scale_factor() as f32`.
///
/// Apps with side effects on resize (e.g. resizing a PTY) need an actual
/// event, not just an updated viewport. `src/gtk/run.rs` wires
/// `DrawingArea::connect_resize` to this translator.
pub fn gdk_resize_to_uievent(width: i32, height: i32, scale: f32) -> UiEvent {
    crate::event::window_resized(width as f32, height as f32, scale)
}

/// Translate a `gtk::DropTarget`'s `drop` signal payload (already
/// resolved from the dragged `gdk::FileList` into real filesystem paths
/// — see `src/gtk/run.rs`'s `connect_drop` closure) into
/// [`UiEvent::FilesDropped`]. `x`/`y` are the signal's own
/// coordinates, already in the same DIP space every other GTK pointer
/// event uses — unlike Win's `WM_DROPFILES` translator, no
/// `scale_factor()` division is needed here.
pub fn gtk_drop_to_uievent(paths: Vec<std::path::PathBuf>, x: f64, y: f64) -> UiEvent {
    crate::event::files_dropped(paths, x as f32, y as f32)
}

/// Translate a `gio::Application`'s `open` signal payload —
/// a slice of `gio::File`s the OS handed the app, either from `argv` at
/// launch (`ApplicationFlags::HANDLES_OPEN` routes file/URI positional
/// arguments to `open` instead of `activate`) or forwarded from a second
/// launch to the already-running primary instance — into
/// [`UiEvent::OpenRequested`].
///
/// Each `gio::File` is classified by `File::path()`: `Some(_)` means a
/// local filesystem path (bucketed into `files`); `None` means a
/// non-local URI (`http://`, a custom app scheme, a GVfs mount) that
/// `File::uri()` still resolves to a string (bucketed into `urls`).
/// Unlike Win's plain-`String` `argv`, GTK's `gio::File` arrives
/// pre-classified by GLib itself, so this doesn't need
/// [`crate::event::classify_open_args`]'s `"://"` heuristic.
pub fn gtk_open_to_uievent(files: &[gtk4::gio::File]) -> UiEvent {
    let mut local_paths = Vec::new();
    let mut urls = Vec::new();
    for file in files {
        match file.path() {
            Some(path) => local_paths.push(path),
            None => urls.push(file.uri().to_string()),
        }
    }
    UiEvent::OpenRequested {
        urls,
        files: local_paths,
    }
}

/// Translate `gdk::ModifierType` to `quadraui::Modifiers`. Maps the
/// four standard modifiers — Ctrl, Shift, Alt, Super (Cmd on macOS;
/// Win/Meta key on X11). The other GDK bits (Lock, Hyper, Mod1–5)
/// don't have quadraui equivalents and are dropped.
pub fn gdk_modifiers_to_quadraui(m: gdk::ModifierType) -> Modifiers {
    Modifiers {
        shift: m.contains(gdk::ModifierType::SHIFT_MASK),
        ctrl: m.contains(gdk::ModifierType::CONTROL_MASK),
        alt: m.contains(gdk::ModifierType::ALT_MASK),
        cmd: m.contains(gdk::ModifierType::SUPER_MASK) || m.contains(gdk::ModifierType::META_MASK),
    }
}

/// Translate a `gdk::Key` keysym to a `quadraui::Key`. Unicode
/// keysyms map to `Key::Char`; named non-printables map to
/// `Key::Named`. Returns `None` for keysyms with no quadraui
/// counterpart (modifier keys, function keys above F24, dead keys,
/// etc.).
pub fn gdk_key_to_quadraui_key(key: gdk::Key) -> Option<Key> {
    if let Some(c) = key.to_unicode() {
        if !c.is_control() {
            return Some(Key::Char(c));
        }
        // Ctrl+letter produces a control character (e.g. \x03 for Ctrl+C).
        // Recover the base letter from the keysym name so the app sees
        // Key::Char('c') with modifiers.ctrl == true.
        if let Some(name) = key.name() {
            let bytes = name.as_bytes();
            if bytes.len() == 1 && bytes[0].is_ascii_alphabetic() {
                return Some(Key::Char(bytes[0] as char));
            }
        }
    }
    let name = key.name()?;
    let named = gdk_keyname_to_named_key(&name)?;
    Some(Key::Named(named))
}

/// Map a GDK keysym name to a `quadraui::NamedKey`. Mirrors the
/// `crossterm_keycode_to_key` shape in `tui_main/events.rs`.
pub fn gdk_keyname_to_named_key(name: &str) -> Option<NamedKey> {
    let named = match name {
        "Escape" => NamedKey::Escape,
        "Tab" => NamedKey::Tab,
        "ISO_Left_Tab" => NamedKey::BackTab,
        "Return" | "KP_Enter" => NamedKey::Enter,
        "BackSpace" => NamedKey::Backspace,
        "Delete" | "KP_Delete" => NamedKey::Delete,
        "Insert" | "KP_Insert" => NamedKey::Insert,
        "Home" | "KP_Home" => NamedKey::Home,
        "End" | "KP_End" => NamedKey::End,
        "Page_Up" | "KP_Page_Up" => NamedKey::PageUp,
        "Page_Down" | "KP_Page_Down" => NamedKey::PageDown,
        "Up" | "KP_Up" => NamedKey::Up,
        "Down" | "KP_Down" => NamedKey::Down,
        "Left" | "KP_Left" => NamedKey::Left,
        "Right" | "KP_Right" => NamedKey::Right,
        "Caps_Lock" => NamedKey::CapsLock,
        "Num_Lock" => NamedKey::NumLock,
        "Scroll_Lock" => NamedKey::ScrollLock,
        "Menu" => NamedKey::Menu,
        s if s.starts_with('F') && s[1..].chars().all(|c| c.is_ascii_digit()) => {
            let n: u8 = s[1..].parse().ok()?;
            if (1..=24).contains(&n) {
                NamedKey::F(n)
            } else {
                return None;
            }
        }
        _ => return None,
    };
    Some(named)
}

/// Map a GDK button index to a `quadraui::MouseButton`.
/// GTK convention: 1 = primary (left), 2 = middle, 3 = secondary
/// (right), 8 / 9 = back / forward (X1 / X2 on most mice).
pub fn gdk_button_to_quadraui(button: u32) -> MouseButton {
    match button {
        1 => MouseButton::Left,
        2 => MouseButton::Middle,
        3 => MouseButton::Right,
        8 => MouseButton::X1,
        9 => MouseButton::X2,
        n => MouseButton::Other(n.min(255) as u8),
    }
}

/// Attach mouse, scroll, and click event controllers to a
/// `DrawingArea` and translate all native events to [`UiEvent`].
///
/// The `on_event` callback fires for every translated event. The
/// consumer routes it (e.g. to `SidebarSystem::handle_cached`) and
/// triggers a redraw if needed.
///
/// Covers: MouseDown (left+right), MouseUp, DoubleClick, MouseMoved
/// (with button mask for drag detection), and Scroll (with correct
/// sign convention).
///
/// This eliminates ~40 lines of per-DrawingArea signal wiring that
/// every GTK consumer otherwise needs to write manually.
///
/// Scroll direction always follows [`gdk_scroll_to_uievent`]'s
/// traditional (`natural_scroll = false`) convention. Use
/// [`wire_da_events_with_scroll_direction`] to make it configurable
pub fn wire_da_events<F>(da: &gtk4::DrawingArea, on_event: F)
where
    F: Fn(UiEvent) + Clone + 'static,
{
    wire_da_events_with_scroll_direction(da, on_event, false);
}

/// Same as [`wire_da_events`], with an explicit natural-scroll flag
/// passed straight through to
/// [`gdk_scroll_to_uievent_with_direction`]. Consumers building their
/// own `DrawingArea` outside [`crate::gtk::run`] (which reads
/// [`crate::AppLogic::natural_scroll`] instead) use this to honour
/// the same preference.
pub fn wire_da_events_with_scroll_direction<F>(
    da: &gtk4::DrawingArea,
    on_event: F,
    natural_scroll: bool,
) where
    F: Fn(UiEvent) + Clone + 'static,
{
    use gtk4::{
        EventControllerMotion, EventControllerScroll, EventControllerScrollFlags, GestureClick,
    };

    let click = GestureClick::builder().button(0).build();
    {
        let on_event = on_event.clone();
        // Double-click detection uses a shared `DoubleClickDetector` instance
        // scoped to this `DrawingArea`, rather than reading GDK's native
        // `n_press` counter, to align with the detector used elsewhere in the crate.
        let double_click = std::rc::Rc::new(std::cell::RefCell::new(
            crate::dispatch::DoubleClickDetector::with_radius(
                super::backend::GTK_DOUBLE_CLICK_RADIUS,
            ),
        ));
        click.connect_pressed(move |gesture, _n_press, x, y| {
            let button = gesture.current_button();
            let modifier = gesture.current_event_state();
            let mut ev = gdk_button_to_mouse_down(button, x, y, modifier);
            double_click
                .borrow_mut()
                .process(std::slice::from_mut(&mut ev));
            on_event(ev);
        });
    }
    {
        let on_event = on_event.clone();
        click.connect_released(move |gesture, _n_press, x, y| {
            on_event(gdk_button_to_mouse_up(gesture.current_button(), x, y));
        });
    }
    da.add_controller(click);

    // `cursor_pos` is shared between the motion and scroll controllers.
    // GTK's `EventControllerScroll` callback only delivers `(dx, dy)`;
    // the pointer coordinates are not available from inside the callback.
    // Tracking the last known position from the motion controller and
    // reading it in the scroll handler is the standard GTK idiom.
    let cursor_pos = std::rc::Rc::new(std::cell::Cell::new((0.0_f64, 0.0_f64)));
    let motion = EventControllerMotion::new();
    {
        let on_event = on_event.clone();
        let cursor_pos = cursor_pos.clone();
        motion.connect_motion(move |ctrl, x, y| {
            cursor_pos.set((x, y));
            let modifier = ctrl.current_event_state();
            let buttons = crate::ButtonMask {
                left: modifier.contains(gdk::ModifierType::BUTTON1_MASK),
                middle: modifier.contains(gdk::ModifierType::BUTTON2_MASK),
                right: modifier.contains(gdk::ModifierType::BUTTON3_MASK),
            };
            on_event(gdk_motion_to_uievent(x, y, buttons));
        });
    }
    da.add_controller(motion);

    let scroll = EventControllerScroll::new(EventControllerScrollFlags::BOTH_AXES);
    {
        let on_event = on_event.clone();
        scroll.connect_scroll(move |_ctrl, dx, dy| {
            let (x, y) = cursor_pos.get();
            on_event(gdk_scroll_to_uievent_with_direction(
                dx,
                dy,
                x,
                y,
                natural_scroll,
            ));
            glib::Propagation::Stop
        });
    }
    da.add_controller(scroll);
}

#[cfg(test)]
mod tests {
    use super::*;

    /// `gtk_drop_to_uievent` builds a `FilesDropped` with the given paths
    /// and position untouched (GTK's drop coordinates are already DIPs,
    /// no scale conversion).
    #[test]
    fn drop_to_uievent_carries_paths_and_position() {
        let paths = vec![
            std::path::PathBuf::from("/tmp/a.txt"),
            std::path::PathBuf::from("/tmp/b.txt"),
        ];
        let ev = gtk_drop_to_uievent(paths.clone(), 12.0, 34.0);
        match ev {
            UiEvent::FilesDropped {
                paths: got,
                position,
            } => {
                assert_eq!(got, paths);
                assert_eq!((position.x, position.y), (12.0, 34.0));
            }
            other => panic!("expected UiEvent::FilesDropped, got {other:?}"),
        }
    }

    /// Local files go to `files` (via `File::path()`), non-local URIs go
    /// to `urls` (via `File::uri()`) — GTK's `open` signal arrives
    /// pre-classified, unlike Win's plain-string `argv`.
    #[test]
    fn open_to_uievent_splits_local_files_from_uris() {
        let files = vec![
            gtk4::gio::File::for_path("/tmp/report.pdf"),
            gtk4::gio::File::for_uri("https://example.com/oauth/callback"),
        ];
        let ev = gtk_open_to_uievent(&files);
        match ev {
            UiEvent::OpenRequested { urls, files } => {
                assert_eq!(files, vec![std::path::PathBuf::from("/tmp/report.pdf")]);
                assert_eq!(urls, vec!["https://example.com/oauth/callback".to_string()]);
            }
            other => panic!("expected UiEvent::OpenRequested, got {other:?}"),
        }
    }

    #[test]
    fn open_to_uievent_handles_empty_list() {
        let ev = gtk_open_to_uievent(&[]);
        assert_eq!(
            ev,
            UiEvent::OpenRequested {
                urls: vec![],
                files: vec![],
            }
        );
    }

    #[test]
    fn modifiers_translate() {
        let m = gdk::ModifierType::CONTROL_MASK | gdk::ModifierType::SHIFT_MASK;
        let q = gdk_modifiers_to_quadraui(m);
        assert!(q.ctrl);
        assert!(q.shift);
        assert!(!q.alt);
        assert!(!q.cmd);
    }

    #[test]
    fn alt_modifier_translates() {
        let q = gdk_modifiers_to_quadraui(gdk::ModifierType::ALT_MASK);
        assert!(q.alt);
        assert!(!q.ctrl);
    }

    #[test]
    fn super_or_meta_maps_to_cmd() {
        assert!(gdk_modifiers_to_quadraui(gdk::ModifierType::SUPER_MASK).cmd);
        assert!(gdk_modifiers_to_quadraui(gdk::ModifierType::META_MASK).cmd);
    }

    #[test]
    fn keyname_named_keys() {
        for (name, expected) in &[
            ("Escape", NamedKey::Escape),
            ("Tab", NamedKey::Tab),
            ("ISO_Left_Tab", NamedKey::BackTab),
            ("Return", NamedKey::Enter),
            ("KP_Enter", NamedKey::Enter),
            ("BackSpace", NamedKey::Backspace),
            ("Delete", NamedKey::Delete),
            ("Up", NamedKey::Up),
            ("Down", NamedKey::Down),
            ("Left", NamedKey::Left),
            ("Right", NamedKey::Right),
            ("Page_Up", NamedKey::PageUp),
            ("Page_Down", NamedKey::PageDown),
            ("Home", NamedKey::Home),
            ("End", NamedKey::End),
            ("F1", NamedKey::F(1)),
            ("F12", NamedKey::F(12)),
        ] {
            assert_eq!(
                gdk_keyname_to_named_key(name),
                Some(*expected),
                "for {name}"
            );
        }
    }

    #[test]
    fn keyname_function_out_of_range() {
        assert_eq!(gdk_keyname_to_named_key("F0"), None);
        assert_eq!(gdk_keyname_to_named_key("F25"), None);
        assert_eq!(gdk_keyname_to_named_key("F99"), None);
    }

    #[test]
    fn keyname_unknown() {
        assert_eq!(gdk_keyname_to_named_key("Unknown_Foo"), None);
        assert_eq!(gdk_keyname_to_named_key(""), None);
    }

    #[test]
    fn button_translates() {
        assert_eq!(gdk_button_to_quadraui(1), MouseButton::Left);
        assert_eq!(gdk_button_to_quadraui(2), MouseButton::Middle);
        assert_eq!(gdk_button_to_quadraui(3), MouseButton::Right);
        assert_eq!(gdk_button_to_quadraui(8), MouseButton::X1);
        assert_eq!(gdk_button_to_quadraui(9), MouseButton::X2);
        assert_eq!(gdk_button_to_quadraui(7), MouseButton::Other(7));
    }

    #[test]
    fn mouse_down_translation() {
        let ev = gdk_button_to_mouse_down(1, 50.0, 100.0, gdk::ModifierType::CONTROL_MASK);
        match ev {
            UiEvent::MouseDown {
                widget,
                button,
                position,
                modifiers,
            } => {
                assert!(widget.is_none());
                assert_eq!(button, MouseButton::Left);
                assert_eq!(position.x, 50.0);
                assert_eq!(position.y, 100.0);
                assert!(modifiers.ctrl);
            }
            other => panic!("expected MouseDown, got {other:?}"),
        }
    }

    #[test]
    fn scroll_negates_dy_for_quadraui_convention() {
        // GTK reports positive dy = scroll down. quadraui's
        // `Scroll.delta.y` follows the convention positive y = up.
        let ev = gdk_scroll_to_uievent(0.0, 1.0, 10.0, 20.0);
        match ev {
            UiEvent::Scroll {
                delta, position, ..
            } => {
                assert_eq!(delta.y, -1.0);
                assert_eq!(delta.x, 0.0);
                assert_eq!(position.x, 10.0);
                assert_eq!(position.y, 20.0);
            }
            _ => panic!(),
        }
    }

    #[test]
    fn scroll_with_direction_false_matches_default_translator() {
        let a = gdk_scroll_to_uievent(0.0, 1.0, 10.0, 20.0);
        let b = gdk_scroll_to_uievent_with_direction(0.0, 1.0, 10.0, 20.0, false);
        match (a, b) {
            (UiEvent::Scroll { delta: da, .. }, UiEvent::Scroll { delta: db, .. }) => {
                assert_eq!(da, db);
            }
            _ => panic!(),
        }
    }

    #[test]
    fn scroll_with_direction_true_flips_sign() {
        // Same raw wheel-down gesture (dy = 1.0), but with the
        // natural-scroll override on: the sign flips relative to
        // `gdk_scroll_to_uievent`'s traditional -1.0.
        let ev = gdk_scroll_to_uievent_with_direction(0.0, 1.0, 10.0, 20.0, true);
        match ev {
            UiEvent::Scroll { delta, .. } => assert_eq!(delta.y, 1.0),
            _ => panic!(),
        }
    }

    #[test]
    fn scroll_preserves_fractional_smooth_scroll_magnitude() {
        // `GDK_SCROLL_SMOOTH` (trackpad) deltas are sub-unit, e.g. a
        // light two-finger nudge might report dy = 0.35. The
        // translator must carry that magnitude through unreduced
        // (not rounded/clamped to a whole row), or sub-row trackpad
        // scrolling degrades back to the old wheel-only ±1 behavior.
        let ev = gdk_scroll_to_uievent(0.2, 0.35, 10.0, 20.0);
        match ev {
            UiEvent::Scroll { delta, .. } => {
                assert_eq!(delta.x, 0.2);
                assert_eq!(delta.y, -0.35);
            }
            _ => panic!(),
        }
    }

    #[test]
    fn scroll_preserves_multi_line_discrete_scroll_magnitude() {
        // An OS-configured "scroll N lines per wheel notch" setting
        // (or a fast flick) reaches this translator as a single
        // `dy` larger than 1.0. That full magnitude must survive,
        // not collapse to a sign-only ±1.
        let ev = gdk_scroll_to_uievent(0.0, 4.5, 10.0, 20.0);
        match ev {
            UiEvent::Scroll { delta, .. } => assert_eq!(delta.y, -4.5),
            _ => panic!(),
        }
    }

    #[test]
    fn resize_translation() {
        let ev = gdk_resize_to_uievent(1920, 1080, 2.0);
        match ev {
            UiEvent::WindowResized { viewport } => {
                assert_eq!(viewport.width, 1920.0);
                assert_eq!(viewport.height, 1080.0);
                assert_eq!(viewport.scale, 2.0);
            }
            _ => panic!(),
        }
    }
}