Enable scrolling with smooth scroll

src/shell.rs

@@ -346,11 +346,15 @@ impl State {

pub struct UiState {
    mouse_pressed: bool,
    scroll_delta: (f64, f64),
}

impl UiState {
    pub fn new() -> UiState {
        UiState { mouse_pressed: false }
        UiState {
            mouse_pressed: false,
            scroll_delta: (0.0, 0.0),
        }
    }
}

@@ -416,8 +420,8 @@ impl Shell {

        state.drawing_area.set_events(
            (gdk_sys::GDK_BUTTON_RELEASE_MASK | gdk_sys::GDK_BUTTON_PRESS_MASK |
                 gdk_sys::GDK_BUTTON_MOTION_MASK |
                 gdk_sys::GDK_SCROLL_MASK)
                 gdk_sys::GDK_BUTTON_MOTION_MASK | gdk_sys::GDK_SCROLL_MASK |
                 gdk_sys::GDK_SMOOTH_SCROLL_MASK)
                .bits() as i32,
        );

@@ -489,8 +493,9 @@ impl Shell {
        });

        let ref_state = self.state.clone();
        let ref_ui_state = self.ui_state.clone();
        state.drawing_area.connect_scroll_event(move |_, ev| {
            gtk_scroll_event(&mut *ref_state.borrow_mut(), ev)
            gtk_scroll_event(&mut *ref_state.borrow_mut(), &mut *ref_ui_state.borrow_mut(), ev)
        });

        let ref_state = self.state.clone();
@@ -626,7 +631,7 @@ fn gtk_focus_out(state: &mut State) -> Inhibit {
    Inhibit(false)
}

fn gtk_scroll_event(state: &mut State, ev: &EventScroll) -> Inhibit {
fn gtk_scroll_event(state: &mut State, ui_state: &mut UiState, ev: &EventScroll) -> Inhibit {
    if !state.mouse_enabled {
        return Inhibit(false);
    }
@@ -646,7 +651,30 @@ fn gtk_scroll_event(state: &mut State, ev: &EventScroll) -> Inhibit {
        gdk_sys::GdkScrollDirection::Down => {
            mouse_input(state, "ScrollWheelDown", ev.get_state(), ev.get_position())
        }
        _ => (),
        gdk_sys::GdkScrollDirection::Smooth => {
            // Remember and accumulate scroll deltas, so slow scrolling still
            // works.
            ui_state.scroll_delta.0 += ev.as_ref().delta_x;
            ui_state.scroll_delta.1 += ev.as_ref().delta_y;
            // Perform scroll action for deltas with abs(delta) >= 1.
            let x = ui_state.scroll_delta.0 as isize;
            let y = ui_state.scroll_delta.1 as isize;
            for _ in 0..x {
                mouse_input(state, "ScrollWheelRight", ev.get_state(), ev.get_position())
            }
            for _ in 0..-x {
                mouse_input(state, "ScrollWheelLeft", ev.get_state(), ev.get_position())
            }
            for _ in 0..y {
                mouse_input(state, "ScrollWheelDown", ev.get_state(), ev.get_position())
            }
            for _ in 0..-y {
                mouse_input(state, "ScrollWheelUp", ev.get_state(), ev.get_position())
            }
            // Subtract performed scroll deltas.
            ui_state.scroll_delta.0 -= x as f64;
            ui_state.scroll_delta.1 -= y as f64;
        }
    }
    Inhibit(false)
}