Pick with the mouse

Click a tile to pick it, scroll to move the selection. Hovering does not
move the selection: the keyboard keeps that, and a click acts on whatever
is under the cursor instead. A click on the margin, on a gap, or on an
empty cell of a ragged last row does nothing.

Tiles are already subsurfaces, so a click on a thumbnail identifies its
tile by which surface the event arrived on — no hit-testing needed. Only
the chrome around them (padding, labels, gaps) needs Layout::hit, which
inverts the same maths elem() lays out with, and is tested against it.

Picking waits for press and release on the same tile, so sliding off a
tile before letting go is not a pick.

wp_cursor_shape_v1 sets the pointer shape, which spares us a cursor theme
and libwayland-cursor; without it the cursor keeps whatever shape the
window underneath gave it. It is optional — a compositor without it just
gets whatever shape was already there.

Cargo.toml

@@ -7,7 +7,7 @@ license = "MIT"
 
 [dependencies]
 wayland-client = "0.31"
-wayland-protocols = { version = "0.32", features = ["client", "staging"] }
+wayland-protocols = { version = "0.32", features = ["client", "staging", "unstable"] }
 wayland-protocols-wlr = { version = "0.3", features = ["client"] }
 memmap2 = "0.9"
 rustix = { version = "1", features = ["fs", "mm", "shm"] }

README.md

@@ -95,8 +95,16 @@ chooser_cmd=wl-pick --format portal
 | `→` `←` / `l` `h` / `Tab` `Shift+Tab` | next / previous tile |
 | `↓` `↑` / `j` `k` | move a row |
 | `Home` `End` | first / last |
-| `Enter` | pick |
+| `Enter` | pick the selection |
 | `Escape` / `q` | cancel |
+| click | pick that tile |
+| scroll | next / previous tile |
+
+Hovering deliberately does not move the selection — the keyboard keeps it, and a
+click acts on whatever is under the cursor. Clicking the margin, a gap, or an
+empty cell of a ragged last row does nothing. Tiles are subsurfaces, so a click
+on a thumbnail identifies its tile by surface; only clicks on the chrome around
+them need hit-testing.
 
 Navigation reads raw evdev keycodes, so it is layout-independent — but it also
 means virtual-keyboard clients such as `wtype` (which invent their own keymap)
@@ -181,5 +189,6 @@ shm.rs      memfd allocation and the ARGB painter
 
 ```
 cargo build --release
-cargo test          # grid geometry, ellipsising, output formats, glyph output
+cargo test          # grid geometry and hit-testing, ellipsising, output
+                    # formats, glyph output
 ```

src/app.rs

@@ -33,12 +33,17 @@ use wayland_protocols::ext::image_capture_source::v1::client::{
     ext_output_image_capture_source_manager_v1::ExtOutputImageCaptureSourceManagerV1,
 };
 use wayland_protocols::ext::image_copy_capture::v1::client::ext_image_copy_capture_manager_v1::ExtImageCopyCaptureManagerV1;
+use wayland_protocols::wp::cursor_shape::v1::client::{
+    wp_cursor_shape_device_v1::WpCursorShapeDeviceV1,
+    wp_cursor_shape_manager_v1::WpCursorShapeManagerV1,
+};
 use wayland_protocols::wp::viewporter::client::{
     wp_viewport::WpViewport, wp_viewporter::WpViewporter,
 };
 use wayland_protocols_wlr::layer_shell::v1::client::zwlr_layer_shell_v1::ZwlrLayerShellV1;
 
 use crate::capture::{Live, Tile};
+use crate::overlay;
 use crate::shm;
 use crate::target::Target;
 use crate::text;
@@ -80,6 +85,16 @@ pub struct App {
     pub(crate) sel: usize,
     pub(crate) shift: bool,
 
+    /// Where the pointer is, and which tile it pressed. Hovering deliberately
+    /// does not move the keyboard selection; a click acts on what is under the
+    /// cursor instead.
+    pub(crate) hover: Option<overlay::Hover>,
+    pub(crate) pressed: Option<usize>,
+    /// Set the cursor shape without shipping a cursor theme. Optional: without
+    /// it the pointer keeps whatever shape it had over the window below.
+    pub(crate) cursor_shape: Option<WpCursorShapeManagerV1>,
+    pub(crate) cursor_device: Option<WpCursorShapeDeviceV1>,
+
     pub(crate) labels: Option<text::Labels>,
     pub(crate) surface: Option<WlSurface>,
     pub(crate) chrome: Option<shm::Chrome>,
@@ -161,6 +176,10 @@ impl App {
             scale,
             sel: 0,
             shift: false,
+            hover: None,
+            pressed: None,
+            cursor_shape: globals.bind(qh, 1..=2, ()).ok(),
+            cursor_device: None,
             labels: None,
             surface: None,
             chrome: None,
@@ -323,4 +342,6 @@ delegate_noop!(App: ExtOutputImageCaptureSourceManagerV1);
 delegate_noop!(App: ignore WlSurface);
 // The chrome's own buffers: two slots alternating on keypresses, so their
 // release timing does not matter.
+delegate_noop!(App: WpCursorShapeManagerV1);
+delegate_noop!(App: WpCursorShapeDeviceV1);
 delegate_noop!(App: ignore WlBuffer);

src/cli.rs

@@ -25,8 +25,10 @@ usage: wl-pick [options]
   -v, --verbose             phase timings, tile list and capture stats
   -h, --help                this
 
-keys: arrows, hjkl or Tab/Shift+Tab move; Home/End jump; Enter picks;
-      Escape or q cancels
+keys:  arrows, hjkl or Tab/Shift+Tab move; Home/End jump; Enter picks;
+       Escape or q cancels
+mouse: click a tile to pick it, scroll to move. Hovering does not move the
+       selection, and a click outside a tile does nothing.
 
 The pick goes to stdout and nothing does if you cancel, so exit status is
 0 for a pick and 1 for a cancel. Acting on it is the caller's job.

src/overlay.rs

@@ -10,8 +10,10 @@ use std::os::fd::AsFd;
 
 use wayland_client::protocol::{
     wl_keyboard::{self, WlKeyboard},
+    wl_pointer::{self, WlPointer},
     wl_seat::{self, WlSeat},
     wl_shm,
+    wl_surface::WlSurface,
 };
 use wayland_client::{Connection, Dispatch, QueueHandle, WEnum};
 use wayland_protocols_wlr::layer_shell::v1::client::{
@@ -19,6 +21,8 @@ use wayland_protocols_wlr::layer_shell::v1::client::{
     zwlr_layer_surface_v1::{self, KeyboardInteractivity, ZwlrLayerSurfaceV1},
 };
 
+use wayland_protocols::wp::cursor_shape::v1::client::wp_cursor_shape_device_v1::Shape;
+
 use crate::app::{App, Ending};
 use crate::shm;
 use crate::theme::{Rect, fit_centred};
@@ -44,6 +48,18 @@ const KEY_RIGHT: u32 = 106;
 const KEY_END: u32 = 107;
 const KEY_DOWN: u32 = 108;
 
+/// evdev button code, as wl_pointer reports it.
+const BTN_LEFT: u32 = 0x110;
+
+/// Where the pointer is: the surface it entered, and the position within it.
+/// Tiles are subsurfaces, so the surface alone usually names a tile; the
+/// position is only needed over the chrome around them.
+pub struct Hover {
+    pub surface: WlSurface,
+    pub x: f64,
+    pub y: f64,
+}
+
 impl App {
     /// Map the overlay: a layer surface sized to hug the grid, plus the shm the
     /// chrome is painted into.
@@ -185,6 +201,36 @@ impl App {
         }
     }
 
+    /// The tile under the pointer, if it is over one. A tile's own subsurface
+    /// answers directly; over the parent surface — padding, labels, gaps — the
+    /// layout is asked instead.
+    fn tile_at_pointer(&self) -> Option<usize> {
+        let hover = self.hover.as_ref()?;
+        let on_tile = self
+            .tiles
+            .iter()
+            .position(|t| t.surface.as_ref() == Some(&hover.surface));
+        on_tile.or_else(|| {
+            (Some(&hover.surface) == self.surface.as_ref())
+                .then(|| self.layout.hit(hover.x as i32, hover.y as i32))
+                .flatten()
+        })
+    }
+
+    /// Press and release on the same tile picks it. Anywhere else — the margin,
+    /// a gap, an empty cell of the last row — does nothing at all.
+    fn click(&mut self, pressed: bool) {
+        if pressed {
+            self.pressed = self.tile_at_pointer();
+            return;
+        }
+        let released = self.tile_at_pointer();
+        if let Some(i) = self.pressed.take().filter(|i| Some(*i) == released) {
+            self.picked = self.tiles.get(i).map(|t| t.target.clone());
+            self.ending = Ending::Picked;
+        }
+    }
+
     fn key(&mut self, code: u32) {
         match code {
             KEY_LEFTSHIFT | KEY_RIGHTSHIFT => self.shift = true,
@@ -235,20 +281,29 @@ impl Dispatch<ZwlrLayerSurfaceV1, ()> for App {
 
 impl Dispatch<WlSeat, ()> for App {
     fn event(
-        _: &mut Self,
+        app: &mut Self,
         seat: &WlSeat,
         event: wl_seat::Event,
         _: &(),
         _: &Connection,
         qh: &QueueHandle<Self>,
     ) {
-        if let wl_seat::Event::Capabilities {
+        let wl_seat::Event::Capabilities {
             capabilities: WEnum::Value(caps),
         } = event
-            && caps.contains(wl_seat::Capability::Keyboard)
-        {
+        else {
+            return;
+        };
+        if caps.contains(wl_seat::Capability::Keyboard) {
             seat.get_keyboard(qh, ());
         }
+        if caps.contains(wl_seat::Capability::Pointer) {
+            let pointer = seat.get_pointer(qh, ());
+            app.cursor_device = app
+                .cursor_shape
+                .as_ref()
+                .map(|mgr| mgr.get_pointer(&pointer, qh, ()));
+        }
     }
 }
 
@@ -274,3 +329,57 @@ impl Dispatch<WlKeyboard, ()> for App {
         }
     }
 }
+
+/// Hovering does not move the selection — that belongs to the keyboard — so the
+/// pointer only tracks where it is and what it clicked. Scrolling is a
+/// deliberate gesture, so that does move the selection.
+impl Dispatch<WlPointer, ()> for App {
+    fn event(
+        app: &mut Self,
+        _: &WlPointer,
+        event: wl_pointer::Event,
+        _: &(),
+        _: &Connection,
+        _: &QueueHandle<Self>,
+    ) {
+        match event {
+            wl_pointer::Event::Enter {
+                serial,
+                surface,
+                surface_x,
+                surface_y,
+            } => {
+                // A client owns the cursor over its own surfaces; without this
+                // the pointer keeps whatever shape the window below gave it.
+                if let Some(device) = &app.cursor_device {
+                    device.set_shape(serial, Shape::Default);
+                }
+                app.hover = Some(Hover {
+                    surface,
+                    x: surface_x,
+                    y: surface_y,
+                });
+            }
+            wl_pointer::Event::Motion {
+                surface_x,
+                surface_y,
+                ..
+            } => {
+                if let Some(hover) = app.hover.as_mut() {
+                    (hover.x, hover.y) = (surface_x, surface_y);
+                }
+            }
+            wl_pointer::Event::Leave { .. } => {
+                app.hover = None;
+                app.pressed = None;
+            }
+            wl_pointer::Event::Button {
+                button: BTN_LEFT,
+                state: WEnum::Value(state),
+                ..
+            } => app.click(state == wl_pointer::ButtonState::Pressed),
+            wl_pointer::Event::Axis { value, .. } => app.move_sel(if value > 0.0 { 1 } else { -1 }),
+            _ => {}
+        }
+    }
+}

src/theme.rs

@@ -67,6 +67,8 @@ impl Default for Theme {
 pub struct Layout {
     pub cols: i32,
     pub rows: i32,
+    /// How many tiles there are, which the last row may not fill.
+    n: i32,
     pub width: i32,
     pub height: i32,
     elem_w: i32,
@@ -96,6 +98,7 @@ impl Layout {
         Self {
             cols,
             rows,
+            n,
             width: cols * elem_w + (cols - 1) * t.gap + 2 * t.margin,
             height: rows * elem_h + (rows - 1) * t.gap + 2 * t.margin,
             elem_w,
@@ -132,6 +135,28 @@ impl Layout {
         }
     }
 
+    /// The tile at a point in surface-local coordinates, if any. Points in the
+    /// gaps between elements and in the window margin belong to nothing, and so
+    /// do the empty cells of a ragged last row.
+    pub fn hit(&self, x: i32, y: i32) -> Option<usize> {
+        let col = self.axis(x, self.margin, self.elem_w, self.cols)?;
+        let row = self.axis(y, self.margin, self.elem_h, self.rows)?;
+        let i = row * self.cols + col;
+        (i < self.n).then_some(i as usize)
+    }
+
+    /// Which cell along one axis a coordinate falls in, or None if it landed in
+    /// the margin or a gap.
+    fn axis(&self, v: i32, margin: i32, elem: i32, count: i32) -> Option<i32> {
+        let pitch = elem + self.gap;
+        let offset = v - margin;
+        if offset < 0 {
+            return None;
+        }
+        let cell = offset / pitch;
+        (cell < count && offset % pitch < elem).then_some(cell)
+    }
+
     /// The single line of text under the thumbnail, if labels are drawn.
     pub fn label(&self, i: i32) -> Option<Rect> {
         if !self.labels {
@@ -253,6 +278,40 @@ mod tests {
         }
     }
 
+    #[test]
+    fn hit_testing_is_the_inverse_of_the_layout() {
+        let t = Theme::default();
+        // 7 tiles over 3 columns: the last row holds one, so two cells are empty.
+        let l = Layout::new(&t, 7);
+        for i in 0..7 {
+            let e = l.elem(i);
+            for (x, y, what) in [
+                (e.x, e.y, "top left"),
+                (e.x + e.w / 2, e.y + e.h / 2, "centre"),
+                (e.x + e.w - 1, e.y + e.h - 1, "bottom right"),
+            ] {
+                assert_eq!(l.hit(x, y), Some(i as usize), "{what} of element {i}");
+            }
+        }
+        // The window margin, the gap between elements, and the empty cells of
+        // the last row all belong to no tile.
+        assert_eq!(l.hit(0, 0), None, "margin");
+        let first = l.elem(0);
+        assert_eq!(
+            l.hit(first.x + first.w + 1, first.y),
+            None,
+            "gap between columns"
+        );
+        assert_eq!(
+            l.hit(first.x, first.y + first.h + 1),
+            None,
+            "gap between rows"
+        );
+        let empty = l.elem(8); // row 2, column 2: past the seventh tile
+        assert_eq!(l.hit(empty.x + 4, empty.y + 4), None, "empty cell");
+        assert_eq!(l.hit(-5, -5), None, "outside");
+    }
+
     #[test]
     fn fit_preserves_aspect_and_centres() {
         let box_ = Rect {