feat: Shift, Alt and Space while selecting a region

src/region.rs

@@ -3,7 +3,10 @@ use std::sync::Arc;
 use anyhow::{Context, Result};
 use smithay_client_toolkit::{
     compositor::FrameCallbackData,
-    seat::pointer::{BTN_LEFT, BTN_RIGHT, PointerEvent, PointerEventKind},
+    seat::{
+        keyboard::Modifiers,
+        pointer::{BTN_LEFT, BTN_RIGHT, PointerEvent, PointerEventKind},
+    },
     shell::{
         WaylandSurface,
         wlr_layer::{Anchor, KeyboardInteractivity, Layer, LayerSurface},
@@ -25,7 +28,7 @@ use wayland_protocols::wp::viewporter::client::wp_viewport::WpViewport;
 use crate::error::{Cancelled, HintExt};
 use crate::frame::{Bgrx, Frame, OutputGeom, PixelRect};
 use crate::render;
-use crate::selection::{self, Point, Selection};
+use crate::selection::{self, Mods, Point, Selection};
 use crate::wayland::{Output, State, Wayland};
 
 pub const NAMESPACE: &str = "valw-overlay";
@@ -45,6 +48,8 @@ pub struct Overlay {
     selection: Selection,
     /// Output where the current drag started; the capture is clipped to it.
     anchor: Option<usize>,
+    /// Shift, Alt and Space as the keyboard last reported them.
+    mods: Mods,
     outcome: Option<Option<Choice>>,
 }
 
@@ -106,6 +111,7 @@ pub fn select(wl: &mut Wayland, outputs: &[Output], frames: &[Frame]) -> Result<
         surfaces,
         selection: Selection::default(),
         anchor: None,
+        mods: Mods::default(),
         outcome: None,
     });
     let result = wl.dispatch_blocking(|s| s.overlay.as_ref().is_some_and(|o| o.outcome.is_some()));
@@ -169,6 +175,30 @@ impl Overlay {
         self.outcome.get_or_insert(None);
     }
 
+    pub fn modifiers(&mut self, m: Modifiers, qh: &QueueHandle<State>) {
+        self.mods.shift = m.shift;
+        self.mods.alt = m.alt;
+        self.apply_mods(qh);
+    }
+
+    /// Space before a drag switches to window mode; during one it moves
+    /// the selection while held.
+    pub fn space(&mut self, down: bool, qh: &QueueHandle<State>) {
+        if down && self.selection.allows_window_switch() {
+            self.switch_to_window();
+            return;
+        }
+        self.mods.space = down;
+        self.apply_mods(qh);
+    }
+
+    fn apply_mods(&mut self, qh: &QueueHandle<State>) {
+        self.selection.set_mods(self.mods);
+        if let Some(a) = self.anchor {
+            self.redraw(a, qh);
+        }
+    }
+
     pub fn switch_to_window(&mut self) {
         if self.selection.allows_window_switch() {
             tracing::info!("switching to window mode");
@@ -184,9 +214,7 @@ impl Overlay {
 
     /// The selection as drawn on surface `i`: only the anchor output shows it.
     fn selection_on(&self, i: usize) -> Option<PixelRect> {
-        let Selection::Dragging { start, end } = self.selection else {
+        let (start, end) = self.selection.corners()?;
-            return None;
-        };
         let s = &self.surfaces[i];
         (self.anchor == Some(i))
             .then(|| selection::clip(start, end, &s.geom, s.width, s.height))
@@ -255,6 +283,8 @@ impl Overlay {
                     button: BTN_LEFT, ..
                 } => {
                     self.selection.press(p);
+                    // Modifiers already held apply from the start.
+                    self.selection.set_mods(self.mods);
                     self.anchor = Some(i);
                 }
                 PointerEventKind::Press {

src/selection.rs

@@ -10,33 +10,138 @@ pub struct Point {
     pub y: f64,
 }
 
+/// Modifier keys that shape a selection while dragging.
+#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
+pub struct Mods {
+    pub shift: bool,
+    pub alt: bool,
+    pub space: bool,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+enum Axis {
+    X,
+    Y,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct Drag {
+    /// The press point (the centre with Alt); Space moves it.
+    start: Point,
+    /// The far corner before Alt is applied.
+    end: Point,
+    /// The last pointer position.
+    last: Point,
+    /// Added to the pointer to get `end` (non-zero after a Space move).
+    offset: (f64, f64),
+    mods: Mods,
+    /// Shift: `end` when Shift went down, and the axis that follows.
+    lock: Option<(Point, Option<Axis>)>,
+}
+
 #[derive(Debug, Clone, Copy, Default, PartialEq)]
 pub enum Selection {
     #[default]
     Idle,
-    Dragging {
+    Dragging(Drag),
-        start: Point,
-        end: Point,
-    },
 }
 
 impl Selection {
     pub fn press(&mut self, p: Point) {
-        *self = Selection::Dragging { start: p, end: p };
+        let mods = match self {
+            Selection::Dragging(d) => d.mods,
+            Selection::Idle => Mods::default(),
+        };
+        *self = Selection::Dragging(Drag {
+            start: p,
+            end: p,
+            last: p,
+            offset: (0.0, 0.0),
+            mods,
+            lock: None,
+        });
     }
 
     pub fn motion(&mut self, p: Point) {
-        if let Selection::Dragging { end, .. } = self {
+        let Selection::Dragging(d) = self else { return };
-            *end = p;
+        if d.mods.space {
+            let (dx, dy) = (p.x - d.last.x, p.y - d.last.y);
+            d.start = Point {
+                x: d.start.x + dx,
+                y: d.start.y + dy,
+            };
+            d.end = Point {
+                x: d.end.x + dx,
+                y: d.end.y + dy,
+            };
+        } else {
+            let target = Point {
+                x: p.x + d.offset.0,
+                y: p.y + d.offset.1,
+            };
+            d.end = match &mut d.lock {
+                Some((frozen, axis)) => {
+                    let axis = *axis.get_or_insert_with(|| {
+                        if (target.x - frozen.x).abs() >= (target.y - frozen.y).abs() {
+                            Axis::X
+                        } else {
+                            Axis::Y
+                        }
+                    });
+                    match axis {
+                        Axis::X => Point {
+                            x: target.x,
+                            y: frozen.y,
+                        },
+                        Axis::Y => Point {
+                            x: frozen.x,
+                            y: target.y,
+                        },
+                    }
+                }
+                None => target,
+            };
+        }
+        d.last = p;
+    }
+
+    /// The keyboard's modifiers changed (also while idle, for the next drag).
+    pub fn set_mods(&mut self, mods: Mods) {
+        let Selection::Dragging(d) = self else { return };
+        if mods.shift && !d.mods.shift {
+            d.lock = Some((d.end, None));
+        } else if !mods.shift {
+            d.lock = None;
+        }
+        if d.mods.space && !mods.space {
+            // Resize again from where the corner is, not where the pointer is.
+            d.offset = (d.end.x - d.last.x, d.end.y - d.last.y);
+        }
+        d.mods = mods;
+    }
+
+    /// The selection's corners in global logical coordinates.
+    pub fn corners(&self) -> Option<(Point, Point)> {
+        let Selection::Dragging(d) = self else {
+            return None;
+        };
+        if d.mods.alt {
+            let opposite = Point {
+                x: 2.0 * d.start.x - d.end.x,
+                y: 2.0 * d.start.y - d.end.y,
+            };
+            Some((opposite, d.end))
+        } else {
+            Some((d.start, d.end))
         }
     }
 
-    /// Ends the drag and returns its start and end. Back to `Idle` either way.
+    /// Ends the drag at `p` and returns its corners. Back to `Idle` either way.
     pub fn release(&mut self, p: Point) -> Option<(Point, Point)> {
-        match std::mem::take(self) {
+        self.motion(p);
-            Selection::Dragging { start, .. } => Some((start, p)),
+        let corners = self.corners();
-            Selection::Idle => None,
+        *self = Selection::Idle;
-        }
+        corners
     }
 
     /// Space switches to window mode only before a drag starts.
@@ -211,17 +316,133 @@ mod tests {
 
         s.press(p(1.0, 2.0));
         s.motion(p(5.0, 6.0));
-        assert_eq!(
+        assert_eq!(s.corners(), Some((p(1.0, 2.0), p(5.0, 6.0))));
-            s,
-            Selection::Dragging {
-                start: p(1.0, 2.0),
-                end: p(5.0, 6.0)
-            }
-        );
         assert_eq!(s.release(p(7.0, 8.0)), Some((p(1.0, 2.0), p(7.0, 8.0))));
         assert_eq!(s, Selection::Idle);
 
         s.motion(p(9.0, 9.0));
         assert_eq!(s, Selection::Idle);
     }
+
+    fn pt(x: f64, y: f64) -> Point {
+        Point { x, y }
+    }
+
+    const SHIFT: Mods = Mods {
+        shift: true,
+        alt: false,
+        space: false,
+    };
+    const ALT: Mods = Mods {
+        shift: false,
+        alt: true,
+        space: false,
+    };
+    const SPACE: Mods = Mods {
+        shift: false,
+        alt: false,
+        space: true,
+    };
+
+    #[test]
+    fn plain_drag_is_press_to_pointer() {
+        let mut s = Selection::default();
+        s.press(pt(10.0, 10.0));
+        s.motion(pt(50.0, 30.0));
+        assert_eq!(s.corners(), Some((pt(10.0, 10.0), pt(50.0, 30.0))));
+    }
+
+    #[test]
+    fn shift_locks_the_dimension_that_moves_first() {
+        let mut s = Selection::default();
+        s.press(pt(0.0, 0.0));
+        s.motion(pt(40.0, 30.0));
+        s.set_mods(SHIFT);
+        s.motion(pt(60.0, 32.0)); // mostly horizontal: width follows
+        assert_eq!(s.corners(), Some((pt(0.0, 0.0), pt(60.0, 30.0))));
+        s.motion(pt(70.0, 90.0)); // the axis stays decided
+        assert_eq!(s.corners(), Some((pt(0.0, 0.0), pt(70.0, 30.0))));
+        s.set_mods(Mods::default());
+        s.motion(pt(70.0, 90.0));
+        assert_eq!(
+            s.corners(),
+            Some((pt(0.0, 0.0), pt(70.0, 90.0))),
+            "plain again"
+        );
+
+        let mut v = Selection::default();
+        v.press(pt(0.0, 0.0));
+        v.motion(pt(40.0, 30.0));
+        v.set_mods(SHIFT);
+        v.motion(pt(41.0, 80.0)); // mostly vertical: height follows
+        assert_eq!(v.corners(), Some((pt(0.0, 0.0), pt(40.0, 80.0))));
+    }
+
+    #[test]
+    fn alt_grows_from_the_centre() {
+        let mut s = Selection::default();
+        s.press(pt(100.0, 100.0));
+        s.set_mods(ALT);
+        s.motion(pt(130.0, 120.0));
+        assert_eq!(s.corners(), Some((pt(70.0, 80.0), pt(130.0, 120.0))));
+    }
+
+    #[test]
+    fn shift_and_alt_combine() {
+        let mut s = Selection::default();
+        s.press(pt(100.0, 100.0));
+        s.motion(pt(120.0, 110.0));
+        s.set_mods(Mods {
+            shift: true,
+            alt: true,
+            space: false,
+        });
+        s.motion(pt(150.0, 112.0));
+        assert_eq!(s.corners(), Some((pt(50.0, 90.0), pt(150.0, 110.0))));
+    }
+
+    #[test]
+    fn space_moves_then_resizing_continues_without_a_jump() {
+        let mut s = Selection::default();
+        s.press(pt(0.0, 0.0));
+        s.motion(pt(40.0, 30.0));
+        s.set_mods(SPACE);
+        s.motion(pt(50.0, 40.0));
+        assert_eq!(s.corners(), Some((pt(10.0, 10.0), pt(50.0, 40.0))));
+        s.motion(pt(60.0, 40.0));
+        assert_eq!(s.corners(), Some((pt(20.0, 10.0), pt(60.0, 40.0))));
+        s.set_mods(Mods::default());
+        s.motion(pt(60.0, 40.0));
+        assert_eq!(
+            s.corners(),
+            Some((pt(20.0, 10.0), pt(60.0, 40.0))),
+            "no jump on release"
+        );
+        s.motion(pt(70.0, 45.0));
+        assert_eq!(s.corners(), Some((pt(20.0, 10.0), pt(70.0, 45.0))));
+    }
+
+    #[test]
+    fn space_with_a_pointer_away_from_the_corner_keeps_the_offset() {
+        let mut s = Selection::default();
+        s.press(pt(0.0, 0.0));
+        s.motion(pt(40.0, 30.0));
+        s.set_mods(SPACE);
+        s.motion(pt(45.0, 30.0));
+        s.set_mods(Mods::default());
+        s.motion(pt(55.0, 40.0));
+        assert_eq!(s.corners(), Some((pt(5.0, 0.0), pt(55.0, 40.0))));
+    }
+
+    #[test]
+    fn release_applies_the_held_modifiers() {
+        let mut s = Selection::default();
+        s.press(pt(100.0, 100.0));
+        s.set_mods(ALT);
+        assert_eq!(
+            s.release(pt(110.0, 105.0)),
+            Some((pt(90.0, 95.0), pt(110.0, 105.0)))
+        );
+        assert_eq!(s, Selection::Idle);
+    }
 }

src/wayland.rs

@@ -483,7 +483,7 @@ impl KeyboardHandler for State {
         if let Some(overlay) = &mut self.overlay {
             match event.keysym {
                 Keysym::Escape => overlay.cancel(),
-                Keysym::space => overlay.switch_to_window(),
+                Keysym::space => overlay.space(true, qh),
                 _ => {}
             }
         }
@@ -508,17 +508,22 @@ impl KeyboardHandler for State {
     fn release_key(
         &mut self,
         _: &Connection,
-        _: &QueueHandle<Self>,
+        qh: &QueueHandle<Self>,
         _: &wl_keyboard::WlKeyboard,
         _: u32,
-        _: KeyEvent,
+        event: KeyEvent,
     ) {
+        if event.keysym == Keysym::space
+            && let Some(overlay) = &mut self.overlay
+        {
+            overlay.space(false, qh);
+        }
     }
 
     fn update_modifiers(
         &mut self,
         _: &Connection,
-        _: &QueueHandle<Self>,
+        qh: &QueueHandle<Self>,
         _: &wl_keyboard::WlKeyboard,
         _: u32,
         modifiers: Modifiers,
@@ -528,6 +533,9 @@ impl KeyboardHandler for State {
         if let Some(zoom) = &mut self.zoom {
             zoom.modifiers(modifiers);
         }
+        if let Some(overlay) = &mut self.overlay {
+            overlay.modifiers(modifiers, qh);
+        }
     }
 }