fix frontend board mapping, game-over handling, and WASM-4

- fix Xform yx and add a shared view-aware board_position helper
- add GTK automatic game-over, restart, status, and multi-capture selection
- pin librsvg to the 2.60 series to match GTK4/glib 0.20
- add WASM orientation, undo/redo/new/flip controls, and winner overlay
- replace WASM crown images with canvas paths and remove dead files/deps
- make WASM-4 playable with mouse input, crowns, winner handling, and correct mapping
- move the WASM-4 release profile to the workspace root
- clean up frontend dead code and update the README

rdraught-ui-common/src/board.rs

@@ -0,0 +1,70 @@
+use rdraught::{DraughtsBoard, Error, Player, Position, RectangularBoard};
+
+/// Maps a screen square to a board square for the given point of view.
+///
+/// Both views place pieces on screen squares where
+/// `(screen_row + screen_col) % 2 == 1`.
+pub fn board_position(view: Player, screen_row: u8, screen_col: u8) -> Result<Position, Error> {
+    let rows = DraughtsBoard::rows() as u8;
+    let columns = DraughtsBoard::columns() as u8;
+    if screen_row >= rows || screen_col >= columns {
+        return Err(Error::InvalidPosition);
+    }
+    match view {
+        Player::White => Position::new(rows - 1 - screen_row, screen_col),
+        Player::Red => Position::new(screen_row, columns - 1 - screen_col),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::board_position;
+    use rdraught::{Player, Position};
+
+    #[test]
+    fn white_view_mapping() {
+        assert_eq!(
+            Position::new(7, 1).unwrap(),
+            board_position(Player::White, 0, 1).unwrap()
+        );
+        assert_eq!(
+            Position::new(0, 0).unwrap(),
+            board_position(Player::White, 7, 0).unwrap()
+        );
+        assert!(board_position(Player::White, 0, 0).is_err());
+    }
+
+    #[test]
+    fn red_view_mapping() {
+        assert_eq!(
+            Position::new(0, 6).unwrap(),
+            board_position(Player::Red, 0, 1).unwrap()
+        );
+        assert_eq!(
+            Position::new(7, 7).unwrap(),
+            board_position(Player::Red, 7, 0).unwrap()
+        );
+        assert!(board_position(Player::Red, 0, 0).is_err());
+    }
+
+    #[test]
+    fn both_views_have_32_squares() {
+        for view in [Player::White, Player::Red] {
+            let mut count = 0;
+            for row in 0..8 {
+                for col in 0..8 {
+                    if board_position(view, row, col).is_ok() {
+                        count += 1;
+                    }
+                }
+            }
+            assert_eq!(32, count);
+        }
+    }
+
+    #[test]
+    fn out_of_bounds_is_rejected() {
+        assert!(board_position(Player::White, 8, 0).is_err());
+        assert!(board_position(Player::Red, 0, 8).is_err());
+    }
+}

rdraught-ui-common/src/geo2d.rs

@@ -205,7 +205,7 @@ impl Xform {
     }
 
     pub fn yx(&self) -> f64 {
-        self.0[(1, 0)]
+        self.0[(0, 1)]
     }
 
     pub fn yy(&self) -> f64 {
@@ -259,3 +259,41 @@ impl Display for Xform {
         self.0.fmt(f)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{Point, Xform};
+    use core::f64::consts::PI;
+
+    fn close(actual: f64, expected: f64) {
+        assert!((actual - expected).abs() < 1e-9);
+    }
+
+    #[test]
+    fn rotation_uses_all_matrix_components() {
+        let rotation = Xform::rot(PI / 2.0);
+        close(rotation.yx(), 1.0);
+        close(rotation.xy(), -1.0);
+
+        let point = Point::new(1.0, 0.0) * &rotation;
+        close(point.x(), 0.0);
+        close(point.y(), 1.0);
+    }
+
+    #[test]
+    fn translation_and_scaling() {
+        let transform = Xform::scale(2.0, 3.0) * Xform::xlate(3.0, 4.0);
+        let point = Point::new(1.0, 2.0) * &transform;
+        close(point.x(), 5.0);
+        close(point.y(), 10.0);
+    }
+
+    #[test]
+    fn inversion_round_trips() {
+        let transform = Xform::xlate(3.0, 4.0) * Xform::rot(0.3) * Xform::scale(2.0, 0.5);
+        let point = Point::new(1.0, 2.0);
+        let result = (point * &transform) * &transform.invert();
+        close(result.x(), point.x());
+        close(result.y(), point.y());
+    }
+}

rdraught-ui-common/src/lib.rs

@@ -1,5 +1,7 @@
+mod board;
 mod geo2d;
 mod types;
 
+pub use board::board_position;
 pub use geo2d::{Point, Rect, Xform};
 pub use types::{SharedMutable, SharedMutableRef, new_shared_mut, new_shared_mut_ref};