fix(stretch): free crossing-window corners from Ortho, draw filled marquee (#291)

STRETCH picks its crossing window as two corner points. After the first
corner set last_point, Ortho/Polar constrained the opposite corner to an axis
through it, collapsing the window to a line and making selection impossible.

Add CadCommand::window_corner_pick(); STRETCH returns true for its two window
steps, and the viewport skips the ortho/polar (and OTRACK) lock for that point
in both the preview and commit paths — the corners are now free.

Also render the window like a normal box selection instead of a bare green
outline: add SelectionState::preview_box (a hit-test-free marquee), draw it
with the shared draw_marquee helper (green crossing fill + stroke), and drive
it from the command's new window_first_corner(). Cleared on command end.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/update/viewport.rs

@@ -909,6 +909,15 @@ pub(super) fn on_tick(&mut self, t: Instant) -> Task<Message> {
                         .as_ref()
                         .map(|c| c.is_selection_gathering())
                         .unwrap_or(false);
+                    // A selection-window corner (STRETCH crossing window) is a
+                    // free point — Ortho/Polar must not pin it to an axis through
+                    // the first corner, or the rectangle collapses to a line
+                    // (#291).
+                    let is_window_corner = self.tabs[i]
+                        .active_cmd
+                        .as_ref()
+                        .map(|c| c.window_corner_pick())
+                        .unwrap_or(false);
                     let needs_tan = self.tabs[i]
                         .active_cmd
                         .as_ref()
@@ -956,7 +965,10 @@ pub(super) fn on_tick(&mut self, t: Instant) -> Task<Message> {
                             Instant::now(),
                         );
                         if self.tabs[i].snap_result.is_none() {
-                            let step = if self.polar_mode {
+                            // A window corner is a free point, so neither the
+                            // Polar increment nor the Ortho lock may pull the
+                            // OTRACK alignment onto an axis (#291).
+                            let step = if self.polar_mode && !is_window_corner {
                                 Some(self.polar_increment_deg)
                             } else {
                                 None
@@ -969,7 +981,7 @@ pub(super) fn on_tick(&mut self, t: Instant) -> Task<Message> {
                                 bounds,
                                 step,
                                 self.last_point,
-                                self.ortho_mode,
+                                self.ortho_mode && !is_window_corner,
                                 ucs,
                             )
                         } else {
@@ -1018,7 +1030,7 @@ pub(super) fn on_tick(&mut self, t: Instant) -> Task<Message> {
                             let osnap_locked = self.tabs[i]
                                 .snap_result
                                 .is_some_and(|s| s.snap_type != crate::snap::SnapType::Grid);
-                            if !osnap_locked {
+                            if !osnap_locked && !is_window_corner {
                                 if let Some(base) = self.last_point {
                                     let ucs_xf = self.tabs[i].ucs_xform();
                                     if self.ortho_mode {
@@ -1075,6 +1087,20 @@ pub(super) fn on_tick(&mut self, t: Instant) -> Task<Message> {
                     self.tabs[i].last_point_screen = lps;
                     self.tabs[i].dyn_ref_screen = drs;
 
+                    // Point-picked selection window (STRETCH): draw a filled
+                    // crossing marquee from the first corner to the cursor so it
+                    // reads like a normal box selection, not a bare outline (#291).
+                    let window_first = self.tabs[i]
+                        .active_cmd
+                        .as_ref()
+                        .and_then(|c| c.window_first_corner());
+                    self.tabs[i].scene.selection.borrow_mut().preview_box =
+                        if is_window_corner {
+                            window_first.map(|c1| (proj(c1.as_vec3()), p_full, true))
+                        } else {
+                            None
+                        };
+
                     // Entity-pick previews (TRIM/EXTEND/FILLET…) compare the
                     // cursor against WCS document entities and return WCS wires.
                     // `effective` is offset-relative, so build a WCS copy for
@@ -1812,6 +1838,13 @@ pub(super) fn on_tick(&mut self, t: Instant) -> Task<Message> {
                     .as_ref()
                     .map(|c| c.is_selection_gathering())
                     .unwrap_or(false);
+                // A committed window corner must stay free of the Ortho/Polar
+                // lock too, so the picked rectangle isn't flattened (#291).
+                let is_window_corner = self.tabs[i]
+                    .active_cmd
+                    .as_ref()
+                    .map(|c| c.window_corner_pick())
+                    .unwrap_or(false);
 
                 if is_down && is_click && self.tabs[i].active_cmd.is_some() && !is_gathering {
                     let (vw, vh) = (tile_vw, tile_vh);
@@ -1876,14 +1909,14 @@ pub(super) fn on_tick(&mut self, t: Instant) -> Task<Message> {
                         // OTRACK alignment wins over ortho/polar; otherwise apply
                         // ortho/polar relative to the last point.
                         let otrack = if snap_hit.is_none() {
-                            let step = if self.polar_mode {
+                            let step = if self.polar_mode && !is_window_corner {
                                 Some(self.polar_increment_deg)
                             } else {
                                 None
                             };
                             let ucs = self.tabs[i].scene.viewcube_ucs_mat();
                             self.snapper
-                                .otrack_snap(raw.as_vec3(), view_rot, eye, bounds, step, self.last_point, self.ortho_mode, ucs)
+                                .otrack_snap(raw.as_vec3(), view_rot, eye, bounds, step, self.last_point, self.ortho_mode && !is_window_corner, ucs)
                         } else {
                             None
                         };
@@ -1892,8 +1925,9 @@ pub(super) fn on_tick(&mut self, t: Instant) -> Task<Message> {
                             if self.tabs[i].active_ucs.is_none() {
                                 pt.z = 0.0;
                             }
-                        } else if !snap_hit
-                            .is_some_and(|s| s.snap_type != crate::snap::SnapType::Grid)
+                        } else if !is_window_corner
+                            && !snap_hit
+                                .is_some_and(|s| s.snap_type != crate::snap::SnapType::Grid)
                         {
                             // Object snap wins over ortho/polar — a snapped point
                             // commits as-is. Grid snap still combines. (#132)

src/command.rs

@@ -702,6 +702,25 @@ pub trait CadCommand: Send {
         CmdResult::Cancel
     }
 
+    /// Returns `true` when the current step picks a corner of a selection
+    /// *window* by point (e.g. STRETCH's crossing window). Such a pick must be a
+    /// free point: applying the Ortho/Polar lock would pin the opposite corner to
+    /// an axis through the first corner, collapsing the rectangle to a line and
+    /// making the window unusable. The host skips the ortho/polar constraint for
+    /// these steps. Default `false`. (#291)
+    fn window_corner_pick(&self) -> bool {
+        false
+    }
+
+    /// The already-picked first corner of the selection window (world space)
+    /// while `window_corner_pick()` is true and the opposite corner is being
+    /// dragged. The host projects it and draws a filled selection marquee to the
+    /// cursor, so a point-picked window (STRETCH) reads like a normal box
+    /// selection. `None` before the first corner is set. (#291)
+    fn window_first_corner(&self) -> Option<glam::DVec3> {
+        None
+    }
+
     /// Returns `true` when the command wants object picks via Tangent snap.
     fn needs_tangent_pick(&self) -> bool {
         false

src/modules/draw/modify/stretch.rs

@@ -130,25 +130,27 @@ impl CadCommand for StretchCommand {
         CmdResult::Cancel
     }
 
+    fn window_corner_pick(&self) -> bool {
+        // The two crossing-window corners are free points; Ortho/Polar must not
+        // pin the opposite corner to an axis or the window becomes a line (#291).
+        matches!(self.step, Step::WindowCorner1 | Step::WindowCorner2(_))
+    }
+
+    fn window_first_corner(&self) -> Option<DVec3> {
+        // Expose the first corner so the host draws a filled crossing marquee to
+        // the cursor, matching a normal box selection instead of a bare outline.
+        match &self.step {
+            Step::WindowCorner2(c1) => Some(c1.as_dvec3()),
+            _ => None,
+        }
+    }
+
     fn on_preview_wires(&mut self, pt: DVec3) -> Vec<WireModel> { let pt = pt.as_vec3();
         match &self.step {
-            Step::WindowCorner2(c1) => {
-                // Show crossing-window rectangle preview (dashed green)
-                let c1 = *c1;
-                let pts = vec![
-                    [c1.x, c1.y, c1.z],
-                    [pt.x, c1.y, c1.z],
-                    [pt.x, pt.y, pt.z],
-                    [c1.x, pt.y, pt.z],
-                    [c1.x, c1.y, c1.z],
-                ];
-                vec![WireModel::solid(
-                    "stretch_window".into(),
-                    pts,
-                    [0.3, 1.0, 0.3, 0.7],
-                    false,
-                )]
-            }
+            // The crossing-window rectangle is drawn as a filled selection
+            // marquee by the host (via window_first_corner) so it matches a
+            // normal box selection — nothing to draw here. (#291)
+            Step::WindowCorner2(_) => vec![],
             Step::Target {
                 win_min,
                 win_max,

src/scene/pick/selection_state.rs

@@ -15,6 +15,12 @@ pub struct SelectionState {
     pub box_last: Option<(Point, Point)>,
     pub box_crossing: bool,
     pub box_last_crossing: bool,
+    /// A preview-only selection marquee `(anchor, current, crossing)` in canvas
+    /// pixels, drawn identically to a real box-selection (green crossing fill /
+    /// blue window fill) but with NO hit-test behaviour. Commands that pick a
+    /// window by point (STRETCH's crossing window) set this so the region reads
+    /// like a normal selection instead of a bare outline. (#291)
+    pub preview_box: Option<(Point, Point, bool)>,
     pub poly_active: bool,
     pub poly_points: Vec<Point>,
     pub poly_crossing: bool,

src/scene/preview.rs

@@ -27,6 +27,9 @@ impl Scene {
         self.preview_wires = vec![];
         self.preview_text = vec![];
         self.interim_wire = None;
+        // Drop any point-picked window marquee (STRETCH) so it doesn't linger
+        // after the command ends before the next mouse move. (#291)
+        self.selection.borrow_mut().preview_box = None;
     }
 
     pub fn wire_models_for(&self, handles: &[acadrust::Handle]) -> Vec<WireModel> {

src/ui/overlay.rs

@@ -430,36 +430,19 @@ impl canvas::Program<Message> for SelectionCanvas {
         }
 
 
-        if let (Some(a), Some(b)) = (self.selection.box_anchor, self.selection.box_current) {
-            let (fill, stroke) = if self.selection.box_crossing {
+        // Draw a selection marquee (green crossing / blue window) as a filled,
+        // stroked rectangle between two canvas points. Shared by the live
+        // box-selection and the preview-only window marquee (#291).
+        fn draw_marquee(frame: &mut canvas::Frame, a: Point, b: Point, crossing: bool) {
+            let (fill, stroke) = if crossing {
                 (
-                    Color {
-                        r: 0.20,
-                        g: 0.72,
-                        b: 0.44,
-                        a: 0.12,
-                    },
-                    Color {
-                        r: 0.20,
-                        g: 0.72,
-                        b: 0.44,
-                        a: 0.9,
-                    },
+                    Color { r: 0.20, g: 0.72, b: 0.44, a: 0.12 },
+                    Color { r: 0.20, g: 0.72, b: 0.44, a: 0.9 },
                 )
             } else {
                 (
-                    Color {
-                        r: 0.20,
-                        g: 0.44,
-                        b: 0.72,
-                        a: 0.12,
-                    },
-                    Color {
-                        r: 0.20,
-                        g: 0.44,
-                        b: 0.72,
-                        a: 0.9,
-                    },
+                    Color { r: 0.20, g: 0.44, b: 0.72, a: 0.12 },
+                    Color { r: 0.20, g: 0.44, b: 0.72, a: 0.9 },
                 )
             };
             let x0 = a.x.min(b.x);
@@ -478,6 +461,14 @@ impl canvas::Program<Message> for SelectionCanvas {
             );
         }
 
+        if let (Some(a), Some(b)) = (self.selection.box_anchor, self.selection.box_current) {
+            draw_marquee(&mut frame, a, b, self.selection.box_crossing);
+        }
+        // Preview marquee for point-picked windows (STRETCH) — same look, no pick.
+        if let Some((a, b, crossing)) = self.selection.preview_box {
+            draw_marquee(&mut frame, a, b, crossing);
+        }
+
         if self.selection.poly_active && self.selection.poly_points.len() > 1 {
             let (fill, stroke) = if self.selection.poly_crossing {
                 (