fix(canvas): snap resize edges only along dragged axes

crates/app/src/ui/canvas/geometry.rs

@@ -1,7 +1,9 @@
 use super::*;
 #[path = "geometry_aspect.rs"]
 mod aspect;
-pub(crate) use aspect::{drag_frame, enforce_min_size, plot_min_size, preserve_aspect_frame};
+pub(crate) use aspect::{
+    drag_frame, enforce_min_size, plot_min_size, preserve_aspect_frame, resize_min_size,
+};
 #[path = "geometry_panels.rs"]
 mod panels;
 pub(crate) use panels::{

crates/app/src/ui/canvas/geometry_aspect.rs

@@ -1,10 +1,22 @@
 use super::*;
 use plotium_core::state::MIN_CONTENT_FRAME_PT;
 
-/// The frame a drag asks for. A resize holds the edges opposite the handle. An
-/// edge already below the object minimum is not forced up to it. An
-/// aspect-locked drag leaves the minimum to `aspect_locked_size`, which needs
-/// the request free of it to scale from either edge.
+/// The smallest size a resize of `frame` may ask for on each axis. An edge
+/// already below the object minimum is not forced up to it. An aspect-locked
+/// resize leaves the minimum to `aspect_locked_size`, which needs the request
+/// free of it to scale from either edge.
+pub(crate) fn resize_min_size(frame: ObjectFrame, keep_aspect: bool) -> [f32; 2] {
+    if keep_aspect {
+        [MIN_CONTENT_FRAME_PT; 2]
+    } else {
+        [
+            MIN_OBJECT_SIZE_PT.min(frame.width),
+            MIN_OBJECT_SIZE_PT.min(frame.height),
+        ]
+    }
+}
+
+/// The frame a drag asks for. A resize holds the edges opposite the handle.
 pub(crate) fn drag_frame(
     frame: ObjectFrame,
     kind: ObjectDragKind,
@@ -15,14 +27,7 @@ pub(crate) fn drag_frame(
     let ObjectDragKind::Resize(handle) = kind else {
         return ObjectFrame::new(frame.x + dx, frame.y + dy, frame.width, frame.height);
     };
-    let min = if keep_aspect {
-        [MIN_CONTENT_FRAME_PT; 2]
-    } else {
-        [
-            MIN_OBJECT_SIZE_PT.min(frame.width),
-            MIN_OBJECT_SIZE_PT.min(frame.height),
-        ]
-    };
+    let min = resize_min_size(frame, keep_aspect);
     let moves_left = matches!(handle, ResizeHandle::TopLeft | ResizeHandle::BottomLeft);
     let moves_top = matches!(handle, ResizeHandle::TopLeft | ResizeHandle::TopRight);
     let width = (frame.width + if moves_left { -dx } else { dx }).max(min[0]);

crates/app/src/ui/canvas/interactions.rs

@@ -514,6 +514,7 @@ pub(crate) fn handle_object_interactions(
                         before,
                         start_pointer: start,
                         start_pointer_screen: [screen_pos.x, screen_pos.y],
+                        snap_axes: [false; 2],
                         others,
                         active: matches!(hit.kind, ObjectDragKind::Resize(_)),
                         space,
@@ -558,7 +559,7 @@ pub(crate) fn handle_object_interactions(
         Interaction::Object(d) if d.canvas == ci => Some(d.clone()),
         _ => None,
     };
-    if let Some(drag) = object_drag {
+    if let Some(mut drag) = object_drag {
         let mut active = drag.active;
         if primary_down
             && let Some(screen_now) = hover
@@ -574,8 +575,10 @@ pub(crate) fn handle_object_interactions(
             let dsx = screen_now.x - drag.start_pointer_screen[0];
             let dsy = screen_now.y - drag.start_pointer_screen[1];
             active |= dsx.hypot(dsy) > DRAG_START_PX;
+            latch_snap_axes(&mut drag.snap_axes, [dsx, dsy]);
             if let Interaction::Object(d) = &mut app.session.ui.interaction {
                 d.active = active;
+                d.snap_axes = drag.snap_axes;
             }
             if active {
                 if let Some(source) = tile_source_for_object(app, &drag)
@@ -596,10 +599,12 @@ pub(crate) fn handle_object_interactions(
                         if let ObjectDragSpace::Panel(panel) = drag.space {
                             snap_panel_content_frame(app, ci, panel, &drag, candidate, ui)
                         } else {
-                            snap_object_frame(app, ci, &drag, candidate, ui)
+                            snap_object_frame(app, ci, &drag, candidate, preserve_aspect, ui)
                         };
                     if preserve_aspect {
-                        snapped = preserve_aspect_frame(drag.before, snapped, drag.kind);
+                        let requested = snapped;
+                        snapped = preserve_aspect_frame(drag.before, requested, drag.kind);
+                        retain_landed_guides(&mut guides, requested, snapped);
                     }
                     if let Some(plot) = app.doc.canvases[ci]
                         .object(drag.object)

crates/app/src/ui/canvas/panel_interactions.rs

@@ -30,8 +30,10 @@ pub(crate) fn handle_panel_drag(
         let dsy = screen_now.y - drag.start_pointer_screen[1];
         active |= dsx.hypot(dsy) > DRAG_START_PX;
         drag.active = active;
+        latch_snap_axes(&mut drag.snap_axes, [dsx, dsy]);
         if let Interaction::Panel(current) = &mut app.session.ui.interaction {
             current.active = active;
+            current.snap_axes = drag.snap_axes;
         }
         if active {
             let candidate = drag_frame(drag.before, drag.kind, dpx, dpy, false);
@@ -187,6 +189,7 @@ pub(crate) fn begin_panel_drag(
         children,
         start_pointer: start,
         start_pointer_screen: [screen_pos.x, screen_pos.y],
+        snap_axes: [false; 2],
         active: matches!(kind, ObjectDragKind::Resize(_)),
         detached_since: None,
     }));

crates/app/src/ui/canvas/panel_interactions/detach/tests.rs

@@ -22,6 +22,7 @@ fn fixture() -> (PlotiumApp, egui::Context, EguiRect, Pos2) {
         children: vec![],
         start_pointer: [20.0, 20.0],
         start_pointer_screen: [origin.x + 20.0, origin.y + 20.0],
+        snap_axes: [false; 2],
         active: false,
         detached_since: None,
     });

crates/app/src/ui/canvas/panel_interactions_tests.rs

@@ -36,6 +36,7 @@ fn clipped_content_cannot_be_committed_out_of_reach() {
                     before,
                     start_pointer: [30.0, 30.0],
                     start_pointer_screen: [30.0, 30.0],
+                    snap_axes: [false; 2],
                     others: vec![],
                     active: true,
                     space: ObjectDragSpace::Panel(panel),
@@ -190,6 +191,7 @@ fn content_move_group_move_and_resize_keep_off_panel_geometry_with_undo_redo() {
                     before,
                     start_pointer: [30.0, 30.0],
                     start_pointer_screen: [30.0, 30.0],
+                    snap_axes: [false; 2],
                     others: if group {
                         vec![(ids[1], before)]
                     } else {