fix(forms): reset replacement sessions and preserve visible scroll

crates/oa-desktop/src/behavior/scenario/focus.rs

@@ -232,25 +232,31 @@ impl Operation for Collect {
         };
         let mut shifts = BTreeMap::new();
         for ancestor in ancestors.iter().rev() {
+            let dx = reveal(
+                bounds.x,
+                bounds.width,
+                ancestor.bounds.x,
+                ancestor.bounds.width,
+            );
+            let dy = reveal(
+                bounds.y,
+                bounds.height,
+                ancestor.bounds.y,
+                ancestor.bounds.height,
+            );
+            // Drawing offsets are rounded; an already-visible axis must not
+            // acquire a scroll delta from a fractional capacity alone.
             let delta = Vector::new(
-                (ancestor.offset.x
-                    + reveal(
-                        bounds.x,
-                        bounds.width,
-                        ancestor.bounds.x,
-                        ancestor.bounds.width,
-                    ))
-                .clamp(0., ancestor.capacity.x)
-                    - ancestor.offset.x,
-                (ancestor.offset.y
-                    + reveal(
-                        bounds.y,
-                        bounds.height,
-                        ancestor.bounds.y,
-                        ancestor.bounds.height,
-                    ))
-                .clamp(0., ancestor.capacity.y)
-                    - ancestor.offset.y,
+                if dx == 0. {
+                    0.
+                } else {
+                    (ancestor.offset.x + dx).clamp(0., ancestor.capacity.x) - ancestor.offset.x
+                },
+                if dy == 0. {
+                    0.
+                } else {
+                    (ancestor.offset.y + dy).clamp(0., ancestor.capacity.y) - ancestor.offset.y
+                },
             );
             if delta != Vector::ZERO {
                 shifts.insert(ancestor.index, delta);

crates/oa-desktop/src/behavior/scenario/workspace.rs

@@ -1,7 +1,7 @@
 //! Scenario presentation. Layout/camera controls never construct model commands.
-use super::super::scenario_scroll;
+use super::super::{form_session, scenario_scroll};
 use super::*;
-use iced::widget::{Space, column, keyed_column, sensor};
+use iced::widget::{Space, column, sensor};
 
 pub(crate) const NAME_INPUT: &str = "scenario-form-name";
 
@@ -754,16 +754,13 @@ fn editor_panel<'a, R: iced::advanced::text::Renderer + 'a>(
     container(
         column![
             container(actions).id("scenario-actions").width(Fill),
-            keyed_column([(
+            form_session::reset_on_change(
                 session,
                 scrollable(fields)
                     .id("scenario-form")
                     .width(Fill)
-                    .height(Fill)
-                    .into(),
-            )])
-            .width(Fill)
-            .height(Fill),
+                    .height(Fill),
+            ),
         ]
         .spacing(6),
     )