Form widgets carry ids scoped by the form's opening and field path

A form's text fields had positional egui ids, so focus and typed text moved to the
field at the same place in the next form (#219).

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/ui-egui/src/context.rs

@@ -75,6 +75,9 @@ fn form(app: &mut ModelApp, ui: &mut egui::Ui, t: &Tokens) {
         app.dialog = None;
         return;
     };
+    // The form's widgets are its own, keyed by this opening: the keyboard focus and typed text of
+    // the form it replaces (egui drops focus from a widget no longer drawn) never land here.
+    let form_id = egui::Id::new(("fc_form", spec.id, d.opening));
     let (mut run, mut cancel) = (false, false);
     heading(ui, t, Level::Title, |ui| {
         ui.label(RichText::new(spec.label.to_uppercase()).font(label_font(ui.ctx(), 12.0)));
@@ -125,7 +128,7 @@ fn form(app: &mut ModelApp, ui: &mut egui::Ui, t: &Tokens) {
     d.advanced = advanced;
     match (spec.form, object) {
         (Some(fields), Some(mut obj)) if !d.advanced => {
-            let cx = crate::form::Context { units, names: &|c| session.names(c), salt: spec.id };
+            let cx = crate::form::Context { units, names: &|c| session.names(c), salt: form_id };
             let out = crate::form::show(ui, t, &cx, fields, &mut obj);
             invalid = out.invalid;
             if out.changed {
@@ -134,7 +137,7 @@ fn form(app: &mut ModelApp, ui: &mut egui::Ui, t: &Tokens) {
             }
         }
         _ => {
-            ui.add(egui::TextEdit::multiline(&mut d.text).code_editor().desired_rows(6).desired_width(f32::INFINITY));
+            ui.add(egui::TextEdit::multiline(&mut d.text).id(form_id.with("json")).code_editor().desired_rows(6).desired_width(f32::INFINITY));
         }
     }
     if let Some(e) = &d.error {

crates/ui-egui/src/fields.rs

@@ -67,7 +67,9 @@ struct Draft {
 }
 
 /// A number field: shows `value` (or the typed text), greys `hint` when empty, and reports a new
-/// value only when the text is a finite number (or empty). `integer` refuses fractions.
+/// value only when the text is a finite number (or empty). `integer` refuses fractions. `id` is the
+/// field's own (unique in the form, and differing between forms): it keys both the typed text and
+/// the widget, so focus and typing never move to another form's field at the same place.
 pub fn number(ui: &mut Ui, s: &Style, id: Id, value: Option<f64>, hint: &str, integer: bool, width: f32) -> NumberEdit {
     let shown = |v: Option<f64>| v.map(format_number).unwrap_or_default();
     let mut draft = ui.data(|d| d.get_temp::<Draft>(id)).filter(|d| d.over == value).unwrap_or_else(|| Draft { text: shown(value), over: value });
@@ -80,7 +82,7 @@ pub fn number(ui: &mut Ui, s: &Style, id: Id, value: Option<f64>, hint: &str, in
         (!integer || x.fract() == 0.0).then_some(Some(x))
     };
     let bad = parse(&draft.text).is_none();
-    let mut edit = egui::TextEdit::singleline(&mut draft.text).desired_width(width).hint_text(RichText::new(hint).italics().color(s.dim));
+    let mut edit = egui::TextEdit::singleline(&mut draft.text).id(id).desired_width(width).hint_text(RichText::new(hint).italics().color(s.dim));
     if bad {
         edit = edit.text_color(s.error);
     }
@@ -124,9 +126,9 @@ pub fn combo(ui: &mut Ui, id: Id, selected: &str, options: &[&str], width: f32)
     picked
 }
 
-/// A one-line text field with a greyed hint; true when it changed.
-pub fn text(ui: &mut Ui, s: &Style, value: &mut String, hint: &str, width: f32) -> bool {
-    ui.add(egui::TextEdit::singleline(value).desired_width(width).hint_text(RichText::new(hint).italics().color(s.dim))).changed()
+/// A one-line text field with a greyed hint, keyed by `id` (see [`number`]); true when it changed.
+pub fn text(ui: &mut Ui, s: &Style, id: Id, value: &mut String, hint: &str, width: f32) -> bool {
+    ui.add(egui::TextEdit::singleline(value).id(id).desired_width(width).hint_text(RichText::new(hint).italics().color(s.dim))).changed()
 }
 
 /// A unit after a field.

crates/ui-egui/src/form.rs

@@ -24,8 +24,9 @@ pub struct Context<'a> {
     pub units: UnitSystem,
     /// The names of a collection's items.
     pub names: &'a dyn Fn(Collection) -> Vec<String>,
-    /// A salt for the widget ids (the command).
-    pub salt: &'a str,
+    /// A salt for the widget ids: the open form (its command and the opening), so no widget
+    /// state is shared with another form.
+    pub salt: Id,
 }
 
 /// What a frame of the form did.
@@ -147,7 +148,7 @@ impl Form<'_> {
             Kind::Integer { .. } => self.number(ui, id, value, f.hint, true, FIELD_W),
             Kind::Text | Kind::Path { .. } => {
                 let mut text = value.and_then(Value::as_str).unwrap_or_default().to_string();
-                fields::text(ui, &s, &mut text, f.hint, FIELD_W + 40.0)
+                fields::text(ui, &s, id, &mut text, f.hint, FIELD_W + 40.0)
                     .then(|| if text.is_empty() && !f.required { Value::Null } else { json!(text) })
             }
             Kind::Bool => {
@@ -273,7 +274,8 @@ impl Form<'_> {
         if names.is_empty() {
             let mut text = current.unwrap_or_default();
             let hint = format!("no {} yet", c.label());
-            return fields::text(ui, &self.style, &mut text, &hint, FIELD_W + 40.0).then(|| if text.is_empty() { Value::Null } else { json!(text) });
+            return fields::text(ui, &self.style, id, &mut text, &hint, FIELD_W + 40.0)
+                .then(|| if text.is_empty() { Value::Null } else { json!(text) });
         }
         let empty = if hint.is_empty() { "—" } else { hint };
         let selected = current.clone().unwrap_or_else(|| empty.to_string());
@@ -311,7 +313,7 @@ impl Form<'_> {
         let shown = value.map(Value::to_string).unwrap_or_default();
         let mut text = ui.data(|d| d.get_temp::<(String, String)>(id)).filter(|(_, over)| *over == shown).map_or_else(|| shown.clone(), |(t, _)| t);
         let bad = !text.trim().is_empty() && serde_json::from_str::<Value>(&text).is_err();
-        let mut edit = egui::TextEdit::singleline(&mut text).code_editor().desired_width(FIELD_W + 40.0);
+        let mut edit = egui::TextEdit::singleline(&mut text).id(id).code_editor().desired_width(FIELD_W + 40.0);
         if bad {
             edit = edit.text_color(self.style.error);
             self.out.invalid += 1;
@@ -436,7 +438,7 @@ mod tests {
                 let width = crate::context::WIDTH - 16.0;
                 let mut used = 0.0;
                 let mut out = ctx.run_ui(egui::RawInput::default(), |ui| {
-                    let cx = Context { units: UnitSystem::MmTonneS, names: &names, salt: c.id };
+                    let cx = Context { units: UnitSystem::MmTonneS, names: &names, salt: Id::new(c.id) };
                     ui.vertical(|ui| {
                         ui.set_max_width(width);
                         outcome = show(ui, &Tokens::get(false), &cx, form, &mut params);

crates/ui-egui/src/lib.rs

@@ -159,6 +159,9 @@ pub struct ParamsDialog {
     pub error: Option<String>,
     /// The JSON text is shown instead of the typed fields.
     pub advanced: bool,
+    /// Which opening of a form this is (counts up): a form opened over another one, even of the
+    /// same command, gets fresh widget ids, so nothing typed into the one it replaces carries over.
+    pub opening: u64,
 }
 
 /// A status bar message.
@@ -263,6 +266,8 @@ pub struct ModelApp {
     pub cam: Camera,
     pub status: Option<Status>,
     pub dialog: Option<ParamsDialog>,
+    /// Forms opened so far (numbers each [`ParamsDialog::opening`]).
+    forms_opened: u64,
     pub viewport: Viewport,
     pub icons: icons::IconCache,
     /// The toolbar's buttons drawn last frame, by catalogue id (for the control channel).
@@ -355,6 +360,7 @@ impl ModelApp {
             cam: Camera::default(),
             status: None,
             dialog: None,
+            forms_opened: 0,
             viewport: Viewport::default(),
             icons: icons::IconCache::default(),
             toolbar_rects: Vec::new(),
@@ -528,7 +534,14 @@ impl ModelApp {
         if let Some(spec) = fieldcraft_engine::find_command(command) {
             // The schema's defaults are filled in, so the form starts as the command would run.
             let params = spec.form.map_or(params.clone(), |form| fieldcraft_engine::schema::prefill(form, &params));
-            self.dialog = Some(ParamsDialog { command: spec.id, text: params.to_string(), error: None, advanced: spec.form.is_none() });
+            self.forms_opened = self.forms_opened.wrapping_add(1);
+            self.dialog = Some(ParamsDialog {
+                command: spec.id,
+                text: params.to_string(),
+                error: None,
+                advanced: spec.form.is_none(),
+                opening: self.forms_opened,
+            });
         }
     }