M5: Alt+Left / Alt+Right go back through the view history with a form field selected, judged by each press's modifiers (#3632)

Prepare's arrow nudge read the frame's Alt, so an Alt+arrow whose Alt was
let go in the same frame nudged the field instead. Each press's own
modifiers now decide, as for objects, pictures and comments.

crates/ui-egui/src/tools/prepare.rs

@@ -618,30 +618,34 @@ pub(crate) fn delete_selected(view: &mut DocView) -> Option<Edit> {
 /// as the object nudge does (`object_ui::nudge_keys`) and as dragging it does (#2608). The keys
 /// are consumed before the view turns the page with them; one press is one undo step.
 pub(crate) fn nudge_keys(ctx: &egui::Context, view: &mut DocView, doc: &Document) {
-    // `consume_key` lets an extra Alt through, and Alt+↑/↓ belongs to Calculation order's move.
-    if ctx.egui_wants_keyboard_input() || view.prepare.grab.is_some() || ctx.input(|i| i.modifiers.alt) {
+    if ctx.egui_wants_keyboard_input() || view.prepare.grab.is_some() {
         return;
     }
     let Some((name, wi)) = view.prepare.selected.clone() else { return };
     let Some(w) = doc.form.iter().find(|f| f.name == name).and_then(|f| f.widgets.get(wi)) else { return };
     let Some(page) = w.page else { return };
     let Some(xf) = view.page_xform(page) else { return };
-    use egui::{Key, Modifiers};
+    use egui::Key;
     let mut step = egui::Vec2::ZERO;
     ctx.input_mut(|i| {
-        for (key, direction) in [
-            (Key::ArrowLeft, egui::vec2(-1.0, 0.0)),
-            (Key::ArrowRight, egui::vec2(1.0, 0.0)),
-            (Key::ArrowUp, egui::vec2(0.0, -1.0)),
-            (Key::ArrowDown, egui::vec2(0.0, 1.0)),
-        ] {
-            // Shift first: a plain key pattern also matches a Shift press.
-            if i.consume_key(Modifiers::SHIFT, key) {
-                step += direction * 10.0;
-            } else if i.consume_key(Modifiers::NONE, key) {
-                step += direction;
+        // Only an arrow pressed alone or with Shift, judged by each press's own modifiers (the
+        // frame's can differ when a key is let go in the same frame). Alt+← / Alt+→ go back and
+        // forward through the view history (#3632) and Alt+↑ / ↓ is Calculation order's move.
+        i.events.retain(|e| {
+            let egui::Event::Key { key, pressed: true, modifiers, .. } = e else { return true };
+            if modifiers.alt || modifiers.ctrl || modifiers.command || modifiers.mac_cmd {
+                return true;
             }
-        }
+            let direction = match key {
+                Key::ArrowLeft => egui::vec2(-1.0, 0.0),
+                Key::ArrowRight => egui::vec2(1.0, 0.0),
+                Key::ArrowUp => egui::vec2(0.0, -1.0),
+                Key::ArrowDown => egui::vec2(0.0, 1.0),
+                _ => return true,
+            };
+            step += direction * if modifiers.shift { 10.0 } else { 1.0 };
+            false
+        });
     });
     if step == egui::Vec2::ZERO {
         return;

crates/ui-egui/tests/it/prepare.rs

@@ -156,6 +156,40 @@ fn arrow_keys_nudge_the_selected_field_instead_of_turning_the_page() {
     assert_eq!(h.state().views[0].current, 0, "the arrows moved the field, not the page");
 }
 
+/// #3632: Alt+← / Alt+→ go back and forward through the view history with a field selected, and
+/// leave the field where it is, even when Alt is let go in the same frame as the arrow, so the
+/// frame has no modifiers and only the press carries Alt.
+#[test]
+fn alt_arrows_navigate_instead_of_nudging_the_selected_field() {
+    let mut h = harness();
+    assert!(h.state_mut().apply_edit(pdfcraft_engine::Edit::InsertBlankPage { at: 1, width: 612.0, height: 792.0 }));
+    h.run_steps(2);
+    h.state_mut().execute("form.add.text");
+    h.run_steps(1);
+    let p = at(&h, 40.0, 250.0);
+    h.hover_at(p);
+    h.run_steps(1);
+    h.drag_at(p);
+    h.run_steps(1);
+    h.drop_at(p);
+    h.run_steps(4);
+    let name = h.state().views[0].prepare.selected.clone().expect("the placed field is selected").0;
+    let before = rect_of(&h, &name);
+    h.state_mut().views[0].go_to_page(1);
+    h.run_steps(2);
+    h.state_mut().views[0].go_to_page(0);
+    h.run_steps(2);
+    assert!(h.state().views[0].prepare.selected.is_some(), "still selected, so a nudge could take the keys");
+    let arrow = |key, modifiers| egui::Event::Key { key, physical_key: None, pressed: true, repeat: false, modifiers };
+    h.event(arrow(egui::Key::ArrowLeft, egui::Modifiers::ALT));
+    h.run_steps(4);
+    assert_eq!(h.state().views[0].current, 1, "an Alt+← press went back");
+    h.event(arrow(egui::Key::ArrowRight, egui::Modifiers::ALT));
+    h.run_steps(4);
+    assert_eq!(h.state().views[0].current, 0, "an Alt+→ press went forward");
+    assert_eq!(rect_of(&h, &name), before, "the field didn't move");
+}
+
 #[test]
 fn format_validate_and_calculate_tabs() {
     use pdfcraft_engine::form_scripts::{Calculate, Format, Validate};