From a30dde2225925abe55366c02cb9532a1c9d0c645 Mon Sep 17 00:00:00 2001
From: Eric Kaden <608341+EricKaden@users.noreply.github.com>
Date: Mon, 19 Oct 2026 12:58:15 -0400
Subject: [PATCH] M6: the date picker follows a whole date typed while it is
 open (#3393)

The calendar took its month once, when it opened, so a date typed while
it was open showed only after leaving the field and coming back. It now
moves to a date as soon as the text becomes one, and stays on the month
it shows while the text is half typed or unchanged, so its arrows still
turn the months.
---
 crates/ui-egui/src/editing.rs  |  1 +
 crates/ui-egui/src/forms_ui.rs | 20 ++++++++++++++++----
 crates/ui-egui/tests/forms.rs  | 33 +++++++++++++++++++++++++++++++++
 parity/acrobat-features.toml   |  4 ++--
 4 files changed, 52 insertions(+), 6 deletions(-)

diff --git a/crates/ui-egui/src/editing.rs b/crates/ui-egui/src/editing.rs
index e554d7a1b0..91480ac7b5 100644
--- a/crates/ui-egui/src/editing.rs
+++ b/crates/ui-egui/src/editing.rs
@@ -1420,6 +1420,7 @@ mod revert_draft_tests {
             press: None,
             calendar: None,
             calendar_rect: None,
+            calendar_text: None,
         }
     }
 
diff --git a/crates/ui-egui/src/forms_ui.rs b/crates/ui-egui/src/forms_ui.rs
index 8020e868b2..612b985e65 100644
--- a/crates/ui-egui/src/forms_ui.rs
+++ b/crates/ui-egui/src/forms_ui.rs
@@ -38,6 +38,9 @@ pub struct Focus {
     /// Date fields: the month the calendar shows (year, month 1–12), and where it was drawn.
     pub calendar: Option<(i32, u32)>,
     pub calendar_rect: Option<egui::Rect>,
+    /// The text the calendar last saw, so it moves to a typed date once, when the typing becomes
+    /// a whole date, and otherwise keeps the month its arrows turned to.
+    pub calendar_text: Option<String>,
 }
 
 #[derive(Clone, Debug, Default)]
@@ -90,6 +93,7 @@ fn open_focus(f: &FormField, widget: usize) -> Focus {
         press: None,
         calendar: None,
         calendar_rect: None,
+        calendar_text: None,
     }
 }
 
@@ -255,11 +259,19 @@ const MONTHS: [&str; 12] = ["January", "February", "March", "April", "May", "Jun
 fn calendar(ctx: &egui::Context, view: &mut DocView, field: egui::Rect, fmt: &str, today: (i64, u32, u32)) -> Option<String> {
     use pdfcraft_engine::form_scripts::{DateTime, format_date, parse_date};
     let fx = view.forms.focus.as_mut()?;
-    let (mut y, mut m) = fx.calendar.unwrap_or_else(|| match parse_date(&fx.text, fmt) {
-        Some(d) => (d.y, d.m),
-        None => (today.0 as i32, today.1),
-    });
     let current = parse_date(&fx.text, fmt);
+    // A whole date typed since the last frame moves the calendar to it; half a date, or text
+    // that hasn't changed, leaves it on the month it shows (the one the arrows turned to).
+    let changed = fx.calendar_text.as_deref() != Some(fx.text.as_str());
+    let (mut y, mut m) = match (fx.calendar, current) {
+        (Some(_), Some(d)) if changed => (d.y, d.m),
+        (Some(shown), _) => shown,
+        (None, Some(d)) => (d.y, d.m),
+        (None, None) => (today.0 as i32, today.1),
+    };
+    if changed {
+        fx.calendar_text = Some(fx.text.clone());
+    }
     let mut picked = None;
     let area = egui::Area::new(egui::Id::new(("date-picker", view.id.0)))
         .order(egui::Order::Foreground)
diff --git a/crates/ui-egui/tests/forms.rs b/crates/ui-egui/tests/forms.rs
index 96a0a6a11e..bd7df61872 100644
--- a/crates/ui-egui/tests/forms.rs
+++ b/crates/ui-egui/tests/forms.rs
@@ -185,6 +185,39 @@ fn date_fields_offer_a_calendar() {
     assert_eq!(value(&h, "due"), vec![format!("{nm:02}/15/{ny}")], "picked in the field's format");
 }
 
+/// The calendar used to keep the month it opened on, so a date typed while it was open showed
+/// only after leaving the field and coming back.
+#[test]
+fn the_calendar_follows_a_complete_date_typed_while_it_is_open() {
+    use egui_kittest::kittest::Queryable;
+    let mut h = harness();
+    h.state_mut().apply_edit(pdfcraft_engine::Edit::AddField {
+        page: 0,
+        rect: [50.0, 40.0, 200.0, 60.0],
+        kind: pdfcraft_engine::NewField::Date,
+        name: Some("due".into()),
+    });
+    h.run_steps(4);
+    click_field(&mut h, "due", 0);
+    let (y, m, _) = h.state().session.today();
+    let month =
+        ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"][(m - 1) as usize];
+    h.get_by_label(&format!("{month} {y}"));
+    // Half a date leaves the calendar where it is.
+    h.event(egui::Event::Text("03/1".into()));
+    h.run_steps(2);
+    h.get_by_label(&format!("{month} {y}"));
+    // The whole date moves it there.
+    h.event(egui::Event::Text("4/2025".into()));
+    h.run_steps(2);
+    h.get_by_label("March 2025");
+    // The arrows still turn the months, and the calendar stays on their month while the text
+    // doesn't change.
+    h.get_by_label("›").click();
+    h.run_steps(3);
+    h.get_by_label("April 2025");
+}
+
 #[test]
 fn lithuanian_calendar_localizes_months_and_weekdays_without_changing_field_values() {
     use egui_kittest::kittest::Queryable;
diff --git a/parity/acrobat-features.toml b/parity/acrobat-features.toml
index 58cc527eaf..1c68d23335 100644
--- a/parity/acrobat-features.toml
+++ b/parity/acrobat-features.toml
@@ -4620,8 +4620,8 @@ milestone = "M6"
 status = "shipped"
 commands = []
 tools = ["form_fill"]
-evidence = ["crates/ui-egui/tests/forms.rs::date_fields_offer_a_calendar"]
-notes = "a month calendar under date fields; the pick is written in the field's own date format"
+evidence = ["crates/ui-egui/tests/forms.rs::date_fields_offer_a_calendar", "crates/ui-egui/tests/forms.rs::the_calendar_follows_a_complete_date_typed_while_it_is_open"]
+notes = "a month calendar under date fields; the pick is written in the field's own date format; it opens on the field's date and moves to a whole date typed while it is open, staying on the month its arrows turned to otherwise"
 
 [[feature]]
 id = "form.auto-complete"