T21b and T21c round 1 fixes

- a page centers only while it fits the view; a wider one starts in reach
- the reveal runs after the pages' prepaint and keys on the hit itself, so a
  new hit at the same index and a hit current from the first frame come into view
- the chapter list scrolls
- zen takes focus when turned on from outside, so Escape leaves it, and hands
  focus back
- the gallery keeps a page's due date and tags

AGENTS.md

@@ -112,6 +112,8 @@ Ely GPUI Component. A component library for GPUI, in light and dark.
 - Tokens live in `src/theme`; the raw `px()` scan skips that folder only.
 - `ScrollHandle` keeps its children's bounds unscrolled: a child paints at its bounds plus the offset. A press on a scrolled child subtracts both, and an offset that brings a child to a place is set whole, not added (`documents::find::reveal`).
 - A find box is `editor::FindWidget`, over code, a terminal or a document's pages. It shows the replace fold and the option toggles only when the owner handles them.
+- Taffy 0.9 hands negative free space to auto margins and centering alike, so a centered child wider than its scroll box starts past the scroll's reach. Center only what fits the measured box (`documents::DocumentViewer`).
+- A mode that leaves on Escape keeps its own focus handle: turned on while focus is elsewhere, it takes focus so Escape reaches it, and hands focus back when it leaves (`documents::ZenMode`).
 - A callback field holds a named `type` alias; clippy's type_complexity rejects `Option<Rc<dyn Fn(..)>>`. A chapter shares one alias per shape.
 - A component that fills its container says `w_full` on its root. As a window's root, or in a flex row, it would shrink to its text's narrowest width.
 - A field's `Highlight` sets color, wash, weight, slant and strike per span; measuring and painting share one set of runs, so wrapped heights match.

TASKS.md

@@ -250,3 +250,5 @@ Per-component lines live in `tasks/`. Tags there:
 | T21a | 1 | FAIL | Enter kept a selection; undo of a split left focus on a gone field; italic inside bold ate the bold; keys went into merged cells; undo kept a changed kind's highlighter |
 | T21a | 2 | FAIL | undo of typing lost the selection it replaced; Up from below a table landed in a hidden merged cell |
 | T21a | 3 | FAIL | undo after a delete or a paste lost the selection they replaced; fixed after the cap by recording the replaced selection where every TextInput edit passes, verified by a red-green test, no fourth review |
+| T21b | 1 | FAIL | a page zoomed wider than the view sat past its left edge; a new hit at the same index kept the old page in view; a hit current from the first frame only scrolled its page to the top; the chapter list did not scroll; Escape could not leave zen turned on from a button |
+| T21c | 1 | FAIL | the gallery's page properties dropped a new due date and tags |

examples/gallery/pages/documents/knowledge.rs

@@ -163,11 +163,20 @@ pub fn knowledge(window: &mut Window, cx: &mut App) -> impl IntoElement + use<>
     let icon = keep("know-icon", || SharedString::from("☀️"), window, cx);
     let status = keep("know-status", || SharedString::from("Drafting"), window, cx);
     let done = keep("know-done", || false, window, cx);
-    let (now_cover, now_icon, now_status, now_done) = (
+    let due = keep("know-due", || jiff::civil::date(2026, 10, 12), window, cx);
+    let tags = keep(
+        "know-tags",
+        || vec![SharedString::from("color"), SharedString::from("theme")],
+        window,
+        cx,
+    );
+    let (now_cover, now_icon, now_status, now_done, now_due, now_tags) = (
         cover.read(cx).clone(),
         icon.read(cx).clone(),
         status.read(cx).clone(),
         *done.read(cx),
+        *due.read(cx),
+        tags.read(cx).clone(),
     );
     let trash = keep(
         "know-trash",
@@ -310,8 +319,8 @@ pub fn knowledge(window: &mut Window, cx: &mut App) -> impl IntoElement + use<>
                                                 .selected(now_status)
                                                 .on_change(move |next, _, cx| set(&status, next.clone(), cx)),
                                         )
-                                        .row("Due", DatePicker::new("know-due", Some(jiff::civil::date(2026, 10, 12))))
-                                        .row("Tags", TagInput::new("know-tags", ["color", "theme"]))
+                                        .row("Due", DatePicker::new("know-due", Some(now_due)).on_change(move |next, _, cx| set(&due, next, cx)))
+                                        .row("Tags", TagInput::new("know-tags", now_tags).on_change(move |next, _, cx| set(&tags, next, cx)))
                                         .row("Published", Checkbox::new("know-published", now_done).on_change(move |on, _, cx| set(&done, on, cx))),
                                 ),
                             ),

src/documents/epub.rs

@@ -104,8 +104,10 @@ impl RenderOnce for EpubReader {
         let shown = &self.chapters[chapter];
         let listed = contents.then(|| {
             div()
+                .id((self.id.clone(), "chapters"))
                 .flex_none()
                 .w(theme.sidebar_width(false))
+                .overflow_y_scroll()
                 .flex()
                 .flex_col()
                 .gap_0p5()

src/documents/find.rs

@@ -10,12 +10,11 @@ pub(crate) struct Find {
     pub current: Option<usize>,
 }
 
-/// Scrolls `hit` a third of the way down the view; before the pages are laid out, its page to the top.
+/// Scrolls `hit` a third of the way down the view; runs after the pages' prepaint, so their bounds are this frame's.
 pub(crate) fn reveal(scroll: &ScrollHandle, hit: &PageHit, zoom: f32) {
-    let Some(page) = scroll.bounds_for_item(hit.page) else {
-        scroll.scroll_to_top_of_item(hit.page);
-        return;
-    };
+    let page = scroll
+        .bounds_for_item(hit.page)
+        .expect("the hit's page is laid out");
     let view = scroll.bounds();
     let target = page.top() + Pixels::from(hit.bounds.origin.y * zoom);
     let offset = scroll.offset();

src/documents/reading.rs

@@ -1,8 +1,9 @@
 use std::{collections::BTreeMap, rc::Rc};
 
 use gpui::{
-    AnyElement, App, Bounds, ElementId, FontWeight, InteractiveElement, IntoElement, ParentElement,
-    RenderOnce, ScrollHandle, SharedString, Styled, Window, canvas, div, fill, prelude::*, size,
+    AnyElement, App, Bounds, ElementId, FocusHandle, FontWeight, InteractiveElement, IntoElement,
+    ParentElement, RenderOnce, ScrollHandle, SharedString, Styled, Window, canvas, div, fill,
+    prelude::*, size,
 };
 use smallvec::SmallVec;
 
@@ -271,12 +272,35 @@ impl ParentElement for ZenMode {
     }
 }
 
+/// Zen's own focus, where focus was before zen took it, and whether zen was on last frame.
+struct Quiet {
+    focus: FocusHandle,
+    previous: Option<FocusHandle>,
+    was_on: bool,
+}
+
 impl RenderOnce for ZenMode {
-    fn render(self, _: &mut Window, cx: &mut App) -> impl IntoElement {
-        let theme = cx.theme();
+    fn render(self, window: &mut Window, cx: &mut App) -> impl IntoElement {
         let (on, exit) = (self.on, self.on_exit);
+        let quiet = window.use_keyed_state((self.id.clone(), "quiet"), cx, |_, cx| Quiet {
+            focus: cx.focus_handle(),
+            previous: None,
+            was_on: false,
+        });
+        let (focus, was_on) = (quiet.read(cx).focus.clone(), quiet.read(cx).was_on);
+        if on && !was_on && !focus.contains_focused(window, cx) {
+            log::info!("zen mode: takes focus, so Escape reaches it");
+            let previous = window.focused(cx);
+            window.focus(&focus);
+            quiet.update(cx, |quiet, _| quiet.previous = previous);
+        }
+        if on != was_on {
+            quiet.update(cx, |quiet, _| quiet.was_on = on);
+        }
+        let theme = cx.theme();
         div()
             .id(self.id.clone())
+            .track_focus(&focus)
             .flex()
             .flex_col()
             .on_key_down(move |event, window, cx| {
@@ -286,6 +310,9 @@ impl RenderOnce for ZenMode {
                 {
                     cx.stop_propagation();
                     log::info!("zen mode: leaves");
+                    if let Some(previous) = quiet.update(cx, |quiet, _| quiet.previous.take()) {
+                        window.focus(&previous);
+                    }
                     exit(window, cx);
                 }
             })

src/documents/tests.rs

@@ -1,23 +1,33 @@
 use std::{cell::RefCell, rc::Rc};
 
 use gpui::{
-    AppContext as _, Bounds, Context, Entity, IntoElement, Modifiers, ParentElement, Pixels, Point,
-    Render, ScrollDelta, ScrollWheelEvent, Styled, TestAppContext, TouchPhase, VisualTestContext,
-    Window, div, point, px, size,
+    AppContext as _, Bounds, Context, Entity, Focusable, IntoElement, Modifiers, ParentElement,
+    Pixels, Point, Render, ScrollDelta, ScrollWheelEvent, Styled, TestAppContext, TouchPhase,
+    VisualTestContext, Window, div, point, px, size,
 };
 
-use super::{DocPage, DocumentViewer, PageHit};
+use super::{DocPage, DocumentViewer, PageHit, ZenMode};
 use crate::{
     editor::FindWidget,
-    forms::TextInput,
+    forms::{Input, TextInput},
     theme::{ActiveTheme, ControlSize, Theme},
 };
 
 type Noted = Rc<RefCell<Option<(usize, Point<f32>)>>>;
 
-/// Three tall pages with one hit on the second; a press while pinning records the note asked.
+/// A hit on `page`, 400 points down.
+fn hit(page: usize) -> PageHit {
+    PageHit {
+        page,
+        bounds: Bounds::new(point(40.0, 400.0), size(60.0, 12.0)),
+    }
+}
+
+/// Three tall pages and the hits found; a press while pinning records the note asked.
 struct Reader {
     query: Entity<TextInput>,
+    width: f32,
+    hits: Vec<PageHit>,
     current: Option<usize>,
     noted: Noted,
 }
@@ -27,20 +37,16 @@ impl Render for Reader {
         let pages: Vec<DocPage> = (0..3)
             .map(|ix| DocPage {
                 source: format!("page-{ix}.png").into(),
-                width: 400.0,
+                width: self.width,
                 height: 1000.0,
             })
             .collect();
-        let hit = PageHit {
-            page: 1,
-            bounds: Bounds::new(point(40.0, 400.0), size(60.0, 12.0)),
-        };
         let noted = self.noted.clone();
         div().size_full().child(
             DocumentViewer::new("viewer", "lift.pdf", pages)
                 .find(
-                    FindWidget::new("find", &self.query, self.current, 1),
-                    vec![hit],
+                    FindWidget::new("find", &self.query, self.current, self.hits.len()),
+                    self.hits.clone(),
                     self.current,
                 )
                 .notes(Vec::new(), move |page, at, _, _| {
@@ -51,12 +57,23 @@ impl Render for Reader {
 }
 
 fn open(cx: &mut TestAppContext) -> (Entity<Reader>, Noted, &mut VisualTestContext) {
+    open_with(400.0, None, cx)
+}
+
+/// Pages `width` points wide, with a hit on the second, current from the first frame when `current` says.
+fn open_with(
+    width: f32,
+    current: Option<usize>,
+    cx: &mut TestAppContext,
+) -> (Entity<Reader>, Noted, &mut VisualTestContext) {
     cx.update(Theme::init);
     let noted = Noted::default();
     let seen = noted.clone();
     let (reader, cx) = cx.add_window_view(move |window, cx| Reader {
         query: cx.new(|cx| TextInput::new(window, cx)),
-        current: None,
+        width,
+        hits: vec![hit(1)],
+        current,
         noted: seen,
     });
     settle(cx);
@@ -85,8 +102,13 @@ fn wheel(down: f32, cx: &mut VisualTestContext) {
     settle(cx);
 }
 
-/// Turns pinning on with the header's last button, then presses the pages; returns the note asked.
+/// Turns pinning on with the header's last button, then presses the pages at their middle; returns the note asked.
 fn pin(cx: &mut VisualTestContext, noted: &Noted) -> (usize, Point<f32>) {
+    let at = on_pages(cx);
+    pin_at(at, cx, noted)
+}
+
+fn pin_at(at: Point<Pixels>, cx: &mut VisualTestContext, noted: &Noted) -> (usize, Point<f32>) {
     let toggle = cx.update(|window, cx| {
         let header = cx
             .theme()
@@ -99,7 +121,6 @@ fn pin(cx: &mut VisualTestContext, noted: &Noted) -> (usize, Point<f32>) {
     });
     cx.simulate_click(toggle, Modifiers::none());
     settle(cx);
-    let at = on_pages(cx);
     cx.simulate_click(at, Modifiers::none());
     settle(cx);
     noted
@@ -143,3 +164,92 @@ fn a_current_hit_comes_to_one_place_from_any_scroll(cx: &mut TestAppContext) {
     assert_eq!(from_top.0, 1, "the hit's page comes into view");
     assert_eq!(from_top, from_below);
 }
+
+#[gpui::test]
+fn a_page_wider_than_the_view_starts_at_its_left_edge(cx: &mut TestAppContext) {
+    let (_, noted, cx) = open_with(3000.0, None, cx);
+    let (page, at) = pin_at(point(px(60.0), px(300.0)), cx, &noted);
+    assert_eq!(page, 0);
+    assert!(
+        at.x < 100.0,
+        "the page's left edge is in reach, not at {}",
+        at.x
+    );
+}
+
+#[gpui::test]
+fn a_new_hit_at_the_same_index_moves_the_view(cx: &mut TestAppContext) {
+    let (reader, noted, cx) = open(cx);
+    reader.update(cx, |reader, cx| {
+        reader.current = Some(0);
+        cx.notify();
+    });
+    settle(cx);
+    reader.update(cx, |reader, cx| {
+        reader.hits = vec![hit(2)];
+        cx.notify();
+    });
+    settle(cx);
+    assert_eq!(pin(cx, &noted).0, 2, "the view follows the new hit");
+}
+
+#[gpui::test]
+fn a_hit_current_from_the_first_frame_comes_into_view(cx: &mut TestAppContext) {
+    let (_, noted, first) = open_with(400.0, Some(0), cx);
+    let at_once = pin(first, &noted);
+    let later = revealed(0.0, cx);
+    assert_eq!(at_once, later);
+}
+
+/// A field outside a zen view, and how often Escape left zen.
+struct Zen {
+    outside: Entity<TextInput>,
+    on: bool,
+    left: usize,
+}
+
+impl Render for Zen {
+    fn render(&mut self, _: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        let me = cx.entity();
+        div().size_full().child(Input::new(&self.outside)).child(
+            ZenMode::new("zen", self.on)
+                .on_exit(move |_, cx| {
+                    me.update(cx, |zen, cx| {
+                        zen.on = false;
+                        zen.left += 1;
+                        cx.notify();
+                    })
+                })
+                .child(div().child("A quiet page")),
+        )
+    }
+}
+
+#[gpui::test]
+fn escape_leaves_zen_turned_on_from_outside_and_hands_focus_back(cx: &mut TestAppContext) {
+    cx.update(|cx| {
+        Theme::init(cx);
+        crate::forms::bind_keys(cx);
+    });
+    let (zen, cx) = cx.add_window_view(|window, cx| Zen {
+        outside: cx.new(|cx| TextInput::new(window, cx)),
+        on: false,
+        left: 0,
+    });
+    cx.update(|window, cx| {
+        window.activate_window();
+        let outside = zen.read(cx).outside.focus_handle(cx);
+        window.focus(&outside);
+    });
+    settle(cx);
+    zen.update(cx, |zen, cx| {
+        zen.on = true;
+        cx.notify();
+    });
+    settle(cx);
+    cx.simulate_keystrokes("escape");
+    settle(cx);
+    assert_eq!(zen.read_with(cx, |zen, _| zen.left), 1);
+    let back = cx.update(|window, cx| zen.read(cx).outside.focus_handle(cx).is_focused(window));
+    assert!(back, "focus returns to where it was");
+}

src/documents/viewer.rs

@@ -146,6 +146,10 @@ impl DocumentViewer {
             "hit {current:?} of {}",
             hits.len()
         );
+        assert!(
+            hits.iter().all(|hit| hit.page < self.pages.len()),
+            "a hit lies past the last page"
+        );
         self.find = Some(Find {
             widget,
             hits,
@@ -173,7 +177,7 @@ struct Desk {
     page: usize,
     width: f32,
     pinning: bool,
-    shown_hit: Option<usize>,
+    shown_hit: Option<PageHit>,
 }
 
 impl RenderOnce for DocumentViewer {
@@ -184,18 +188,6 @@ impl RenderOnce for DocumentViewer {
             (desk.scroll.clone(), desk.page, desk.width, desk.pinning)
         };
         let zoom = self.zoom;
-        if let Some(Find {
-            hits,
-            current: Some(current),
-            ..
-        }) = &self.find
-            && desk.read(cx).shown_hit != Some(*current)
-        {
-            let hit = &hits[*current];
-            log::info!("document viewer: hit {current} on page {}", hit.page);
-            reveal(&scroll, hit, zoom);
-            desk.update(cx, |desk, _| desk.shown_hit = Some(*current));
-        }
         let theme = cx.theme();
         let colors = theme.colors.clone();
         let count = self.pages.len();
@@ -294,12 +286,16 @@ impl RenderOnce for DocumentViewer {
             }) => (Some(widget), hits, current),
             None => (None, Vec::new(), None),
         };
+        let target = current.map(|current| hits[current].clone());
         let pages = self.pages.iter().enumerate().map(|(ix, page)| {
             let (on_note, scroll) = (self.on_note.clone().filter(|_| pinning), scroll.clone());
             div()
                 .id((self.id.clone(), format!("page-{ix}")))
                 .relative()
                 .flex_none()
+                .when(width == 0.0 || page.width * zoom <= width, |page| {
+                    page.mx_auto()
+                })
                 .w(Pixels::from(page.width * zoom))
                 .h(Pixels::from(page.height * zoom))
                 .bg(colors.paper)
@@ -406,7 +402,6 @@ impl RenderOnce for DocumentViewer {
                             .track_scroll(&scroll)
                             .flex()
                             .flex_col()
-                            .items_center()
                             .gap_4()
                             .p_6()
                             .children(pages),
@@ -430,6 +425,14 @@ impl RenderOnce for DocumentViewer {
                                     });
                                     window.request_animation_frame();
                                 }
+                                if tracked.read(cx).shown_hit != target {
+                                    if let Some(hit) = &target {
+                                        log::info!("document viewer: hit on page {}", hit.page);
+                                        reveal(&tracked.read(cx).scroll, hit, zoom);
+                                        window.request_animation_frame();
+                                    }
+                                    measured.update(cx, |desk, _| desk.shown_hit = target.clone());
+                                }
                             },
                             |_, _, _, _| {},
                         )