T22: Collaboration

- presence: avatars ringed in each peer's color with where they are, press to
  follow; a breathing live dot; follow mode frames the view and stops on Escape
- remote cursors and selections painted over a field from its own layout
- comment threads with replies, reactions and resolve; a marker that opens a
  thread in a bubble; a sidebar of open and resolved threads
- annotations washed in their authors' colors, notes on hover
- suggestion mode: edits become suggestions word by word; track changes shows
  them struck and underlined, to accept or reject
- sharing: invite by email with checked chips, roles, the access list and who
  the link lets in, in one dialog
- primitives::hold_focus gives a mode its own focus, shared with ZenMode
- AvatarGroup's tuck and count shared; Avatar::ring_color; TagInput::check;
  TextInput::bounds_for_range; Popover::size
- icons: smile-plus, user-plus, message-square-diff
- gallery: the Collaboration page with scripted states

src/documents/mod.rs

@@ -29,6 +29,7 @@ pub use blocks::{Align, BlockData, BlockEditor, BlockEvent, BlockKind, Media};
 pub use counts::{ReadingTime, WordCount};
 pub use epub::{Chapter, EpubReader};
 pub use format::{Format, format};
+pub(crate) use history::Change;
 pub use history::{PageHistoryDiff, Version, VersionHistory};
 pub use knowledge::{Backlink, Backlinks, Favorite, Favorites, TrashBin, Trashed};
 pub use link::LinkEditor;

src/documents/reading.rs

@@ -1,9 +1,8 @@
 use std::{collections::BTreeMap, rc::Rc};
 
 use gpui::{
-    AnyElement, App, Bounds, ElementId, FocusHandle, FontWeight, InteractiveElement, IntoElement,
-    ParentElement, RenderOnce, ScrollHandle, SharedString, Styled, Window, canvas, div, fill,
-    prelude::*, size,
+    AnyElement, App, Bounds, ElementId, FontWeight, InteractiveElement, IntoElement, ParentElement,
+    RenderOnce, ScrollHandle, SharedString, Styled, Window, canvas, div, fill, prelude::*, size,
 };
 use smallvec::SmallVec;
 
@@ -11,6 +10,7 @@ use crate::{
     forms::Run,
     layout::Collapsible,
     overlays::HoverCard,
+    primitives::{hand_back, hold_focus},
     theme::{ActiveTheme, ContainerSize, TextSize},
 };
 
@@ -272,31 +272,11 @@ 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, 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 held = hold_focus((self.id.clone(), "held"), on, window, cx);
+        let focus = held.read(cx).focus.clone();
         let theme = cx.theme();
         div()
             .id(self.id.clone())
@@ -310,9 +290,7 @@ 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);
-                    }
+                    hand_back(&held, window, cx);
                     exit(window, cx);
                 }
             })