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/primitives/focus.rs

@@ -170,6 +170,46 @@ pub(crate) fn give_back(state: &Entity<Takeover>, window: &mut Window, cx: &mut
     }
 }
 
+/// A mode's own focus, where focus was before the mode took it, and whether the mode was on last frame.
+pub(crate) struct Held {
+    pub focus: FocusHandle,
+    previous: Option<FocusHandle>,
+    was_on: bool,
+}
+
+/// The focus a mode keyed `key` holds: turned on while focus is elsewhere, it takes focus so Escape reaches it.
+pub(crate) fn hold_focus(
+    key: impl Into<ElementId>,
+    on: bool,
+    window: &mut Window,
+    cx: &mut App,
+) -> Entity<Held> {
+    let held = window.use_keyed_state(key, cx, |_, cx| Held {
+        focus: cx.focus_handle(),
+        previous: None,
+        was_on: false,
+    });
+    let (focus, was_on) = (held.read(cx).focus.clone(), held.read(cx).was_on);
+    if on && !was_on && !focus.contains_focused(window, cx) {
+        log::info!("focus: a mode takes it, so Escape reaches it");
+        let previous = window.focused(cx);
+        window.focus(&focus);
+        held.update(cx, |held, _| held.previous = previous);
+    }
+    if on != was_on {
+        held.update(cx, |held, _| held.was_on = on);
+    }
+    held
+}
+
+/// Hands focus back to where it was before the mode took it.
+pub(crate) fn hand_back(held: &Entity<Held>, window: &mut Window, cx: &mut App) {
+    if let Some(previous) = held.update(cx, |held, _| held.previous.take()) {
+        log::info!("focus: handed back after a mode");
+        window.focus(&previous);
+    }
+}
+
 /// A focus handle kept for `id`, a Tab stop while enabled.
 pub(crate) fn tab_stop(
     id: ElementId,

src/primitives/icon.rs

@@ -187,6 +187,7 @@ icons! {
     Menu => "menu",
     Merge => "merge",
     MessageSquare => "message-square",
+    MessageSquareDiff => "message-square-diff",
     MicOff => "mic-off",
     Mic => "mic",
     Minimize2 => "minimize-2",
@@ -242,6 +243,7 @@ icons! {
     SlidersHorizontal => "sliders-horizontal",
     Smartphone => "smartphone",
     Smile => "smile",
+    SmilePlus => "smile-plus",
     Sparkles => "sparkles",
     Spline => "spline",
     SquareCheck => "square-check",
@@ -267,6 +269,7 @@ icons! {
     Undo2 => "undo-2",
     Upload => "upload",
     User => "user",
+    UserPlus => "user-plus",
     Users => "users",
     Variable => "variable",
     VideoOff => "video-off",

src/primitives/mod.rs

@@ -14,7 +14,7 @@ pub use backdrop::{Backdrop, Place};
 pub use disclosure::Disclosure;
 pub use divider::Divider;
 pub use focus::{FocusNext, FocusPrev, FocusRing, FocusScope};
-pub(crate) use focus::{Takeover, give_back, tab_stop, take_focus};
+pub(crate) use focus::{Takeover, give_back, hand_back, hold_focus, tab_stop, take_focus};
 pub use ghost::DragGhost;
 pub use icon::{Icon, IconName};
 pub use image::Image;