Hand out an AccessKit focus request at the start of the pass

AccessKit asks for focus by node id, and `Focus::interested_in_focus` only picks
the request up once the widget itself runs. Everything that reads the focus
before the widget — styling it, for one — therefore saw the old focus, so a text
edit was styled unfocused in the very pass it got focused, and lost its focus
ring for a frame.

A widget in `focus_widgets_cache` has asked for focus in an earlier pass, so it
is one we can hand focus to in `begin_pass`, the same way a `request_focus` from
the last pass is handed out. Memory then holds the focus before any widget runs,
and `Ui::widget_style` needs to know nothing about focus at all.

`interested_in_focus` keeps the same grant as a fallback, for the first pass a
widget is focusable in, and the two share `take_focus_from_accesskit`.

The four `text_edit_*` snapshots gain a caret along with the ring, because the
field is now focused for real in that pass rather than a pass later.

Also drops `fallback_gap` from `TextEdit`, which has no `gap` of its own to defer
to, and moves the `DragValue` `HasClasses` impl above its test module.

crates/egui/src/memory/mod.rs

@@ -618,6 +618,27 @@ impl Focus {
                 self.id_requested_by_accesskit = Some(*target_node);
             }
         }
+
+        // `interested_in_focus` only picks the request up once the widget runs, which is too late
+        // for anything that reads the focus before it — styling the widget, for one. A widget in
+        // the cache asked for focus in an earlier pass, so it is one we can hand focus to now.
+        let accesskit_focus = self.id_requested_by_accesskit.and_then(|node_id| {
+            self.focus_widgets_cache
+                .keys()
+                .find(|id| id.accesskit_id() == node_id)
+                .copied()
+        });
+        if let Some(id) = accesskit_focus {
+            self.take_focus_from_accesskit(id);
+        }
+    }
+
+    /// Give a widget the focus that AccessKit asked for.
+    fn take_focus_from_accesskit(&mut self, id: Id) {
+        self.focused_widget = Some(FocusWidget::new(id));
+        self.id_requested_by_accesskit = None;
+        self.give_to_next = false;
+        self.reset_focus();
     }
 
     pub(crate) fn end_pass(&mut self, used_ids: &IdMap<Rect>) {
@@ -645,11 +666,10 @@ impl Focus {
     }
 
     fn interested_in_focus(&mut self, id: Id) {
+        // `begin_pass` hands out the request as soon as it can, but it can only recognize a widget
+        // that has been here before. This catches the first pass a widget is focusable in.
         if self.id_requested_by_accesskit == Some(id.accesskit_id()) {
-            self.focused_widget = Some(FocusWidget::new(id));
+            self.take_focus_from_accesskit(id);
-            self.id_requested_by_accesskit = None;
-            self.give_to_next = false;
-            self.reset_focus();
         }
 
         // The rect is updated at the end of the frame.

crates/egui/src/widgets/drag_value.rs

@@ -603,7 +603,7 @@ impl Widget for DragValue<'_> {
                     .clip_text(false)
                     .horizontal_align(ui.layout().horizontal_align())
                     .vertical_align(ui.layout().vertical_align())
-                    .min_size(min_size.unwrap_or(ui.spacing().interact_size))
+                    .min_size(min_size.unwrap_or_else(|| ui.spacing().interact_size))
                     .id(id)
                     .desired_width(
                         ui.spacing().interact_size.x - 2.0 * ui.spacing().button_padding.x,
@@ -654,7 +654,7 @@ impl Widget for DragValue<'_> {
                 .wrap_mode(TextWrapMode::Extend)
                 .sense(Sense::click_and_drag())
                 .gap(0.0)
-                .min_size(min_size.unwrap_or(ui.spacing().interact_size)); // TODO(emilk): find some more generic solution to `min_size`
+                .min_size(min_size.unwrap_or_else(|| ui.spacing().interact_size)); // TODO(emilk): find some more generic solution to `min_size`
 
             let cursor_icon = if value <= *range.start() {
                 CursorIcon::ResizeEast
@@ -822,6 +822,16 @@ fn select_all_text(ui: &Ui, widget_id: Id, response_id: Id, value_text: &str) {
     state.store(ui.ctx(), response_id);
 }
 
+impl HasClasses for DragValue<'_> {
+    fn classes(&self) -> &Classes {
+        &self.classes
+    }
+
+    fn classes_mut(&mut self) -> &mut Classes {
+        &mut self.classes
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::clamp_value_to_range;
@@ -881,13 +891,3 @@ mod tests {
         );
     }
 }
-
-impl HasClasses for DragValue<'_> {
-    fn classes(&self) -> &Classes {
-        &self.classes
-    }
-
-    fn classes_mut(&mut self) -> &mut Classes {
-        &mut self.classes
-    }
-}

crates/egui/src/widgets/text_edit/builder.rs

@@ -745,7 +745,7 @@ impl TextEdit<'_> {
 
             let allocated = AtomLayout::new(atoms)
                 .id(id)
-                .fallback_gap(gap)
+                .gap(gap)
                 .min_size(Vec2::new(allocate_width, min_height.at_least(min_size.y)))
                 .max_width(allocate_width)
                 .sense(sense)

tests/egui_tests/tests/snapshots/text_edit_delay_0_empty.png

@@ -1,3 +1,3 @@
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-oid sha256:570216d6ffa3cc278705582d95b96200bc3ef1608b8f2983a6ed3f8b2ee7276c
+oid sha256:806f3f69228e62d9d0838fb27a02f46cae29efffee54d8182ecbfd2c12f405ba
-size 2280
+size 2413

tests/egui_tests/tests/snapshots/text_edit_halign.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:b66afca19d0a0a6fac4737816443fbd481635897807689dbd75321360ffa079d
+oid sha256:2ae71de200dfb36f64e1ce95c2ad78ef3c1e88e792ada5b5fa1d8fa8c938d8fd
-size 13803
+size 13806

tests/egui_tests/tests/snapshots/text_edit_rtl_0.png

@@ -1,3 +1,3 @@
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-oid sha256:20afbde3e1edc7a599936f83188fb1a2c35d2d1344ce7ad8e115b937266481fc
+oid sha256:10459c5ac931ee55d814e7e4122167f1d4050fff39c409cef995c91d6deaef55
-size 2547
+size 2563

tests/egui_tests/tests/snapshots/text_edit_scroll_0_focus.png

@@ -1,3 +1,3 @@
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-oid sha256:4b0af10fca47b33752aed2549528dba6b6e8c4818f2fc2b9de60451afdd30a2b
+oid sha256:123f7d1a86d644d2e830a2c8b73e8c509ce33fd5d3ead28d3eccf6180a2fcfc5
-size 1690
+size 1790

tests/egui_tests/tests/snapshots/visuals/drag_value.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:76be7b08da637ecbf898efd8322615d5e2f1cb1757665e5486db86ccb7fb3438
+oid sha256:f916e217bd4beb3637acb5394a7da876f9ec684860c9ca922f8bfa3ded6a2684
 size 9462