event_loop: drop the text-input focus when the focused field vanishes from a rebuilt view

A view rebuild that no longer contains the focused text field left `focused_idx` pointing at a stale index and the `zwp_text_input_v3` object enabled. The compositor kept seeing an active text-input, so the on-screen keyboard stayed up over a screen with nothing to type into. The lockscreen's inactivity return from the password form to the idle screen is the visible case: the form disappears, the keyboard does not.
`focus.rs` gains `surface_focused_text_input`, which resolves the focused widget by id when it has one and by index otherwise and reports whether it is a text input, and `reconcile_text_focus`, which clears the focus, deactivates the text-input and calls `on_text_input_focused( false )` when it no longer resolves to one. `draw_frame` notes, before drawing the main surface and each overlay, whether its focus was a text input, and reconciles those surfaces once every draw is done and no view borrow is live. Focus that lands on the field again through `take_focus_request` re-enables the text-input as before.

src/event_loop/focus.rs

@@ -80,6 +80,23 @@ impl<A: App> AppData<A>
 			.and_then( |s| s.on_dismiss )
 	}
 
+	/// After a rebuild: a focused text input that vanished from the frame
+	/// would otherwise keep the text-input protocol (and the OSK) active.
+	pub( crate ) fn reconcile_text_focus( &mut self, focus: SurfaceFocus )
+	{
+		if surface_focused_text_input( self.surface( focus ) ) { return; }
+		let ss = self.surface_mut( focus );
+		if let Some( idx ) = ss.focused_idx.take()
+		{
+			ss.pending_text_values.remove( &idx );
+		}
+		ss.focused_id = None;
+		ss.request_redraw();
+		self.deactivate_text_input();
+		self.app.on_text_input_focused( false );
+		self.dirty_caches();
+	}
+
 	pub( crate ) fn set_focus( &mut self, focus: SurfaceFocus, idx: Option<usize>, qh: &QueueHandle<Self> )
 	{
 		let was_text_input;
@@ -168,3 +185,15 @@ impl<A: App> AppData<A>
 		}
 	}
 }
+
+/// Whether the surface's focused widget is a text input in its current frame.
+pub( crate ) fn surface_focused_text_input<Msg: Clone>( ss: &super::surface::SurfaceState<Msg> ) -> bool
+{
+	let by_id = ss.focused_id.and_then( |id|
+	{
+		ss.frame.widget_rects.iter().find( |w| w.id == Some( id ) ).map( |w| &w.handlers )
+	} );
+	by_id
+		.or_else( || ss.focused_idx.and_then( |i| find_handlers( &ss.frame.widget_rects, i ) ) )
+		.is_some_and( |h| h.is_text_input() )
+}

src/event_loop/frame.rs

@@ -12,6 +12,7 @@ use crate::types::{ Color, Rect };
 use crate::widget::Element;
 
 use super::AppData;
+use super::focus::surface_focused_text_input;
 use super::surface::{ SurfaceFocus, SurfaceState };
 use crate::draw::gles::{ draw_surface_full_gpu, draw_surface_partial_gpu };
 use crate::draw::software::{ draw_surface_full, draw_surface_partial };
@@ -47,8 +48,13 @@ pub( crate ) fn draw_frame<A: App>( data: &mut AppData<A> ) -> bool
 	let qh      = &data.qh;
 
 	let mut first_commit_now = false;
+	let mut text_focus_rebuilt: Vec<SurfaceFocus> = Vec::new();
 	if data.main.configured && data.main.needs_redraw && !data.main.frame_pending
 	{
+		if surface_focused_text_input( &data.main )
+		{
+			text_focus_rebuilt.push( SurfaceFocus::Main );
+		}
 		let req_frame = | wl: &WlSurface | { let _ = wl.frame( qh, SurfaceFocus::Main ); };
 		draw_surface::<A::Message>(
 			&mut data.main,
@@ -104,6 +110,10 @@ pub( crate ) fn draw_frame<A: App>( data: &mut AppData<A> ) -> bool
 		{
 			if !ss.configured || !ss.needs_redraw || ss.frame_pending { continue; }
 			let focus     = SurfaceFocus::Overlay( spec.id );
+			if surface_focused_text_input( ss )
+			{
+				text_focus_rebuilt.push( focus );
+			}
 			let req_frame = | wl: &WlSurface | { let _ = wl.frame( qh, focus ); };
 			let bg        = Color::rgba( 0.0, 0.0, 0.0, 0.0 );
 			draw_surface::<A::Message>(
@@ -123,6 +133,11 @@ pub( crate ) fn draw_frame<A: App>( data: &mut AppData<A> ) -> bool
 		}
 	}
 
+	for focus in text_focus_rebuilt
+	{
+		data.reconcile_text_focus( focus );
+	}
+
 	first_commit_now
 }