App::take_blur_request, and a press on a focused select_on_focus field positions the cursor

Two gaps found while using trust's address box on a phone, both about what happens to a text field once it holds the focus.
Dropping the focus. An app could ask for the focus of a widget, through `App::take_focus_request`, but had no way to give it up. A browser needs to: once an address is submitted the field has done its job, yet it kept the focus, so the on-screen keyboard stayed over the page that had just been asked for, and came back whenever the window was raised, since ltk enables the input method again on the text-input `enter` that follows while a text field holds the focus. `App::take_blur_request` is the counterpart: return `true` once and the run loop calls `set_focus( keyboard_focus, None )`, the same call the back request already uses to blur a text field, so the text-input disable and `on_text_input_focused( false )` come with it. It is handled just before the focus request, so an app that asks for both in one cycle ends up focused, which is what "open a new tab and type" needs; a pending `focus_retry` from an earlier cycle is cleared, or it would hand the focus straight back to the widget it was taken from.
Positioning the cursor in a `select_on_focus` field. `handle_text_pointer_down` and `handle_text_pointer_drag` returned at once for a field built with `.select_on_focus( true )`, so that the press that focuses it keeps the whole-value selection `set_focus` has just installed. The guard did not distinguish that press from a later one: in a field that already had the focus, no press ever placed the cursor and no drag ever selected a range, with a finger or with a mouse. That suits a numeric picker poorly and an address box not at all, where correcting one character of a long URL meant retyping it. `AppData` gains `press_on_focused`, computed in both press paths, touch and pointer, right before their `set_focus`: whether the press landed on the widget that already held the focus. The two guards now apply only when it did not. The first press on such a field selects everything, as before; a press on it while focused collapses the selection to the byte offset under it, and a drag from there extends the selection.
Not changed. `handle_text_select_word` keeps its `select_on_focus` guard, so a double press on such a field still leaves the whole value selected rather than a word. The right-button path, which opens the context menu without touching the selection, never reached these functions and is unaffected. `set_focus` still moves the cursor to the end and reselects when it is called for the widget that already has the focus; a programmatic focus request on a focused `select_on_focus` field therefore selects everything again, which is what an address-box shortcut wants.

src/app.rs

@@ -865,6 +865,9 @@ pub trait App: 'static
 	/// view before it is focused. A widget that never appears is dropped.
 	fn take_focus_request( &mut self ) -> Option<crate::types::WidgetId> { None }
 
+	/// Return `true` once to drop the keyboard focus, which folds the on-screen keyboard; a [`take_focus_request`](Self::take_focus_request) in the same cycle wins.
+	fn take_blur_request( &mut self ) -> bool { false }
+
 	/// Called on every pointer motion (mouse move, button press, button
 	/// release). `x`, `y` are in physical pixels of the main surface,
 	/// the same coordinate space as widget rects. Default: no-op.

src/event_loop/app_data.rs

@@ -259,6 +259,8 @@ pub struct AppData<A: App>
 	/// Surface currently holding keyboard focus (updated on keyboard
 	/// enter/leave).
 	pub keyboard_focus:      SurfaceFocus,
+	/// The current press landed on the widget that already held the focus, not the press that gives it.
+	pub press_on_focused:    bool,
 	/// Per-touch-id tracking of which surface each active touch belongs to
 	/// (populated on `down`, cleared on `up`/`cancel`).
 	pub touch_focus:         HashMap<i32, SurfaceFocus>,

src/event_loop/run.rs

@@ -362,6 +362,7 @@ pub( crate ) fn try_run<A: App>( mut app: A ) -> Result<(), RunError>
 		canvas_pool:         Vec::new(),
 		pointer_focus:       SurfaceFocus::Main,
 		keyboard_focus:      SurfaceFocus::Main,
+		press_on_focused:    false,
 		touch_focus:         std::collections::HashMap::new(),
 		cached_view:            None,
 		cached_overlays: None,
@@ -912,6 +913,14 @@ pub( crate ) fn try_run<A: App>( mut app: A ) -> Result<(), RunError>
 			}
 		}
 
+		if data.app.take_blur_request()
+		{
+			let qh    = data.qh.clone();
+			let focus = data.keyboard_focus;
+			data.set_focus( focus, None, &qh );
+			data.focus_retry = None;
+		}
+
 		// Focus the widget with the requested WidgetId if the app requests it.
 		// Walks main + every overlay because the targeted widget can live
 		// on any of them (a search field on a launcher overlay, a text

src/event_loop/text_editing/selection.rs

@@ -127,7 +127,7 @@ impl<A: App> AppData<A>
 			find_handlers( &self.surface( focus ).frame.widget_rects, idx ),
 			Some( WidgetHandlers::TextEdit { select_on_focus: true, .. } ),
 		);
-		if select_on_focus { return; }
+		if select_on_focus && !self.press_on_focused { return; }
 		let ( rect, value, multiline, secure, align, font_size ) = match self.text_input_geometry( focus, idx )
 		{
 			Some( v ) => v,
@@ -161,7 +161,7 @@ impl<A: App> AppData<A>
 			find_handlers( &self.surface( focus ).frame.widget_rects, idx ),
 			Some( WidgetHandlers::TextEdit { select_on_focus: true, .. } ),
 		);
-		if select_on_focus { return; }
+		if select_on_focus && !self.press_on_focused { return; }
 		let ( rect, value, multiline, secure, align, font_size ) = match self.text_input_geometry( focus, idx )
 		{
 			Some( v ) => v,

src/input/pointer/press.rs

@@ -181,6 +181,7 @@ impl<A: App> AppData<A>
 			ss.needs_redraw = true;
 			result
 		};
+		self.press_on_focused = outcome.hit_idx.is_some() && self.surface( focus ).focused_idx == outcome.hit_idx;
 		self.set_focus( focus, outcome.hit_idx, qh );
 		if let Some( msg ) = outcome.initial_slider_msg
 		{

src/input/touch/mod.rs

@@ -159,6 +159,7 @@ impl<A: App> TouchHandler for AppData<A>
 			ss.needs_redraw = true;
 			result
 		};
+		self.press_on_focused = outcome.hit_idx.is_some() && self.surface( focus ).focused_idx == outcome.hit_idx;
 		self.set_focus( focus, outcome.hit_idx, qh );
 		if let Some( msg ) = outcome.initial_slider_msg
 		{