Add `SurrenderFocusOn` option (#7471)

* [X] I have followed the instructions in the PR template

On touch devices you don't want the keyboard to disappear when
scrolling, so this PR adds a `SurrenderFocusOn` enum to configure on
what interaction to surrender focus.

crates/egui/src/context.rs

@@ -38,10 +38,10 @@ use crate::{
     viewport::ViewportClass,
 };
 
+use self::{hit_test::WidgetHits, interaction::InteractionSnapshot};
 #[cfg(feature = "accesskit")]
 use crate::IdMap;
-
-use self::{hit_test::WidgetHits, interaction::InteractionSnapshot};
+use crate::input_state::SurrenderFocusOn;
 
 /// Information given to the backend about when it is time to repaint the ui.
 ///
@@ -1430,8 +1430,14 @@ impl Context {
                 res.flags.set(Flags::HOVERED, false);
             }
 
-            let pointer_pressed_elsewhere = any_press && !res.hovered();
-            if pointer_pressed_elsewhere && memory.has_focus(id) {
+            let should_surrender_focus = match memory.options.input_options.surrender_focus_on {
+                SurrenderFocusOn::Presses => any_press,
+                SurrenderFocusOn::Clicks => input.pointer.any_click(),
+                SurrenderFocusOn::Never => false,
+            };
+
+            let pointer_clicked_elsewhere = should_surrender_focus && !res.hovered();
+            if pointer_clicked_elsewhere && memory.has_focus(id) {
                 memory.surrender_focus(id);
             }
         });

crates/egui/src/input_state/mod.rs

@@ -17,6 +17,37 @@ pub use crate::Key;
 pub use touch_state::MultiTouchInfo;
 use touch_state::TouchState;
 
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub enum SurrenderFocusOn {
+    /// Surrender focus if the user _presses_ somewhere outside the focused widget.
+    Presses,
+
+    /// Surrender focus if the user _clicks_ somewhere outside the focused widget.
+    #[default]
+    Clicks,
+
+    /// Never surrender focus.
+    Never,
+}
+
+impl SurrenderFocusOn {
+    pub fn ui(&mut self, ui: &mut crate::Ui) {
+        ui.horizontal(|ui| {
+            ui.selectable_value(self, Self::Presses, "Presses")
+                .on_hover_text(
+                    "Surrender focus if the user presses somewhere outside the focused widget.",
+                );
+            ui.selectable_value(self, Self::Clicks, "Clicks")
+                .on_hover_text(
+                    "Surrender focus if the user clicks somewhere outside the focused widget.",
+                );
+            ui.selectable_value(self, Self::Never, "Never")
+                .on_hover_text("Never surrender focus.");
+        });
+    }
+}
+
 /// Options for input state handling.
 #[derive(Clone, Copy, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
@@ -58,6 +89,9 @@ pub struct InputOptions {
     /// and when combined with [`Self::zoom_modifier`] it will result in zooming
     /// on only the vertical axis.
     pub vertical_scroll_modifier: Modifiers,
+
+    /// When should we surrender focus from the focused widget?
+    pub surrender_focus_on: SurrenderFocusOn,
 }
 
 impl Default for InputOptions {
@@ -79,6 +113,7 @@ impl Default for InputOptions {
             zoom_modifier: Modifiers::COMMAND,
             horizontal_scroll_modifier: Modifiers::SHIFT,
             vertical_scroll_modifier: Modifiers::ALT,
+            surrender_focus_on: SurrenderFocusOn::default(),
         }
     }
 }
@@ -95,6 +130,7 @@ impl InputOptions {
             zoom_modifier,
             horizontal_scroll_modifier,
             vertical_scroll_modifier,
+            surrender_focus_on,
         } = self;
         crate::Grid::new("InputOptions")
             .num_columns(2)
@@ -155,6 +191,10 @@ impl InputOptions {
                 vertical_scroll_modifier.ui(ui);
                 ui.end_row();
 
+                ui.label("surrender_focus_on");
+                surrender_focus_on.ui(ui);
+                ui.end_row();
+
             });
     }
 }

crates/egui/src/lib.rs

@@ -495,7 +495,7 @@ pub use self::{
     epaint::text::TextWrapMode,
     grid::Grid,
     id::{Id, IdMap},
-    input_state::{InputOptions, InputState, MultiTouchInfo, PointerState},
+    input_state::{InputOptions, InputState, MultiTouchInfo, PointerState, SurrenderFocusOn},
     layers::{LayerId, Order},
     layout::*,
     load::SizeHint,