Shrink the byte-size of Response slightly (#8011)

Small optimization! 96 -> 88 bytes, so no huge win.

crates/egui/src/atomics/atom_layout.rs

@@ -318,8 +318,9 @@ impl<'a> AtomLayout<'a> {
         let (_, rect) = ui.allocate_space(frame_size);
         let mut response = ui.interact(rect, id, sense);
 
-        response.intrinsic_size =
-            Some((Vec2::new(intrinsic_width, intrinsic_height) + margin.sum()).at_least(min_size));
+        response.set_intrinsic_size(
+            (Vec2::new(intrinsic_width, intrinsic_height) + margin.sum()).at_least(min_size),
+        );
 
         AllocatedAtomLayout {
             sized_atoms: sized_items,

crates/egui/src/context.rs

@@ -1378,8 +1378,8 @@ impl Context {
             interact_rect,
             sense,
             flags: Flags::empty(),
-            interact_pointer_pos: None,
-            intrinsic_size: None,
+            interact_pointer_pos_or_nan: Pos2::NAN,
+            intrinsic_size_or_nan: Vec2::NAN,
         };
 
         res.flags.set(Flags::ENABLED, enabled);
@@ -1470,14 +1470,11 @@ impl Context {
                 || res.long_touched()
                 || clicked
                 || res.drag_stopped();
-            if is_interacted_with {
-                res.interact_pointer_pos = input.pointer.interact_pos();
-                if let (Some(to_global), Some(pos)) = (
-                    memory.to_global.get(&res.layer_id),
-                    &mut res.interact_pointer_pos,
-                ) {
-                    *pos = to_global.inverse() * *pos;
+            if is_interacted_with && let Some(mut pos) = input.pointer.interact_pos() {
+                if let Some(to_global) = memory.to_global.get(&res.layer_id) {
+                    pos = to_global.inverse() * pos;
                 }
+                res.interact_pointer_pos_or_nan = pos;
             }
 
             if input.pointer.any_down() && !is_interacted_with {

crates/egui/src/response.rs

@@ -55,7 +55,7 @@ pub struct Response {
     /// Where the pointer (mouse/touch) were when this widget was clicked or dragged.
     /// `None` if the widget is not being interacted with.
     #[doc(hidden)]
-    pub interact_pointer_pos: Option<Pos2>,
+    pub interact_pointer_pos_or_nan: Pos2,
 
     /// The intrinsic / desired size of the widget.
     ///
@@ -67,12 +67,22 @@ pub struct Response {
     /// At the time of writing, this is only used by external crates
     /// for improved layouting.
     /// See for instance [`egui_flex`](https://github.com/lucasmerlin/hello_egui/tree/main/crates/egui_flex).
-    pub intrinsic_size: Option<Vec2>,
+    #[doc(hidden)]
+    pub intrinsic_size_or_nan: Vec2,
 
     #[doc(hidden)]
     pub flags: Flags,
 }
 
+#[test]
+fn test_response_size() {
+    assert_eq!(
+        std::mem::size_of::<Response>(),
+        88,
+        "Keep Response small, because we create them often, and we want to keep it lean and fast"
+    );
+}
+
 /// A bit set for various boolean properties of `Response`.
 #[doc(hidden)]
 #[derive(Copy, Clone, Debug)]
@@ -489,7 +499,26 @@ impl Response {
     /// `None` if the widget is not being interacted with.
     #[inline]
     pub fn interact_pointer_pos(&self) -> Option<Pos2> {
-        self.interact_pointer_pos
+        let pos = self.interact_pointer_pos_or_nan;
+        if pos.any_nan() { None } else { Some(pos) }
+    }
+
+    /// The intrinsic / desired size of the widget.
+    ///
+    /// This is the size that a non-wrapped, non-truncated, non-justified version of the widget
+    /// would have.
+    ///
+    /// If this is `None`, use [`Self::rect`] instead.
+    #[inline]
+    pub fn intrinsic_size(&self) -> Option<Vec2> {
+        let size = self.intrinsic_size_or_nan;
+        if size.any_nan() { None } else { Some(size) }
+    }
+
+    /// Set the intrinsic / desired size of the widget.
+    #[inline]
+    pub fn set_intrinsic_size(&mut self, size: Vec2) {
+        self.intrinsic_size_or_nan = size;
     }
 
     /// If it is a good idea to show a tooltip, where is pointer?
@@ -1007,8 +1036,10 @@ impl Response {
             interact_rect: self.interact_rect.union(other.interact_rect),
             sense: self.sense.union(other.sense),
             flags: self.flags | other.flags,
-            interact_pointer_pos: self.interact_pointer_pos.or(other.interact_pointer_pos),
-            intrinsic_size: None,
+            interact_pointer_pos_or_nan: self
+                .interact_pointer_pos()
+                .unwrap_or(other.interact_pointer_pos_or_nan),
+            intrinsic_size_or_nan: Vec2::NAN,
         }
     }
 }

crates/egui/src/ui.rs

@@ -1281,7 +1281,7 @@ impl Ui {
     pub fn allocate_response(&mut self, desired_size: Vec2, sense: Sense) -> Response {
         let (id, rect) = self.allocate_space(desired_size);
         let mut response = self.interact(rect, id, sense);
-        response.intrinsic_size = Some(desired_size);
+        response.set_intrinsic_size(desired_size);
         response
     }
 

crates/egui/src/widgets/label.rs

@@ -220,7 +220,7 @@ impl Label {
                 .rect_without_leading_space()
                 .translate(pos.to_vec2());
             let mut response = ui.allocate_rect(rect, sense);
-            response.intrinsic_size = Some(galley.intrinsic_size());
+            response.set_intrinsic_size(galley.intrinsic_size());
             for placed_row in galley.rows.iter().skip(1) {
                 let rect = placed_row.rect().translate(pos.to_vec2());
                 response |= ui.allocate_rect(rect, sense);
@@ -256,7 +256,7 @@ impl Label {
 
             let galley = ui.fonts_mut(|fonts| fonts.layout_job(layout_job));
             let (rect, mut response) = ui.allocate_exact_size(galley.size(), sense);
-            response.intrinsic_size = Some(galley.intrinsic_size());
+            response.set_intrinsic_size(galley.intrinsic_size());
             let galley_pos = match galley.job.halign {
                 Align::LEFT => rect.left_top(),
                 Align::Center => rect.center_top(),

crates/emath/src/pos2.rs

@@ -119,6 +119,11 @@ impl Pos2 {
     /// Same as `Pos2::default()`.
     pub const ZERO: Self = Self { x: 0.0, y: 0.0 };
 
+    pub const NAN: Self = Self {
+        x: f32::NAN,
+        y: f32::NAN,
+    };
+
     #[inline(always)]
     pub const fn new(x: f32, y: f32) -> Self {
         Self { x, y }

tests/egui_tests/tests/test_atoms.rs

@@ -92,17 +92,17 @@ fn test_intrinsic_size() {
                     if let Some(current_intrinsic_size) = intrinsic_size {
                         assert_eq!(
                             Some(current_intrinsic_size),
-                            response.intrinsic_size,
+                            response.intrinsic_size(),
                             "For wrapping: {wrapping:?}"
                         );
                     }
                     assert!(
-                        response.intrinsic_size.is_some(),
+                        response.intrinsic_size().is_some(),
                         "intrinsic_size should be set for `Button`"
                     );
-                    intrinsic_size = response.intrinsic_size;
+                    intrinsic_size = response.intrinsic_size();
                     if wrapping == TextWrapMode::Extend {
-                        assert_eq!(Some(response.rect.size()), response.intrinsic_size);
+                        assert_eq!(Some(response.rect.size()), response.intrinsic_size());
                     }
                 });
         }