[culling] full widget culling

egui/src/containers/collapsing_header.rs

@@ -180,6 +180,8 @@ impl CollapsingHeader {
 
         let id = ui.make_persistent_id(id_source);
 
+        let mut state = State::from_memory_with_default_open(ui.ctx(), id, default_open);
+
         let available = ui.available_finite();
         let text_pos = available.min + vec2(ui.style().spacing.indent, 0.0);
         let galley = label.layout_width(ui, available.right() - text_pos.x);
@@ -192,15 +194,16 @@ impl CollapsingHeader {
             galley.size.y + 2.0 * ui.style().spacing.button_padding.y,
         );
         desired_size = desired_size.at_least(ui.style().spacing.interact_size);
-        let rect = ui.allocate_space(desired_size);
 
-        let header_response = ui.interact(rect, id, Sense::click());
+        let header_response;
+
+        if let Some(rect) = ui.request_space(desired_size) {
+            header_response = ui.interact(rect, id, Sense::click());
             let text_pos = pos2(
                 text_pos.x,
                 header_response.rect.center().y - galley.size.y / 2.0,
             );
 
-        let mut state = State::from_memory_with_default_open(ui.ctx(), id, default_open);
             if header_response.clicked {
                 state.toggle(ui);
             }
@@ -238,6 +241,9 @@ impl CollapsingHeader {
                     stroke: Default::default(),
                 },
             );
+        } else {
+            header_response = Default::default();
+        }
 
         Prepared {
             id,

egui/src/containers/combo_box.rs

@@ -38,7 +38,7 @@ pub fn combo_box(
             let advance = full_minimum_width - icon_width - ui.min_rect().width();
             ui.advance_cursor(advance.at_least(0.0));
 
-            let icon_rect = ui.allocate_space(Vec2::splat(icon_width));
+            let icon_rect = unwrap_or_return_default!(ui.request_space(Vec2::splat(icon_width)));
             let button_rect = ui.min_rect().expand2(ui.style().spacing.button_padding);
             let mut response = ui.interact(button_rect, button_id, Sense::click());
             response.active |= button_active;
@@ -91,6 +91,7 @@ fn button_frame(
     add_contents(&mut content_ui);
 
     let outer_rect = Rect::from_min_max(outer_rect_bounds.min, content_ui.min_rect().max + margin);
+    ui.allocate_space(outer_rect.size());
 
     let mut response = ui.interact(outer_rect, id, sense);
     response.active |= button_active;
@@ -106,8 +107,6 @@ fn button_frame(
         },
     );
 
-    ui.allocate_space(outer_rect.size());
-
     response
 }
 

egui/src/context.rs

@@ -436,7 +436,7 @@ impl Context {
         if id.is_none() || sense == Sense::nothing() || !layer_id.allow_interaction() {
             // Not interested or allowed input:
             return Response {
-                ctx: self.clone(),
+                ctx: Some(self.clone()),
                 sense,
                 rect,
                 hovered,
@@ -461,7 +461,7 @@ impl Context {
         if self.input.mouse.pressed {
             if hovered {
                 let mut response = Response {
-                    ctx: self.clone(),
+                    ctx: Some(self.clone()),
                     sense,
                     rect,
                     hovered: true,
@@ -491,7 +491,7 @@ impl Context {
             } else {
                 // miss
                 Response {
-                    ctx: self.clone(),
+                    ctx: Some(self.clone()),
                     sense,
                     rect,
                     hovered,
@@ -504,7 +504,7 @@ impl Context {
         } else if self.input.mouse.released {
             let clicked = hovered && active && self.input.mouse.could_be_click;
             Response {
-                ctx: self.clone(),
+                ctx: Some(self.clone()),
                 sense,
                 rect,
                 hovered,
@@ -515,7 +515,7 @@ impl Context {
             }
         } else if self.input.mouse.down {
             Response {
-                ctx: self.clone(),
+                ctx: Some(self.clone()),
                 sense,
                 rect,
                 hovered: hovered && active,
@@ -526,7 +526,7 @@ impl Context {
             }
         } else {
             Response {
-                ctx: self.clone(),
+                ctx: Some(self.clone()),
                 sense,
                 rect,
                 hovered,

egui/src/demos/app.rs

@@ -105,7 +105,9 @@ impl FrameHistory {
 
         // TODO: we should not use `slider_width` as default graph width.
         let height = ui.style().spacing.slider_width;
-        let rect = ui.allocate_space(vec2(ui.available_finite().width(), height));
+        let rect = unwrap_or_return_default!(
+            ui.request_space(vec2(ui.available_finite().width(), height))
+        );
         let style = ui.style().noninteractive();
 
         let mut cmds = vec![PaintCmd::Rect {

egui/src/demos/color_test.rs

@@ -267,7 +267,7 @@ impl ColorTest {
 
 fn vertex_gradient(ui: &mut Ui, bg_fill: Srgba, gradient: &Gradient) -> Response {
     use crate::paint::*;
-    let rect = ui.allocate_space(GRADIENT_SIZE);
+    let rect = unwrap_or_return_default!(ui.request_space(GRADIENT_SIZE));
     if bg_fill != Default::default() {
         let mut triangles = Triangles::default();
         triangles.add_colored_rect(rect, bg_fill);

egui/src/demos/demo_window.rs

@@ -93,7 +93,7 @@ impl DemoWindow {
             .show(ui, |ui| {
                 ui.horizontal(|ui| {
                     ui.label("You can pretty easily paint your own small icons:");
-                    let rect = ui.allocate_space(Vec2::splat(16.0));
+                    if let Some(rect) = ui.request_space(Vec2::splat(16.0)) {
                         let painter = ui.painter();
                         let c = rect.center();
                         let r = rect.width() / 2.0 - 1.0;
@@ -103,6 +103,7 @@ impl DemoWindow {
                         painter.line_segment([c - vec2(0.0, r), c + vec2(0.0, r)], stroke);
                         painter.line_segment([c, c + r * Vec2::angled(TAU * 1.0 / 8.0)], stroke);
                         painter.line_segment([c, c + r * Vec2::angled(TAU * 3.0 / 8.0)], stroke);
+                    }
                 });
             });
     }
@@ -210,9 +211,9 @@ impl BoxPainting {
         ui.add(Slider::f32(&mut self.stroke_width, 0.0..=10.0).text("stroke_width"));
         ui.add(Slider::usize(&mut self.num_boxes, 0..=5).text("num_boxes"));
 
-        let pos = ui
+        let rect = ui.request_space(vec2(self.size.x * (self.num_boxes as f32), self.size.y));
-            .allocate_space(vec2(self.size.x * (self.num_boxes as f32), self.size.y))
+        let rect = unwrap_or_return_default!(rect);
-            .min;
+        let pos = rect.min;
 
         let mut cmds = vec![];
         for i in 0..self.num_boxes {
@@ -265,7 +266,7 @@ impl Painting {
     }
 
     fn content(&mut self, ui: &mut Ui) {
-        let rect = ui.allocate_space(ui.available_finite().size());
+        let rect = unwrap_or_return_default!(ui.request_space(ui.available_finite().size()));
         let response = ui.interact(rect, ui.id(), Sense::drag());
         let rect = response.rect;
         let clip_rect = ui.clip_rect().intersect(rect); // Make sure we don't paint out of bounds

egui/src/demos/toggle_switch.rs

@@ -13,7 +13,7 @@ use crate::*;
 pub fn toggle(ui: &mut Ui, on: &mut bool) -> Response {
     // Widget code can be broken up in four steps:
     //  1. Decide a size for the widget
-    //  2. Allocate space for it
+    //  2. Request space for it
     //  3. Handle interactions with the widget (if any)
     //  4. Paint the widget
 
@@ -22,9 +22,14 @@ pub fn toggle(ui: &mut Ui, on: &mut bool) -> Response {
     // but in this example we have a fixed size widget of the default size for a button:
     let desired_size = ui.style().spacing.interact_size;
 
-    // 2. Allocating space:
+    // 2. Requesting space:
     // This is where we get a region (`Rect`) of the screen assigned.
-    let rect = ui.allocate_space(desired_size);
+    let rect = ui.request_space(desired_size);
+
+    // If we get `None` back from `request_space`, it means this widgets isn't visible.
+    // In this case we shouldn't do anything else and just return early.
+    // Egui has a helper macro for this:
+    let rect = unwrap_or_return_default!(rect);
 
     // 3. Interact: Time to check for clicks!
     // To do that we need an `Id` for the button.

egui/src/introspection.rs

@@ -19,7 +19,7 @@ impl Texture {
         if size.x > ui.available().width() {
             size *= ui.available().width() / size.x;
         }
-        let rect = ui.allocate_space(size);
+        let rect = unwrap_or_return_default!(ui.request_space(size));
         let mut triangles = Triangles::default();
         triangles.add_rect_with_uv(rect, [pos2(0.0, 0.0), pos2(1.0, 1.0)].into(), WHITE);
         ui.painter().add(PaintCmd::triangles(triangles));
@@ -34,7 +34,7 @@ impl Texture {
                     .mouse
                     .pos
                     .unwrap_or_else(|| ui.min_rect().left_top());
-                let zoom_rect = ui.allocate_space(vec2(128.0, 128.0));
+                let zoom_rect = unwrap_or_return_default!(ui.request_space(vec2(128.0, 128.0)));
                 let u = remap_clamp(pos.x, rect.x_range(), 0.0..=tex_w);
                 let v = remap_clamp(pos.y, rect.y_range(), 0.0..=tex_h);
 

egui/src/lib.rs

@@ -120,3 +120,15 @@ pub fn text_egui_e2e() {
         assert!(!paint_jobs.is_empty());
     }
 }
+
+#[macro_export]
+macro_rules! unwrap_or_return_default {
+    ($option:expr) => {
+        match $option {
+            Some(value) => value,
+            None => {
+                return Default::default();
+            }
+        }
+    };
+}

egui/src/style.rs

@@ -1,11 +1,6 @@
 #![allow(clippy::if_same_then_else)]
 
-use crate::{
+use crate::{color::*, *};
-    color::*,
-    math::*,
-    paint::{Stroke, TextStyle},
-    types::*,
-};
 
 /// Specifies the look and feel of a `Ui`.
 #[derive(Clone, Debug, PartialEq)]
@@ -474,7 +469,8 @@ impl Stroke {
             ui.label(text);
 
             // stroke preview:
-            let stroke_rect = ui.allocate_space(ui.style().spacing.interact_size);
+            let stroke_rect =
+                unwrap_or_return_default!(ui.request_space(ui.style().spacing.interact_size));
             let left = stroke_rect.left_center();
             let right = stroke_rect.right_center();
             ui.painter().line_segment([left, right], (*width, *color));

egui/src/types.rs

@@ -56,8 +56,10 @@ impl Default for CursorIcon {
 #[derive(Clone)]
 pub struct Response {
     // CONTEXT:
-    /// Used for optionally showing a tooltip
+    /// Used for optionally showing a tooltip.
-    pub ctx: Arc<Context>,
+    /// If `None`, we likely come from a cull widgets and shouldn't show any
+    /// tooltip.
+    pub ctx: Option<Arc<Context>>,
 
     // IN:
     /// The area of the screen we are talking about
@@ -83,17 +85,18 @@ pub struct Response {
     pub has_kb_focus: bool,
 }
 
-impl std::fmt::Debug for Response {
+impl Default for Response {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+    fn default() -> Self {
-        f.debug_struct("Response")
+        Self {
-            .field("rect", &self.rect)
+            ctx: None,
-            .field("sense", &self.sense)
+            rect: Rect::nothing(),
-            .field("hovered", &self.hovered)
+            sense: Sense::nothing(),
-            .field("clicked", &self.clicked)
+            hovered: false,
-            .field("double_clicked", &self.double_clicked)
+            clicked: false,
-            .field("active", &self.active)
+            double_clicked: false,
-            .field("has_kb_focus", &self.has_kb_focus)
+            active: false,
-            .finish()
+            has_kb_focus: false,
+        }
     }
 }
 
@@ -101,7 +104,11 @@ impl Response {
     /// Show this UI if the item was hovered (i.e. a tooltip)
     pub fn on_hover_ui(self, add_contents: impl FnOnce(&mut Ui)) -> Self {
         if self.hovered {
-            crate::containers::show_tooltip(&self.ctx, add_contents);
+            if let Some(ctx) = &self.ctx {
+                crate::containers::show_tooltip(ctx, add_contents);
+            } else {
+                panic!("We shouldn't be able to hover something without a Context");
+            }
         }
         self
     }
@@ -123,9 +130,12 @@ impl Response {
     /// A logical "or" operation.
     /// For instance `a.union(b).hovered` means "was either a or b hovered?".
     pub fn union(&self, other: Self) -> Self {
-        assert!(Arc::ptr_eq(&self.ctx, &other.ctx));
+        if let (Some(lc), Some(rc)) = (&self.ctx, &other.ctx) {
+            debug_assert!(Arc::ptr_eq(lc, rc));
+        }
+
         Self {
-            ctx: other.ctx,
+            ctx: other.ctx.or_else(|| self.ctx.clone()),
             rect: self.rect.union(other.rect),
             sense: self.sense.union(other.sense),
             hovered: self.hovered || other.hovered,
@@ -137,6 +147,23 @@ impl Response {
     }
 }
 
+impl std::fmt::Debug for Response {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Response")
+            .field("ctx", &self.ctx.is_some())
+            .field("rect", &self.rect)
+            .field("sense", &self.sense)
+            .field("hovered", &self.hovered)
+            .field("clicked", &self.clicked)
+            .field("double_clicked", &self.double_clicked)
+            .field("active", &self.active)
+            .field("has_kb_focus", &self.has_kb_focus)
+            .finish()
+    }
+}
+
+// ----------------------------------------------------------------------------
+
 /// To summarize the response from many widgets you can use this pattern:
 ///
 /// ```

egui/src/ui.rs

@@ -462,6 +462,26 @@ impl Ui {
         rect
     }
 
+    /// Potential future of `allocate_space`.
+    /// Returns `None` if the allocated rectangle is outside the clip rect and is thus invisible.
+    /// Works well together with the `unwrap_or_return_default!` macro:
+    /// ```
+    ///     # use egui::*;
+    ///     # let mut ui = Ui::test();
+    ///     let desired_size = vec2(100.0, 200.0);
+    ///     let rect = unwrap_or_return_default!(ui.request_space(desired_size));
+    ///     assert_eq!(rect, Rect::from_min_size(pos2(0.0, 0.0), desired_size));
+    /// ```
+    ///
+    pub fn request_space(&mut self, desired_size: Vec2) -> Option<Rect> {
+        let rect = self.allocate_space(desired_size);
+        if self.clip_rect().intersects(rect) {
+            Some(rect)
+        } else {
+            None
+        }
+    }
+
     /// Reserve this much space and move the cursor.
     /// Returns where to put the widget.
     fn reserve_space_impl(&mut self, child_size: Vec2) -> Rect {

egui/src/widgets/color_picker.rs

@@ -43,7 +43,7 @@ pub fn show_color(ui: &mut Ui, color: impl Into<Srgba>, desired_size: Vec2) -> R
 }
 
 fn show_srgba(ui: &mut Ui, srgba: Srgba, desired_size: Vec2) -> Response {
-    let rect = ui.allocate_space(desired_size);
+    let rect = unwrap_or_return_default!(ui.request_space(desired_size));
     background_checkers(ui.painter(), rect);
     ui.painter().add(PaintCmd::Rect {
         rect,
@@ -56,7 +56,7 @@ fn show_srgba(ui: &mut Ui, srgba: Srgba, desired_size: Vec2) -> Response {
 
 fn color_button(ui: &mut Ui, color: Srgba) -> Response {
     let desired_size = ui.style().spacing.interact_size;
-    let rect = ui.allocate_space(desired_size);
+    let rect = unwrap_or_return_default!(ui.request_space(desired_size));
     let id = ui.make_position_id();
     let response = ui.interact(rect, id, Sense::click());
     let visuals = ui.style().interact(&response);
@@ -77,7 +77,7 @@ fn color_slider_1d(ui: &mut Ui, value: &mut f32, color_at: impl Fn(f32) -> Srgba
         ui.style().spacing.slider_width,
         ui.style().spacing.interact_size.y * 2.0,
     );
-    let rect = ui.allocate_space(desired_size);
+    let rect = unwrap_or_return_default!(ui.request_space(desired_size));
 
     let id = ui.make_position_id();
     let response = ui.interact(rect, id, Sense::click_and_drag());
@@ -136,7 +136,7 @@ fn color_slider_2d(
     color_at: impl Fn(f32, f32) -> Srgba,
 ) -> Response {
     let desired_size = Vec2::splat(ui.style().spacing.slider_width);
-    let rect = ui.allocate_space(desired_size);
+    let rect = unwrap_or_return_default!(ui.request_space(desired_size));
 
     let id = ui.make_position_id();
     let response = ui.interact(rect, id, Sense::click_and_drag());

egui/src/widgets/image.rs

@@ -49,7 +49,7 @@ impl Widget for Image {
             bg_fill,
             tint,
         } = self;
-        let rect = ui.allocate_space(desired_size);
+        let rect = unwrap_or_return_default!(ui.request_space(desired_size));
         if bg_fill != Default::default() {
             let mut triangles = Triangles::default();
             triangles.add_colored_rect(rect, bg_fill);

egui/src/widgets/mod.rs

@@ -135,7 +135,7 @@ macro_rules! label {
 impl Widget for Label {
     fn ui(self, ui: &mut Ui) -> Response {
         let galley = self.layout(ui);
-        let rect = ui.allocate_space(galley.size);
+        let rect = unwrap_or_return_default!(ui.request_space(galley.size));
         self.paint_galley(ui, rect.min, galley);
         ui.interact_hover(rect)
     }
@@ -207,7 +207,7 @@ impl Widget for Hyperlink {
         let text_style = text_style.unwrap_or_else(|| ui.style().body_text_style);
         let font = &ui.fonts()[text_style];
         let galley = font.layout_multiline(text, ui.available().width());
-        let rect = ui.allocate_space(galley.size);
+        let rect = unwrap_or_return_default!(ui.request_space(galley.size));
 
         let id = ui.make_position_id();
         let response = ui.interact(rect, id, Sense::click());
@@ -318,7 +318,7 @@ impl Widget for Button {
         let galley = font.layout_multiline(text, ui.available().width());
         let mut desired_size = galley.size + 2.0 * button_padding;
         desired_size = desired_size.at_least(ui.style().spacing.interact_size);
-        let rect = ui.allocate_space(desired_size);
+        let rect = unwrap_or_return_default!(ui.request_space(desired_size));
 
         let id = ui.make_position_id();
         let response = ui.interact(rect, id, sense);
@@ -390,7 +390,7 @@ impl<'a> Widget for Checkbox<'a> {
             button_padding + vec2(icon_width + icon_spacing, 0.0) + galley.size + button_padding;
         desired_size = desired_size.at_least(spacing.interact_size);
         desired_size.y = desired_size.y.max(icon_width);
-        let rect = ui.allocate_space(desired_size);
+        let rect = unwrap_or_return_default!(ui.request_space(desired_size));
 
         let id = ui.make_position_id();
         let response = ui.interact(rect, id, Sense::click());
@@ -475,7 +475,7 @@ impl Widget for RadioButton {
             button_padding + vec2(icon_width + icon_spacing, 0.0) + galley.size + button_padding;
         desired_size = desired_size.at_least(ui.style().spacing.interact_size);
         desired_size.y = desired_size.y.max(icon_width);
-        let rect = ui.allocate_space(desired_size);
+        let rect = unwrap_or_return_default!(ui.request_space(desired_size));
 
         let id = ui.make_position_id();
         let response = ui.interact(rect, id, Sense::click());
@@ -544,7 +544,8 @@ impl Widget for Separator {
 
         let (points, rect) = match ui.layout().dir() {
             Direction::Horizontal => {
-                let rect = ui.allocate_space(vec2(spacing, available_space.y));
+                let rect =
+                    unwrap_or_return_default!(ui.request_space(vec2(spacing, available_space.y)));
                 (
                     [
                         pos2(rect.center().x, rect.top()),
@@ -554,7 +555,8 @@ impl Widget for Separator {
                 )
             }
             Direction::Vertical => {
-                let rect = ui.allocate_space(vec2(available_space.x, spacing));
+                let rect =
+                    unwrap_or_return_default!(ui.request_space(vec2(available_space.x, spacing)));
                 (
                     [
                         pos2(rect.left(), rect.center().y),

egui/src/widgets/text_edit.rs

@@ -122,7 +122,7 @@ impl<'t> Widget for TextEdit<'t> {
             galley.size.x.max(desired_width.min(available_width)),
             galley.size.y.max(line_spacing),
         );
-        let rect = ui.allocate_space(desired_size);
+        let rect = unwrap_or_return_default!(ui.request_space(desired_size));
         let sense = if enabled {
             Sense::click_and_drag()
         } else {