Add ui.allocate_at_least and ui.allocate_exact_size

egui/src/introspection.rs

@@ -7,6 +7,7 @@ use crate::{
 
 impl Texture {
     pub fn ui(&self, ui: &mut Ui) {
+        // Show font texture in demo Ui
         ui.label(format!(
             "Texture size: {} x {} (hover to zoom)",
             self.width, self.height
@@ -18,8 +19,7 @@ impl Texture {
         if size.x > ui.available_width() {
             size *= ui.available_width() / size.x;
         }
-        let response = ui.allocate_response(size, Sense::hover());
-        let rect = response.rect;
+        let (rect, response) = ui.allocate_at_least(size, Sense::hover());
         let mut triangles = Triangles::default();
         triangles.add_rect_with_uv(
             rect,

egui/src/ui.rs

@@ -468,6 +468,27 @@ impl Ui {
         self.interact(rect, id, sense)
     }
 
+    /// Returns a `Rect` with exactly what you asked for.
+    ///
+    /// The response rect will be larger if this is part of a justified layout or similar.
+    /// This means that iof this is a narrow widget in a wide justified layout, then
+    /// the widget will react to interactions outside the returned `Rect`.
+    pub fn allocate_exact_size(&mut self, desired_size: Vec2, sense: Sense) -> (Rect, Response) {
+        let response = self.allocate_response(desired_size, sense);
+        let rect = self
+            .layout()
+            .align_size_within_rect(desired_size, response.rect);
+        (rect, response)
+    }
+
+    /// Allocate at least as much space as needed, and interact with that rect.
+    ///
+    /// The returned `Rect` will be the same size as `Response::rect`.
+    pub fn allocate_at_least(&mut self, desired_size: Vec2, sense: Sense) -> (Rect, Response) {
+        let response = self.allocate_response(desired_size, sense);
+        (response.rect, response)
+    }
+
     /// Reserve this much space and move the cursor.
     /// Returns where to put the widget.
     ///

egui/src/widgets/button.rs

@@ -106,23 +106,19 @@ impl Widget for Button {
             desired_size.y = desired_size.y.at_least(ui.style().spacing.interact_size.y);
         }
 
-        let response = ui.allocate_response(desired_size, sense);
+        let (rect, response) = ui.allocate_at_least(desired_size, sense);
 
-        if ui.clip_rect().intersects(response.rect) {
+        if ui.clip_rect().intersects(rect) {
             let visuals = ui.style().interact(&response);
             let text_cursor = ui
                 .layout()
-                .align_size_within_rect(galley.size, response.rect.shrink2(button_padding))
+                .align_size_within_rect(galley.size, rect.shrink2(button_padding))
                 .min;
 
             if frame {
                 let fill = fill.unwrap_or(visuals.bg_fill);
-                ui.painter().rect(
-                    response.rect,
-                    visuals.corner_radius,
-                    fill,
-                    visuals.bg_stroke,
-                );
+                ui.painter()
+                    .rect(rect, visuals.corner_radius, fill, visuals.bg_stroke);
             }
 
             let text_color = text_color
@@ -189,10 +185,7 @@ impl<'a> Widget for Checkbox<'a> {
         let mut desired_size = total_extra + galley.size;
         desired_size = desired_size.at_least(spacing.interact_size);
         desired_size.y = desired_size.y.max(icon_width);
-        let response = ui.allocate_response(desired_size, Sense::click());
-        let rect = ui
-            .layout()
-            .align_size_within_rect(desired_size, response.rect);
+        let (rect, response) = ui.allocate_exact_size(desired_size, Sense::click());
         if response.clicked {
             *checked = !*checked;
         }
@@ -283,10 +276,7 @@ impl Widget for RadioButton {
         let mut desired_size = total_extra + galley.size;
         desired_size = desired_size.at_least(ui.style().spacing.interact_size);
         desired_size.y = desired_size.y.max(icon_width);
-        let response = ui.allocate_response(desired_size, Sense::click());
-        let rect = ui
-            .layout()
-            .align_size_within_rect(desired_size, response.rect);
+        let (rect, response) = ui.allocate_exact_size(desired_size, Sense::click());
 
         let text_cursor = pos2(
             rect.min.x + button_padding.x + icon_width + icon_spacing,
@@ -390,28 +380,27 @@ impl Widget for ImageButton {
 
         let button_padding = ui.style().spacing.button_padding;
         let desired_size = image.desired_size() + 2.0 * button_padding;
-        let response = ui.allocate_response(desired_size, sense);
+        let (rect, response) = ui.allocate_at_least(desired_size, sense);
 
-        if ui.clip_rect().intersects(response.rect) {
+        if ui.clip_rect().intersects(rect) {
             let visuals = ui.style().interact(&response);
 
             if selected {
                 let selection = ui.style().visuals.selection;
                 ui.painter()
-                    .rect(response.rect, 0.0, selection.bg_fill, selection.stroke);
+                    .rect(rect, 0.0, selection.bg_fill, selection.stroke);
             } else if frame {
                 ui.painter().rect(
-                    response.rect,
+                    rect,
                     visuals.corner_radius,
                     visuals.bg_fill,
                     visuals.bg_stroke,
                 );
             }
 
-            let image_rect = ui.layout().align_size_within_rect(
-                image.desired_size(),
-                response.rect.shrink2(button_padding),
-            );
+            let image_rect = ui
+                .layout()
+                .align_size_within_rect(image.desired_size(), rect.shrink2(button_padding));
             image.paint_at(ui, image_rect);
         }
 

egui/src/widgets/color_picker.rs

@@ -45,10 +45,10 @@ pub fn show_color(ui: &mut Ui, color: impl Into<Color32>, desired_size: Vec2) ->
 }
 
 fn show_srgba(ui: &mut Ui, srgba: Color32, desired_size: Vec2) -> Response {
-    let response = ui.allocate_response(desired_size, Sense::hover());
-    background_checkers(ui.painter(), response.rect);
+    let (rect, response) = ui.allocate_at_least(desired_size, Sense::hover());
+    background_checkers(ui.painter(), rect);
     ui.painter().add(PaintCmd::Rect {
-        rect: response.rect,
+        rect,
         corner_radius: 2.0,
         fill: srgba,
         stroke: Stroke::new(3.0, srgba.to_opaque()),
@@ -58,11 +58,11 @@ fn show_srgba(ui: &mut Ui, srgba: Color32, desired_size: Vec2) -> Response {
 
 fn color_button(ui: &mut Ui, color: Color32) -> Response {
     let desired_size = ui.style().spacing.interact_size;
-    let response = ui.allocate_response(desired_size, Sense::click());
+    let (rect, response) = ui.allocate_at_least(desired_size, Sense::click());
     let visuals = ui.style().interact(&response);
-    background_checkers(ui.painter(), response.rect);
+    background_checkers(ui.painter(), rect);
     ui.painter().add(PaintCmd::Rect {
-        rect: response.rect,
+        rect,
         corner_radius: visuals.corner_radius.at_most(2.0),
         fill: color,
         stroke: visuals.fg_stroke,
@@ -77,8 +77,7 @@ fn color_slider_1d(ui: &mut Ui, value: &mut f32, color_at: impl Fn(f32) -> Color
         ui.style().spacing.slider_width,
         ui.style().spacing.interact_size.y * 2.0,
     );
-    let response = ui.allocate_response(desired_size, Sense::click_and_drag());
-    let rect = response.rect;
+    let (rect, response) = ui.allocate_at_least(desired_size, Sense::click_and_drag());
 
     if response.active {
         if let Some(mpos) = ui.input().mouse.pos {
@@ -135,8 +134,7 @@ fn color_slider_2d(
     color_at: impl Fn(f32, f32) -> Color32,
 ) -> Response {
     let desired_size = Vec2::splat(ui.style().spacing.slider_width);
-    let response = ui.allocate_response(desired_size, Sense::click_and_drag());
-    let rect = response.rect;
+    let (rect, response) = ui.allocate_at_least(desired_size, Sense::click_and_drag());
 
     if response.active {
         if let Some(mpos) = ui.input().mouse.pos {

egui/src/widgets/hyperlink.rs

@@ -46,7 +46,7 @@ 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 response = ui.allocate_response(galley.size, Sense::click());
+        let (rect, response) = ui.allocate_exact_size(galley.size, Sense::click());
 
         if response.hovered {
             ui.ctx().output().cursor_icon = CursorIcon::PointingHand;
@@ -61,7 +61,7 @@ impl Widget for Hyperlink {
         if response.hovered {
             // Underline:
             for line in &galley.rows {
-                let pos = response.rect.min;
+                let pos = rect.min;
                 let y = pos.y + line.y_max;
                 let y = ui.painter().round_to_pixel(y);
                 let min_x = pos.x + line.min_x();
@@ -73,8 +73,7 @@ impl Widget for Hyperlink {
             }
         }
 
-        ui.painter()
-            .galley(response.rect.min, galley, text_style, color);
+        ui.painter().galley(rect.min, galley, text_style, color);
 
         response.on_hover_text(url)
     }

egui/src/widgets/image.rs

@@ -73,8 +73,8 @@ impl Image {
 
 impl Widget for Image {
     fn ui(self, ui: &mut Ui) -> Response {
-        let response = ui.allocate_response(self.desired_size, Sense::hover());
-        self.paint_at(ui, response.rect);
+        let (rect, response) = ui.allocate_at_least(self.desired_size, Sense::hover());
+        self.paint_at(ui, rect);
         response
     }
 }

egui/src/widgets/label.rs

@@ -157,10 +157,7 @@ impl Widget for Label {
             total_response
         } else {
             let galley = self.layout(ui);
-            let response = ui.allocate_response(galley.size, Sense::click());
-            let rect = ui
-                .layout()
-                .align_size_within_rect(galley.size, response.rect);
+            let (rect, response) = ui.allocate_exact_size(galley.size, Sense::click());
             self.paint_galley(ui, rect.min, galley);
             response
         }

egui/src/widgets/selected_label.rs

@@ -33,11 +33,11 @@ impl Widget for SelectableLabel {
 
         let mut desired_size = total_extra + galley.size;
         desired_size = desired_size.at_least(ui.style().spacing.interact_size);
-        let response = ui.allocate_response(desired_size, Sense::click());
+        let (rect, response) = ui.allocate_at_least(desired_size, Sense::click());
 
         let text_cursor = pos2(
-            response.rect.min.x + button_padding.x,
-            response.rect.center().y - 0.5 * galley.size.y,
+            rect.min.x + button_padding.x,
+            rect.center().y - 0.5 * galley.size.y,
         );
 
         let visuals = ui.style().interact(&response);
@@ -48,8 +48,7 @@ impl Widget for SelectableLabel {
             } else {
                 Default::default()
             };
-            ui.painter()
-                .rect(response.rect, 0.0, bg_fill, visuals.bg_stroke);
+            ui.painter().rect(rect, 0.0, bg_fill, visuals.bg_stroke);
         }
 
         let text_color = ui

egui/src/widgets/separator.rs

@@ -30,8 +30,7 @@ impl Widget for Separator {
             vec2(available_space.x, spacing)
         };
 
-        let response = ui.allocate_response(size, Sense::hover());
-        let rect = response.rect;
+        let (rect, response) = ui.allocate_at_least(size, Sense::hover());
         let points = if ui.layout().main_dir().is_horizontal() {
             [
                 pos2(rect.center().x, rect.top()),