Control Separator widths, and less clipping in ScrollArea (#2665)

* Add Separator::grow and Separator::shrink

* Be more conservative with the clipping in ScrollArea:s

* Add test of the growing separator

* Improve test output

* Update changelog

* Add back a little bit more clipping

* Make the minimum scroll handle length a bit longer

* More clip rect tweaks

CHANGELOG.md

@@ -25,12 +25,14 @@ NOTE: [`epaint`](crates/epaint/CHANGELOG.md), [`eframe`](crates/eframe/CHANGELOG
 * Add `Context::screen_rect` and `Context::set_cursor_icon` ([#2625](https://github.com/emilk/egui/pull/2625)).
 * You can turn off the vertical line left of indented regions with `Visuals::indent_has_left_vline` ([#2636](https://github.com/emilk/egui/pull/2636)).
 * Add `Response.highlight` to highlight a widget ([#2632](https://github.com/emilk/egui/pull/2632)).
+* Add `Separator::grow` and `Separator::shrink` ([#2665](https://github.com/emilk/egui/pull/2665)).
 
 ### Changed 🔧
 * Improved plot grid appearance ([#2412](https://github.com/emilk/egui/pull/2412)).
 * Improved the algorithm for picking the number of decimals to show when hovering values in the `Plot`.
 * Default `ComboBox` is now controlled with `Spacing::combo_width` ([#2621](https://github.com/emilk/egui/pull/2621)).
 * `DragValue` and `Slider` now use the proportional font ([#2638](https://github.com/emilk/egui/pull/2638)).
+* `ScrollArea` is less aggressive about clipping its contents ([#2665](https://github.com/emilk/egui/pull/2665)).
 
 ### Fixed 🐛
 * Trigger `PointerEvent::Released` for drags ([#2507](https://github.com/emilk/egui/pull/2507)).

crates/egui/src/containers/scroll_area.rs

@@ -426,15 +426,34 @@ impl ScrollArea {
 
         let content_max_rect = Rect::from_min_size(inner_rect.min - state.offset, content_max_size);
         let mut content_ui = ui.child_ui(content_max_rect, *ui.layout());
-        let mut content_clip_rect = inner_rect.expand(ui.visuals().clip_rect_margin);
+
-        content_clip_rect = content_clip_rect.intersect(ui.clip_rect());
+        {
-        // Nice handling of forced resizing beyond the possible:
+            // Clip the content, but only when we really need to:
-        for d in 0..2 {
+            let clip_rect_margin = ui.visuals().clip_rect_margin;
-            if !has_bar[d] {
+            let scroll_bar_inner_margin = ui.spacing().scroll_bar_inner_margin;
-                content_clip_rect.max[d] = ui.clip_rect().max[d] - current_bar_use[d];
+            let mut content_clip_rect = ui.clip_rect();
+            for d in 0..2 {
+                if has_bar[d] {
+                    if state.content_is_too_large[d] {
+                        content_clip_rect.min[d] = inner_rect.min[d] - clip_rect_margin;
+                        content_clip_rect.max[d] = inner_rect.max[d] + clip_rect_margin;
+                    }
+
+                    if state.show_scroll[d] {
+                        // Make sure content doesn't cover scroll bars
+                        let tiny_gap = 1.0;
+                        content_clip_rect.max[1 - d] =
+                            inner_rect.max[1 - d] + scroll_bar_inner_margin - tiny_gap;
+                    }
+                } else {
+                    // Nice handling of forced resizing beyond the possible:
+                    content_clip_rect.max[d] = ui.clip_rect().max[d] - current_bar_use[d];
+                }
             }
+            // Make sure we din't accidentally expand the clip rect
+            content_clip_rect = content_clip_rect.intersect(ui.clip_rect());
+            content_ui.set_clip_rect(content_clip_rect);
         }
-        content_ui.set_clip_rect(content_clip_rect);
 
         let viewport = Rect::from_min_size(Pos2::ZERO + state.offset, inner_size);
 
@@ -822,7 +841,7 @@ impl Prepared {
                         ),
                     )
                 };
-                let min_handle_size = ui.spacing().scroll_bar_width;
+                let min_handle_size = ui.spacing().scroll_handle_min_length;
                 if handle_rect.size()[d] < min_handle_size {
                     handle_rect = Rect::from_center_size(
                         handle_rect.center(),

crates/egui/src/style.rs

@@ -300,6 +300,9 @@ pub struct Spacing {
 
     pub scroll_bar_width: f32,
 
+    /// Make sure the scroll handle is at least this big
+    pub scroll_handle_min_length: f32,
+
     /// Margin between contents and scroll bar.
     pub scroll_bar_inner_margin: f32,
     /// Margin between scroll bar and the outer container (e.g. right of a vertical scroll bar).
@@ -713,6 +716,7 @@ impl Default for Spacing {
             tooltip_width: 600.0,
             combo_height: 200.0,
             scroll_bar_width: 8.0,
+            scroll_handle_min_length: 12.0,
             scroll_bar_inner_margin: 4.0,
             scroll_bar_outer_margin: 0.0,
             indent_ends_with_horizontal_line: false,
@@ -1040,6 +1044,7 @@ impl Spacing {
             indent_ends_with_horizontal_line,
             combo_height,
             scroll_bar_width,
+            scroll_handle_min_length,
             scroll_bar_inner_margin,
             scroll_bar_outer_margin,
         } = self;
@@ -1072,6 +1077,10 @@ impl Spacing {
             ui.add(DragValue::new(scroll_bar_width).clamp_range(0.0..=32.0));
             ui.label("Scroll-bar width");
         });
+        ui.horizontal(|ui| {
+            ui.add(DragValue::new(scroll_handle_min_length).clamp_range(0.0..=32.0));
+            ui.label("Scroll-bar handle min length");
+        });
         ui.horizontal(|ui| {
             ui.add(DragValue::new(scroll_bar_inner_margin).clamp_range(0.0..=32.0));
             ui.label("Scroll-bar inner margin");

crates/egui/src/widgets/separator.rs

@@ -14,6 +14,7 @@ use crate::*;
 #[must_use = "You should put this widget in an ui with `ui.add(widget);`"]
 pub struct Separator {
     spacing: f32,
+    grow: f32,
     is_horizontal_line: Option<bool>,
 }
 
@@ -21,6 +22,7 @@ impl Default for Separator {
     fn default() -> Self {
         Self {
             spacing: 6.0,
+            grow: 0.0,
             is_horizontal_line: None,
         }
     }
@@ -28,12 +30,19 @@ impl Default for Separator {
 
 impl Separator {
     /// How much space we take up. The line is painted in the middle of this.
+    ///
+    /// In a vertical layout, with a horizontal Separator,
+    /// this is the height of the separator widget.
+    ///
+    /// In a horizontal layout, with a vertical Separator,
+    /// this is the width of the separator widget.
     pub fn spacing(mut self, spacing: f32) -> Self {
         self.spacing = spacing;
         self
     }
 
     /// Explicitly ask for a horizontal line.
+    ///
     /// By default you will get a horizontal line in vertical layouts,
     /// and a vertical line in horizontal layouts.
     pub fn horizontal(mut self) -> Self {
@@ -42,18 +51,40 @@ impl Separator {
     }
 
     /// Explicitly ask for a vertical line.
+    ///
     /// By default you will get a horizontal line in vertical layouts,
     /// and a vertical line in horizontal layouts.
     pub fn vertical(mut self) -> Self {
         self.is_horizontal_line = Some(false);
         self
     }
+
+    /// Extend each end of the separator line by this much.
+    ///
+    /// The default is to take up the available width/height of the parent.
+    ///
+    /// This will make the line extend outside the parent ui.
+    pub fn grow(mut self, extra: f32) -> Self {
+        self.grow += extra;
+        self
+    }
+
+    /// Contract each end of the separator line by this much.
+    ///
+    /// The default is to take up the available width/height of the parent.
+    ///
+    /// This effectively adds margins to the line.
+    pub fn shrink(mut self, shrink: f32) -> Self {
+        self.grow -= shrink;
+        self
+    }
 }
 
 impl Widget for Separator {
     fn ui(self, ui: &mut Ui) -> Response {
         let Separator {
             spacing,
+            grow,
             is_horizontal_line,
         } = self;
 
@@ -75,14 +106,14 @@ impl Widget for Separator {
             let painter = ui.painter();
             if is_horizontal_line {
                 painter.hline(
-                    rect.x_range(),
+                    (rect.left() - grow)..=(rect.right() + grow),
                     painter.round_to_pixel(rect.center().y),
                     stroke,
                 );
             } else {
                 painter.vline(
                     painter.round_to_pixel(rect.center().x),
-                    rect.y_range(),
+                    (rect.top() - grow)..=(rect.bottom() + grow),
                     stroke,
                 );
             }

crates/egui_demo_lib/src/demo/window_with_panels.rs

@@ -85,6 +85,8 @@ fn lorem_ipsum(ui: &mut egui::Ui) {
         egui::Layout::top_down(egui::Align::LEFT).with_cross_justify(true),
         |ui| {
             ui.label(egui::RichText::new(crate::LOREM_IPSUM_LONG).small().weak());
+            ui.add(egui::Separator::default().grow(8.0));
+            ui.label(egui::RichText::new(crate::LOREM_IPSUM_LONG).small().weak());
         },
     );
 }

crates/egui_demo_lib/src/lib.rs

@@ -92,7 +92,8 @@ fn test_egui_zero_window_size() {
         let clipped_primitives = ctx.tessellate(full_output.shapes);
         assert!(
             clipped_primitives.is_empty(),
-            "There should be nothing to show"
+            "There should be nothing to show, has at least one primitive with clip_rect: {:?}",
+            clipped_primitives[0].clip_rect
         );
     }
 }