Add Painter::hline and Painter::vline

CHANGELOG.md

@@ -13,6 +13,7 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui_w
 * Added `Plot::allow_scroll`, `Plot::allow_zoom` no longer affects scrolling ([#1382](https://github.com/emilk/egui/pull/1382)).
 * Added `Ui::push_id` to resolve id clashes ([#1374](https://github.com/emilk/egui/pull/1374)).
 * Added `Frame::outer_margin`.
+* Added `Painter::hline` and `Painter::vline`.
 
 ### Changed 🔧
 * `ClippedMesh` has been replaced with `ClippedPrimitive` ([#1351](https://github.com/emilk/egui/pull/1351)).

egui/src/containers/panel.rs

@@ -273,11 +273,9 @@ impl SidePanel {
             // draw on top of ALL panels so that the resize line won't be covered by subsequent panels
             let resize_layer = LayerId::new(Order::Foreground, Id::new("panel_resize"));
             let resize_x = side.opposite().side_x(rect);
-            let top = pos2(resize_x, rect.top());
-            let bottom = pos2(resize_x, rect.bottom());
             ui.ctx()
                 .layer_painter(resize_layer)
-                .line_segment([top, bottom], stroke);
+                .vline(resize_x, rect.y_range(), stroke);
         }
 
         inner_response
@@ -560,11 +558,9 @@ impl TopBottomPanel {
             // draw on top of ALL panels so that the resize line won't be covered by subsequent panels
             let resize_layer = LayerId::new(Order::Foreground, Id::new("panel_resize"));
             let resize_y = side.opposite().side_y(rect);
-            let left = pos2(rect.left(), resize_y);
-            let right = pos2(rect.right(), resize_y);
             ui.ctx()
                 .layer_painter(resize_layer)
-                .line_segment([left, right], stroke);
+                .hline(rect.x_range(), resize_y, stroke);
         }
 
         inner_response

egui/src/containers/window.rs

@@ -882,14 +882,10 @@ impl TitleBar {
 
         if let Some(content_response) = &content_response {
             // paint separator between title and content:
-            let left = outer_rect.left();
-            let right = outer_rect.right();
             let y = content_response.rect.top() + ui.spacing().item_spacing.y * 0.5;
             // let y = lerp(self.rect.bottom()..=content_response.rect.top(), 0.5);
-            ui.painter().line_segment(
-                [pos2(left, y), pos2(right, y)],
-                ui.visuals().widgets.noninteractive.bg_stroke,
-            );
+            let stroke = ui.visuals().widgets.noninteractive.bg_stroke;
+            ui.painter().hline(outer_rect.x_range(), y, stroke);
         }
 
         if ui

egui/src/painter.rs

@@ -1,5 +1,7 @@
+use std::ops::RangeInclusive;
+
 use crate::{
-    emath::{Align2, Pos2, Rect, Vec2},
+    emath::{pos2, Align2, Pos2, Rect, Vec2},
     layers::{LayerId, PaintList, ShapeIdx},
     Color32, Context, FontId,
 };
@@ -233,8 +235,7 @@ impl Painter {
 
 /// # Paint different primitives
 impl Painter {
-    /// Paints the line from the first point to the second using the `stroke`
-    /// for outlining shape.
+    /// Paints a line from the first point to the second.
     pub fn line_segment(&self, points: [Pos2; 2], stroke: impl Into<Stroke>) {
         self.add(Shape::LineSegment {
             points,
@@ -242,6 +243,22 @@ impl Painter {
         });
     }
 
+    /// Paints a horizontal line.
+    pub fn hline(&self, x: RangeInclusive<f32>, y: f32, stroke: impl Into<Stroke>) {
+        self.add(Shape::LineSegment {
+            points: [pos2(*x.start(), y), pos2(*x.end(), y)],
+            stroke: stroke.into(),
+        });
+    }
+
+    /// Paints a vertical line.
+    pub fn vline(&self, x: f32, y: RangeInclusive<f32>, stroke: impl Into<Stroke>) {
+        self.add(Shape::LineSegment {
+            points: [pos2(x, *y.start()), pos2(x, *y.end())],
+            stroke: stroke.into(),
+        });
+    }
+
     pub fn circle(
         &self,
         center: Pos2,

egui/src/widgets/separator.rs

@@ -71,19 +71,12 @@ impl Widget for Separator {
         let (rect, response) = ui.allocate_at_least(size, Sense::hover());
 
         if ui.is_rect_visible(response.rect) {
-            let points = if is_horizontal_line {
-                [
-                    pos2(rect.left(), rect.center().y),
-                    pos2(rect.right(), rect.center().y),
-                ]
-            } else {
-                [
-                    pos2(rect.center().x, rect.top()),
-                    pos2(rect.center().x, rect.bottom()),
-                ]
-            };
             let stroke = ui.visuals().widgets.noninteractive.bg_stroke;
-            ui.painter().line_segment(points, stroke);
+            if is_horizontal_line {
+                ui.painter().hline(rect.x_range(), rect.center().y, stroke);
+            } else {
+                ui.painter().vline(rect.center().x, rect.y_range(), stroke);
+            }
         }
 
         response