Require a StrokeKind when painting rectangles with strokes (#5648)

This is a breaking change, requiring users to think about wether the
stroke is inside/centered/outside the rect.

When in doubt, add `egui::StrokeKind::Inside` to the function call.

crates/egui_demo_lib/src/demo/misc_demo_window.rs

@@ -390,6 +390,7 @@ impl BoxPainting {
                     self.rounding,
                     ui.visuals().text_color().gamma_multiply(0.5),
                     Stroke::new(self.stroke_width, Color32::WHITE),
+                    egui::StrokeKind::Inside,
                 );
             }
         });

crates/egui_demo_lib/src/demo/paint_bezier.rs

@@ -1,6 +1,7 @@
-use egui::epaint::{CubicBezierShape, PathShape, QuadraticBezierShape};
 use egui::{
-    emath, epaint, pos2, Color32, Context, Frame, Grid, Pos2, Rect, Sense, Shape, Stroke, Ui, Vec2,
+    emath,
+    epaint::{self, CubicBezierShape, PathShape, QuadraticBezierShape},
+    pos2, Color32, Context, Frame, Grid, Pos2, Rect, Sense, Shape, Stroke, StrokeKind, Ui, Vec2,
     Widget, Window,
 };
 
@@ -132,6 +133,7 @@ impl PaintBezier {
                     shape.visual_bounding_rect(),
                     0.0,
                     self.bounding_box_stroke,
+                    StrokeKind::Outside,
                 ));
                 painter.add(shape);
             }
@@ -143,6 +145,7 @@ impl PaintBezier {
                     shape.visual_bounding_rect(),
                     0.0,
                     self.bounding_box_stroke,
+                    StrokeKind::Outside,
                 ));
                 painter.add(shape);
             }

crates/egui_demo_lib/src/demo/toggle_switch.rs

@@ -56,8 +56,13 @@ pub fn toggle_ui(ui: &mut egui::Ui, on: &mut bool) -> egui::Response {
         // All coordinates are in absolute screen coordinates so we use `rect` to place the elements.
         let rect = rect.expand(visuals.expansion);
         let radius = 0.5 * rect.height();
-        ui.painter()
-            .rect(rect, radius, visuals.bg_fill, visuals.bg_stroke);
+        ui.painter().rect(
+            rect,
+            radius,
+            visuals.bg_fill,
+            visuals.bg_stroke,
+            egui::StrokeKind::Inside,
+        );
         // Paint the circle, animating it from left to right with `how_on`:
         let circle_x = egui::lerp((rect.left() + radius)..=(rect.right() - radius), how_on);
         let center = egui::pos2(circle_x, rect.center().y);
@@ -88,8 +93,13 @@ fn toggle_ui_compact(ui: &mut egui::Ui, on: &mut bool) -> egui::Response {
         let visuals = ui.style().interact_selectable(&response, *on);
         let rect = rect.expand(visuals.expansion);
         let radius = 0.5 * rect.height();
-        ui.painter()
-            .rect(rect, radius, visuals.bg_fill, visuals.bg_stroke);
+        ui.painter().rect(
+            rect,
+            radius,
+            visuals.bg_fill,
+            visuals.bg_stroke,
+            egui::StrokeKind::Inside,
+        );
         let circle_x = egui::lerp((rect.left() + radius)..=(rect.right() - radius), how_on);
         let center = egui::pos2(circle_x, rect.center().y);
         ui.painter()

crates/egui_demo_lib/src/rendering_test.rs

@@ -452,7 +452,12 @@ fn pixel_test_strokes(ui: &mut Ui) {
                 Pos2::new(cursor_pixel.x, cursor_pixel.y),
                 Vec2::splat(size as f32),
             );
-            painter.rect_stroke(rect_points / pixels_per_point, 0.0, stroke);
+            painter.rect_stroke(
+                rect_points / pixels_per_point,
+                0.0,
+                stroke,
+                egui::StrokeKind::Outside,
+            );
             cursor_pixel.x += (1 + size) as f32 + thickness_pixels * 2.0;
         }
     }