Fix path fitting

Include the stroke width in the boundaries when fitting a path into the
size of a `Path` element.

sixtyfps_runtime/corelib/items.rs

@@ -25,6 +25,7 @@ When adding an item or a property, it needs to be kept in sync with different pl
 #![allow(missing_docs)] // because documenting each property of items is redundent
 
 use crate::component::ComponentVTable;
+use crate::graphics::PathDataIterator;
 use crate::graphics::{Brush, Color, PathData, Point, Rect, Size};
 use crate::input::{
     FocusEvent, InputEventResult, KeyEvent, KeyEventResult, KeyEventType, MouseEvent,
@@ -600,6 +601,22 @@ impl Item for Path {
     }
 }
 
+impl Path {
+    /// Returns an iterator of the events of the path and an offset, so that the
+    /// shape fits into the width/height of the path while respecting the stroke
+    /// width.
+    pub fn fitted_path_events(
+        self: Pin<&Self>,
+    ) -> (euclid::default::Vector2D<f32>, PathDataIterator) {
+        let stroke_width = self.stroke_width();
+        let bounds_width = (self.width() - stroke_width).max(0.);
+        let bounds_height = (self.height() - stroke_width).max(0.);
+        let offset = euclid::default::Vector2D::new(stroke_width / 2., stroke_width / 2.);
+        let event_iterator = self.elements().iter_fitted(bounds_width, bounds_height);
+        (offset, event_iterator)
+    }
+}
+
 impl ItemConsts for Path {
     const cached_rendering_data_offset: const_field_offset::FieldOffset<Path, CachedRenderingData> =
         Path::FIELD_OFFSETS.cached_rendering_data.as_unpinned_projection();

sixtyfps_runtime/rendering_backends/gl/lib.rs

@@ -954,8 +954,11 @@ impl ItemRenderer for GLItemRenderer {
         if matches!(elements, sixtyfps_corelib::PathData::None) {
             return;
         }
+
+        let (offset, path_events) = path.fitted_path_events();
+
         let mut fpath = femtovg::Path::new();
-        for x in elements.iter_fitted(path.width(), path.height()).iter() {
+        for x in path_events.iter() {
             match x {
                 lyon_path::Event::Begin { at } => {
                     fpath.move_to(at.x, at.y);
@@ -983,7 +986,7 @@ impl ItemRenderer for GLItemRenderer {
         border_paint.set_line_width(path.stroke_width());
 
         self.shared_data.canvas.borrow_mut().save_with(|canvas| {
-            canvas.translate(pos.x + path.x(), pos.y + path.y());
+            canvas.translate(pos.x + path.x() + offset.x, pos.y + path.y() + offset.y);
             canvas.fill_path(&mut fpath, fill_paint);
             canvas.stroke_path(&mut fpath, border_paint);
         })

sixtyfps_runtime/rendering_backends/qt/qt_window.rs

@@ -372,12 +372,16 @@ impl ItemRenderer for QtItemRenderer<'_> {
         }
         // FIXME: handle width/height
         //let rect: qttypes::QRectF = get_geometry!(pos, items::Path, path);
-        let pos = qttypes::QPoint { x: (pos.x + path.x()) as _, y: (pos.y + path.y()) as _ };
         let fill_brush: qttypes::QBrush = path.fill().into();
         let stroke_brush: qttypes::QBrush = path.stroke().into();
         let stroke_width: f32 = path.stroke_width();
+        let (offset, path_events) = path.fitted_path_events();
+        let pos = qttypes::QPoint {
+            x: (pos.x + path.x() + offset.x) as _,
+            y: (pos.y + path.y() + offset.y) as _,
+        };
         let mut painter_path = QPainterPath::default();
-        for x in elements.iter_fitted(path.width(), path.height()).iter() {
+        for x in path_events.iter() {
             impl From<Point> for qttypes::QPointF {
                 fn from(p: Point) -> Self {
                     qttypes::QPointF { x: p.x as _, y: p.y as _ }