fix draw_filled_rect panic for empty image

src/drawing/rect.rs

@@ -52,12 +52,17 @@ pub fn draw_filled_rect_mut<C>(canvas: &mut C, rect: Rect, color: C::Pixel)
 where
     C: Canvas,
 {
+    if canvas.width() == 0 || canvas.height() == 0 {
+        return;
+    }
     let canvas_bounds = Rect::at(0, 0).of_size(canvas.width(), canvas.height());
     if let Some(intersection) = canvas_bounds.intersect(rect) {
         for dy in 0..intersection.height() {
             for dx in 0..intersection.width() {
                 let x = intersection.left() as u32 + dx;
                 let y = intersection.top() as u32 + dy;
+                debug_assert!(x < canvas.width());
+                debug_assert!(y < canvas.height());
                 canvas.draw_pixel(x, y, color);
             }
         }
@@ -139,6 +144,31 @@ mod tests {
     }
 }
 
+#[cfg(not(miri))]
+#[cfg(test)]
+mod proptests {
+    use super::*;
+    use crate::{proptest_utils::arbitrary_image, rect::Rect};
+    use image::Luma;
+    use proptest::prelude::*;
+
+    proptest! {
+        #[test]
+        fn proptest_draw_filled_rect_luma(
+            image in arbitrary_image::<Luma<u8>>(0..50, 0..50),
+            (x, y) in (-50..50, -50..50),
+            (w, h) in (1..50u32, 1..50u32),
+            color in 0..255u8,
+        ) {
+            let rect = Rect::at(x, y).of_size(w, h);
+            let color = Luma([color]);
+
+            let out = draw_filled_rect(&image, rect, color);
+            assert_eq!(out.dimensions(), image.dimensions());
+        }
+    }
+}
+
 #[cfg(not(miri))]
 #[cfg(test)]
 mod benches {

src/rect.rs

@@ -1,7 +1,5 @@
 //! Basic manipulation of rectangles.
 
-use std::cmp;
-
 /// A rectangular region of non-zero width and height.
 /// # Examples
 /// ```
@@ -62,14 +60,14 @@ impl Rect {
     ///
     /// See the [struct-level documentation](Rect) for examples.
     pub fn bottom(&self) -> i32 {
-        self.top + (self.height as i32) - 1
+        self.top + i32::try_from(self.height).unwrap() - 1
     }
 
     /// Greatest x-coordinate reached by rect.
     ///
     /// See the [struct-level documentation](Rect) for examples.
     pub fn right(&self) -> i32 {
-        self.left + (self.width as i32) - 1
+        self.left + i32::try_from(self.width).unwrap() - 1
     }
 
     /// Width of rect.
@@ -105,21 +103,18 @@ impl Rect {
     /// assert_eq!(r.intersect(s), None);
     /// ```
     pub fn intersect(&self, other: Rect) -> Option<Rect> {
-        let left = cmp::max(self.left, other.left);
-        let top = cmp::max(self.top, other.top);
-        let right = cmp::min(self.right(), other.right());
-        let bottom = cmp::min(self.bottom(), other.bottom());
+        let left = self.left.max(other.left);
+        let top = self.top.max(other.top);
+        let right = self.right().min(other.right());
+        let bottom = self.bottom().min(other.bottom());
 
         if right < left || bottom < top {
             return None;
         }
 
-        Some(Rect {
-            left,
-            top,
-            width: (right - left) as u32 + 1,
-            height: (bottom - top) as u32 + 1,
-        })
+        let width = u32::try_from(right - left).unwrap() + 1;
+        let height = u32::try_from(bottom - top).unwrap() + 1;
+        Some(Rect::at(left, top).of_size(width, height))
     }
 }
 
@@ -189,3 +184,29 @@ mod tests {
         assert!(!r.contains(10.1f32, 10f32));
     }
 }
+
+#[cfg(not(miri))]
+#[cfg(test)]
+mod proptests {
+    use super::*;
+    use proptest::prelude::*;
+
+    proptest! {
+        #[test]
+        fn proptest_intersect(
+            (x1, y1) in (-50..50, -50..50),
+            (w1, h1) in (1..50u32, 1..50u32),
+
+            (x2, y2) in (-50..50, -50..50),
+            (w2, h2) in (1..50u32, 1..50u32),
+        ) {
+            let rect1 = Rect::at(x1, y1).of_size(w1, h1);
+            let rect2 = Rect::at(x2, y2).of_size(w2, h2);
+
+            if let Some(intersect) = rect1.intersect(rect2) {
+                assert!(intersect.width() > 0);
+                assert!(intersect.height() > 0);
+            };
+        }
+    }
+}