fix: backdrop filter capture size never goes below 0

src/renderer/passes.rs

@@ -850,8 +850,8 @@ fn resolve_capture_region_to_viewport(
     let overlap_right = capture_right.min(physical_size.0 as i32);
     let overlap_bottom = capture_bottom.min(physical_size.1 as i32);
 
-    let overlap_width = overlap_right.saturating_sub(overlap_left) as u32;
-    let overlap_height = overlap_bottom.saturating_sub(overlap_top) as u32;
+    let overlap_width = overlap_right.saturating_sub(overlap_left).max(0) as u32;
+    let overlap_height = overlap_bottom.saturating_sub(overlap_top).max(0) as u32;
     let has_overlap = overlap_width > 0 && overlap_height > 0;
 
     BackdropCaptureRegion {
@@ -1918,6 +1918,17 @@ mod tests {
         assert_eq!(region.copy_size, (30, 20));
     }
 
+    #[test]
+    fn capture_region_skips_copy_when_fully_offscreen() {
+        let offscreen_right = resolve_capture_region_to_viewport((110, 5, 20, 20), (100, 100));
+        let offscreen_bottom = resolve_capture_region_to_viewport((5, 110, 20, 20), (100, 100));
+
+        assert_eq!(offscreen_right.copy_source_origin, None);
+        assert_eq!(offscreen_right.copy_size, (0, 20));
+        assert_eq!(offscreen_bottom.copy_source_origin, None);
+        assert_eq!(offscreen_bottom.copy_size, (20, 0));
+    }
+
     #[test]
     fn inflate_logical_rect_expands_symmetrically() {
         let rect = inflate_logical_rect([(10.0, 20.0), (30.0, 40.0)], 5.0);

src/shape.rs

@@ -653,7 +653,7 @@ fn normalized_float_bits(value: f32) -> u32 {
 fn build_boundary_data(vertices: &[CustomVertex], indices: &[u16], scratch: &mut AaFringeScratch) {
     scratch.clear();
 
-    for (triangle_index, tri) in indices.chunks_exact(3).enumerate() {
+    for (triangle_index, tri) in indices.as_chunks::<3>().0.iter().enumerate() {
         let a = tri[0];
         let b = tri[1];
         let c = tri[2];