disable covers_opaque optimization for images

hui/src/frame/impls.rs

@@ -16,8 +16,9 @@ impl Frame for ImageHandle {
       rounded_corners: None,
     })
   }
+
   fn covers_opaque(&self) -> bool {
-    true
+    false
   }
 }
 
@@ -31,6 +32,7 @@ impl Frame for FillColor {
       rounded_corners: None,
     })
   }
+
   fn covers_opaque(&self) -> bool {
     self.is_opaque()
   }

hui/src/frame/rect.rs

@@ -139,6 +139,7 @@ impl Frame for FrameRect {
     self.bottom_right.x.relative >= 1. &&
     self.bottom_right.y.absolute >= 0. &&
     self.bottom_right.y.relative >= 1. &&
-    self.color.is_opaque()
+    self.color.is_opaque() &&
+    self.image.is_none()
   }
 }