[librsvg: 5/8] Restrict elements that can be reference from Use inside a clipPath

[Federico Mena Quintero <federico src gnome org>]

commit e08ad08c2855f7d36d8c5880e24dcb0f05540453
Author: Federico Mena Quintero <federico gnome org>
Date:   Tue Jun 1 20:47:20 2021 -0500

    Restrict elements that can be reference from Use inside a clipPath

 src/drawing_ctx.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
---
diff --git a/src/drawing_ctx.rs b/src/drawing_ctx.rs
index 01a9ae81..d7bc5e6e 100644
--- a/src/drawing_ctx.rs
+++ b/src/drawing_ctx.rs
@@ -1581,6 +1581,10 @@ impl DrawingCtx {
 
         let child = acquired.get();
 
+        if clipping && !element_can_be_used_inside_use_inside_clip_path(&child.borrow_element()) {
+            return Ok(self.empty_bbox());
+        }
+
         let orig_transform = self.get_transform();
 
         self.cr
@@ -1685,6 +1689,22 @@ fn element_can_be_used_inside_clip_path(element: &Element) -> bool {
     }
 }
 
+// https://www.w3.org/TR/css-masking-1/#ClipPathElement
+fn element_can_be_used_inside_use_inside_clip_path(element: &Element) -> bool {
+    match *element {
+        Element::Circle(_)
+        | Element::Ellipse(_)
+        | Element::Line(_)
+        | Element::Path(_)
+        | Element::Polygon(_)
+        | Element::Polyline(_)
+        | Element::Rect(_)
+        | Element::Text(_) => true,
+
+        _ => false,
+    }
+}
+
 #[derive(Debug)]
 struct CompositingAffines {
     pub outside_temporary_surface: Transform,