[librsvg: 2/4] pattern: Don't panic when trying to resolve with an empty bounding box

[Marge Bot <marge-bot src gnome org>]

commit f9e15ff9a85b3e0b02f31b6297295b38a70d36c0
Author: Federico Mena Quintero <federico gnome org>
Date:   Thu Nov 11 17:46:21 2021 -0600

    pattern: Don't panic when trying to resolve with an empty bounding box
    
    This got triggered from DrawingCtx::with_discrete_layer(), where it
    tries to resolve the paint servers to pass on to the filters code.
    
    Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/631>

 src/pattern.rs                                           |  7 ++++++-
 tests/fixtures/render-crash/gradient-with-empty-bbox.svg | 14 ++++++++++++++
 tests/fixtures/render-crash/pattern-with-empty-bbox.svg  | 16 ++++++++++++++++
 tests/src/render_crash.rs                                |  2 +-
 4 files changed, 37 insertions(+), 2 deletions(-)
---
diff --git a/src/pattern.rs b/src/pattern.rs
index 96778e401..5d887266d 100644
--- a/src/pattern.rs
+++ b/src/pattern.rs
@@ -337,7 +337,12 @@ impl ResolvedPattern {
         let params = NormalizeParams::new(values, &view_params);
 
         let rect = self.get_rect(&params);
-        let bbrect = bbox.rect.unwrap();
+
+        let bbrect = match bbox.rect {
+            None => return None,
+            Some(r) if r.is_empty() => return None,
+            Some(r) => r,
+        };
 
         // Create the pattern coordinate system
         let (width, height, coord_transform) = match self.units {
diff --git a/tests/fixtures/render-crash/gradient-with-empty-bbox.svg 
b/tests/fixtures/render-crash/gradient-with-empty-bbox.svg
new file mode 100644
index 000000000..d98b5cfb3
--- /dev/null
+++ b/tests/fixtures/render-crash/gradient-with-empty-bbox.svg
@@ -0,0 +1,14 @@
+<svg width="400" height="400" xmlns="http://www.w3.org/2000/svg";>
+  <defs>
+    <linearGradient id="grad1">
+    </linearGradient>
+    <radialGradient id="grad2">
+    </radialGradient>
+  </defs>
+
+  <!-- Use an empty group with a filter, so it will try to resolve the stroke/fill paint servers.
+       Since the group has no children, the paint servers will get an empty bbox.
+  -->
+  <g fill="url(#grad1)" filter="opacity(0.5)"/>
+  <g fill="url(#grad2)" filter="opacity(0.5)"/>
+</svg>
diff --git a/tests/fixtures/render-crash/pattern-with-empty-bbox.svg 
b/tests/fixtures/render-crash/pattern-with-empty-bbox.svg
new file mode 100644
index 000000000..8ffa7daf4
--- /dev/null
+++ b/tests/fixtures/render-crash/pattern-with-empty-bbox.svg
@@ -0,0 +1,16 @@
+<svg width="400" height="400" xmlns="http://www.w3.org/2000/svg";>
+  <defs>
+    <pattern id="pat1" patternUnits="objectBoundingBox">
+      <circle cx="5" cy="5" r="5" fill="lime"/>
+    </pattern>
+    <pattern id="pat2" patternUnits="userSpaceOnUse">
+      <circle cx="5" cy="5" r="5" fill="lime"/>
+    </pattern>
+  </defs>
+
+  <!-- Use an empty group with a filter, so it will try to resolve the stroke/fill paint servers.
+       Since the group has no children, the paint servers will get an empty bbox.
+  -->
+  <g fill="url(#pat1)" filter="opacity(0.5)"/>
+  <g fill="url(#pat2)" filter="opacity(0.5)"/>
+</svg>
diff --git a/tests/src/render_crash.rs b/tests/src/render_crash.rs
index ce8dfc72b..f89285d32 100644
--- a/tests/src/render_crash.rs
+++ b/tests/src/render_crash.rs
@@ -10,7 +10,7 @@ use cairo;
 use librsvg::{CairoRenderer, Loader};
 
 #[test_resources("tests/fixtures/render-crash/*.svg")]
-fn loading_crash(path: &str) {
+fn render_crash(path: &str) {
     let handle = Loader::new()
         .read_path(path)
         .unwrap_or_else(|e| panic!("could not load: {}", e));