[librsvg] (#590): Fix regression when rendering masks

[Federico Mena Quintero <federico src gnome org>]

commit 38602be9f484d2e24ad1b360e72b6caec5c9759a
Author: Federico Mena Quintero <federico gnome org>
Date:   Thu Apr 23 11:24:08 2020 -0500

    (#590): Fix regression when rendering masks
    
    There was a cut&paste error in Mask::get_units().  I'm not sure why
    the test suite didn't catch this; maybe we don't have a test with the
    defaults for maskUnits and maskContentUnits?
    
    Fixes https://gitlab.gnome.org/GNOME/librsvg/-/issues/590

 rsvg_internals/src/structure.rs                    |   2 +-
 .../fixtures/reftests/bugs/590-mask-units-ref.png  | Bin 0 -> 2701 bytes
 tests/fixtures/reftests/bugs/590-mask-units.svg    |  26 +++++++++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)
---
diff --git a/rsvg_internals/src/structure.rs b/rsvg_internals/src/structure.rs
index d1325bbb..3d3ff469 100644
--- a/rsvg_internals/src/structure.rs
+++ b/rsvg_internals/src/structure.rs
@@ -427,7 +427,7 @@ impl Default for Mask {
 
 impl Mask {
     pub fn get_units(&self) -> CoordUnits {
-        CoordUnits::from(self.content_units)
+        CoordUnits::from(self.units)
     }
 
     pub fn get_content_units(&self) -> CoordUnits {
diff --git a/tests/fixtures/reftests/bugs/590-mask-units-ref.png 
b/tests/fixtures/reftests/bugs/590-mask-units-ref.png
new file mode 100644
index 00000000..3647c930
Binary files /dev/null and b/tests/fixtures/reftests/bugs/590-mask-units-ref.png differ
diff --git a/tests/fixtures/reftests/bugs/590-mask-units.svg b/tests/fixtures/reftests/bugs/590-mask-units.svg
new file mode 100644
index 00000000..14e2e719
--- /dev/null
+++ b/tests/fixtures/reftests/bugs/590-mask-units.svg
@@ -0,0 +1,26 @@
+<svg preserveAspectRatio="xMidYMid" viewBox="-70 -100 140 200" xmlns="http://www.w3.org/2000/svg"; 
xmlns:xlink="http://www.w3.org/1999/xlink";>
+  <defs>
+    <!-- A square mask -->
+    <mask id="square-mask">
+      <rect fill="#ffffff" height="49" stroke="none" width="49" x="-49" y="24.5"/>
+    </mask>
+  </defs>
+  <g fill="none" stroke="#292d2f" stroke-width="0.14">
+    <!-- Black background rectangle -->
+    <rect fill="#292d2f" height="200" stroke="#292d2f" width="140" x="-70" y="-100"/>
+    
+    <!-- Draw a filled white circle and apply a square mask to only show the bottom left 90 degree arc -->
+    <g mask="url(#square-mask)">
+      <g fill="#ffffff" stroke="none" transform="matrix(-1.8369701987210297e-16 -1 1 -1.8369701987210297e-16 
-24.5 49)">
+        <circle cx="24.5" cy="24.5" r="49"/>
+      </g>
+    </g>
+    
+    <!-- Magenta outline of the square mask -->
+    <rect stroke="#ff00ff" height="49" fill="none" width="49" x="-49" y="24.5"/>
+    <!-- Yellow outline of the entire circle to mask -->
+    <g fill="none" stroke="#ffff00" transform="matrix(-1.8369701987210297e-16 -1 1 -1.8369701987210297e-16 
-24.5 49)">
+      <circle cx="24.5" cy="24.5" r="49" />
+    </g>
+  </g>
+</svg>