[librsvg: 58/90] New test for masking to a viewport offsetted by a transformation

[Federico Mena Quintero <federico src gnome org>]

commit 8dc1cd13fbc76ad88e849813970f09d081eeb6f4
Author: Federico Mena Quintero <federico gnome org>
Date:   Wed Mar 20 10:05:01 2019 -0600

    New test for masking to a viewport offsetted by a transformation

 .../mask-on-transformed-viewport-200x200.png       | Bin 0 -> 1117 bytes
 librsvg_crate/tests/render_to_viewport.rs          |  65 +++++++++++++++++++++
 2 files changed, 65 insertions(+)
---
diff --git a/librsvg_crate/tests/fixtures/mask-on-transformed-viewport-200x200.png 
b/librsvg_crate/tests/fixtures/mask-on-transformed-viewport-200x200.png
new file mode 100644
index 00000000..2aa259d7
Binary files /dev/null and b/librsvg_crate/tests/fixtures/mask-on-transformed-viewport-200x200.png differ
diff --git a/librsvg_crate/tests/render_to_viewport.rs b/librsvg_crate/tests/render_to_viewport.rs
index 9092508a..5da9d09b 100644
--- a/librsvg_crate/tests/render_to_viewport.rs
+++ b/librsvg_crate/tests/render_to_viewport.rs
@@ -256,3 +256,68 @@ fn clip_on_transformed_viewport() {
         }
     }
 }
+
+#[test]
+fn mask_on_transformed_viewport() {
+    let svg = load_svg(
+        br##"<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg"; width="100" height="100">
+  <defs>
+    <mask id="one" maskContentUnits="objectBoundingBox">
+      <circle cx="0.5" cy="0.5" r="0.5" fill="white"/>
+    </mask>
+  </defs>
+  <g mask="url(#one)">
+    <rect x="10" y="10" width="40" height="40" fill="blue"/>
+    <rect x="50" y="50" width="40" height="40" fill="limegreen"/>
+  </g>
+</svg>
+"##,
+    );
+
+    let renderer = CairoRenderer::new(&svg);
+
+    let output = cairo::ImageSurface::create(cairo::Format::ARgb32, 200, 200).unwrap();
+
+    {
+        let cr = cairo::Context::new(&output);
+        cr.translate(50.0, 50.0);
+        renderer
+            .render_element_to_viewport(
+                &cr,
+                None,
+                &cairo::Rectangle {
+                    x: 0.0,
+                    y: 0.0,
+                    width: 100.0,
+                    height: 100.0,
+                },
+            )
+            .unwrap();
+    }
+
+    let mut output_file = File::create(Path::new("output.png")).unwrap();
+    output.write_to_png(&mut output_file).unwrap();
+
+    let output_surf = SharedImageSurface::new(output, SurfaceType::SRgb).unwrap();
+
+    let fixture_path = Path::new("tests/fixtures/mask-on-transformed-viewport-200x200.png");
+    let mut fixture_file = BufReader::new(File::open(fixture_path).unwrap());
+
+    let expected = cairo::ImageSurface::create_from_png(&mut fixture_file).unwrap();
+    let expected_surf = SharedImageSurface::new(expected, SurfaceType::SRgb).unwrap();
+
+    let diff = compare_surfaces(&output_surf, &expected_surf).unwrap();
+
+    match diff {
+        BufferDiff::DifferentSizes => unreachable!("surfaces should be of the same size"),
+
+        BufferDiff::Diff(diff) => {
+            let surf = diff.surface.into_image_surface().unwrap();
+            let mut output_file = File::create(Path::new("diff.png")).unwrap();
+            surf.write_to_png(&mut output_file).unwrap();
+
+            assert_eq!(diff.num_pixels_changed, 0);
+        }
+    }
+}