[librsvg: 1/6] float_eq_cairo: add an assertion macro

[Federico Mena Quintero <federico src gnome org>]

commit 569a15812a948150a7694f75ca1b2003f0bb94b6
Author: Paolo Borelli <pborelli gnome org>
Date:   Mon May 14 20:12:21 2018 +0200

    float_eq_cairo: add an assertion macro

 rsvg_internals/src/float_eq_cairo.rs | 30 +++++++++++++++++++++++++++++-
 rsvg_internals/src/lib.rs            |  4 +++-
 2 files changed, 32 insertions(+), 2 deletions(-)
---
diff --git a/rsvg_internals/src/float_eq_cairo.rs b/rsvg_internals/src/float_eq_cairo.rs
index 09bfc8d9..09351149 100644
--- a/rsvg_internals/src/float_eq_cairo.rs
+++ b/rsvg_internals/src/float_eq_cairo.rs
@@ -1,6 +1,7 @@
 use float_cmp::ApproxEq;
 
-// The following are copied from cairo/src/{cairo-fixed-private.h, cairo-fixed-type-private.h}
+// The following are copied from cairo/src/{cairo-fixed-private.h,
+// cairo-fixed-type-private.h}
 
 const CAIRO_FIXED_FRAC_BITS: u64 = 8;
 const CAIRO_MAGIC_NUMBER_FIXED: f64 = (1u64 << (52 - CAIRO_FIXED_FRAC_BITS)) as f64 * 1.5;
@@ -62,6 +63,22 @@ impl ApproxEqCairo for f64 {
     }
 }
 
+// Macro for usage in unit tests
+#[macro_export]
+macro_rules! assert_approx_eq_cairo {
+    ($left:expr, $right:expr) => ({
+        match (&$left, &$right) {
+            (l, r) => {
+                if !l.approx_eq_cairo(r) {
+                    panic!(r#"assertion failed: `(left == right)`
+  left: `{:?}`,
+ right: `{:?}`"#, l, r)
+                }
+            }
+        }
+    });
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -118,4 +135,15 @@ mod tests {
         assert!(9_007_199_254_740_992.0.approx_eq_cairo(&9_007_199_254_740_994.0));
         assert!(!9_007_199_254_740_992.0.approx_eq_cairo(&9_007_199_254_740_996.0));
     }
+
+    #[test]
+    fn assert_approx_eq_cairo_should_not_panic() {
+        assert_approx_eq_cairo!(42_f64, 42_f64);
+    }
+
+    #[test]
+    #[should_panic]
+    fn assert_approx_eq_cairo_should_panic() {
+        assert_approx_eq_cairo!(3_f64, 42_f64);
+    }
 }
diff --git a/rsvg_internals/src/lib.rs b/rsvg_internals/src/lib.rs
index 2333e32e..85194dcc 100644
--- a/rsvg_internals/src/lib.rs
+++ b/rsvg_internals/src/lib.rs
@@ -153,6 +153,9 @@ pub use viewbox::RsvgViewBox;
 #[macro_use]
 mod coord_units;
 
+#[macro_use]
+mod float_eq_cairo;
+
 #[macro_use]
 mod property_macros;
 
@@ -166,7 +169,6 @@ mod cond;
 mod draw;
 mod drawing_ctx;
 mod error;
-mod float_eq_cairo;
 mod gradient;
 mod handle;
 mod image;