[librsvg] aspect_ratio.rs: New function for the C code, rsvg_aspect_ratio_parse()

[Federico Mena Quintero <federico src gnome org>]

commit 0cde6ad587116931d6039936b42e893a9322d5b1
Author: Federico Mena Quintero <federico gnome org>
Date:   Wed Feb 1 14:33:17 2017 -0600

    aspect_ratio.rs: New function for the C code, rsvg_aspect_ratio_parse()

 rust/src/aspect_ratio.rs |   29 +++++++++++++++++++++++++++++
 rust/src/lib.rs          |    1 +
 2 files changed, 30 insertions(+), 0 deletions(-)
---
diff --git a/rust/src/aspect_ratio.rs b/rust/src/aspect_ratio.rs
index 33d52f0..5f8f5a8 100644
--- a/rust/src/aspect_ratio.rs
+++ b/rust/src/aspect_ratio.rs
@@ -15,6 +15,10 @@
 //! [`AspectRatio`]: struct.AspectRatio.html
 //! [spec]: https://www.w3.org/TR/SVG/coords.html#PreserveAspectRatioAttribute
 
+extern crate libc;
+extern crate glib;
+
+use self::glib::translate::*;
 
 use std::fmt;
 use std::str::FromStr;
@@ -62,6 +66,15 @@ impl Default for Align {
     }
 }
 
+impl Default for AspectRatio {
+    fn default () -> AspectRatio {
+        AspectRatio {
+            defer: false,
+            align: Default::default ()
+        }
+    }
+}
+
 bitflags! {
     flags AspectRatioFlags: u32 {
         const XMIN_YMIN = (1 << 0),
@@ -259,6 +272,22 @@ impl fmt::Display for ParseAspectRatioError {
     }
 }
 
+#[no_mangle]
+pub extern fn rsvg_aspect_ratio_parse (c_str: *const libc::c_char) -> u32 {
+    let my_str = unsafe { &String::from_glib_none (c_str) };
+    let parsed = AspectRatio::from_str (my_str);
+
+    match parsed {
+        Ok (aspect_ratio) => { aspect_ratio_to_u32 (aspect_ratio) },
+        Err (_) => {
+            // We can't propagate the error here, so just return a default value
+            let a: AspectRatio = Default::default ();
+            aspect_ratio_to_u32 (a)
+        }
+    }
+}
+
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/rust/src/lib.rs b/rust/src/lib.rs
index 32da440..e643d81 100644
--- a/rust/src/lib.rs
+++ b/rust/src/lib.rs
@@ -7,6 +7,7 @@ pub use aspect_ratio::{
     Align,
     AspectRatio,
     ParseAspectRatioError,
+    rsvg_aspect_ratio_parse
 };
 
 pub use bbox::{