[librsvg] property_bag.rs: New function transform_or_none() to parse transformation matrixes

[Federico Mena Quintero <federico src gnome org>]

commit 24d736b58569b4af756f0613c8785e418bc4b65d
Author: Federico Mena Quintero <federico gnome org>
Date:   Mon May 22 07:49:55 2017 -0500

    property_bag.rs: New function transform_or_none() to parse transformation matrixes

 rust/src/property_bag.rs |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)
---
diff --git a/rust/src/property_bag.rs b/rust/src/property_bag.rs
index 87d432c..4fa07a1 100644
--- a/rust/src/property_bag.rs
+++ b/rust/src/property_bag.rs
@@ -4,10 +4,13 @@ extern crate glib;
 use std::str::FromStr;
 
 use self::glib::translate::*;
+use ::cairo;
+use ::cairo::MatrixTrait;
 
 use error::*;
 use length::*;
 use parsers::ParseError;
+use transform::*;
 
 pub enum RsvgPropertyBag {}
 
@@ -105,3 +108,13 @@ pub fn parse_or_value<T> (pbag: *const RsvgPropertyBag, key: &'static str, value
         Err (e)       => Err (e)
     }
 }
+
+pub fn transform_or_none (pbag: *const RsvgPropertyBag, key: &'static str) -> Result <Option<cairo::Matrix>, 
NodeError> {
+    if let Some (s) = lookup (pbag, key) {
+        parse_transform (&s)
+            .map (|v| Some (v))
+            .map_err (|e| NodeError::attribute_error (key, e))
+    } else {
+        Ok (None)
+    }
+}