[librsvg] paint_server.rs: New file with a PaintServerUnits enum

[Federico Mena Quintero <federico src gnome org>]

commit 69903c259ec2f52538ef9b5e4f044afb9a3f9b62
Author: Federico Mena Quintero <federico gnome org>
Date:   Tue Mar 21 14:06:54 2017 -0600

    paint_server.rs: New file with a PaintServerUnits enum
    
    This has the userSpaceOnUse and objectBoundingBox values from the SVG
    spec.  We'll use this enum instead of boolean values for obj_bbox and
    similar.

 rust/src/lib.rs          |    1 +
 rust/src/paint_server.rs |   42 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 0 deletions(-)
---
diff --git a/rust/src/lib.rs b/rust/src/lib.rs
index d3456de..7ae50cb 100644
--- a/rust/src/lib.rs
+++ b/rust/src/lib.rs
@@ -112,6 +112,7 @@ mod gradient;
 mod length;
 mod marker;
 mod node;
+mod paint_server;
 mod parsers;
 mod path_builder;
 mod path_parser;
diff --git a/rust/src/paint_server.rs b/rust/src/paint_server.rs
new file mode 100644
index 0000000..ecdb216
--- /dev/null
+++ b/rust/src/paint_server.rs
@@ -0,0 +1,42 @@
+use std::str::FromStr;
+
+use parsers::ParseError;
+
+/// Defines the units to be used for scaling paint servers, per the [svg specification].
+///
+/// [svg spec]: https://www.w3.org/TR/SVG/pservers.html
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum PaintServerUnits {
+    UserSpaceOnUse,
+    ObjectBoundingBox
+}
+
+impl FromStr for PaintServerUnits {
+    type Err = ParseError;
+
+    fn from_str (s: &str) -> Result<PaintServerUnits, ParseError> {
+        match s {
+            "userSpaceOnUse"    => Ok (PaintServerUnits::UserSpaceOnUse),
+            "objectBoundingBox" => Ok (PaintServerUnits::ObjectBoundingBox),
+            _                   => Err (ParseError::new ("expected 'userSpaceOnUse' or 'objectBoundingBox'"))
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::str::FromStr;
+
+    #[test]
+    fn parsing_invalid_strings_yields_error () {
+        assert! (PaintServerUnits::from_str ("").is_err ());
+        assert! (PaintServerUnits::from_str ("foo").is_err ());
+    }
+
+    #[test]
+    fn parses_paint_server_units () {
+        assert_eq! (PaintServerUnits::from_str ("userSpaceOnUse"), Ok (PaintServerUnits::UserSpaceOnUse));
+        assert_eq! (PaintServerUnits::from_str ("objectBoundingBox"), Ok 
(PaintServerUnits::ObjectBoundingBox));
+    }
+}