[librsvg: 10/15] Export intrinsic_size_in_pixels from the Rust API

[Federico Mena Quintero <federico src gnome org>]

commit 6e9f846e5491fa63474ed7c46763158a125926fd
Author: Federico Mena Quintero <federico gnome org>
Date:   Tue Oct 27 14:16:42 2020 -0600

    Export intrinsic_size_in_pixels from the Rust API

 librsvg_crate/src/lib.rs                           | 18 ++++++++
 .../tests/standalone/intrinsic_dimensions.rs       | 51 ++++++++++++++++++++++
 2 files changed, 69 insertions(+)
---
diff --git a/librsvg_crate/src/lib.rs b/librsvg_crate/src/lib.rs
index b9294e65..e140a594 100644
--- a/librsvg_crate/src/lib.rs
+++ b/librsvg_crate/src/lib.rs
@@ -459,7 +459,11 @@ impl<'a> CairoRenderer<'a> {
     /// consider simply using [`render_document`] instead; it will do the scaling
     /// computations automatically.
     ///
+    /// See also [`intrinsic_size_in_pixels`], which does the conversion to pixels if
+    /// possible.
+    ///
     /// [`render_document`]: #method.render_document
+    /// [`intrinsic_size_in_pixels`]: #method.intrinsic_size_in_pixels
     pub fn intrinsic_dimensions(&self) -> IntrinsicDimensions {
         let d = self.handle.0.get_intrinsic_dimensions();
 
@@ -470,6 +474,20 @@ impl<'a> CairoRenderer<'a> {
         }
     }
 
+    /// Converts the SVG document's intrinsic dimensions to pixels, if possible.
+    ///
+    /// Returns `Some(width, height)` in pixel units if the SVG document has `width` and
+    /// `height` attributes with physical dimensions (CSS pixels, cm, in, etc.) or
+    /// font-based dimensions (em, ex).
+    ///
+    /// If the SVG document has percentage-based `width` and `height` attributes, or if
+    /// either of those attributes are not present, returns `None`.  Dimensions of that
+    /// kind require more information to be resolved to pixels; for example, the calling
+    /// application can use a viewport size to scale percentage-based dimensions.
+    pub fn intrinsic_size_in_pixels(&self) -> Option<(f64, f64)> {
+        self.handle.0.get_intrinsic_size_in_pixels(self.dpi)
+    }
+
     /// Renders the whole SVG document fitted to a viewport
     ///
     /// The `viewport` gives the position and size at which the whole SVG
diff --git a/librsvg_crate/tests/standalone/intrinsic_dimensions.rs 
b/librsvg_crate/tests/standalone/intrinsic_dimensions.rs
index aa8a50b2..9851302e 100644
--- a/librsvg_crate/tests/standalone/intrinsic_dimensions.rs
+++ b/librsvg_crate/tests/standalone/intrinsic_dimensions.rs
@@ -53,6 +53,57 @@ fn has_intrinsic_dimensions() {
     );
 }
 
+#[test]
+fn intrinsic_size_in_pixels() {
+    let svg = load_svg(
+        br#"<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg"; width="10" height="20" viewBox="0 0 100 200"/>
+"#,
+    )
+    .unwrap();
+
+    assert_eq!(
+        CairoRenderer::new(&svg).intrinsic_size_in_pixels(),
+        Some((10.0, 20.0)),
+    );
+}
+
+#[test]
+fn no_intrinsic_size_in_pixels_with_percent_dimensions() {
+    let svg = load_svg(
+        br#"<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg"; width="100%" height="100%" viewBox="0 0 100 200"/>
+"#,
+    )
+    .unwrap();
+
+    assert_eq!(CairoRenderer::new(&svg).intrinsic_size_in_pixels(), None);
+}
+
+#[test]
+fn no_intrinsic_size_in_pixels_with_no_dimensions() {
+    let svg = load_svg(
+        br#"<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg"; viewBox="0 0 100 200"/>
+"#,
+    )
+    .unwrap();
+
+    assert_eq!(CairoRenderer::new(&svg).intrinsic_size_in_pixels(), None);
+}
+
+#[test]
+fn no_intrinsic_size_in_pixels_with_one_missing_dimension() {
+    let svg = load_svg(
+        br#"<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg"; width="100" viewBox="0 0 100 200"/>
+"#,
+    )
+    .unwrap();
+
+    assert_eq!(CairoRenderer::new(&svg).intrinsic_size_in_pixels(), None);
+}
+
 #[test]
 fn root_geometry_with_percent_viewport() {
     let svg = load_svg(