[librsvg: 69/90] Extract function to copy a surface to a SharedImageSurface

[Federico Mena Quintero <federico src gnome org>]

commit be320659469520eb81fd75487907ac91820d4cde
Author: Federico Mena Quintero <federico gnome org>
Date:   Thu Mar 21 17:14:43 2019 -0600

    Extract function to copy a surface to a SharedImageSurface

 rsvg_internals/src/filters/mod.rs | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)
---
diff --git a/rsvg_internals/src/filters/mod.rs b/rsvg_internals/src/filters/mod.rs
index 7b3137ce..32c08ac3 100644
--- a/rsvg_internals/src/filters/mod.rs
+++ b/rsvg_internals/src/filters/mod.rs
@@ -228,6 +228,24 @@ impl Deref for PrimitiveWithInput {
     }
 }
 
+/// Creates a `SharedImageSurface` from an `ImageSurface`, even if the former
+/// does not have a reference count of 1.
+fn copy_to_shared_surface(
+    surface: &cairo::ImageSurface,
+) -> Result<SharedImageSurface, cairo::Status> {
+    let copy = cairo::ImageSurface::create(
+        cairo::Format::ARgb32,
+        surface.get_width(),
+        surface.get_height(),
+    )?;
+    {
+        let cr = cairo::Context::new(&copy);
+        cr.set_source_surface(surface, 0f64, 0f64);
+        cr.paint();
+    }
+    SharedImageSurface::new(copy, SurfaceType::SRgb)
+}
+
 /// Applies a filter and returns the resulting surface.
 pub fn render(
     filter_node: &RsvgNode,
@@ -242,17 +260,7 @@ pub fn render(
 
     // The source surface has multiple references. We need to copy it to a new surface to have a
     // unique reference to be able to safely access the pixel data.
-    let source_surface = cairo::ImageSurface::create(
-        cairo::Format::ARgb32,
-        source.get_width(),
-        source.get_height(),
-    )?;
-    {
-        let cr = cairo::Context::new(&source_surface);
-        cr.set_source_surface(source, 0f64, 0f64);
-        cr.paint();
-    }
-    let source_surface = SharedImageSurface::new(source_surface, SurfaceType::SRgb)?;
+    let source_surface = copy_to_shared_surface(source)?;
 
     let mut filter_ctx = FilterContext::new(
         filter_node,