[librsvg: 1/2] Cleanup for "pattern: respect fill-opacity"

[Federico Mena Quintero <federico src gnome org>]

commit 47de7a1b7ca3f191bb808bea203059f62de66c5f
Author: Sven Neumann <sven svenfoo org>
Date:   Fri Jan 31 23:00:58 2020 +0100

    Cleanup for "pattern: respect fill-opacity"
    
    This is a follow-up for #510. Moves drawing code to a function so
    that the check for fill-opacity only has to be done once.

 rsvg_internals/src/pattern.rs | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)
---
diff --git a/rsvg_internals/src/pattern.rs b/rsvg_internals/src/pattern.rs
index e583437f..671f2da8 100644
--- a/rsvg_internals/src/pattern.rs
+++ b/rsvg_internals/src/pattern.rs
@@ -344,26 +344,30 @@ impl AsPaintSource for ResolvedPattern {
         draw_ctx.set_cairo_context(&cr_pattern);
 
         // Set up transformations to be determined by the contents units
-
-        // Draw everything
-        let pattern_cascaded = CascadedValues::new_from_node(&node_with_children);
-        let pattern_values = pattern_cascaded.get();
-
         cr_pattern.set_matrix(caffine.into());
 
-        let UnitInterval(o) = opacity;
-        if o < 1.0 {
-            cr_pattern.push_group();
+        // Declare a drawing function
+        fn draw_children(
+            ctx: &mut DrawingCtx,
+            node: &RsvgNode,
+        ) -> Result<BoundingBox, RenderingError> {
+            let pattern_cascaded = CascadedValues::new_from_node(&node);
+            let pattern_values = pattern_cascaded.get();
+            ctx.with_discrete_layer(&node, pattern_values, false, &mut |dc| {
+                node.draw_children(&pattern_cascaded, dc, false)
+            })
         }
 
-        let res =
-            draw_ctx.with_discrete_layer(&node_with_children, pattern_values, false, &mut |dc| {
-                node_with_children.draw_children(&pattern_cascaded, dc, false)
-            });
-
+        // Draw everything
+        let res;
+        let UnitInterval(o) = opacity;
         if o < 1.0 {
+            cr_pattern.push_group();
+            res = draw_children(draw_ctx, &node_with_children);
             cr_pattern.pop_group_to_source();
             cr_pattern.paint_with_alpha(o);
+        } else {
+            res = draw_children(draw_ctx, &node_with_children);
         }
 
         // Return to the original coordinate system and rendering context