[librsvg] draw_in_viewport(): Take in a clip_before_layer_push argument

[Federico Mena Quintero <federico src gnome org>]

commit c658b84f04df09825a11ef78084b42d404536536
Author: Federico Mena Quintero <federico gnome org>
Date:   Wed Sep 27 10:58:49 2017 -0500

    draw_in_viewport(): Take in a clip_before_layer_push argument
    
    I'm not sure if this is because adding the clip rect before pushing a
    layer is different from pushing after, *OR* if it is because the clip
    should be set from the vbox (when it exists) vs. setting it from the
    viewport area.

 rust/src/structure.rs |    1 +
 rust/src/viewport.rs  |    7 ++++++-
 2 files changed, 7 insertions(+), 1 deletions(-)
---
diff --git a/rust/src/structure.rs b/rust/src/structure.rs
index 523e935..d8b7355 100644
--- a/rust/src/structure.rs
+++ b/rust/src/structure.rs
@@ -176,6 +176,7 @@ impl NodeTrait for NodeSvg {
         let do_clip = !drawing_ctx::state_is_overflow (state) && node.get_parent ().is_some ();
 
         draw_in_viewport(nx, ny, nw, nh,
+                         false,
                          do_clip,
                          self.vbox.get(),
                          self.preserve_aspect_ratio.get(),
diff --git a/rust/src/viewport.rs b/rust/src/viewport.rs
index 63ef312..86113f1 100644
--- a/rust/src/viewport.rs
+++ b/rust/src/viewport.rs
@@ -8,6 +8,7 @@ use util::*;
 use viewbox::*;
 
 pub fn draw_in_viewport<F>(vx: f64, vy: f64, vw: f64, vh: f64,
+                           clip_before_layer_push: bool,
                            do_clip: bool,
                            vbox: Option<ViewBox>,
                            preserve_aspect_ratio: AspectRatio,
@@ -40,6 +41,10 @@ pub fn draw_in_viewport<F>(vx: f64, vy: f64, vw: f64, vh: f64,
         affine.translate(-vbox.0.x, -vbox.0.y);
 
         vbox_size = (vbox.0.width, vbox.0.height);
+
+        if clip_before_layer_push && do_clip {
+            drawing_ctx::add_clipping_rect(draw_ctx, vbox.0.x, vbox.0.y, vbox.0.width, vbox.0.height);
+        }
     } else {
         affine.translate(vx, vy);
         vbox_size = (vw, vh);
@@ -48,7 +53,7 @@ pub fn draw_in_viewport<F>(vx: f64, vy: f64, vw: f64, vh: f64,
     drawing_ctx::push_view_box(draw_ctx, vbox_size.0, vbox_size.1);
     drawing_ctx::push_discrete_layer(draw_ctx);
 
-    if do_clip {
+    if !clip_before_layer_push && do_clip {
         drawing_ctx::add_clipping_rect(draw_ctx, vx, vy, vw, vh);
     }