[librsvg: 1/3] marker: operate on the transform rather than cr

[Federico Mena Quintero <federico src gnome org>]

commit 75a4e40f75d8954fb6202d9b4938b098a1815a3b
Author: Paolo Borelli <pborelli gnome org>
Date:   Wed Jan 22 15:15:49 2020 +0100

    marker: operate on the transform rather than cr
    
    Translate, rotate and scale our transform and then set it on the
    cr at once, so that we reduce direct cairo api usage.

 rsvg_internals/src/marker.rs | 57 ++++++++++++++++++++++----------------------
 1 file changed, 29 insertions(+), 28 deletions(-)
---
diff --git a/rsvg_internals/src/marker.rs b/rsvg_internals/src/marker.rs
index 5c31439d..b5d6d75b 100644
--- a/rsvg_internals/src/marker.rs
+++ b/rsvg_internals/src/marker.rs
@@ -21,6 +21,7 @@ use crate::path_builder::*;
 use crate::properties::{ComputedValues, SpecifiedValue, SpecifiedValues};
 use crate::property_bag::PropertyBag;
 use crate::rect::Rect;
+use crate::transform::Transform;
 use crate::viewbox::*;
 
 // markerUnits attribute: https://www.w3.org/TR/SVG/painting.html#MarkerElement
@@ -119,43 +120,43 @@ impl Marker {
             return Ok(draw_ctx.empty_bbox());
         }
 
-        draw_ctx.with_saved_cr(&mut |dc| {
-            let cr = dc.get_cairo_context();
+        let rotation = match self.orient {
+            MarkerOrient::Auto => computed_angle,
+            MarkerOrient::Angle(a) => a,
+        };
 
-            cr.translate(xpos, ypos);
+        let mut transform = Transform::new_translate(xpos, ypos).pre_rotate(rotation);
 
-            let rotation = match self.orient {
-                MarkerOrient::Auto => computed_angle,
-                MarkerOrient::Angle(a) => a,
-            };
-
-            cr.rotate(rotation.radians());
+        if self.units == MarkerUnits::StrokeWidth {
+            transform = transform.pre_scale(line_width, line_width);
+        }
 
-            if self.units == MarkerUnits::StrokeWidth {
-                cr.scale(line_width, line_width);
+        let params = if let Some(vbox) = self.vbox {
+            if vbox.0.is_empty() {
+                return Ok(draw_ctx.empty_bbox());
             }
 
-            let params = if let Some(vbox) = self.vbox {
-                if vbox.0.is_empty() {
-                    return Ok(dc.empty_bbox());
-                }
+            let r = self
+                .aspect
+                .compute(&vbox, &Rect::from_size(marker_width, marker_height));
 
-                let r = self
-                    .aspect
-                    .compute(&vbox, &Rect::from_size(marker_width, marker_height));
+            let (vb_width, vb_height) = vbox.0.size();
+            transform = transform.pre_scale(r.width() / vb_width, r.height() / vb_height);
 
-                let (vb_width, vb_height) = vbox.0.size();
-                cr.scale(r.width() / vb_width, r.height() / vb_height);
+            draw_ctx.push_view_box(vb_width, vb_height)
+        } else {
+            draw_ctx.push_view_box(marker_width, marker_height)
+        };
 
-                dc.push_view_box(vb_width, vb_height)
-            } else {
-                dc.push_view_box(marker_width, marker_height)
-            };
+        transform = transform.pre_translate(
+            -self.ref_x.normalize(&values, &params),
+            -self.ref_y.normalize(&values, &params),
+        );
+
+        draw_ctx.with_saved_cr(&mut |dc| {
+            let cr = dc.get_cairo_context();
 
-            cr.translate(
-                -self.ref_x.normalize(&values, &params),
-                -self.ref_y.normalize(&values, &params),
-            );
+            cr.transform(transform.into());
 
             if !values.is_overflow() {
                 let clip_rect = self