[librsvg/rustify-rsvg-convert] rsvg-convert: use legacy sizing also for layers

[Paolo Borelli <pborelli src gnome org>]

commit 2937392e1bb69a951bb72a8ac3bccf803645823b
Author: Paolo Borelli <pborelli gnome org>
Date:   Sat Jan 9 10:54:41 2021 +0100

    rsvg-convert: use legacy sizing also for layers

 src/bin/rsvg-convert/main.rs | 20 ++++++++++----------
 src/c_api/handle.rs          | 19 +++++--------------
 src/c_api/sizing.rs          | 20 ++++++++++++++++++--
 3 files changed, 33 insertions(+), 26 deletions(-)
---
diff --git a/src/bin/rsvg-convert/main.rs b/src/bin/rsvg-convert/main.rs
index e0719080..78fee0f2 100644
--- a/src/bin/rsvg-convert/main.rs
+++ b/src/bin/rsvg-convert/main.rs
@@ -65,8 +65,15 @@ fn main() {
 
         if target.is_none() {
             let (width, height) = renderer
-                .legacy_document_size_in_pixels()
-                .unwrap_or_else(|e| exit!("Error rendering SVG {}: {}", input, e));
+                .legacy_layer_size_in_pixels(args.export_id())
+                .unwrap_or_else(|e| match e {
+                    RenderingError::IdNotFound => exit!(
+                        "File {} does not have an object with id \"{}\")",
+                        input,
+                        args.export_id().unwrap()
+                    ),
+                    _ => exit!("Error rendering SVG {}: {}", input, e),
+                });
 
             let strategy = match (args.width, args.height) {
                 // when w and h are not specified, scale to the requested zoom (if any)
@@ -116,14 +123,7 @@ fn main() {
 
             surface
                 .render(&renderer, &cr, args.export_id())
-                .unwrap_or_else(|e| match e {
-                    RenderingError::IdNotFound => exit!(
-                        "File {} does not have an object with id \"{}\")",
-                        input,
-                        args.export_id().unwrap()
-                    ),
-                    _ => exit!("Error rendering SVG {}: {}", input, e),
-                });
+                .unwrap_or_else(|e| exit!("Error rendering SVG {}: {}", input, e));
         }
     }
 
diff --git a/src/c_api/handle.rs b/src/c_api/handle.rs
index c17fb73c..c328d0af 100644
--- a/src/c_api/handle.rs
+++ b/src/c_api/handle.rs
@@ -658,8 +658,7 @@ impl Drop for SizeCallback {
         }
     }
 }
-
-trait CairoRectangleExt {
+pub trait CairoRectangleExt {
     fn from_size(width: f64, height: f64) -> Self;
 }
 
@@ -976,14 +975,10 @@ impl CHandle {
         let handle = self.get_handle_ref()?;
         let renderer = self.make_renderer(&handle);
 
-        match id {
-            Some(id) => Ok(renderer.geometry_for_layer(Some(id), &unit_rectangle())?),
-
-            None => Ok(renderer.legacy_document_size_in_pixels().map(|(w, h)| {
-                let rect = cairo::Rectangle::from_size(w, h);
-                (rect, rect)
-            })?),
-        }
+        Ok(renderer.legacy_layer_size_in_pixels(id).map(|(w, h)| {
+            let rect = cairo::Rectangle::from_size(w, h);
+            (rect, rect)
+        })?)
     }
 
     fn set_stylesheet(&self, css: &str) -> Result<(), LoadingError> {
@@ -1133,10 +1128,6 @@ impl CHandle {
     }
 }
 
-pub(crate) fn unit_rectangle() -> cairo::Rectangle {
-    cairo::Rectangle::from_size(1.0, 1.0)
-}
-
 fn is_rsvg_handle(obj: *const RsvgHandle) -> bool {
     unsafe { instance_of::<CHandle>(obj as *const _) }
 }
diff --git a/src/c_api/sizing.rs b/src/c_api/sizing.rs
index fe1e893d..213f5d4f 100644
--- a/src/c_api/sizing.rs
+++ b/src/c_api/sizing.rs
@@ -1,7 +1,7 @@
 use crate::api::{CairoRenderer, IntrinsicDimensions, Length, RenderingError};
 use float_cmp::approx_eq;
 
-use super::handle::unit_rectangle;
+use super::handle::CairoRectangleExt;
 
 pub trait LegacySize {
     /// Returns the SVG's size suitable for the legacy C API.
@@ -13,6 +13,9 @@ pub trait LegacySize {
     ///
     /// See https://www.w3.org/TR/css-images-3/#sizing-terms for terminology and logic.
     fn legacy_document_size_in_pixels(&self) -> Result<(f64, f64), RenderingError>;
+
+    /// Returns the specified layer's size suitable for the legacy C API.
+    fn legacy_layer_size_in_pixels(&self, id: Option<&str>) -> Result<(f64, f64), RenderingError>;
 }
 
 impl<'a> LegacySize for CairoRenderer<'a> {
@@ -25,11 +28,24 @@ impl<'a> LegacySize for CairoRenderer<'a> {
             // We have a size directly computed from the <svg> attributes
             Ok(dim)
         } else {
-            // Compute the extents of all objects in the SVG
             let (ink_r, _) = self.geometry_for_layer(None, &unit_rectangle())?;
             Ok((ink_r.width, ink_r.height))
         }
     }
+
+    fn legacy_layer_size_in_pixels(&self, id: Option<&str>) -> Result<(f64, f64), RenderingError> {
+        match id {
+            Some(_) => {
+                let (ink_r, _) = self.geometry_for_layer(id, &unit_rectangle())?;
+                Ok((ink_r.width, ink_r.height))
+            }
+            None => self.legacy_document_size_in_pixels(),
+        }
+    }
+}
+
+fn unit_rectangle() -> cairo::Rectangle {
+    cairo::Rectangle::from_size(1.0, 1.0)
 }
 
 /// If the width and height are in percentage units, computes a size equal to the