[librsvg] shared_surface: shorten code

[Paolo Borelli <pborelli src gnome org>]

commit 40ee738c7dabbaf8eae0137d13edb1594d5d8539
Author: Paolo Borelli <pborelli gnome org>
Date:   Tue Jan 5 14:36:06 2021 +0100

    shared_surface: shorten code

 src/surface_utils/shared_surface.rs | 16 +++++++---------
 src/surface_utils/srgb.rs           |  9 ++-------
 2 files changed, 9 insertions(+), 16 deletions(-)
---
diff --git a/src/surface_utils/shared_surface.rs b/src/surface_utils/shared_surface.rs
index 86123512..b2dbe17d 100644
--- a/src/surface_utils/shared_surface.rs
+++ b/src/surface_utils/shared_surface.rs
@@ -334,7 +334,7 @@ impl ImageSurface<Shared> {
 
     /// Returns `true` if the surface contains meaningful data only in the alpha channel.
     #[inline]
-    pub fn is_alpha_only(&self) -> bool {
+    fn is_alpha_only(&self) -> bool {
         self.surface_type == SurfaceType::AlphaOnly
     }
 
@@ -519,20 +519,18 @@ impl ImageSurface<Shared> {
     /// Converts the surface to the linear sRGB color space.
     #[inline]
     pub fn to_linear_rgb(&self, bounds: IRect) -> Result<SharedImageSurface, cairo::Status> {
-        if self.surface_type == SurfaceType::LinearRgb {
-            Ok(self.clone())
-        } else {
-            srgb::linearize_surface(self, bounds)
+        match self.surface_type {
+            SurfaceType::LinearRgb | SurfaceType::AlphaOnly => Ok(self.clone()),
+            _ => srgb::linearize_surface(self, bounds),
         }
     }
 
     /// Converts the surface to the sRGB color space.
     #[inline]
     pub fn to_srgb(&self, bounds: IRect) -> Result<SharedImageSurface, cairo::Status> {
-        if self.surface_type == SurfaceType::SRgb {
-            Ok(self.clone())
-        } else {
-            srgb::unlinearize_surface(self, bounds)
+        match self.surface_type {
+            SurfaceType::SRgb | SurfaceType::AlphaOnly => Ok(self.clone()),
+            _ => srgb::unlinearize_surface(self, bounds),
         }
     }
 
diff --git a/src/surface_utils/srgb.rs b/src/surface_utils/srgb.rs
index b88f486e..a6676a57 100644
--- a/src/surface_utils/srgb.rs
+++ b/src/surface_utils/srgb.rs
@@ -65,11 +65,6 @@ fn map_unpremultiplied_components<F: Fn(u8) -> u8>(
     f: F,
     new_type: SurfaceType,
 ) -> Result<SharedImageSurface, cairo::Status> {
-    // This function doesn't affect the alpha channel.
-    if surface.is_alpha_only() {
-        return Ok(surface.clone());
-    }
-
     let (width, height) = (surface.width(), surface.height());
     let mut output_surface = ExclusiveImageSurface::new(width, height, new_type)?;
     map_unpremultiplied_components_loop(surface, &mut output_surface, bounds, f);
@@ -83,7 +78,7 @@ pub fn linearize_surface(
     surface: &SharedImageSurface,
     bounds: IRect,
 ) -> Result<SharedImageSurface, cairo::Status> {
-    assert_ne!(surface.surface_type(), SurfaceType::LinearRgb);
+    assert_eq!(surface.surface_type(), SurfaceType::SRgb);
 
     map_unpremultiplied_components(surface, bounds, linearize, SurfaceType::LinearRgb)
 }
@@ -94,7 +89,7 @@ pub fn unlinearize_surface(
     surface: &SharedImageSurface,
     bounds: IRect,
 ) -> Result<SharedImageSurface, cairo::Status> {
-    assert_ne!(surface.surface_type(), SurfaceType::SRgb);
+    assert_eq!(surface.surface_type(), SurfaceType::LinearRgb);
 
     map_unpremultiplied_components(surface, bounds, unlinearize, SurfaceType::SRgb)
 }