Introduce backend feature flags in `iced_renderer`

6 files changed, 149 insertions, 95 deletions

diff --git a/Cargo.toml b/Cargo.toml
index a677569a..38c35f43 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,6 +12,11 @@ keywords = ["gui", "ui", "graphics", "interface", "widgets"]
 categories = ["gui"]
 
 [features]
+default = ["wgpu", "tiny-skia"]
+# Enable the `wgpu` GPU-accelerated renderer backend
+wgpu = ["iced_renderer/wgpu"]
+# Enable the `tiny-skia` software renderer backend
+tiny-skia = ["iced_renderer/tiny-skia"]
 # Enables the `Image` widget
 image = ["iced_widget/image", "image_rs"]
 # Enables the `Svg` widget
@@ -58,6 +63,7 @@ members = [
 [dependencies]
 iced_core = { version = "0.8", path = "core" }
 iced_futures = { version = "0.6", path = "futures" }
+iced_renderer = { version = "0.1", path = "renderer" }
 iced_widget = { version = "0.1", path = "widget" }
 iced_winit = { version = "0.8", path = "winit", features = ["application"] }
 thiserror = "1"
diff --git a/renderer/Cargo.toml b/renderer/Cargo.toml
index 560bf2e1..629c11ba 100644
--- a/renderer/Cargo.toml
+++ b/renderer/Cargo.toml
@@ -4,9 +4,11 @@ version = "0.1.0"
 edition = "2021"
 
 [features]
+wgpu = ["iced_wgpu"]
+tiny-skia = ["iced_tiny_skia"]
 image = ["iced_wgpu/image", "iced_tiny_skia/image"]
 svg = ["iced_wgpu/svg", "iced_tiny_skia/svg"]
-geometry = ["iced_wgpu/geometry", "iced_tiny_skia/geometry"]
+geometry = ["iced_graphics/geometry", "iced_wgpu?/geometry", "iced_tiny_skia?/geometry"]
 tracing = ["iced_wgpu/tracing"]
 
 [dependencies]
@@ -20,7 +22,9 @@ path = "../graphics"
 [dependencies.iced_wgpu]
 version = "0.9"
 path = "../wgpu"
+optional = true
 
 [dependencies.iced_tiny_skia]
 version = "0.1"
 path = "../tiny_skia"
+optional = true
diff --git a/renderer/src/backend.rs b/renderer/src/backend.rs
index bf5da322..e77b708b 100644
--- a/renderer/src/backend.rs
+++ b/renderer/src/backend.rs
@@ -6,16 +6,26 @@ use std::borrow::Cow;
 
 #[allow(clippy::large_enum_variant)]
 pub enum Backend {
+    #[cfg(feature = "wgpu")]
     Wgpu(iced_wgpu::Backend),
+    #[cfg(feature = "tiny-skia")]
     TinySkia(iced_tiny_skia::Backend),
 }
 
+macro_rules! delegate {
+    ($backend:expr, $name:ident, $body:expr) => {
+        match $backend {
+            #[cfg(feature = "wgpu")]
+            Self::Wgpu($name) => $body,
+            #[cfg(feature = "tiny-skia")]
+            Self::TinySkia($name) => $body,
+        }
+    };
+}
+
 impl iced_graphics::Backend for Backend {
     fn trim_measurements(&mut self) {
-        match self {
-            Self::Wgpu(backend) => backend.trim_measurements(),
-            Self::TinySkia(backend) => backend.trim_measurements(),
-        }
+        delegate!(self, backend, backend.trim_measurements());
     }
 }
 
@@ -25,17 +35,11 @@ impl backend::Text for Backend {
     const ARROW_DOWN_ICON: char = '\u{e800}';
 
     fn default_font(&self) -> Font {
-        match self {
-            Self::Wgpu(backend) => backend.default_font(),
-            Self::TinySkia(backend) => backend.default_font(),
-        }
+        delegate!(self, backend, backend.default_font())
     }
 
     fn default_size(&self) -> f32 {
-        match self {
-            Self::Wgpu(backend) => backend.default_size(),
-            Self::TinySkia(backend) => backend.default_size(),
-        }
+        delegate!(self, backend, backend.default_size())
     }
 
     fn measure(
@@ -45,14 +49,7 @@ impl backend::Text for Backend {
         font: Font,
         bounds: Size,
     ) -> (f32, f32) {
-        match self {
-            Self::Wgpu(backend) => {
-                backend.measure(contents, size, font, bounds)
-            }
-            Self::TinySkia(backend) => {
-                backend.measure(contents, size, font, bounds)
-            }
-        }
+        delegate!(self, backend, backend.measure(contents, size, font, bounds))
     }
 
     fn hit_test(
@@ -64,45 +61,29 @@ impl backend::Text for Backend {
         position: Point,
         nearest_only: bool,
     ) -> Option<text::Hit> {
-        match self {
-            Self::Wgpu(backend) => backend.hit_test(
-                contents,
-                size,
-                font,
-                bounds,
-                position,
-                nearest_only,
-            ),
-            Self::TinySkia(backend) => backend.hit_test(
+        delegate!(
+            self,
+            backend,
+            backend.hit_test(
                 contents,
                 size,
                 font,
                 bounds,
                 position,
-                nearest_only,
-            ),
-        }
+                nearest_only
+            )
+        )
     }
 
     fn load_font(&mut self, font: Cow<'static, [u8]>) {
-        match self {
-            Self::Wgpu(backend) => {
-                backend.load_font(font);
-            }
-            Self::TinySkia(backend) => {
-                backend.load_font(font);
-            }
-        }
+        delegate!(self, backend, backend.load_font(font));
     }
 }
 
 #[cfg(feature = "image")]
 impl backend::Image for Backend {
     fn dimensions(&self, handle: &crate::core::image::Handle) -> Size<u32> {
-        match self {
-            Self::Wgpu(backend) => backend.dimensions(handle),
-            Self::TinySkia(backend) => backend.dimensions(handle),
-        }
+        delegate!(self, backend, backend.dimensions(handle))
     }
 }
 
@@ -112,9 +93,6 @@ impl backend::Svg for Backend {
         &self,
         handle: &crate::core::svg::Handle,
     ) -> Size<u32> {
-        match self {
-            Self::Wgpu(backend) => backend.viewport_dimensions(handle),
-            Self::TinySkia(backend) => backend.viewport_dimensions(handle),
-        }
+        delegate!(self, backend, backend.viewport_dimensions(handle))
     }
 }
diff --git a/renderer/src/compositor.rs b/renderer/src/compositor.rs
index 0cdcb293..218e7e33 100644
--- a/renderer/src/compositor.rs
+++ b/renderer/src/compositor.rs
@@ -1,17 +1,21 @@
 use crate::core::Color;
 use crate::graphics::compositor::{Information, SurfaceError};
 use crate::graphics::{Error, Viewport};
-use crate::{Backend, Renderer, Settings};
+use crate::{Renderer, Settings};
 
 use raw_window_handle::{HasRawDisplayHandle, HasRawWindowHandle};
 
 pub enum Compositor<Theme> {
+    #[cfg(feature = "wgpu")]
     Wgpu(iced_wgpu::window::Compositor<Theme>),
+    #[cfg(feature = "tiny-skia")]
     TinySkia(iced_tiny_skia::window::Compositor<Theme>),
 }
 
 pub enum Surface {
+    #[cfg(feature = "wgpu")]
     Wgpu(iced_wgpu::window::Surface),
+    #[cfg(feature = "tiny-skia")]
     TinySkia(iced_tiny_skia::window::Surface),
 }
 
@@ -22,32 +26,65 @@ impl<Theme> crate::graphics::Compositor for Compositor<Theme> {
 
     fn new<W: HasRawWindowHandle + HasRawDisplayHandle>(
         settings: Self::Settings,
-        _compatible_window: Option<&W>,
+        compatible_window: Option<&W>,
     ) -> Result<(Self, Self::Renderer), Error> {
-        //let (compositor, backend) = iced_wgpu::window::compositor::new(
-        //    iced_wgpu::Settings {
-        //        default_font: settings.default_font,
-        //        default_text_size: settings.default_text_size,
-        //        antialiasing: settings.antialiasing,
-        //        ..iced_wgpu::Settings::from_env()
-        //    },
-        //    compatible_window,
-        //)?;
-
-        //Ok((
-        //    Self::Wgpu(compositor),
-        //    Renderer::new(Backend::Wgpu(backend)),
-        //))
-        let (compositor, backend) =
-            iced_tiny_skia::window::compositor::new(iced_tiny_skia::Settings {
-                default_font: settings.default_font,
-                default_text_size: settings.default_text_size,
-            });
-
-        Ok((
-            Self::TinySkia(compositor),
-            Renderer::new(Backend::TinySkia(backend)),
-        ))
+        #[cfg(feature = "wgpu")]
+        let new_wgpu = |settings: Self::Settings, compatible_window| {
+            let (compositor, backend) = iced_wgpu::window::compositor::new(
+                iced_wgpu::Settings {
+                    default_font: settings.default_font,
+                    default_text_size: settings.default_text_size,
+                    antialiasing: settings.antialiasing,
+                    ..iced_wgpu::Settings::from_env()
+                },
+                compatible_window,
+            )?;
+
+            Ok((
+                Self::Wgpu(compositor),
+                Renderer::new(crate::Backend::Wgpu(backend)),
+            ))
+        };
+
+        #[cfg(feature = "tiny-skia")]
+        let new_tiny_skia = |settings: Self::Settings, _compatible_window| {
+            let (compositor, backend) = iced_tiny_skia::window::compositor::new(
+                iced_tiny_skia::Settings {
+                    default_font: settings.default_font,
+                    default_text_size: settings.default_text_size,
+                },
+            );
+
+            Ok((
+                Self::TinySkia(compositor),
+                Renderer::new(crate::Backend::TinySkia(backend)),
+            ))
+        };
+
+        let fail = |_, _| Err(Error::GraphicsAdapterNotFound);
+
+        let candidates = &[
+            #[cfg(feature = "wgpu")]
+            new_wgpu,
+            #[cfg(feature = "tiny-skia")]
+            new_tiny_skia,
+            fail,
+        ];
+
+        let mut error = Error::GraphicsAdapterNotFound;
+
+        for candidate in candidates {
+            match candidate(settings, compatible_window) {
+                Ok((compositor, renderer)) => {
+                    return Ok((compositor, renderer))
+                }
+                Err(new_error) => {
+                    error = new_error;
+                }
+            }
+        }
+
+        Err(error)
     }
 
     fn create_surface<W: HasRawWindowHandle + HasRawDisplayHandle>(
@@ -57,9 +94,11 @@ impl<Theme> crate::graphics::Compositor for Compositor<Theme> {
         height: u32,
     ) -> Surface {
         match self {
+            #[cfg(feature = "wgpu")]
             Self::Wgpu(compositor) => {
                 Surface::Wgpu(compositor.create_surface(window, width, height))
             }
+            #[cfg(feature = "tiny-skia")]
             Self::TinySkia(compositor) => Surface::TinySkia(
                 compositor.create_surface(window, width, height),
             ),
@@ -73,19 +112,26 @@ impl<Theme> crate::graphics::Compositor for Compositor<Theme> {
         height: u32,
     ) {
         match (self, surface) {
+            #[cfg(feature = "wgpu")]
             (Self::Wgpu(compositor), Surface::Wgpu(surface)) => {
                 compositor.configure_surface(surface, width, height);
             }
+            #[cfg(feature = "tiny-skia")]
             (Self::TinySkia(compositor), Surface::TinySkia(surface)) => {
                 compositor.configure_surface(surface, width, height);
             }
-            _ => unreachable!(),
+            #[allow(unreachable_patterns)]
+            _ => panic!(
+                "The provided surface is not compatible with the compositor."
+            ),
         }
     }
 
     fn fetch_information(&self) -> Information {
         match self {
+            #[cfg(feature = "wgpu")]
             Self::Wgpu(compositor) => compositor.fetch_information(),
+            #[cfg(feature = "tiny-skia")]
             Self::TinySkia(compositor) => compositor.fetch_information(),
         }
     }
@@ -100,9 +146,10 @@ impl<Theme> crate::graphics::Compositor for Compositor<Theme> {
     ) -> Result<(), SurfaceError> {
         renderer.with_primitives(|backend, primitives| {
             match (self, backend, surface) {
+                #[cfg(feature = "wgpu")]
                 (
                     Self::Wgpu(compositor),
-                    Backend::Wgpu(backend),
+                    crate::Backend::Wgpu(backend),
                     Surface::Wgpu(surface),
                 ) => iced_wgpu::window::compositor::present(
                     compositor,
@@ -113,9 +160,10 @@ impl<Theme> crate::graphics::Compositor for Compositor<Theme> {
                     background_color,
                     overlay,
                 ),
+                #[cfg(feature = "tiny-skia")]
                 (
                     Self::TinySkia(compositor),
-                    Backend::TinySkia(backend),
+                    crate::Backend::TinySkia(backend),
                     Surface::TinySkia(surface),
                 ) => iced_tiny_skia::window::compositor::present(
                     compositor,
@@ -126,7 +174,11 @@ impl<Theme> crate::graphics::Compositor for Compositor<Theme> {
                     background_color,
                     overlay,
                 ),
-                _ => unreachable!(),
+                #[allow(unreachable_patterns)]
+                _ => panic!(
+                    "The provided renderer or surface are not compatible \
+                    with the compositor."
+                ),
             }
         })
     }
diff --git a/renderer/src/geometry.rs b/renderer/src/geometry.rs
index 361fc86b..21ef2c06 100644
--- a/renderer/src/geometry.rs
+++ b/renderer/src/geometry.rs
@@ -7,14 +7,18 @@ use crate::graphics::geometry::{Fill, Geometry, Path, Stroke, Text};
 use crate::Backend;
 
 pub enum Frame {
+    #[cfg(feature = "wgpu")]
     Wgpu(iced_wgpu::geometry::Frame),
+    #[cfg(feature = "tiny-skia")]
     TinySkia(iced_tiny_skia::geometry::Frame),
 }
 
 macro_rules! delegate {
-    ($frame:expr, $name:ident => $body:expr) => {
+    ($frame:expr, $name:ident, $body:expr) => {
         match $frame {
+            #[cfg(feature = "wgpu")]
             Self::Wgpu($name) => $body,
+            #[cfg(feature = "tiny-skia")]
             Self::TinySkia($name) => $body,
         }
     };
@@ -23,9 +27,11 @@ macro_rules! delegate {
 impl Frame {
     pub fn new<Theme>(renderer: &crate::Renderer<Theme>, size: Size) -> Self {
         match renderer.backend() {
+            #[cfg(feature = "wgpu")]
             Backend::Wgpu(_) => {
                 Frame::Wgpu(iced_wgpu::geometry::Frame::new(size))
             }
+            #[cfg(feature = "tiny-skia")]
             Backend::TinySkia(_) => {
                 Frame::TinySkia(iced_tiny_skia::geometry::Frame::new(size))
             }
@@ -35,31 +41,31 @@ impl Frame {
     /// Returns the width of the [`Frame`].
     #[inline]
     pub fn width(&self) -> f32 {
-        delegate!(self, frame => frame.width())
+        delegate!(self, frame, frame.width())
     }
 
     /// Returns the height of the [`Frame`].
     #[inline]
     pub fn height(&self) -> f32 {
-        delegate!(self, frame => frame.height())
+        delegate!(self, frame, frame.height())
     }
 
     /// Returns the dimensions of the [`Frame`].
     #[inline]
     pub fn size(&self) -> Size {
-        delegate!(self, frame => frame.size())
+        delegate!(self, frame, frame.size())
     }
 
     /// Returns the coordinate of the center of the [`Frame`].
     #[inline]
     pub fn center(&self) -> Point {
-        delegate!(self, frame => frame.center())
+        delegate!(self, frame, frame.center())
     }
 
     /// Draws the given [`Path`] on the [`Frame`] by filling it with the
     /// provided style.
     pub fn fill(&mut self, path: &Path, fill: impl Into<Fill>) {
-        delegate!(self, frame => frame.fill(path, fill));
+        delegate!(self, frame, frame.fill(path, fill));
     }
 
     /// Draws an axis-aligned rectangle given its top-left corner coordinate and
@@ -70,13 +76,13 @@ impl Frame {
         size: Size,
         fill: impl Into<Fill>,
     ) {
-        delegate!(self, frame => frame.fill_rectangle(top_left, size, fill));
+        delegate!(self, frame, frame.fill_rectangle(top_left, size, fill));
     }
 
     /// Draws the stroke of the given [`Path`] on the [`Frame`] with the
     /// provided style.
     pub fn stroke<'a>(&mut self, path: &Path, stroke: impl Into<Stroke<'a>>) {
-        delegate!(self, frame => frame.stroke(path, stroke));
+        delegate!(self, frame, frame.stroke(path, stroke));
     }
 
     /// Draws the characters of the given [`Text`] on the [`Frame`], filling
@@ -95,7 +101,7 @@ impl Frame {
     ///
     /// [`Canvas`]: crate::widget::Canvas
     pub fn fill_text(&mut self, text: impl Into<Text>) {
-        delegate!(self, frame => frame.fill_text(text));
+        delegate!(self, frame, frame.fill_text(text));
     }
 
     /// Stores the current transform of the [`Frame`] and executes the given
@@ -105,11 +111,11 @@ impl Frame {
     /// operations in different coordinate systems.
     #[inline]
     pub fn with_save(&mut self, f: impl FnOnce(&mut Frame)) {
-        delegate!(self, frame => frame.push_transform());
+        delegate!(self, frame, frame.push_transform());
 
         f(self);
 
-        delegate!(self, frame => frame.pop_transform());
+        delegate!(self, frame, frame.pop_transform());
     }
 
     /// Executes the given drawing operations within a [`Rectangle`] region,
@@ -121,9 +127,11 @@ impl Frame {
     #[inline]
     pub fn with_clip(&mut self, region: Rectangle, f: impl FnOnce(&mut Frame)) {
         let mut frame = match self {
+            #[cfg(feature = "wgpu")]
             Self::Wgpu(_) => {
                 Self::Wgpu(iced_wgpu::geometry::Frame::new(region.size()))
             }
+            #[cfg(feature = "tiny-skia")]
             Self::TinySkia(_) => Self::TinySkia(
                 iced_tiny_skia::geometry::Frame::new(region.size()),
             ),
@@ -134,12 +142,15 @@ impl Frame {
         let translation = Vector::new(region.x, region.y);
 
         match (self, frame) {
+            #[cfg(feature = "wgpu")]
             (Self::Wgpu(target), Self::Wgpu(frame)) => {
                 target.clip(frame, translation);
             }
+            #[cfg(feature = "tiny-skia")]
             (Self::TinySkia(target), Self::TinySkia(frame)) => {
                 target.clip(frame, translation);
             }
+            #[allow(unreachable_patterns)]
             _ => unreachable!(),
         };
     }
@@ -147,22 +158,22 @@ impl Frame {
     /// Applies a translation to the current transform of the [`Frame`].
     #[inline]
     pub fn translate(&mut self, translation: Vector) {
-        delegate!(self, frame => frame.translate(translation));
+        delegate!(self, frame, frame.translate(translation));
     }
 
     /// Applies a rotation in radians to the current transform of the [`Frame`].
     #[inline]
     pub fn rotate(&mut self, angle: f32) {
-        delegate!(self, frame => frame.rotate(angle));
+        delegate!(self, frame, frame.rotate(angle));
     }
 
     /// Applies a scaling to the current transform of the [`Frame`].
     #[inline]
     pub fn scale(&mut self, scale: f32) {
-        delegate!(self, frame => frame.scale(scale));
+        delegate!(self, frame, frame.scale(scale));
     }
 
     pub fn into_geometry(self) -> Geometry {
-        Geometry(delegate!(self, frame => frame.into_primitive()))
+        Geometry(delegate!(self, frame, frame.into_primitive()))
     }
 }
diff --git a/renderer/src/lib.rs b/renderer/src/lib.rs
index 22ec7bd1..ba737b11 100644
--- a/renderer/src/lib.rs
+++ b/renderer/src/lib.rs
@@ -1,3 +1,6 @@
+#[cfg(not(any(feature = "wgpu", feature = "tiny-skia")))]
+compile_error!("No backend selected. Enable at least one backend feature: `wgpu` or `tiny-skia`.");
+
 pub mod compositor;
 
 #[cfg(feature = "geometry")]