canvas: Gate raqote backend behind feature (enabled for now) (#38312)

We want to eventually remove raqote backend, but for now we can gate it
behind a feature (still enabled by default in servoshell) like the rest
of backends. `dom_canvas_backend=auto` will select first available
backend. Builds on top of https://github.com/servo/servo/pull/38310 to
support cases where no backend is available.

Testing: It compiles with or without feature

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

components/canvas/Cargo.toml

@@ -14,6 +14,7 @@ path = "lib.rs"
 [features]
 vello = ["dep:vello", "dep:pollster", "dep:futures-intrusive", "dep:peniko"]
 vello_cpu = ["dep:vello_cpu", "dep:peniko"]
+raqote = ["dep:raqote", "dep:font-kit"]
 
 [dependencies]
 app_units = { workspace = true }
@@ -23,7 +24,7 @@ compositing_traits = { workspace = true }
 crossbeam-channel = { workspace = true }
 cssparser = { workspace = true }
 euclid = { workspace = true }
-font-kit = "0.14"
+font-kit = { version = "0.14", optional = true }
 fonts = { path = "../fonts" }
 ipc-channel = { workspace = true }
 kurbo = { workspace = true }
@@ -32,7 +33,7 @@ net_traits = { workspace = true }
 peniko = { workspace = true, optional = true }
 pixels = { path = "../pixels" }
 range = { path = "../range" }
-raqote = "0.8.5"
+raqote = { version = "0.8.5", optional = true }
 servo_arc = { workspace = true }
 stylo = { workspace = true }
 unicode-script = { workspace = true }

components/canvas/canvas_paint_thread.rs

@@ -3,6 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 #![allow(clippy::too_many_arguments)]
+#![allow(unreachable_patterns)]
 
 use std::borrow::ToOwned;
 use std::collections::HashMap;
@@ -292,6 +293,7 @@ impl CanvasPaintThread {
 
 #[allow(clippy::large_enum_variant)]
 enum Canvas {
+    #[cfg(feature = "raqote")]
     Raqote(CanvasData<raqote::DrawTarget>),
     #[cfg(feature = "vello")]
     Vello(CanvasData<crate::vello_backend::VelloDrawTarget>),
@@ -309,19 +311,20 @@ impl Canvas {
             .to_lowercase()
             .as_str()
         {
+            #[cfg(feature = "raqote")]
+            "" | "auto" | "raqote" => Some(Self::Raqote(CanvasData::new(
+                size,
+                compositor_api,
+                font_context,
+            ))),
             #[cfg(feature = "vello")]
-            "vello" => Some(Self::Vello(CanvasData::new(
+            "" | "auto" | "vello" => Some(Self::Vello(CanvasData::new(
                 size,
                 compositor_api,
                 font_context,
             ))),
             #[cfg(feature = "vello_cpu")]
-            "vello_cpu" => Some(Self::VelloCPU(CanvasData::new(
+            "" | "auto" | "vello_cpu" => Some(Self::VelloCPU(CanvasData::new(
-                size,
-                compositor_api,
-                font_context,
-            ))),
-            "" | "auto" | "raqote" => Some(Self::Raqote(CanvasData::new(
                 size,
                 compositor_api,
                 font_context,
@@ -335,21 +338,25 @@ impl Canvas {
 
     fn image_key(&self) -> ImageKey {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.image_key(),
             #[cfg(feature = "vello")]
             Canvas::Vello(canvas_data) => canvas_data.image_key(),
             #[cfg(feature = "vello_cpu")]
             Canvas::VelloCPU(canvas_data) => canvas_data.image_key(),
+            _ => unreachable!(),
         }
     }
 
     fn pop_clip(&mut self) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.pop_clip(),
             #[cfg(feature = "vello")]
             Canvas::Vello(canvas_data) => canvas_data.pop_clip(),
             #[cfg(feature = "vello_cpu")]
             Canvas::VelloCPU(canvas_data) => canvas_data.pop_clip(),
+            _ => unreachable!(),
         }
     }
 
@@ -367,6 +374,7 @@ impl Canvas {
         transform: Transform2D<f32>,
     ) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.fill_text(
                 text,
                 x,
@@ -405,6 +413,7 @@ impl Canvas {
                 composition_options,
                 transform,
             ),
+            _ => unreachable!(),
         }
     }
 
@@ -417,6 +426,7 @@ impl Canvas {
         transform: Transform2D<f32>,
     ) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => {
                 canvas_data.fill_rect(rect, style, shadow_options, composition_options, transform)
             },
@@ -428,6 +438,7 @@ impl Canvas {
             Canvas::VelloCPU(canvas_data) => {
                 canvas_data.fill_rect(rect, style, shadow_options, composition_options, transform)
             },
+            _ => unreachable!(),
         }
     }
 
@@ -441,6 +452,7 @@ impl Canvas {
         transform: Transform2D<f32>,
     ) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.stroke_rect(
                 rect,
                 style,
@@ -467,6 +479,7 @@ impl Canvas {
                 composition_options,
                 transform,
             ),
+            _ => unreachable!(),
         }
     }
 
@@ -480,6 +493,7 @@ impl Canvas {
         transform: Transform2D<f32>,
     ) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.fill_path(
                 path,
                 fill_rule,
@@ -506,6 +520,7 @@ impl Canvas {
                 composition_options,
                 transform,
             ),
+            _ => unreachable!(),
         }
     }
 
@@ -519,6 +534,7 @@ impl Canvas {
         transform: Transform2D<f32>,
     ) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.stroke_path(
                 path,
                 style,
@@ -545,16 +561,19 @@ impl Canvas {
                 composition_options,
                 transform,
             ),
+            _ => unreachable!(),
         }
     }
 
     fn clear_rect(&mut self, rect: &Rect<f32>, transform: Transform2D<f32>) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.clear_rect(rect, transform),
             #[cfg(feature = "vello")]
             Canvas::Vello(canvas_data) => canvas_data.clear_rect(rect, transform),
             #[cfg(feature = "vello_cpu")]
             Canvas::VelloCPU(canvas_data) => canvas_data.clear_rect(rect, transform),
+            _ => unreachable!(),
         }
     }
 
@@ -569,6 +588,7 @@ impl Canvas {
         transform: Transform2D<f32>,
     ) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.draw_image(
                 snapshot,
                 dest_rect,
@@ -598,66 +618,79 @@ impl Canvas {
                 composition_options,
                 transform,
             ),
+            _ => unreachable!(),
         }
     }
 
     fn read_pixels(&mut self, read_rect: Option<Rect<u32>>) -> Snapshot {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.read_pixels(read_rect),
             #[cfg(feature = "vello")]
             Canvas::Vello(canvas_data) => canvas_data.read_pixels(read_rect),
             #[cfg(feature = "vello_cpu")]
             Canvas::VelloCPU(canvas_data) => canvas_data.read_pixels(read_rect),
+            _ => unreachable!(),
         }
     }
 
     fn measure_text(&mut self, text: String, text_options: TextOptions) -> TextMetrics {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.measure_text(text, text_options),
             #[cfg(feature = "vello")]
             Canvas::Vello(canvas_data) => canvas_data.measure_text(text, text_options),
             #[cfg(feature = "vello_cpu")]
             Canvas::VelloCPU(canvas_data) => canvas_data.measure_text(text, text_options),
+            _ => unreachable!(),
         }
     }
 
     fn clip_path(&mut self, path: &Path, fill_rule: FillRule, transform: Transform2D<f32>) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.clip_path(path, fill_rule, transform),
             #[cfg(feature = "vello")]
             Canvas::Vello(canvas_data) => canvas_data.clip_path(path, fill_rule, transform),
             #[cfg(feature = "vello_cpu")]
             Canvas::VelloCPU(canvas_data) => canvas_data.clip_path(path, fill_rule, transform),
+            _ => unreachable!(),
         }
     }
 
     fn put_image_data(&mut self, snapshot: Snapshot, rect: Rect<u32>) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.put_image_data(snapshot, rect),
             #[cfg(feature = "vello")]
             Canvas::Vello(canvas_data) => canvas_data.put_image_data(snapshot, rect),
             #[cfg(feature = "vello_cpu")]
             Canvas::VelloCPU(canvas_data) => canvas_data.put_image_data(snapshot, rect),
+            _ => unreachable!(),
         }
     }
 
     fn update_image_rendering(&mut self) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.update_image_rendering(),
             #[cfg(feature = "vello")]
             Canvas::Vello(canvas_data) => canvas_data.update_image_rendering(),
             #[cfg(feature = "vello_cpu")]
             Canvas::VelloCPU(canvas_data) => canvas_data.update_image_rendering(),
+            _ => unreachable!(),
         }
     }
 
     fn recreate(&mut self, size: Option<Size2D<u64>>) {
         match self {
+            #[cfg(feature = "raqote")]
             Canvas::Raqote(canvas_data) => canvas_data.recreate(size),
             #[cfg(feature = "vello")]
             Canvas::Vello(canvas_data) => canvas_data.recreate(size),
             #[cfg(feature = "vello_cpu")]
             Canvas::VelloCPU(canvas_data) => canvas_data.recreate(size),
+            _ => unreachable!(),
         }
     }
 }

components/canvas/lib.rs

@@ -5,11 +5,16 @@
 #![deny(unsafe_code)]
 
 mod backend;
+
+#[cfg(feature = "raqote")]
+mod raqote_backend;
+
 #[cfg(any(feature = "vello", feature = "vello_cpu"))]
 mod peniko_conversions;
-mod raqote_backend;
+
 #[cfg(feature = "vello")]
 mod vello_backend;
+
 #[cfg(feature = "vello_cpu")]
 mod vello_cpu_backend;
 

components/constellation/Cargo.toml

@@ -18,6 +18,7 @@ tracing = ["dep:tracing"]
 webgpu = ["script_traits/webgpu"]
 vello = ["canvas/vello"]
 vello_cpu = ["canvas/vello_cpu"]
+raqote = ["canvas/raqote"]
 
 [dependencies]
 background_hang_monitor = { path = "../background_hang_monitor" }

components/servo/Cargo.toml

@@ -21,7 +21,7 @@ bluetooth = [
     "script/bluetooth",
     "script_traits/bluetooth",
 ]
-default = ["clipboard"]
+default = ["clipboard", "raqote"]
 clipboard = ["dep:arboard"]
 crown = ["script/crown"]
 debugmozjs = ["script/debugmozjs"]
@@ -64,6 +64,7 @@ webgpu = [
 ]
 vello = ["constellation/vello"]
 vello_cpu = ["constellation/vello_cpu"]
+raqote = ["constellation/raqote"]
 
 [dependencies]
 background_hang_monitor = { path = "../background_hang_monitor" }

ports/servoshell/Cargo.toml

@@ -54,6 +54,7 @@ webgpu = ["libservo/webgpu"]
 webxr = ["libservo/webxr"]
 vello = ["libservo/vello"]
 vello_cpu = ["libservo/vello_cpu"]
+raqote = ["libservo/raqote"]
 
 [dependencies]
 cfg-if = { workspace = true }