canvas: Fully stateless backend (#38214)

I think this simplifies canvas backends greatly. Before there were many
(needless) hoops from abstract to concrete (backend) and back, now we
can do most stuff on abstract types.

Testing: Existing WPT tests
Fixes: #38022 

try run: https://github.com/sagudev/servo/actions/runs/16450978211

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

components/canvas/backend.rs

@@ -3,55 +3,26 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use canvas_traits::canvas::{
-    CompositionOrBlending, FillOrStrokeStyle, LineCapStyle, LineJoinStyle, Path,
+    CompositionOptions, FillOrStrokeStyle, LineOptions, Path, ShadowOptions,
 };
 use compositing_traits::SerializableImageData;
-use euclid::default::{Point2D, Rect, Size2D, Transform2D, Vector2D};
+use euclid::default::{Point2D, Rect, Size2D, Transform2D};
 use pixels::Snapshot;
-use style::color::AbsoluteColor;
 use webrender_api::ImageDescriptor;
 
-use crate::canvas_data::{CanvasPaintState, Filter, TextRun};
+use crate::canvas_data::{Filter, TextRun};
 
 pub(crate) trait Backend: Clone + Sized {
-    type Pattern<'a>: PatternHelpers + Clone;
-    type StrokeOptions: StrokeOptionsHelpers + Clone;
-    type Color: Clone;
-    type DrawOptions: DrawOptionsHelpers + Clone;
-    type CompositionOp;
     type DrawTarget: GenericDrawTarget<Self>;
     type SourceSurface;
-    type GradientStop;
-    type GradientStops;
 
-    fn get_composition_op(&self, opts: &Self::DrawOptions) -> Self::CompositionOp;
-    fn need_to_draw_shadow(&self, color: &Self::Color) -> bool;
-    fn set_shadow_color(&mut self, color: AbsoluteColor, state: &mut CanvasPaintState<'_, Self>);
-    fn set_fill_style(
-        &mut self,
-        style: FillOrStrokeStyle,
-        state: &mut CanvasPaintState<'_, Self>,
-        drawtarget: &Self::DrawTarget,
-    );
-    fn set_stroke_style(
-        &mut self,
-        style: FillOrStrokeStyle,
-        state: &mut CanvasPaintState<'_, Self>,
-        drawtarget: &Self::DrawTarget,
-    );
-    fn set_global_composition(
-        &mut self,
-        op: CompositionOrBlending,
-        state: &mut CanvasPaintState<'_, Self>,
-    );
     fn create_drawtarget(&self, size: Size2D<u64>) -> Self::DrawTarget;
-    fn new_paint_state<'a>(&self) -> CanvasPaintState<'a, Self>;
 }
 
 // This defines required methods for a DrawTarget (currently only implemented for raqote).  The
 // prototypes are derived from the now-removed Azure backend's methods.
 pub(crate) trait GenericDrawTarget<B: Backend> {
-    fn clear_rect(&mut self, rect: &Rect<f32>);
+    fn clear_rect(&mut self, rect: &Rect<f32>, transform: Transform2D<f32>);
     fn copy_surface(
         &mut self,
         surface: B::SourceSurface,
@@ -66,72 +37,59 @@ pub(crate) trait GenericDrawTarget<B: Backend> {
         dest: Rect<f64>,
         source: Rect<f64>,
         filter: Filter,
-        draw_options: &B::DrawOptions,
+        composition_options: CompositionOptions,
+        transform: Transform2D<f32>,
     );
     fn draw_surface_with_shadow(
         &self,
         surface: B::SourceSurface,
         dest: &Point2D<f32>,
-        color: &B::Color,
-        offset: &Vector2D<f32>,
-        sigma: f32,
-        operator: B::CompositionOp,
+        shadow_options: ShadowOptions,
+        composition_options: CompositionOptions,
+    );
+    fn fill(
+        &mut self,
+        path: &Path,
+        style: FillOrStrokeStyle,
+        composition_options: CompositionOptions,
+        transform: Transform2D<f32>,
     );
-    fn fill(&mut self, path: &Path, pattern: &B::Pattern<'_>, draw_options: &B::DrawOptions);
     fn fill_text(
         &mut self,
         text_runs: Vec<TextRun>,
         start: Point2D<f32>,
-        pattern: &B::Pattern<'_>,
-        draw_options: &B::DrawOptions,
+        style: FillOrStrokeStyle,
+        composition_options: CompositionOptions,
+        transform: Transform2D<f32>,
     );
     fn fill_rect(
         &mut self,
         rect: &Rect<f32>,
-        pattern: &B::Pattern<'_>,
-        draw_options: &B::DrawOptions,
+        style: FillOrStrokeStyle,
+        composition_options: CompositionOptions,
+        transform: Transform2D<f32>,
     );
     fn get_size(&self) -> Size2D<i32>;
-    fn get_transform(&self) -> Transform2D<f32>;
     fn pop_clip(&mut self);
-    fn push_clip(&mut self, path: &Path);
+    fn push_clip(&mut self, path: &Path, transform: Transform2D<f32>);
     fn push_clip_rect(&mut self, rect: &Rect<i32>);
-    fn set_transform(&mut self, matrix: &Transform2D<f32>);
     fn stroke(
         &mut self,
         path: &Path,
-        pattern: &B::Pattern<'_>,
-        stroke_options: &B::StrokeOptions,
-        draw_options: &B::DrawOptions,
+        style: FillOrStrokeStyle,
+        line_options: LineOptions,
+        composition_options: CompositionOptions,
+        transform: Transform2D<f32>,
     );
     fn stroke_rect(
         &mut self,
         rect: &Rect<f32>,
-        pattern: &B::Pattern<'_>,
-        stroke_options: &B::StrokeOptions,
-        draw_options: &B::DrawOptions,
+        style: FillOrStrokeStyle,
+        line_options: LineOptions,
+        composition_options: CompositionOptions,
+        transform: Transform2D<f32>,
     );
     fn surface(&self) -> B::SourceSurface;
     fn image_descriptor_and_serializable_data(&self) -> (ImageDescriptor, SerializableImageData);
     fn snapshot(&self) -> Snapshot;
 }
-
-pub(crate) trait PatternHelpers {
-    fn is_zero_size_gradient(&self) -> bool;
-    fn x_bound(&self) -> Option<u32>;
-    fn y_bound(&self) -> Option<u32>;
-}
-
-pub(crate) trait StrokeOptionsHelpers {
-    fn set_line_width(&mut self, _val: f32);
-    fn set_miter_limit(&mut self, _val: f32);
-    fn set_line_join(&mut self, val: LineJoinStyle);
-    fn set_line_cap(&mut self, val: LineCapStyle);
-    fn set_line_dash(&mut self, items: Vec<f32>);
-    fn set_line_dash_offset(&mut self, offset: f32);
-}
-
-pub(crate) trait DrawOptionsHelpers {
-    fn set_alpha(&mut self, val: f32);
-    fn is_clear(&self) -> bool;
-}