Add transform stack to `canvas::Frame`

core/src/color.rs

@@ -44,11 +44,18 @@ impl Color {
     ///
     /// [`Color`]: struct.Color.html
     pub fn from_rgb8(r: u8, g: u8, b: u8) -> Color {
+        Color::from_rgba8(r, g, b, 1.0)
+    }
+
+    /// Creates a [`Color`] from its RGB8 components and an alpha value.
+    ///
+    /// [`Color`]: struct.Color.html
+    pub fn from_rgba8(r: u8, g: u8, b: u8, a: f32) -> Color {
         Color {
             r: f32::from(r) / 255.0,
             g: f32::from(g) / 255.0,
             b: f32::from(b) / 255.0,
-            a: 1.0,
+            a,
         }
     }
 

core/src/point.rs

@@ -11,10 +11,15 @@ pub struct Point {
 }
 
 impl Point {
+    /// The origin (i.e. a [`Point`] with both X=0 and Y=0).
+    ///
+    /// [`Point`]: struct.Point.html
+    pub const ORIGIN: Point = Point::new(0.0, 0.0);
+
     /// Creates a new [`Point`] with the given coordinates.
     ///
     /// [`Point`]: struct.Point.html
-    pub fn new(x: f32, y: f32) -> Self {
+    pub const fn new(x: f32, y: f32) -> Self {
         Self { x, y }
     }
 }

src/lib.rs

@@ -204,5 +204,5 @@ use iced_web as common;
 
 pub use common::{
     futures, Align, Background, Color, Command, Font, HorizontalAlignment,
-    Length, Point, Space, Subscription, Vector, VerticalAlignment,
+    Length, Point, Size, Space, Subscription, Vector, VerticalAlignment,
 };

web/src/lib.rs

@@ -73,8 +73,8 @@ pub use dodrio;
 pub use element::Element;
 pub use hasher::Hasher;
 pub use iced_core::{
-    Align, Background, Color, Font, HorizontalAlignment, Length, Point, Vector,
-    VerticalAlignment,
+    Align, Background, Color, Font, HorizontalAlignment, Length, Point, Size,
+    Vector, VerticalAlignment,
 };
 pub use iced_futures::{executor, futures, Command};
 pub use subscription::Subscription;

wgpu/src/widget/canvas/frame.rs

@@ -1,4 +1,4 @@
-use iced_native::Point;
+use iced_native::{Point, Size, Vector};
 
 use crate::{
     canvas::{Fill, Path, Stroke},
@@ -10,6 +10,20 @@ pub struct Frame {
     width: f32,
     height: f32,
     buffers: lyon::tessellation::VertexBuffers<triangle::Vertex2D, u16>,
+
+    transforms: Transforms,
+}
+
+#[derive(Debug)]
+struct Transforms {
+    previous: Vec<Transform>,
+    current: Transform,
+}
+
+#[derive(Debug, Clone, Copy)]
+struct Transform {
+    raw: lyon::math::Transform,
+    is_identity: bool,
 }
 
 impl Frame {
@@ -18,17 +32,32 @@ impl Frame {
             width,
             height,
             buffers: lyon::tessellation::VertexBuffers::new(),
+            transforms: Transforms {
+                previous: Vec::new(),
+                current: Transform {
+                    raw: lyon::math::Transform::identity(),
+                    is_identity: true,
+                },
+            },
         }
     }
 
+    #[inline]
     pub fn width(&self) -> f32 {
         self.width
     }
 
+    #[inline]
     pub fn height(&self) -> f32 {
         self.height
     }
 
+    #[inline]
+    pub fn size(&self) -> Size {
+        Size::new(self.width, self.height)
+    }
+
+    #[inline]
     pub fn center(&self) -> Point {
         Point::new(self.width / 2.0, self.height / 2.0)
     }
@@ -47,9 +76,23 @@ impl Frame {
 
         let mut tessellator = FillTessellator::new();
 
-        let _ = tessellator
-            .tessellate_path(path.raw(), &FillOptions::default(), &mut buffers)
-            .expect("Tessellate path");
+        let result = if self.transforms.current.is_identity {
+            tessellator.tessellate_path(
+                path.raw(),
+                &FillOptions::default(),
+                &mut buffers,
+            )
+        } else {
+            let path = path.transformed(&self.transforms.current.raw);
+
+            tessellator.tessellate_path(
+                path.raw(),
+                &FillOptions::default(),
+                &mut buffers,
+            )
+        };
+
+        let _ = result.expect("Tessellate path");
     }
 
     pub fn stroke(&mut self, path: &Path, stroke: Stroke) {
@@ -70,9 +113,54 @@ impl Frame {
         options.end_cap = stroke.line_cap.into();
         options.line_join = stroke.line_join.into();
 
-        let _ = tessellator
-            .tessellate_path(path.raw(), &options, &mut buffers)
-            .expect("Stroke path");
+        let result = if self.transforms.current.is_identity {
+            tessellator.tessellate_path(path.raw(), &options, &mut buffers)
+        } else {
+            let path = path.transformed(&self.transforms.current.raw);
+
+            tessellator.tessellate_path(path.raw(), &options, &mut buffers)
+        };
+
+        let _ = result.expect("Stroke path");
+    }
+
+    #[inline]
+    pub fn with_save(&mut self, f: impl FnOnce(&mut Frame)) {
+        self.transforms.previous.push(self.transforms.current);
+
+        f(self);
+
+        self.transforms.current = self.transforms.previous.pop().unwrap();
+    }
+
+    #[inline]
+    pub fn translate(&mut self, translation: Vector) {
+        self.transforms.current.raw = self
+            .transforms
+            .current
+            .raw
+            .pre_translate(lyon::math::Vector::new(
+                translation.x,
+                translation.y,
+            ));
+        self.transforms.current.is_identity = false;
+    }
+
+    #[inline]
+    pub fn rotate(&mut self, angle: f32) {
+        self.transforms.current.raw = self
+            .transforms
+            .current
+            .raw
+            .pre_rotate(lyon::math::Angle::radians(-angle));
+        self.transforms.current.is_identity = false;
+    }
+
+    #[inline]
+    pub fn scale(&mut self, scale: f32) {
+        self.transforms.current.raw =
+            self.transforms.current.raw.pre_scale(scale, scale);
+        self.transforms.current.is_identity = false;
     }
 
     pub fn into_mesh(self) -> triangle::Mesh2D {

wgpu/src/widget/canvas/path.rs

@@ -21,6 +21,16 @@ impl Path {
     pub(crate) fn raw(&self) -> &lyon::path::Path {
         &self.raw
     }
+
+    #[inline]
+    pub(crate) fn transformed(
+        &self,
+        transform: &lyon::math::Transform,
+    ) -> Path {
+        Path {
+            raw: self.raw.transformed(transform),
+        }
+    }
 }
 
 #[allow(missing_debug_implementations)]