implement text support in canvas widget

wgpu/src/widget/canvas.rs

@@ -20,6 +20,7 @@ mod drawable;
 mod fill;
 mod frame;
 mod stroke;
+mod text;
 
 pub use drawable::Drawable;
 pub use fill::Fill;
@@ -27,6 +28,7 @@ pub use frame::Frame;
 pub use layer::Layer;
 pub use path::Path;
 pub use stroke::{LineCap, LineJoin, Stroke};
+pub use text::TextNode;
 
 /// A widget capable of drawing 2D graphics.
 ///
@@ -121,10 +123,7 @@ impl<'a, Message> Widget<Message, Renderer> for Canvas<'a> {
                 primitives: self
                     .layers
                     .iter()
-                    .map(|layer| Primitive::Mesh2D {
-                        origin,
-                        buffers: layer.draw(size),
-                    })
+                    .map(|layer| layer.draw(origin, size))
                     .collect(),
             },
             MouseCursor::Idle,

wgpu/src/widget/canvas/frame.rs

@@ -1,10 +1,12 @@
 use iced_native::{Point, Size, Vector};
 
 use crate::{
-    canvas::{Fill, Path, Stroke},
-    triangle,
+    canvas::{Fill, Path, Stroke, TextNode},
+    triangle, Primitive,
 };
 
+use std::sync::Arc;
+
 /// The frame of a [`Canvas`].
 ///
 /// [`Canvas`]: struct.Canvas.html
@@ -14,6 +16,7 @@ pub struct Frame {
     height: f32,
     buffers: lyon::tessellation::VertexBuffers<triangle::Vertex2D, u32>,
     transforms: Transforms,
+    texts: Vec<TextNode>,
 }
 
 #[derive(Debug)]
@@ -40,6 +43,7 @@ impl Frame {
             width,
             height,
             buffers: lyon::tessellation::VertexBuffers::new(),
+            texts: Vec::new(),
             transforms: Transforms {
                 previous: Vec::new(),
                 current: Transform {
@@ -154,6 +158,14 @@ impl Frame {
         let _ = result.expect("Stroke path");
     }
 
+    /// Draws the text of the given [`TextNode`] on the [`Frame`]
+    ///
+    /// [`TextNode`]: struct.TextNode.html
+    /// [`Frame`]: struct.Frame.html
+    pub fn text(&mut self, text: TextNode) {
+        self.texts.push(text);
+    }
+
     /// Stores the current transform of the [`Frame`] and executes the given
     /// drawing operations, restoring the transform afterwards.
     ///
@@ -209,14 +221,38 @@ impl Frame {
         self.transforms.current.is_identity = false;
     }
 
-    /// Produces the geometry that has been drawn on the [`Frame`].
+    /// Produces the primitive representing everything drawn on the [`Frame`].
     ///
     /// [`Frame`]: struct.Frame.html
-    pub fn into_mesh(self) -> triangle::Mesh2D {
-        triangle::Mesh2D {
-            vertices: self.buffers.vertices,
-            indices: self.buffers.indices,
-        }
+    pub fn into_primitive(self, origin: Point) -> Primitive {
+        let mut primitives: Vec<Primitive> = self
+            .texts
+            .into_iter()
+            .map(|mut t| {
+                t.bounds.x += origin.x;
+                t.bounds.y += origin.y;
+
+                Primitive::Text {
+                    content: t.content,
+                    bounds: t.bounds,
+                    color: t.color,
+                    size: t.size,
+                    font: t.font,
+                    horizontal_alignment: t.horizontal_alignment,
+                    vertical_alignment: t.vertical_alignment,
+                }
+            })
+            .collect();
+
+        primitives.push(Primitive::Mesh2D {
+            origin,
+            buffers: Arc::new(triangle::Mesh2D {
+                vertices: self.buffers.vertices,
+                indices: self.buffers.indices,
+            }),
+        });
+
+        Primitive::Group { primitives }
     }
 }
 

wgpu/src/widget/canvas/layer.rs

@@ -3,10 +3,9 @@ mod cache;
 
 pub use cache::Cache;
 
-use crate::triangle;
+use crate::Primitive;
 
-use iced_native::Size;
-use std::sync::Arc;
+use iced_native::{Point, Size};
 
 /// A layer that can be presented at a [`Canvas`].
 ///
@@ -21,5 +20,5 @@ pub trait Layer: std::fmt::Debug {
     ///
     /// [`Layer`]: trait.Layer.html
     /// [`Mesh2D`]: ../../../triangle/struct.Mesh2D.html
-    fn draw(&self, bounds: Size) -> Arc<triangle::Mesh2D>;
+    fn draw(&self, origin: Point, bounds: Size) -> Primitive;
 }

wgpu/src/widget/canvas/layer/cache.rs

@@ -1,12 +1,10 @@
 use crate::{
     canvas::{Drawable, Frame, Layer},
-    triangle,
+    Primitive,
 };
 
-use iced_native::Size;
-use std::cell::RefCell;
-use std::marker::PhantomData;
-use std::sync::Arc;
+use iced_native::{Point, Size};
+use std::{cell::RefCell, marker::PhantomData};
 
 /// A simple cache that stores generated geometry to avoid recomputation.
 ///
@@ -24,10 +22,7 @@ pub struct Cache<T: Drawable> {
 #[derive(Debug)]
 enum State {
     Empty,
-    Filled {
-        mesh: Arc<triangle::Mesh2D>,
-        bounds: Size,
-    },
+    Filled { bounds: Size, primitive: Primitive },
 }
 
 impl<T> Cache<T>
@@ -75,27 +70,27 @@ impl<'a, T> Layer for Bind<'a, T>
 where
     T: Drawable + std::fmt::Debug,
 {
-    fn draw(&self, current_bounds: Size) -> Arc<triangle::Mesh2D> {
+    fn draw(&self, origin: Point, current_bounds: Size) -> Primitive {
         use std::ops::Deref;
 
-        if let State::Filled { mesh, bounds } =
+        if let State::Filled { bounds, primitive } =
             self.cache.state.borrow().deref()
         {
             if *bounds == current_bounds {
-                return mesh.clone();
+                return primitive.clone();
             }
         }
 
         let mut frame = Frame::new(current_bounds.width, current_bounds.height);
         self.input.draw(&mut frame);
 
-        let mesh = Arc::new(frame.into_mesh());
+        let primitive = frame.into_primitive(origin);
 
         *self.cache.state.borrow_mut() = State::Filled {
-            mesh: mesh.clone(),
             bounds: current_bounds,
+            primitive: primitive.clone(),
         };
 
-        mesh
+        primitive
     }
 }

wgpu/src/widget/canvas/text.rs

@@ -0,0 +1,20 @@
+use iced_native::{Color, Font, HorizontalAlignment, Rectangle, VerticalAlignment};
+
+/// A text node to be drawn to a canvas
+#[derive(Debug, Clone)]
+pub struct TextNode {
+    /// The contents of the text
+    pub content: String,
+    /// The bounds of the text
+    pub bounds: Rectangle,
+    /// The color of the text
+    pub color: Color,
+    /// The size of the text
+    pub size: f32,
+    /// The font of the text
+    pub font: Font,
+    /// The horizontal alignment of the text
+    pub horizontal_alignment: HorizontalAlignment,
+    /// The vertical alignment of the text
+    pub vertical_alignment: VerticalAlignment,
+}