Merge pull request #214 from artursapek/artur/canvas-text

Implement text support in canvas widget

5 files changed, 117 insertions, 28 deletions

diff --git a/wgpu/src/widget/canvas.rs b/wgpu/src/widget/canvas.rs
index 38c1ce62..3a9605c9 100644
--- a/wgpu/src/widget/canvas.rs
+++ b/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::Text;
 
 /// A widget capable of drawing 2D graphics.
 ///
@@ -121,9 +123,9 @@ impl<'a, Message> Widget<Message, Renderer> for Canvas<'a> {
                 primitives: self
                     .layers
                     .iter()
-                    .map(|layer| Primitive::Mesh2D {
+                    .map(|layer| Primitive::Cached {
                         origin,
-                        buffers: layer.draw(size),
+                        cache: layer.draw(size),
                     })
                     .collect(),
             },
diff --git a/wgpu/src/widget/canvas/frame.rs b/wgpu/src/widget/canvas/frame.rs
index fa6d8c0a..7d7ce06a 100644
--- a/wgpu/src/widget/canvas/frame.rs
+++ b/wgpu/src/widget/canvas/frame.rs
@@ -1,8 +1,8 @@
-use iced_native::{Point, Size, Vector};
+use iced_native::{Point, Rectangle, Size, Vector};
 
 use crate::{
-    canvas::{Fill, Path, Stroke},
-    triangle,
+    canvas::{Fill, Path, Stroke, Text},
+    triangle, Primitive,
 };
 
 /// The frame of a [`Canvas`].
@@ -13,6 +13,7 @@ pub struct Frame {
     width: f32,
     height: f32,
     buffers: lyon::tessellation::VertexBuffers<triangle::Vertex2D, u32>,
+    primitives: Vec<Primitive>,
     transforms: Transforms,
 }
 
@@ -40,6 +41,7 @@ impl Frame {
             width,
             height,
             buffers: lyon::tessellation::VertexBuffers::new(),
+            primitives: Vec::new(),
             transforms: Transforms {
                 previous: Vec::new(),
                 current: Transform {
@@ -154,6 +156,52 @@ impl Frame {
         let _ = result.expect("Stroke path");
     }
 
+    /// Draws the characters of the given [`Text`] on the [`Frame`], filling
+    /// them with the given color.
+    ///
+    /// __Warning:__ Text currently does not work well with rotations and scale
+    /// transforms! The position will be correctly transformed, but the
+    /// resulting glyphs will not be rotated or scaled properly.
+    ///
+    /// Additionally, all text will be rendered on top of all the layers of
+    /// a [`Canvas`]. Therefore, it is currently only meant to be used for
+    /// overlays, which is the most common use case.
+    ///
+    /// Support for vectorial text is planned, and should address all these
+    /// limitations.
+    ///
+    /// [`Text`]: struct.Text.html
+    /// [`Frame`]: struct.Frame.html
+    pub fn fill_text(&mut self, text: Text) {
+        use std::f32;
+
+        let position = if self.transforms.current.is_identity {
+            text.position
+        } else {
+            let transformed = self.transforms.current.raw.transform_point(
+                lyon::math::Point::new(text.position.x, text.position.y),
+            );
+
+            Point::new(transformed.x, transformed.y)
+        };
+
+        // TODO: Use vectorial text instead of primitive
+        self.primitives.push(Primitive::Text {
+            content: text.content,
+            bounds: Rectangle {
+                x: position.x,
+                y: position.y,
+                width: f32::INFINITY,
+                height: f32::INFINITY,
+            },
+            color: text.color,
+            size: text.size,
+            font: text.font,
+            horizontal_alignment: text.horizontal_alignment,
+            vertical_alignment: text.vertical_alignment,
+        });
+    }
+
     /// Stores the current transform of the [`Frame`] and executes the given
     /// drawing operations, restoring the transform afterwards.
     ///
@@ -209,13 +257,20 @@ 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(mut self) -> Primitive {
+        self.primitives.push(Primitive::Mesh2D {
+            origin: Point::ORIGIN,
+            buffers: triangle::Mesh2D {
+                vertices: self.buffers.vertices,
+                indices: self.buffers.indices,
+            },
+        });
+
+        Primitive::Group {
+            primitives: self.primitives,
         }
     }
 }
diff --git a/wgpu/src/widget/canvas/layer.rs b/wgpu/src/widget/canvas/layer.rs
index 82d647bb..a46b7fb1 100644
--- a/wgpu/src/widget/canvas/layer.rs
+++ b/wgpu/src/widget/canvas/layer.rs
@@ -3,23 +3,23 @@ mod cache;
 
 pub use cache::Cache;
 
-use crate::triangle;
-
+use crate::Primitive;
 use iced_native::Size;
+
 use std::sync::Arc;
 
 /// A layer that can be presented at a [`Canvas`].
 ///
 /// [`Canvas`]: ../struct.Canvas.html
 pub trait Layer: std::fmt::Debug {
-    /// Draws the [`Layer`] in the given bounds and produces [`Mesh2D`] as a
-    /// result.
+    /// Draws the [`Layer`] in the given bounds and produces a [`Primitive`] as
+    /// a result.
     ///
-    /// The [`Layer`] may choose to store the produced [`Mesh2D`] locally and
+    /// The [`Layer`] may choose to store the produced [`Primitive`] locally and
     /// only recompute it when the bounds change, its contents change, or is
     /// otherwise explicitly cleared by other means.
     ///
     /// [`Layer`]: trait.Layer.html
-    /// [`Mesh2D`]: ../../../triangle/struct.Mesh2D.html
-    fn draw(&self, bounds: Size) -> Arc<triangle::Mesh2D>;
+    /// [`Primitive`]: ../../../enum.Primitive.html
+    fn draw(&self, bounds: Size) -> Arc<Primitive>;
 }
diff --git a/wgpu/src/widget/canvas/layer/cache.rs b/wgpu/src/widget/canvas/layer/cache.rs
index 3071cce0..6b69f01e 100644
--- a/wgpu/src/widget/canvas/layer/cache.rs
+++ b/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 std::{cell::RefCell, marker::PhantomData, sync::Arc};
 
 /// A simple cache that stores generated geometry to avoid recomputation.
 ///
@@ -25,8 +23,8 @@ pub struct Cache<T: Drawable> {
 enum State {
     Empty,
     Filled {
-        mesh: Arc<triangle::Mesh2D>,
         bounds: Size,
+        primitive: Arc<Primitive>,
     },
 }
 
@@ -75,27 +73,27 @@ 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, current_bounds: Size) -> Arc<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 = Arc::new(frame.into_primitive());
 
         *self.cache.state.borrow_mut() = State::Filled {
-            mesh: mesh.clone(),
             bounds: current_bounds,
+            primitive: primitive.clone(),
         };
 
-        mesh
+        primitive
     }
 }
diff --git a/wgpu/src/widget/canvas/text.rs b/wgpu/src/widget/canvas/text.rs
new file mode 100644
index 00000000..d1cf1a0f
--- /dev/null
+++ b/wgpu/src/widget/canvas/text.rs
@@ -0,0 +1,34 @@
+use iced_native::{Color, Font, HorizontalAlignment, Point, VerticalAlignment};
+
+/// A bunch of text that can be drawn to a canvas
+#[derive(Debug, Clone)]
+pub struct Text {
+    /// The contents of the text
+    pub content: String,
+    /// The position where to begin drawing the text (top-left corner coordinates)
+    pub position: Point,
+    /// 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,
+}
+
+impl Default for Text {
+    fn default() -> Text {
+        Text {
+            content: String::new(),
+            position: Point::ORIGIN,
+            color: Color::BLACK,
+            size: 16.0,
+            font: Font::Default,
+            horizontal_alignment: HorizontalAlignment::Left,
+            vertical_alignment: VerticalAlignment::Top,
+        }
+    }
+}