Draft basic text rendering using wgpu_glyph

wgpu/src/lib.rs

@@ -1,7 +1,7 @@
 use iced_native::{
     button, checkbox, column, image, radio, renderer::Debugger, row, slider,
     text, Button, Checkbox, Color, Column, Image, Layout, Node, Point, Radio,
-    Row, Slider, Style, Text, Widget,
+    Rectangle, Row, Slider, Style, Text, Widget,
 };
 
 use raw_window_handle::HasRawWindowHandle;
@@ -10,28 +10,34 @@ use wgpu::{
     Instance, Limits, PowerPreference, RequestAdapterOptions, Surface,
     SwapChain, SwapChainDescriptor, TextureFormat, TextureUsage,
 };
+use wgpu_glyph::{GlyphBrush, GlyphBrushBuilder, GlyphCruncher, Section};
+
+use std::f32;
+use std::{cell::RefCell, rc::Rc};
 
 pub struct Renderer {
     instance: Instance,
     surface: Surface,
     adapter: Adapter,
     device: Device,
+    glyph_brush: Rc<RefCell<GlyphBrush<'static, ()>>>,
+}
+
+pub struct Target {
+    width: u16,
+    height: u16,
     swap_chain: SwapChain,
 }
 
 impl Renderer {
-    pub fn new<W: HasRawWindowHandle>(
-        window: &W,
-        width: u32,
-        height: u32,
-    ) -> Self {
+    pub fn new<W: HasRawWindowHandle>(window: &W) -> Self {
         let instance = Instance::new();
 
         let adapter = instance.request_adapter(&RequestAdapterOptions {
             power_preference: PowerPreference::LowPower,
         });
 
-        let device = adapter.request_device(&DeviceDescriptor {
+        let mut device = adapter.request_device(&DeviceDescriptor {
             extensions: Extensions {
                 anisotropic_filtering: false,
             },
@@ -40,28 +46,40 @@ impl Renderer {
 
         let surface = instance.create_surface(window.raw_window_handle());
 
-        let swap_chain = device.create_swap_chain(
-            &surface,
-            &SwapChainDescriptor {
-                usage: TextureUsage::OUTPUT_ATTACHMENT,
-                format: TextureFormat::Bgra8UnormSrgb,
-                width,
-                height,
-                present_mode: wgpu::PresentMode::Vsync,
-            },
-        );
+        let font: &[u8] =
+            include_bytes!("../../examples/tour/resources/Roboto-Regular.ttf");
+
+        let glyph_brush = GlyphBrushBuilder::using_font_bytes(font)
+            .build(&mut device, TextureFormat::Bgra8UnormSrgb);
 
         Self {
             instance,
             surface,
             adapter,
             device,
-            swap_chain,
+            glyph_brush: Rc::new(RefCell::new(glyph_brush)),
         }
     }
 
-    pub fn draw(&mut self) {
-        let frame = self.swap_chain.get_next_texture();
+    pub fn target(&self, width: u16, height: u16) -> Target {
+        Target {
+            width,
+            height,
+            swap_chain: self.device.create_swap_chain(
+                &self.surface,
+                &SwapChainDescriptor {
+                    usage: TextureUsage::OUTPUT_ATTACHMENT,
+                    format: TextureFormat::Bgra8UnormSrgb,
+                    width: u32::from(width),
+                    height: u32::from(height),
+                    present_mode: wgpu::PresentMode::Vsync,
+                },
+            ),
+        }
+    }
+
+    pub fn draw(&mut self, target: &mut Target, primitive: &Primitive) {
+        let frame = target.swap_chain.get_next_texture();
 
         let mut encoder = self
             .device
@@ -83,39 +101,169 @@ impl Renderer {
             depth_stencil_attachment: None,
         });
 
+        self.draw_primitive(primitive);
+
+        self.glyph_brush
+            .borrow_mut()
+            .draw_queued(
+                &mut self.device,
+                &mut encoder,
+                &frame.view,
+                u32::from(target.width),
+                u32::from(target.height),
+            )
+            .expect("Draw text");
+
         self.device.get_queue().submit(&[encoder.finish()]);
     }
+
+    fn draw_primitive(&mut self, primitive: &Primitive) {
+        match primitive {
+            Primitive::None => {}
+            Primitive::Group { primitives } => {
+                for primitive in primitives {
+                    self.draw_primitive(primitive)
+                }
+            }
+            Primitive::Text {
+                content,
+                bounds,
+                size,
+            } => self.glyph_brush.borrow_mut().queue(Section {
+                text: &content,
+                screen_position: (bounds.x, bounds.y),
+                bounds: (bounds.width, bounds.height),
+                scale: wgpu_glyph::Scale { x: *size, y: *size },
+                ..Default::default()
+            }),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum Primitive {
+    None,
+    Group {
+        primitives: Vec<Primitive>,
+    },
+    Text {
+        content: String,
+        bounds: Rectangle,
+        size: f32,
+    },
+}
+
+impl iced_native::Renderer for Renderer {
+    type Primitive = Primitive;
 }
 
 impl column::Renderer for Renderer {
     fn draw<Message>(
         &mut self,
-        _column: &Column<'_, Message, Self>,
-        _layout: Layout<'_>,
-        _cursor_position: Point,
+        column: &Column<'_, Message, Self>,
+        layout: Layout<'_>,
+        cursor_position: Point,
     ) -> Self::Primitive {
-        ()
+        Primitive::Group {
+            primitives: column
+                .children
+                .iter()
+                .zip(layout.children())
+                .map(|(child, layout)| {
+                    child.draw(self, layout, cursor_position)
+                })
+                .collect(),
+        }
     }
 }
 
 impl row::Renderer for Renderer {
     fn draw<Message>(
         &mut self,
-        _column: &Row<'_, Message, Self>,
-        _layout: Layout<'_>,
-        _cursor_position: Point,
+        row: &Row<'_, Message, Self>,
+        layout: Layout<'_>,
+        cursor_position: Point,
     ) -> Self::Primitive {
-        ()
+        Primitive::Group {
+            primitives: row
+                .children
+                .iter()
+                .zip(layout.children())
+                .map(|(child, layout)| {
+                    child.draw(self, layout, cursor_position)
+                })
+                .collect(),
+        }
     }
 }
 
 impl text::Renderer for Renderer {
-    fn node(&self, _text: &Text) -> Node {
-        Node::new(Style::default())
+    fn node(&self, text: &Text) -> Node {
+        let glyph_brush = self.glyph_brush.clone();
+        let content = text.content.clone();
+
+        // TODO: Investigate why stretch tries to measure this MANY times
+        // with every ancestor's bounds.
+        // Bug? Using the library wrong? I should probably open an issue on
+        // the stretch repository.
+        // I noticed that the first measure is the one that matters in
+        // practice. Here, we use a RefCell to store the cached measurement.
+        let measure = RefCell::new(None);
+        let size = text.size.map(f32::from).unwrap_or(20.0);
+
+        let style = Style::default().width(text.width);
+
+        iced_native::Node::with_measure(style, move |bounds| {
+            let mut measure = measure.borrow_mut();
+
+            if measure.is_none() {
+                let bounds = (
+                    match bounds.width {
+                        iced_native::Number::Undefined => f32::INFINITY,
+                        iced_native::Number::Defined(w) => w,
+                    },
+                    match bounds.height {
+                        iced_native::Number::Undefined => f32::INFINITY,
+                        iced_native::Number::Defined(h) => h,
+                    },
+                );
+
+                let text = Section {
+                    text: &content,
+                    scale: wgpu_glyph::Scale { x: size, y: size },
+                    bounds,
+                    ..Default::default()
+                };
+
+                let (width, height) = if let Some(bounds) =
+                    glyph_brush.borrow_mut().glyph_bounds(&text)
+                {
+                    (bounds.width(), bounds.height())
+                } else {
+                    (0.0, 0.0)
+                };
+
+                let size = iced_native::Size { width, height };
+
+                // If the text has no width boundary we avoid caching as the
+                // layout engine may just be measuring text in a row.
+                if bounds.0 == f32::INFINITY {
+                    return size;
+                } else {
+                    *measure = Some(size);
+                }
+            }
+
+            measure.unwrap()
+        })
     }
 
-    fn draw(&mut self, _text: &Text, _layout: Layout<'_>) -> Self::Primitive {
-        ()
+    fn draw(&mut self, text: &Text, layout: Layout<'_>) -> Self::Primitive {
+        Primitive::Text {
+            content: text.content.clone(),
+            size: f32::from(text.size.unwrap_or(20)),
+            bounds: layout.bounds(),
+        }
     }
 }
 
@@ -130,7 +278,7 @@ impl checkbox::Renderer for Renderer {
         _layout: Layout<'_>,
         _cursor_position: Point,
     ) -> Self::Primitive {
-        ()
+        Primitive::None
     }
 }
 
@@ -145,7 +293,7 @@ impl radio::Renderer for Renderer {
         _layout: Layout<'_>,
         _cursor_position: Point,
     ) -> Self::Primitive {
-        ()
+        Primitive::None
     }
 }
 
@@ -160,7 +308,7 @@ impl slider::Renderer for Renderer {
         _layout: Layout<'_>,
         _cursor_position: Point,
     ) -> Self::Primitive {
-        ()
+        Primitive::None
     }
 }
 
@@ -174,7 +322,7 @@ impl image::Renderer<&str> for Renderer {
         _checkbox: &Image<&str>,
         _layout: Layout<'_>,
     ) -> Self::Primitive {
-        ()
+        Primitive::None
     }
 }
 
@@ -189,14 +337,10 @@ impl button::Renderer for Renderer {
         _layout: Layout<'_>,
         _cursor_position: Point,
     ) -> Self::Primitive {
-        ()
+        Primitive::None
     }
 }
 
-impl iced_native::Renderer for Renderer {
-    type Primitive = ();
-}
-
 impl Debugger for Renderer {
     fn explain<Message>(
         &mut self,