From 08b376c6d7d2f3c1fab1328202325cb47ce369e5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?H=C3=A9ctor=20Ram=C3=B3n=20Jim=C3=A9nez?=
 <hector0193@gmail.com>
Date: Fri, 1 May 2020 04:33:17 +0200
Subject: [PATCH] Implement `Frame::fill_rectangle`

This method greatly improves performance when drawing axis-aligned rectangles.
---
 wgpu/src/widget/canvas/frame.rs | 51 +++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/wgpu/src/widget/canvas/frame.rs b/wgpu/src/widget/canvas/frame.rs
index 1c4a038a..5262ab4e 100644
--- a/wgpu/src/widget/canvas/frame.rs
+++ b/wgpu/src/widget/canvas/frame.rs
@@ -120,6 +120,43 @@ impl Frame {
         let _ = result.expect("Tessellate path");
     }
 
+    /// Draws an axis-aligned rectangle given its top-left corner coordinate and
+    /// its `Size` on the [`Frame`] by filling it with the provided style.
+    ///
+    /// [`Frame`]: struct.Frame.html
+    pub fn fill_rectangle(
+        &mut self,
+        top_left: Point,
+        size: Size,
+        fill: impl Into<Fill>,
+    ) {
+        use lyon::tessellation::{BuffersBuilder, FillOptions};
+
+        let mut buffers = BuffersBuilder::new(
+            &mut self.buffers,
+            FillVertex(match fill.into() {
+                Fill::Color(color) => color.into_linear(),
+            }),
+        );
+
+        let top_left =
+            self.transforms.current.raw.transform_point(
+                lyon::math::Point::new(top_left.x, top_left.y),
+            );
+
+        let size =
+            self.transforms.current.raw.transform_vector(
+                lyon::math::Vector::new(size.width, size.height),
+            );
+
+        let _ = lyon::tessellation::basic_shapes::fill_rectangle(
+            &lyon::math::Rect::new(top_left, size.into()),
+            &FillOptions::default(),
+            &mut buffers,
+        )
+        .expect("Fill rectangle");
+    }
+
     /// Draws the stroke of the given [`Path`] on the [`Frame`] with the
     /// provided style.
     ///
@@ -283,6 +320,20 @@ impl Frame {
 
 struct FillVertex([f32; 4]);
 
+impl lyon::tessellation::BasicVertexConstructor<triangle::Vertex2D>
+    for FillVertex
+{
+    fn new_vertex(
+        &mut self,
+        position: lyon::math::Point,
+    ) -> triangle::Vertex2D {
+        triangle::Vertex2D {
+            position: [position.x, position.y],
+            color: self.0,
+        }
+    }
+}
+
 impl lyon::tessellation::FillVertexConstructor<triangle::Vertex2D>
     for FillVertex
 {