Re-introduce the `geometry` example

5 files changed, 244 insertions, 0 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 2644f508..d0243dfd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -66,6 +66,7 @@ members = [
     "examples/events",
     "examples/exit",
     "examples/game_of_life",
+    "examples/geometry",
     "examples/integration_opengl",
     "examples/integration_wgpu",
     "examples/lazy",
diff --git a/examples/README.md b/examples/README.md
index 8d9718a4..bb15dc2e 100644
--- a/examples/README.md
+++ b/examples/README.md
@@ -92,6 +92,7 @@ A bunch of simpler examples exist:
 - [`custom_widget`](custom_widget), a demonstration of how to build a custom widget that draws a circle.
 - [`download_progress`](download_progress), a basic application that asynchronously downloads a dummy file of 100 MB and tracks the download progress.
 - [`events`](events), a log of native events displayed using a conditional `Subscription`.
+- [`geometry`](geometry), a custom widget showcasing how to draw geometry with the `Mesh2D` primitive in [`iced_wgpu`](../wgpu).
 - [`integration_opengl`](integration_opengl), a demonstration of how to integrate Iced in an existing OpenGL application.
 - [`integration_wgpu`](integration_wgpu), a demonstration of how to integrate Iced in an existing [`wgpu`] application.
 - [`pane_grid`](pane_grid), a grid of panes that can be split, resized, and reorganized.
diff --git a/examples/geometry/Cargo.toml b/examples/geometry/Cargo.toml
new file mode 100644
index 00000000..22ede0e0
--- /dev/null
+++ b/examples/geometry/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "geometry"
+version = "0.1.0"
+authors = ["Héctor Ramón Jiménez <hector0193@gmail.com>"]
+edition = "2021"
+publish = false
+
+[dependencies]
+iced = { path = "../.." }
+iced_native = { path = "../../native" }
+iced_graphics = { path = "../../graphics" }
diff --git a/examples/geometry/README.md b/examples/geometry/README.md
new file mode 100644
index 00000000..4d5c81cb
--- /dev/null
+++ b/examples/geometry/README.md
@@ -0,0 +1,18 @@
+## Geometry
+
+A custom widget showcasing how to draw geometry with the `Mesh2D` primitive in [`iced_wgpu`](../../wgpu).
+
+The __[`main`]__ file contains all the code of the example.
+
+<div align="center">
+  <a href="https://gfycat.com/activeunfitkangaroo">
+    <img src="https://thumbs.gfycat.com/ActiveUnfitKangaroo-small.gif">
+  </a>
+</div>
+
+You can run it with `cargo run`:
+```
+cargo run --package geometry
+```
+
+[`main`]: src/main.rs
diff --git a/examples/geometry/src/main.rs b/examples/geometry/src/main.rs
new file mode 100644
index 00000000..4de281fe
--- /dev/null
+++ b/examples/geometry/src/main.rs
@@ -0,0 +1,213 @@
+//! This example showcases a simple native custom widget that renders using
+//! arbitrary low-level geometry.
+mod rainbow {
+    // For now, to implement a custom native widget you will need to add
+    // `iced_native` and `iced_wgpu` to your dependencies.
+    //
+    // Then, you simply need to define your widget type and implement the
+    // `iced_native::Widget` trait with the `iced_wgpu::Renderer`.
+    //
+    // Of course, you can choose to make the implementation renderer-agnostic,
+    // if you wish to, by creating your own `Renderer` trait, which could be
+    // implemented by `iced_wgpu` and other renderers.
+    use iced_graphics::renderer::{self, Renderer};
+    use iced_graphics::triangle::ColoredVertex2D;
+    use iced_graphics::{Backend, Primitive};
+
+    use iced_native::layout;
+    use iced_native::widget::{self, Widget};
+    use iced_native::{
+        Element, Layout, Length, Point, Rectangle, Size, Vector,
+    };
+
+    pub struct Rainbow;
+
+    impl Rainbow {
+        pub fn new() -> Self {
+            Self
+        }
+    }
+
+    impl<Message, B, T> Widget<Message, Renderer<B, T>> for Rainbow
+    where
+        B: Backend,
+    {
+        fn width(&self) -> Length {
+            Length::Fill
+        }
+
+        fn height(&self) -> Length {
+            Length::Shrink
+        }
+
+        fn layout(
+            &self,
+            _renderer: &Renderer<B, T>,
+            limits: &layout::Limits,
+        ) -> layout::Node {
+            let size = limits.width(Length::Fill).resolve(Size::ZERO);
+
+            layout::Node::new(Size::new(size.width, size.width))
+        }
+
+        fn draw(
+            &self,
+            _tree: &widget::Tree,
+            renderer: &mut Renderer<B, T>,
+            _theme: &T,
+            _style: &renderer::Style,
+            layout: Layout<'_>,
+            cursor_position: Point,
+            _viewport: &Rectangle,
+        ) {
+            use iced_graphics::triangle::Mesh2D;
+            use iced_native::Renderer as _;
+
+            let b = layout.bounds();
+
+            // R O Y G B I V
+            let color_r = [1.0, 0.0, 0.0, 1.0];
+            let color_o = [1.0, 0.5, 0.0, 1.0];
+            let color_y = [1.0, 1.0, 0.0, 1.0];
+            let color_g = [0.0, 1.0, 0.0, 1.0];
+            let color_gb = [0.0, 1.0, 0.5, 1.0];
+            let color_b = [0.0, 0.2, 1.0, 1.0];
+            let color_i = [0.5, 0.0, 1.0, 1.0];
+            let color_v = [0.75, 0.0, 0.5, 1.0];
+
+            let posn_center = {
+                if b.contains(cursor_position) {
+                    [cursor_position.x - b.x, cursor_position.y - b.y]
+                } else {
+                    [b.width / 2.0, b.height / 2.0]
+                }
+            };
+
+            let posn_tl = [0.0, 0.0];
+            let posn_t = [b.width / 2.0, 0.0];
+            let posn_tr = [b.width, 0.0];
+            let posn_r = [b.width, b.height / 2.0];
+            let posn_br = [b.width, b.height];
+            let posn_b = [(b.width / 2.0), b.height];
+            let posn_bl = [0.0, b.height];
+            let posn_l = [0.0, b.height / 2.0];
+
+            let mesh = Primitive::SolidMesh {
+                size: b.size(),
+                buffers: Mesh2D {
+                    vertices: vec![
+                        ColoredVertex2D {
+                            position: posn_center,
+                            color: [1.0, 1.0, 1.0, 1.0],
+                        },
+                        ColoredVertex2D {
+                            position: posn_tl,
+                            color: color_r,
+                        },
+                        ColoredVertex2D {
+                            position: posn_t,
+                            color: color_o,
+                        },
+                        ColoredVertex2D {
+                            position: posn_tr,
+                            color: color_y,
+                        },
+                        ColoredVertex2D {
+                            position: posn_r,
+                            color: color_g,
+                        },
+                        ColoredVertex2D {
+                            position: posn_br,
+                            color: color_gb,
+                        },
+                        ColoredVertex2D {
+                            position: posn_b,
+                            color: color_b,
+                        },
+                        ColoredVertex2D {
+                            position: posn_bl,
+                            color: color_i,
+                        },
+                        ColoredVertex2D {
+                            position: posn_l,
+                            color: color_v,
+                        },
+                    ],
+                    indices: vec![
+                        0, 1, 2, // TL
+                        0, 2, 3, // T
+                        0, 3, 4, // TR
+                        0, 4, 5, // R
+                        0, 5, 6, // BR
+                        0, 6, 7, // B
+                        0, 7, 8, // BL
+                        0, 8, 1, // L
+                    ],
+                },
+            };
+
+            renderer.with_translation(Vector::new(b.x, b.y), |renderer| {
+                renderer.draw_primitive(mesh);
+            });
+        }
+    }
+
+    impl<'a, Message, B, T> From<Rainbow> for Element<'a, Message, Renderer<B, T>>
+    where
+        B: Backend,
+    {
+        fn from(rainbow: Rainbow) -> Self {
+            Self::new(rainbow)
+        }
+    }
+}
+
+use iced::widget::{column, container, scrollable};
+use iced::{Element, Length, Sandbox, Settings};
+use rainbow::Rainbow;
+
+pub fn main() -> iced::Result {
+    Example::run(Settings::default())
+}
+
+struct Example;
+
+impl Sandbox for Example {
+    type Message = ();
+
+    fn new() -> Self {
+        Self
+    }
+
+    fn title(&self) -> String {
+        String::from("Custom 2D geometry - Iced")
+    }
+
+    fn update(&mut self, _: ()) {}
+
+    fn view(&self) -> Element<()> {
+        let content = column![
+            Rainbow::new(),
+            "In this example we draw a custom widget Rainbow, using \
+                 the Mesh2D primitive. This primitive supplies a list of \
+                 triangles, expressed as vertices and indices.",
+            "Move your cursor over it, and see the center vertex \
+                 follow you!",
+            "Every Vertex2D defines its own color. You could use the \
+                 Mesh2D primitive to render virtually any two-dimensional \
+                 geometry for your widget.",
+        ]
+        .padding(20)
+        .spacing(20)
+        .max_width(500);
+
+        let scrollable =
+            scrollable(container(content).width(Length::Fill).center_x());
+
+        container(scrollable)
+            .width(Length::Fill)
+            .height(Length::Fill)
+            .center_y()
+            .into()
+    }
+}