Unify `web` and `ggez` tour examples :tada:

15 files changed, 1484 insertions, 0 deletions

diff --git a/examples/tour/src/iced_ggez.rs b/examples/tour/src/iced_ggez.rs
new file mode 100644
index 00000000..4a9c0ef4
--- /dev/null
+++ b/examples/tour/src/iced_ggez.rs
@@ -0,0 +1,6 @@
+mod renderer;
+mod widget;
+
+pub use renderer::Cache as ImageCache;
+pub use renderer::Renderer;
+pub use widget::*;
diff --git a/examples/tour/src/iced_ggez/main.rs b/examples/tour/src/iced_ggez/main.rs
new file mode 100644
index 00000000..a8cf09e5
--- /dev/null
+++ b/examples/tour/src/iced_ggez/main.rs
@@ -0,0 +1,189 @@
+use iced_tour::{iced_ggez, Tour};
+
+use ggez;
+use ggez::event;
+use ggez::filesystem;
+use ggez::graphics;
+use ggez::input::mouse;
+
+pub fn main() -> ggez::GameResult {
+    let (context, event_loop) = {
+        &mut ggez::ContextBuilder::new("iced", "ggez")
+            .window_mode(ggez::conf::WindowMode {
+                width: 1280.0,
+                height: 1024.0,
+                resizable: true,
+                ..ggez::conf::WindowMode::default()
+            })
+            .build()?
+    };
+
+    filesystem::mount(
+        context,
+        std::path::Path::new(env!("CARGO_MANIFEST_DIR")),
+        true,
+    );
+
+    let state = &mut Game::new(context)?;
+
+    event::run(context, event_loop, state)
+}
+
+struct Game {
+    spritesheet: graphics::Image,
+    font: graphics::Font,
+    images: iced_ggez::ImageCache,
+    tour: Tour,
+
+    events: Vec<iced::Event>,
+    cache: Option<iced::Cache>,
+}
+
+impl Game {
+    fn new(context: &mut ggez::Context) -> ggez::GameResult<Game> {
+        graphics::set_default_filter(context, graphics::FilterMode::Nearest);
+
+        Ok(Game {
+            spritesheet: graphics::Image::new(context, "/resources/ui.png")
+                .unwrap(),
+            font: graphics::Font::new(context, "/resources/Roboto-Regular.ttf")
+                .unwrap(),
+            images: iced_ggez::ImageCache::new(),
+            tour: Tour::new(),
+
+            events: Vec::new(),
+            cache: Some(iced::Cache::default()),
+        })
+    }
+}
+
+impl event::EventHandler for Game {
+    fn update(&mut self, _ctx: &mut ggez::Context) -> ggez::GameResult {
+        Ok(())
+    }
+
+    fn mouse_button_down_event(
+        &mut self,
+        _context: &mut ggez::Context,
+        _button: mouse::MouseButton,
+        _x: f32,
+        _y: f32,
+    ) {
+        self.events.push(iced::Event::Mouse(
+            iced::input::mouse::Event::Input {
+                state: iced::input::ButtonState::Pressed,
+                button: iced::input::mouse::Button::Left, // TODO: Map `button`
+            },
+        ));
+    }
+
+    fn mouse_button_up_event(
+        &mut self,
+        _context: &mut ggez::Context,
+        _button: mouse::MouseButton,
+        _x: f32,
+        _y: f32,
+    ) {
+        self.events.push(iced::Event::Mouse(
+            iced::input::mouse::Event::Input {
+                state: iced::input::ButtonState::Released,
+                button: iced::input::mouse::Button::Left, // TODO: Map `button`
+            },
+        ));
+    }
+
+    fn mouse_motion_event(
+        &mut self,
+        _context: &mut ggez::Context,
+        x: f32,
+        y: f32,
+        _dx: f32,
+        _dy: f32,
+    ) {
+        self.events.push(iced::Event::Mouse(
+            iced::input::mouse::Event::CursorMoved { x, y },
+        ));
+    }
+
+    fn resize_event(
+        &mut self,
+        context: &mut ggez::Context,
+        width: f32,
+        height: f32,
+    ) {
+        graphics::set_screen_coordinates(
+            context,
+            graphics::Rect {
+                x: 0.0,
+                y: 0.0,
+                w: width,
+                h: height,
+            },
+        )
+        .expect("Set screen coordinates");
+    }
+
+    fn draw(&mut self, context: &mut ggez::Context) -> ggez::GameResult {
+        graphics::clear(context, graphics::WHITE);
+
+        let screen = graphics::screen_coordinates(context);
+
+        let (messages, cursor) = {
+            let view = self.tour.view();
+
+            let content = iced_ggez::Column::new()
+                .width(screen.w as u16)
+                .height(screen.h as u16)
+                .padding(20)
+                .align_items(iced::Align::Center)
+                .justify_content(iced::Justify::Center)
+                .push(view);
+
+            let renderer = &mut iced_ggez::Renderer::new(
+                context,
+                &mut self.images,
+                self.spritesheet.clone(),
+                self.font,
+            );
+
+            let mut ui = iced::UserInterface::build(
+                content,
+                self.cache.take().unwrap(),
+                renderer,
+            );
+
+            let messages = ui.update(self.events.drain(..));
+            let cursor = ui.draw(renderer);
+
+            self.cache = Some(ui.into_cache());
+
+            renderer.flush();
+
+            (messages, cursor)
+        };
+
+        for message in messages {
+            self.tour.update(message);
+        }
+
+        let cursor_type = into_cursor_type(cursor);
+
+        if mouse::cursor_type(context) != cursor_type {
+            mouse::set_cursor_type(context, cursor_type);
+        }
+
+        graphics::present(context)?;
+        Ok(())
+    }
+}
+
+fn into_cursor_type(cursor: iced::MouseCursor) -> mouse::MouseCursor {
+    match cursor {
+        iced::MouseCursor::OutOfBounds => mouse::MouseCursor::Default,
+        iced::MouseCursor::Idle => mouse::MouseCursor::Default,
+        iced::MouseCursor::Pointer => mouse::MouseCursor::Hand,
+        iced::MouseCursor::Working => mouse::MouseCursor::Progress,
+        iced::MouseCursor::Grab => mouse::MouseCursor::Grab,
+        iced::MouseCursor::Grabbing => mouse::MouseCursor::Grabbing,
+    }
+}
diff --git a/examples/tour/src/iced_ggez/renderer.rs b/examples/tour/src/iced_ggez/renderer.rs
new file mode 100644
index 00000000..e3181eaa
--- /dev/null
+++ b/examples/tour/src/iced_ggez/renderer.rs
@@ -0,0 +1,77 @@
+mod button;
+mod checkbox;
+mod debugger;
+mod image;
+mod radio;
+mod slider;
+mod text;
+
+use ggez::graphics::{
+    self, spritebatch::SpriteBatch, Font, Image, MeshBuilder,
+};
+use ggez::Context;
+
+pub use image::Cache;
+
+pub struct Renderer<'a> {
+    pub context: &'a mut Context,
+    pub images: &'a mut image::Cache,
+    pub sprites: SpriteBatch,
+    pub spritesheet: Image,
+    pub font: Font,
+    font_size: f32,
+    debug_mesh: Option<MeshBuilder>,
+}
+
+impl<'a> Renderer<'a> {
+    pub fn new(
+        context: &'a mut Context,
+        images: &'a mut image::Cache,
+        spritesheet: Image,
+        font: Font,
+    ) -> Renderer<'a> {
+        Renderer {
+            context,
+            images,
+            sprites: SpriteBatch::new(spritesheet.clone()),
+            spritesheet,
+            font,
+            font_size: 20.0,
+            debug_mesh: None,
+        }
+    }
+
+    pub fn flush(&mut self) {
+        graphics::draw(
+            self.context,
+            &self.sprites,
+            graphics::DrawParam::default(),
+        )
+        .expect("Draw sprites");
+
+        graphics::draw_queued_text(
+            self.context,
+            graphics::DrawParam::default(),
+            Default::default(),
+            graphics::FilterMode::Linear,
+        )
+        .expect("Draw text");
+
+        if let Some(debug_mesh) = self.debug_mesh.take() {
+            let mesh =
+                debug_mesh.build(self.context).expect("Build debug mesh");
+
+            graphics::draw(self.context, &mesh, graphics::DrawParam::default())
+                .expect("Draw debug mesh");
+        }
+    }
+}
+
+pub fn into_color(color: iced::Color) -> graphics::Color {
+    graphics::Color {
+        r: color.r,
+        g: color.g,
+        b: color.b,
+        a: color.a,
+    }
+}
diff --git a/examples/tour/src/iced_ggez/renderer/button.rs b/examples/tour/src/iced_ggez/renderer/button.rs
new file mode 100644
index 00000000..486e07ed
--- /dev/null
+++ b/examples/tour/src/iced_ggez/renderer/button.rs
@@ -0,0 +1,145 @@
+use super::Renderer;
+use ggez::graphics::{
+    self, Align, Color, DrawParam, Rect, Scale, Text, TextFragment, WHITE,
+};
+use iced::{button, MouseCursor};
+
+const LEFT: Rect = Rect {
+    x: 0.0,
+    y: 34.0,
+    w: 6.0,
+    h: 49.0,
+};
+
+const BACKGROUND: Rect = Rect {
+    x: LEFT.w,
+    y: LEFT.y,
+    w: 1.0,
+    h: LEFT.h,
+};
+
+const RIGHT: Rect = Rect {
+    x: LEFT.h - LEFT.w,
+    y: LEFT.y,
+    w: LEFT.w,
+    h: LEFT.h,
+};
+
+impl button::Renderer for Renderer<'_> {
+    fn draw(
+        &mut self,
+        cursor_position: iced::Point,
+        mut bounds: iced::Rectangle,
+        state: &button::State,
+        label: &str,
+        class: button::Class,
+    ) -> MouseCursor {
+        let mouse_over = bounds.contains(cursor_position);
+
+        let mut state_offset = 0.0;
+
+        if mouse_over {
+            if state.is_pressed() {
+                bounds.y += 4.0;
+                state_offset = RIGHT.x + RIGHT.w;
+            } else {
+                bounds.y -= 1.0;
+            }
+        }
+
+        let class_index = match class {
+            button::Class::Primary => 0,
+            button::Class::Secondary => 1,
+            button::Class::Positive => 2,
+        };
+
+        let width = self.spritesheet.width() as f32;
+        let height = self.spritesheet.height() as f32;
+
+        self.sprites.add(DrawParam {
+            src: Rect {
+                x: (LEFT.x + state_offset) / width,
+                y: (LEFT.y + class_index as f32 * LEFT.h) / height,
+                w: LEFT.w / width,
+                h: LEFT.h / height,
+            },
+            dest: ggez::mint::Point2 {
+                x: bounds.x,
+                y: bounds.y,
+            },
+            ..DrawParam::default()
+        });
+
+        self.sprites.add(DrawParam {
+            src: Rect {
+                x: (BACKGROUND.x + state_offset) / width,
+                y: (BACKGROUND.y + class_index as f32 * BACKGROUND.h) / height,
+                w: BACKGROUND.w / width,
+                h: BACKGROUND.h / height,
+            },
+            dest: ggez::mint::Point2 {
+                x: bounds.x + LEFT.w,
+                y: bounds.y,
+            },
+            scale: ggez::mint::Vector2 {
+                x: bounds.width - LEFT.w - RIGHT.w,
+                y: 1.0,
+            },
+            ..DrawParam::default()
+        });
+
+        self.sprites.add(DrawParam {
+            src: Rect {
+                x: (RIGHT.x + state_offset) / width,
+                y: (RIGHT.y + class_index as f32 * RIGHT.h) / height,
+                w: RIGHT.w / width,
+                h: RIGHT.h / height,
+            },
+            dest: ggez::mint::Point2 {
+                x: bounds.x + bounds.width - RIGHT.w,
+                y: bounds.y,
+            },
+            ..DrawParam::default()
+        });
+
+        let mut text = Text::new(TextFragment {
+            text: String::from(label),
+            font: Some(self.font),
+            scale: Some(Scale { x: 20.0, y: 20.0 }),
+            ..Default::default()
+        });
+
+        text.set_bounds(
+            ggez::mint::Point2 {
+                x: bounds.width,
+                y: bounds.height,
+            },
+            Align::Center,
+        );
+
+        graphics::queue_text(
+            self.context,
+            &text,
+            ggez::mint::Point2 {
+                x: bounds.x,
+                y: bounds.y + BACKGROUND.h / 4.0,
+            },
+            Some(if mouse_over {
+                WHITE
+            } else {
+                Color {
+                    r: 0.9,
+                    g: 0.9,
+                    b: 0.9,
+                    a: 1.0,
+                }
+            }),
+        );
+
+        if mouse_over {
+            MouseCursor::Pointer
+        } else {
+            MouseCursor::OutOfBounds
+        }
+    }
+}
diff --git a/examples/tour/src/iced_ggez/renderer/checkbox.rs b/examples/tour/src/iced_ggez/renderer/checkbox.rs
new file mode 100644
index 00000000..20a91be5
--- /dev/null
+++ b/examples/tour/src/iced_ggez/renderer/checkbox.rs
@@ -0,0 +1,64 @@
+use super::Renderer;
+
+use ggez::graphics::{DrawParam, Rect};
+use iced::{checkbox, MouseCursor};
+
+const SPRITE: Rect = Rect {
+    x: 98.0,
+    y: 0.0,
+    w: 28.0,
+    h: 28.0,
+};
+
+impl checkbox::Renderer for Renderer<'_> {
+    fn draw(
+        &mut self,
+        cursor_position: iced::Point,
+        bounds: iced::Rectangle,
+        text_bounds: iced::Rectangle,
+        is_checked: bool,
+    ) -> MouseCursor {
+        let mouse_over = bounds.contains(cursor_position)
+            || text_bounds.contains(cursor_position);
+
+        let width = self.spritesheet.width() as f32;
+        let height = self.spritesheet.height() as f32;
+
+        self.sprites.add(DrawParam {
+            src: Rect {
+                x: (SPRITE.x + (if mouse_over { SPRITE.w } else { 0.0 }))
+                    / width,
+                y: SPRITE.y / height,
+                w: SPRITE.w / width,
+                h: SPRITE.h / height,
+            },
+            dest: ggez::mint::Point2 {
+                x: bounds.x,
+                y: bounds.y,
+            },
+            ..DrawParam::default()
+        });
+
+        if is_checked {
+            self.sprites.add(DrawParam {
+                src: Rect {
+                    x: (SPRITE.x + SPRITE.w * 2.0) / width,
+                    y: SPRITE.y / height,
+                    w: SPRITE.w / width,
+                    h: SPRITE.h / height,
+                },
+                dest: ggez::mint::Point2 {
+                    x: bounds.x,
+                    y: bounds.y,
+                },
+                ..DrawParam::default()
+            });
+        }
+
+        if mouse_over {
+            MouseCursor::Pointer
+        } else {
+            MouseCursor::OutOfBounds
+        }
+    }
+}
diff --git a/examples/tour/src/iced_ggez/renderer/debugger.rs b/examples/tour/src/iced_ggez/renderer/debugger.rs
new file mode 100644
index 00000000..c6727881
--- /dev/null
+++ b/examples/tour/src/iced_ggez/renderer/debugger.rs
@@ -0,0 +1,30 @@
+use super::{into_color, Renderer};
+use ggez::graphics::{DrawMode, MeshBuilder, Rect};
+
+impl iced::renderer::Debugger for Renderer<'_> {
+    type Color = iced::Color;
+
+    fn explain(&mut self, layout: &iced::Layout<'_>, color: iced::Color) {
+        let bounds = layout.bounds();
+
+        let mut debug_mesh =
+            self.debug_mesh.take().unwrap_or(MeshBuilder::new());
+
+        debug_mesh.rectangle(
+            DrawMode::stroke(1.0),
+            Rect {
+                x: bounds.x,
+                y: bounds.y,
+                w: bounds.width,
+                h: bounds.height,
+            },
+            into_color(color),
+        );
+
+        self.debug_mesh = Some(debug_mesh);
+
+        for child in layout.children() {
+            self.explain(&child, color);
+        }
+    }
+}
diff --git a/examples/tour/src/iced_ggez/renderer/image.rs b/examples/tour/src/iced_ggez/renderer/image.rs
new file mode 100644
index 00000000..17c6a56e
--- /dev/null
+++ b/examples/tour/src/iced_ggez/renderer/image.rs
@@ -0,0 +1,86 @@
+use super::Renderer;
+
+use ggez::{graphics, nalgebra};
+use iced::image;
+
+pub struct Cache {
+    images: std::collections::HashMap<String, graphics::Image>,
+}
+
+impl Cache {
+    pub fn new() -> Self {
+        Self {
+            images: std::collections::HashMap::new(),
+        }
+    }
+
+    fn get<'a>(
+        &mut self,
+        name: &'a str,
+        context: &mut ggez::Context,
+    ) -> graphics::Image {
+        if let Some(image) = self.images.get(name) {
+            return image.clone();
+        }
+
+        let mut image = graphics::Image::new(context, &format!("/{}", name))
+            .expect("Load ferris image");
+
+        image.set_filter(graphics::FilterMode::Linear);
+
+        self.images.insert(name.to_string(), image.clone());
+
+        image
+    }
+}
+
+impl<'a> image::Renderer<&'a str> for Renderer<'_> {
+    fn node(
+        &mut self,
+        style: iced::Style,
+        name: &&'a str,
+        width: Option<u16>,
+        height: Option<u16>,
+        _source: Option<iced::Rectangle<u16>>,
+    ) -> iced::Node {
+        let image = self.images.get(name, self.context);
+
+        let aspect_ratio = image.width() as f32 / image.height() as f32;
+
+        let style = match (width, height) {
+            (Some(width), Some(height)) => style.width(width).height(height),
+            (Some(width), None) => style
+                .width(width)
+                .height((width as f32 / aspect_ratio).round() as u16),
+            (None, Some(height)) => style
+                .height(height)
+                .width((height as f32 * aspect_ratio).round() as u16),
+            (None, None) => style.width(image.width()).height(image.height()),
+        };
+
+        iced::Node::new(style)
+    }
+
+    fn draw(
+        &mut self,
+        name: &&'a str,
+        bounds: iced::Rectangle,
+        _source: Option<iced::Rectangle<u16>>,
+    ) {
+        let image = self.images.get(name, self.context);
+
+        // We should probably use batches to draw images efficiently and keep
+        // draw side-effect free, but this is good enough for the example.
+        graphics::draw(
+            self.context,
+            &image,
+            graphics::DrawParam::new()
+                .dest(nalgebra::Point2::new(bounds.x, bounds.y))
+                .scale(nalgebra::Vector2::new(
+                    bounds.width / image.width() as f32,
+                    bounds.height / image.height() as f32,
+                )),
+        )
+        .expect("Draw image");
+    }
+}
diff --git a/examples/tour/src/iced_ggez/renderer/radio.rs b/examples/tour/src/iced_ggez/renderer/radio.rs
new file mode 100644
index 00000000..0f7815d6
--- /dev/null
+++ b/examples/tour/src/iced_ggez/renderer/radio.rs
@@ -0,0 +1,63 @@
+use super::Renderer;
+
+use ggez::graphics::{DrawParam, Rect};
+use iced::{radio, MouseCursor, Point, Rectangle};
+
+const SPRITE: Rect = Rect {
+    x: 98.0,
+    y: 28.0,
+    w: 28.0,
+    h: 28.0,
+};
+
+impl radio::Renderer for Renderer<'_> {
+    fn draw(
+        &mut self,
+        cursor_position: Point,
+        bounds: Rectangle,
+        bounds_with_label: Rectangle,
+        is_selected: bool,
+    ) -> MouseCursor {
+        let mouse_over = bounds_with_label.contains(cursor_position);
+
+        let width = self.spritesheet.width() as f32;
+        let height = self.spritesheet.height() as f32;
+
+        self.sprites.add(DrawParam {
+            src: Rect {
+                x: (SPRITE.x + (if mouse_over { SPRITE.w } else { 0.0 }))
+                    / width,
+                y: SPRITE.y / height,
+                w: SPRITE.w / width,
+                h: SPRITE.h / height,
+            },
+            dest: ggez::mint::Point2 {
+                x: bounds.x,
+                y: bounds.y,
+            },
+            ..DrawParam::default()
+        });
+
+        if is_selected {
+            self.sprites.add(DrawParam {
+                src: Rect {
+                    x: (SPRITE.x + SPRITE.w * 2.0) / width,
+                    y: SPRITE.y / height,
+                    w: SPRITE.w / width,
+                    h: SPRITE.h / height,
+                },
+                dest: ggez::mint::Point2 {
+                    x: bounds.x,
+                    y: bounds.y,
+                },
+                ..DrawParam::default()
+            });
+        }
+
+        if mouse_over {
+            MouseCursor::Pointer
+        } else {
+            MouseCursor::OutOfBounds
+        }
+    }
+}
diff --git a/examples/tour/src/iced_ggez/renderer/slider.rs b/examples/tour/src/iced_ggez/renderer/slider.rs
new file mode 100644
index 00000000..146cee18
--- /dev/null
+++ b/examples/tour/src/iced_ggez/renderer/slider.rs
@@ -0,0 +1,82 @@
+use super::Renderer;
+
+use ggez::graphics::{DrawParam, Rect};
+use iced::{slider, MouseCursor, Point, Rectangle};
+use std::ops::RangeInclusive;
+
+const RAIL: Rect = Rect {
+    x: 98.0,
+    y: 56.0,
+    w: 1.0,
+    h: 4.0,
+};
+
+const MARKER: Rect = Rect {
+    x: RAIL.x + 28.0,
+    y: RAIL.y,
+    w: 16.0,
+    h: 24.0,
+};
+
+impl slider::Renderer for Renderer<'_> {
+    fn draw(
+        &mut self,
+        cursor_position: Point,
+        bounds: Rectangle,
+        state: &slider::State,
+        range: RangeInclusive<f32>,
+        value: f32,
+    ) -> MouseCursor {
+        let width = self.spritesheet.width() as f32;
+        let height = self.spritesheet.height() as f32;
+
+        self.sprites.add(DrawParam {
+            src: Rect {
+                x: RAIL.x / width,
+                y: RAIL.y / height,
+                w: RAIL.w / width,
+                h: RAIL.h / height,
+            },
+            dest: ggez::mint::Point2 {
+                x: bounds.x + MARKER.w as f32 / 2.0,
+                y: bounds.y + 12.5,
+            },
+            scale: ggez::mint::Vector2 {
+                x: bounds.width - MARKER.w as f32,
+                y: 1.0,
+            },
+            ..DrawParam::default()
+        });
+
+        let (range_start, range_end) = range.into_inner();
+
+        let marker_offset = (bounds.width - MARKER.w as f32)
+            * ((value - range_start) / (range_end - range_start).max(1.0));
+
+        let mouse_over = bounds.contains(cursor_position);
+        let is_active = state.is_dragging() || mouse_over;
+
+        self.sprites.add(DrawParam {
+            src: Rect {
+                x: (MARKER.x + (if is_active { MARKER.w } else { 0.0 }))
+                    / width,
+                y: MARKER.y / height,
+                w: MARKER.w / width,
+                h: MARKER.h / height,
+            },
+            dest: ggez::mint::Point2 {
+                x: bounds.x + marker_offset.round(),
+                y: bounds.y + (if state.is_dragging() { 2.0 } else { 0.0 }),
+            },
+            ..DrawParam::default()
+        });
+
+        if state.is_dragging() {
+            MouseCursor::Grabbing
+        } else if mouse_over {
+            MouseCursor::Grab
+        } else {
+            MouseCursor::OutOfBounds
+        }
+    }
+}
diff --git a/examples/tour/src/iced_ggez/renderer/text.rs b/examples/tour/src/iced_ggez/renderer/text.rs
new file mode 100644
index 00000000..b5010639
--- /dev/null
+++ b/examples/tour/src/iced_ggez/renderer/text.rs
@@ -0,0 +1,118 @@
+use super::{into_color, Renderer};
+use ggez::graphics::{self, mint, Align, Scale, Text, TextFragment};
+
+use iced::text;
+use std::cell::RefCell;
+use std::f32;
+
+impl text::Renderer<iced::Color> for Renderer<'_> {
+    fn node(
+        &self,
+        style: iced::Style,
+        content: &str,
+        size: Option<u16>,
+    ) -> iced::Node {
+        let font = self.font;
+        let font_cache = graphics::font_cache(self.context);
+        let content = String::from(content);
+
+        // 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 = size.map(f32::from).unwrap_or(self.font_size);
+
+        iced::Node::with_measure(style, move |bounds| {
+            let mut measure = measure.borrow_mut();
+
+            if measure.is_none() {
+                let bounds = (
+                    match bounds.width {
+                        iced::Number::Undefined => f32::INFINITY,
+                        iced::Number::Defined(w) => w,
+                    },
+                    match bounds.height {
+                        iced::Number::Undefined => f32::INFINITY,
+                        iced::Number::Defined(h) => h,
+                    },
+                );
+
+                let mut text = Text::new(TextFragment {
+                    text: content.clone(),
+                    font: Some(font),
+                    scale: Some(Scale { x: size, y: size }),
+                    ..Default::default()
+                });
+
+                text.set_bounds(
+                    mint::Point2 {
+                        x: bounds.0,
+                        y: bounds.1,
+                    },
+                    Align::Left,
+                );
+
+                let (width, height) = font_cache.dimensions(&text);
+
+                let size = iced::Size {
+                    width: width as f32,
+                    height: height as f32,
+                };
+
+                // 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,
+        bounds: iced::Rectangle,
+        content: &str,
+        size: Option<u16>,
+        color: Option<iced::Color>,
+        horizontal_alignment: text::HorizontalAlignment,
+        _vertical_alignment: text::VerticalAlignment,
+    ) {
+        let size = size.map(f32::from).unwrap_or(self.font_size);
+
+        let mut text = Text::new(TextFragment {
+            text: String::from(content),
+            font: Some(self.font),
+            scale: Some(Scale { x: size, y: size }),
+            ..Default::default()
+        });
+
+        text.set_bounds(
+            mint::Point2 {
+                x: bounds.width,
+                y: bounds.height,
+            },
+            match horizontal_alignment {
+                text::HorizontalAlignment::Left => graphics::Align::Left,
+                text::HorizontalAlignment::Center => graphics::Align::Center,
+                text::HorizontalAlignment::Right => graphics::Align::Right,
+            },
+        );
+
+        graphics::queue_text(
+            self.context,
+            &text,
+            mint::Point2 {
+                x: bounds.x,
+                y: bounds.y,
+            },
+            color.or(Some(iced::Color::BLACK)).map(into_color),
+        );
+    }
+}
diff --git a/examples/tour/src/iced_ggez/widget.rs b/examples/tour/src/iced_ggez/widget.rs
new file mode 100644
index 00000000..a365daca
--- /dev/null
+++ b/examples/tour/src/iced_ggez/widget.rs
@@ -0,0 +1,12 @@
+use super::Renderer;
+
+pub use iced::{button, slider, text, Align, Button, Color, Slider};
+
+pub type Text = iced::Text<Color>;
+pub type Checkbox<Message> = iced::Checkbox<Color, Message>;
+pub type Radio<Message> = iced::Radio<Color, Message>;
+pub type Image<'a> = iced::Image<&'a str>;
+
+pub type Column<'a, Message> = iced::Column<'a, Message, Renderer<'a>>;
+pub type Row<'a, Message> = iced::Row<'a, Message, Renderer<'a>>;
+pub type Element<'a, Message> = iced::Element<'a, Message, Renderer<'a>>;
diff --git a/examples/tour/src/lib.rs b/examples/tour/src/lib.rs
new file mode 100644
index 00000000..eb41fcd9
--- /dev/null
+++ b/examples/tour/src/lib.rs
@@ -0,0 +1,11 @@
+pub mod tour;
+
+pub use tour::{Message, Tour};
+
+mod widget;
+
+#[cfg(target_arch = "wasm32")]
+mod web;
+
+#[cfg(not(target_arch = "wasm32"))]
+pub mod iced_ggez;
diff --git a/examples/tour/src/tour.rs b/examples/tour/src/tour.rs
new file mode 100644
index 00000000..4bd7c8a3
--- /dev/null
+++ b/examples/tour/src/tour.rs
@@ -0,0 +1,563 @@
+use crate::widget::{
+    button, slider, text::HorizontalAlignment, Align, Button, Checkbox, Color,
+    Column, Element, Image, Radio, Row, Slider, Text,
+};
+
+pub struct Tour {
+    steps: Steps,
+    back_button: button::State,
+    next_button: button::State,
+    debug: bool,
+}
+
+impl Tour {
+    pub fn new() -> Tour {
+        Tour {
+            steps: Steps::new(),
+            back_button: button::State::new(),
+            next_button: button::State::new(),
+            debug: false,
+        }
+    }
+
+    pub fn update(&mut self, event: Message) {
+        match event {
+            Message::BackPressed => {
+                self.steps.go_back();
+            }
+            Message::NextPressed => {
+                self.steps.advance();
+            }
+            Message::StepMessage(step_msg) => {
+                self.steps.update(step_msg, &mut self.debug);
+            }
+        }
+    }
+
+    pub fn view(&mut self) -> Element<Message> {
+        let Tour {
+            steps,
+            back_button,
+            next_button,
+            ..
+        } = self;
+
+        let mut controls = Row::new();
+
+        if steps.has_previous() {
+            controls = controls.push(
+                Button::new(back_button, "Back")
+                    .on_press(Message::BackPressed)
+                    .class(button::Class::Secondary),
+            );
+        }
+
+        controls = controls.push(Column::new());
+
+        if steps.can_continue() {
+            controls = controls.push(
+                Button::new(next_button, "Next").on_press(Message::NextPressed),
+            );
+        }
+
+        let element: Element<_> = Column::new()
+            .max_width(500)
+            .spacing(20)
+            .push(steps.view(self.debug).map(Message::StepMessage))
+            .push(controls)
+            .into();
+
+        if self.debug {
+            element.explain(Color::BLACK)
+        } else {
+            element
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum Message {
+    BackPressed,
+    NextPressed,
+    StepMessage(StepMessage),
+}
+
+struct Steps {
+    steps: Vec<Step>,
+    current: usize,
+}
+
+impl Steps {
+    fn new() -> Steps {
+        Steps {
+            steps: vec![
+                Step::Welcome,
+                Step::Slider {
+                    state: slider::State::new(),
+                    value: 50,
+                },
+                Step::RowsAndColumns {
+                    layout: Layout::Row,
+                    spacing_slider: slider::State::new(),
+                    spacing: 20,
+                },
+                Step::Text {
+                    size_slider: slider::State::new(),
+                    size: 30,
+                    color_sliders: [slider::State::new(); 3],
+                    color: Color::BLACK,
+                },
+                Step::Radio { selection: None },
+                Step::Image {
+                    width: 300,
+                    slider: slider::State::new(),
+                },
+                Step::Debugger,
+                Step::End,
+            ],
+            current: 0,
+        }
+    }
+
+    fn update(&mut self, msg: StepMessage, debug: &mut bool) {
+        self.steps[self.current].update(msg, debug);
+    }
+
+    fn view(&mut self, debug: bool) -> Element<StepMessage> {
+        self.steps[self.current].view(debug)
+    }
+
+    fn advance(&mut self) {
+        if self.can_continue() {
+            self.current += 1;
+        }
+    }
+
+    fn go_back(&mut self) {
+        if self.has_previous() {
+            self.current -= 1;
+        }
+    }
+
+    fn has_previous(&self) -> bool {
+        self.current > 0
+    }
+
+    fn can_continue(&self) -> bool {
+        self.current + 1 < self.steps.len()
+            && self.steps[self.current].can_continue()
+    }
+}
+
+enum Step {
+    Welcome,
+    Slider {
+        state: slider::State,
+        value: u16,
+    },
+    RowsAndColumns {
+        layout: Layout,
+        spacing_slider: slider::State,
+        spacing: u16,
+    },
+    Text {
+        size_slider: slider::State,
+        size: u16,
+        color_sliders: [slider::State; 3],
+        color: Color,
+    },
+    Radio {
+        selection: Option<Language>,
+    },
+    Image {
+        width: u16,
+        slider: slider::State,
+    },
+    Debugger,
+    End,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum StepMessage {
+    SliderChanged(f32),
+    LayoutChanged(Layout),
+    SpacingChanged(f32),
+    TextSizeChanged(f32),
+    TextColorChanged(Color),
+    LanguageSelected(Language),
+    ImageWidthChanged(f32),
+    DebugToggled(bool),
+}
+
+impl<'a> Step {
+    fn update(&mut self, msg: StepMessage, debug: &mut bool) {
+        match msg {
+            StepMessage::DebugToggled(value) => {
+                if let Step::Debugger = self {
+                    *debug = value;
+                }
+            }
+            StepMessage::LanguageSelected(language) => {
+                if let Step::Radio { selection } = self {
+                    *selection = Some(language);
+                }
+            }
+            StepMessage::SliderChanged(new_value) => {
+                if let Step::Slider { value, .. } = self {
+                    *value = new_value.round() as u16;
+                }
+            }
+            StepMessage::TextSizeChanged(new_size) => {
+                if let Step::Text { size, .. } = self {
+                    *size = new_size.round() as u16;
+                }
+            }
+            StepMessage::TextColorChanged(new_color) => {
+                if let Step::Text { color, .. } = self {
+                    *color = new_color;
+                }
+            }
+            StepMessage::LayoutChanged(new_layout) => {
+                if let Step::RowsAndColumns { layout, .. } = self {
+                    *layout = new_layout;
+                }
+            }
+            StepMessage::SpacingChanged(new_spacing) => {
+                if let Step::RowsAndColumns { spacing, .. } = self {
+                    *spacing = new_spacing.round() as u16;
+                }
+            }
+            StepMessage::ImageWidthChanged(new_width) => {
+                if let Step::Image { width, .. } = self {
+                    *width = new_width.round() as u16;
+                }
+            }
+        };
+    }
+
+    fn can_continue(&self) -> bool {
+        match self {
+            Step::Welcome => true,
+            Step::Radio { selection } => *selection == Some(Language::Rust),
+            Step::Slider { .. } => true,
+            Step::Text { .. } => true,
+            Step::Image { .. } => true,
+            Step::RowsAndColumns { .. } => true,
+            Step::Debugger => true,
+            Step::End => false,
+        }
+    }
+
+    fn view(&mut self, debug: bool) -> Element<StepMessage> {
+        match self {
+            Step::Welcome => Self::welcome().into(),
+            Step::Radio { selection } => Self::radio(*selection).into(),
+            Step::Slider { state, value } => Self::slider(state, *value).into(),
+            Step::Text {
+                size_slider,
+                size,
+                color_sliders,
+                color,
+            } => Self::text(size_slider, *size, color_sliders, *color).into(),
+            Step::Image { width, slider } => Self::image(*width, slider).into(),
+            Step::RowsAndColumns {
+                layout,
+                spacing_slider,
+                spacing,
+            } => {
+                Self::rows_and_columns(*layout, spacing_slider, *spacing).into()
+            }
+            Step::Debugger => Self::debugger(debug).into(),
+            Step::End => Self::end().into(),
+        }
+    }
+
+    fn container(title: &str) -> Column<'a, StepMessage> {
+        Column::new()
+            .spacing(20)
+            .align_items(Align::Stretch)
+            .push(Text::new(title).size(50))
+    }
+
+    fn welcome() -> Column<'a, StepMessage> {
+        Self::container("Welcome!")
+            .push(Text::new(
+                "This a simple tour meant to showcase a bunch of widgets that \
+                 can be easily implemented on top of Iced.",
+            ))
+            .push(Text::new(
+                "Iced is a renderer-agnostic GUI library for Rust focused on \
+                 simplicity and type-safety. It is heavily inspired by Elm.",
+            ))
+            .push(Text::new(
+                "It was originally born as part of Coffee, an opinionated \
+                 2D game engine for Rust.",
+            ))
+            .push(Text::new(
+                "Iced does not provide a built-in renderer. This example runs \
+                 on WebAssembly using dodrio, an experimental VDOM library \
+                 for Rust.",
+            ))
+            .push(Text::new(
+                "You will need to interact with the UI in order to reach the \
+                 end!",
+            ))
+    }
+
+    fn slider(
+        state: &'a mut slider::State,
+        value: u16,
+    ) -> Column<'a, StepMessage> {
+        Self::container("Slider")
+            .push(Text::new(
+                "A slider allows you to smoothly select a value from a range \
+                 of values.",
+            ))
+            .push(Text::new(
+                "The following slider lets you choose an integer from \
+                 0 to 100:",
+            ))
+            .push(Slider::new(
+                state,
+                0.0..=100.0,
+                value as f32,
+                StepMessage::SliderChanged,
+            ))
+            .push(
+                Text::new(&value.to_string())
+                    .horizontal_alignment(HorizontalAlignment::Center),
+            )
+    }
+
+    fn rows_and_columns(
+        layout: Layout,
+        spacing_slider: &'a mut slider::State,
+        spacing: u16,
+    ) -> Column<'a, StepMessage> {
+        let row_radio = Radio::new(
+            Layout::Row,
+            "Row",
+            Some(layout),
+            StepMessage::LayoutChanged,
+        );
+
+        let column_radio = Radio::new(
+            Layout::Column,
+            "Column",
+            Some(layout),
+            StepMessage::LayoutChanged,
+        );
+
+        let layout_section: Element<_> = match layout {
+            Layout::Row => Row::new()
+                .spacing(spacing)
+                .push(row_radio)
+                .push(column_radio)
+                .into(),
+            Layout::Column => Column::new()
+                .spacing(spacing)
+                .push(row_radio)
+                .push(column_radio)
+                .into(),
+        };
+
+        let spacing_section = Column::new()
+            .spacing(10)
+            .push(Slider::new(
+                spacing_slider,
+                0.0..=80.0,
+                spacing as f32,
+                StepMessage::SpacingChanged,
+            ))
+            .push(
+                Text::new(&format!("{} px", spacing))
+                    .horizontal_alignment(HorizontalAlignment::Center),
+            );
+
+        Self::container("Rows and columns")
+            .spacing(spacing)
+            .push(Text::new(
+                "Iced uses a layout model based on flexbox to position UI \
+                 elements.",
+            ))
+            .push(Text::new(
+                "Rows and columns can be used to distribute content \
+                 horizontally or vertically, respectively.",
+            ))
+            .push(layout_section)
+            .push(Text::new(
+                "You can also easily change the spacing between elements:",
+            ))
+            .push(spacing_section)
+    }
+
+    fn text(
+        size_slider: &'a mut slider::State,
+        size: u16,
+        color_sliders: &'a mut [slider::State; 3],
+        color: Color,
+    ) -> Column<'a, StepMessage> {
+        let size_section = Column::new()
+            .padding(20)
+            .spacing(20)
+            .push(Text::new("You can change its size:"))
+            .push(
+                Text::new(&format!("This text is {} pixels", size)).size(size),
+            )
+            .push(Slider::new(
+                size_slider,
+                10.0..=70.0,
+                size as f32,
+                StepMessage::TextSizeChanged,
+            ));
+
+        let [red, green, blue] = color_sliders;
+        let color_section = Column::new()
+            .padding(20)
+            .spacing(20)
+            .push(Text::new("And its color:"))
+            .push(Text::new(&format!("{:?}", color)).color(color))
+            .push(
+                Row::new()
+                    .spacing(10)
+                    .push(Slider::new(red, 0.0..=1.0, color.r, move |r| {
+                        StepMessage::TextColorChanged(Color { r, ..color })
+                    }))
+                    .push(Slider::new(green, 0.0..=1.0, color.g, move |g| {
+                        StepMessage::TextColorChanged(Color { g, ..color })
+                    }))
+                    .push(Slider::new(blue, 0.0..=1.0, color.b, move |b| {
+                        StepMessage::TextColorChanged(Color { b, ..color })
+                    })),
+            );
+
+        Self::container("Text")
+            .push(Text::new(
+                "Text is probably the most essential widget for your UI. \
+                 It will try to adapt to the dimensions of its container.",
+            ))
+            .push(size_section)
+            .push(color_section)
+    }
+
+    fn radio(selection: Option<Language>) -> Column<'a, StepMessage> {
+        let question = Column::new()
+            .padding(20)
+            .spacing(10)
+            .push(Text::new("Iced is written in...").size(24))
+            .push(Language::all().iter().cloned().fold(
+                Column::new().padding(10).spacing(20),
+                |choices, language| {
+                    choices.push(Radio::new(
+                        language,
+                        language.into(),
+                        selection,
+                        StepMessage::LanguageSelected,
+                    ))
+                },
+            ));
+
+        Self::container("Radio button")
+            .push(Text::new(
+                "A radio button is normally used to represent a choice... \
+                 Surprise test!",
+            ))
+            .push(question)
+            .push(Text::new(
+                "Iced works very well with iterators! The list above is \
+                 basically created by folding a column over the different \
+                 choices, creating a radio button for each one of them!",
+            ))
+    }
+
+    fn image(
+        width: u16,
+        slider: &'a mut slider::State,
+    ) -> Column<'a, StepMessage> {
+        Self::container("Image")
+            .push(Text::new("An image that tries to keep its aspect ratio."))
+            .push(
+                Image::new("resources/ferris.png")
+                    .width(width)
+                    .align_self(Align::Center),
+            )
+            .push(Slider::new(
+                slider,
+                100.0..=500.0,
+                width as f32,
+                StepMessage::ImageWidthChanged,
+            ))
+            .push(
+                Text::new(&format!("Width: {} px", width.to_string()))
+                    .horizontal_alignment(HorizontalAlignment::Center),
+            )
+    }
+
+    fn debugger(debug: bool) -> Column<'a, StepMessage> {
+        Self::container("Debugger")
+            .push(Text::new(
+                "You can ask Iced to visually explain the layouting of the \
+                 different elements comprising your UI!",
+            ))
+            .push(Text::new(
+                "Give it a shot! Check the following checkbox to be able to \
+                 see element boundaries.",
+            ))
+            .push(Checkbox::new(
+                debug,
+                "Explain layout",
+                StepMessage::DebugToggled,
+            ))
+            .push(Text::new("Feel free to go back and take a look."))
+    }
+
+    fn end() -> Column<'a, StepMessage> {
+        Self::container("You reached the end!")
+            .push(Text::new(
+                "This tour will be updated as more features are added.",
+            ))
+            .push(Text::new("Make sure to keep an eye on it!"))
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Language {
+    Rust,
+    Elm,
+    Ruby,
+    Haskell,
+    C,
+    Other,
+}
+
+impl Language {
+    fn all() -> [Language; 6] {
+        [
+            Language::C,
+            Language::Elm,
+            Language::Ruby,
+            Language::Haskell,
+            Language::Rust,
+            Language::Other,
+        ]
+    }
+}
+
+impl From<Language> for &str {
+    fn from(language: Language) -> &'static str {
+        match language {
+            Language::Rust => "Rust",
+            Language::Elm => "Elm",
+            Language::Ruby => "Ruby",
+            Language::Haskell => "Haskell",
+            Language::C => "C",
+            Language::Other => "Other",
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Layout {
+    Row,
+    Column,
+}
diff --git a/examples/tour/src/web.rs b/examples/tour/src/web.rs
new file mode 100644
index 00000000..a0a3060f
--- /dev/null
+++ b/examples/tour/src/web.rs
@@ -0,0 +1,33 @@
+use futures::Future;
+use iced_web::UserInterface;
+use wasm_bindgen::prelude::*;
+
+use crate::tour::{self, Tour};
+
+#[wasm_bindgen(start)]
+pub fn run() {
+    console_error_panic_hook::set_once();
+    console_log::init_with_level(log::Level::Trace)
+        .expect("Initialize logging");
+
+    let tour = Tour::new();
+
+    tour.run();
+}
+
+impl iced_web::UserInterface for Tour {
+    type Message = tour::Message;
+
+    fn update(
+        &mut self,
+        message: tour::Message,
+    ) -> Option<Box<dyn Future<Output = tour::Message>>> {
+        self.update(message);
+
+        None
+    }
+
+    fn view(&mut self) -> iced_web::Element<tour::Message> {
+        self.view()
+    }
+}
diff --git a/examples/tour/src/widget.rs b/examples/tour/src/widget.rs
new file mode 100644
index 00000000..9c2c4d5b
--- /dev/null
+++ b/examples/tour/src/widget.rs
@@ -0,0 +1,5 @@
+#[cfg(target_arch = "wasm32")]
+pub use iced_web::*;
+
+#[cfg(not(target_arch = "wasm32"))]
+pub use crate::iced_ggez::*;