Add example program: color palette

Sliders for many color spaces update as any other sliders are moved
around. Color is space is clamped to sRGB, so Lab and Lch color spaces
cannot be fully expressed.

TODO:
- Real-time manipulation of base color to create a color scheme.
- Show slider value under each slider
- Show output values in text boxes for each color space

4 files changed, 274 insertions, 0 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 9b88f9ec..8f0a95c3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -41,6 +41,7 @@ members = [
     "winit",
     "examples/bezier_tool",
     "examples/clock",
+    "examples/color_palette",
     "examples/counter",
     "examples/custom_widget",
     "examples/download_progress",
diff --git a/examples/color_palette/Cargo.toml b/examples/color_palette/Cargo.toml
new file mode 100644
index 00000000..0ad6708c
--- /dev/null
+++ b/examples/color_palette/Cargo.toml
@@ -0,0 +1,14 @@
+[package]
+name = "color_palette"
+version = "0.1.0"
+authors = ["Clark Moody <clark@clarkmoody.com>"]
+edition = "2018"
+publish = false
+
+[features]
+palette = []
+
+[dependencies]
+iced = { path = "../..", features = ["palette"] }
+iced_core = { path = "../../core" }
+iced_native = { path = "../../native" }
diff --git a/examples/color_palette/README.md b/examples/color_palette/README.md
new file mode 100644
index 00000000..b646f3b3
--- /dev/null
+++ b/examples/color_palette/README.md
@@ -0,0 +1,9 @@
+## Color Palette
+
+A color palette generator, based on a user-defined root color.
+
+You can run it with `cargo run`:
+
+```
+cargo run --package color_palette
+```
diff --git a/examples/color_palette/src/main.rs b/examples/color_palette/src/main.rs
new file mode 100644
index 00000000..1c9fffbc
--- /dev/null
+++ b/examples/color_palette/src/main.rs
@@ -0,0 +1,250 @@
+use iced::{
+    slider, Color, Column, Element, Row, Sandbox, Settings, Slider, Text,
+};
+use iced_core::palette::{self, Limited};
+
+pub fn main() {
+    ColorPalette::run(Settings::default())
+}
+
+#[derive(Default)]
+pub struct ColorPalette {
+    base_color: Color,
+    rgb_sliders: [slider::State; 3],
+    hsl_sliders: [slider::State; 3],
+    hsv_sliders: [slider::State; 3],
+    hwb_sliders: [slider::State; 3],
+    lab_sliders: [slider::State; 3],
+    lch_sliders: [slider::State; 3],
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum Message {
+    RgbColorChanged(Color),
+    HslColorChanged(palette::Hsl),
+    HsvColorChanged(palette::Hsv),
+    HwbColorChanged(palette::Hwb),
+    LabColorChanged(palette::Lab),
+    LchColorChanged(palette::Lch),
+}
+
+impl Sandbox for ColorPalette {
+    type Message = Message;
+
+    fn new() -> Self {
+        let mut s = Self::default();
+        s.base_color = Color::from_rgb8(27, 135, 199);
+        s
+    }
+
+    fn title(&self) -> String {
+        String::from("Color Palette")
+    }
+
+    fn update(&mut self, message: Message) {
+        let mut srgb = match message {
+            Message::RgbColorChanged(rgb) => palette::Srgb::from(rgb),
+            Message::HslColorChanged(hsl) => palette::Srgb::from(hsl),
+            Message::HsvColorChanged(hsv) => palette::Srgb::from(hsv),
+            Message::HwbColorChanged(hwb) => palette::Srgb::from(hwb),
+            Message::LabColorChanged(lab) => palette::Srgb::from(lab),
+            Message::LchColorChanged(lch) => palette::Srgb::from(lch),
+        };
+        srgb.clamp_self();
+        self.base_color = Color::from(srgb);
+    }
+
+    fn view(&mut self) -> Element<Message> {
+        let [rgb1, rgb2, rgb3] = &mut self.rgb_sliders;
+        let [hsl1, hsl2, hsl3] = &mut self.hsl_sliders;
+        let [hsv1, hsv2, hsv3] = &mut self.hsv_sliders;
+        let [hwb1, hwb2, hwb3] = &mut self.hwb_sliders;
+        let [lab1, lab2, lab3] = &mut self.lab_sliders;
+        let [lch1, lch2, lch3] = &mut self.lch_sliders;
+
+        let color = self.base_color;
+        let srgb = palette::Srgb::from(self.base_color);
+        let hsl = palette::Hsl::from(srgb);
+        let hsv = palette::Hsv::from(srgb);
+        let hwb = palette::Hwb::from(srgb);
+        let lab = palette::Lab::from(srgb);
+        let lch = palette::Lch::from(srgb);
+
+        Column::new()
+            .padding(20)
+            .spacing(20)
+            .push(
+                Row::new()
+                    .spacing(10)
+                    .push(Text::new("RGB"))
+                    .push(Slider::new(rgb1, 0.0..=1.0, color.r, move |r| {
+                        Message::RgbColorChanged(Color { r, ..color })
+                    }))
+                    .push(Slider::new(rgb2, 0.0..=1.0, color.g, move |g| {
+                        Message::RgbColorChanged(Color { g, ..color })
+                    }))
+                    .push(Slider::new(rgb3, 0.0..=1.0, color.b, move |b| {
+                        Message::RgbColorChanged(Color { b, ..color })
+                    })),
+            )
+            .push(
+                Row::new()
+                    .spacing(10)
+                    .push(Text::new("HSL"))
+                    .push(Slider::new(
+                        hsl1,
+                        0.0..=360.0,
+                        hsl.hue.to_positive_degrees(),
+                        move |hue| {
+                            Message::HslColorChanged(palette::Hsl {
+                                hue: palette::RgbHue::from_degrees(hue),
+                                ..hsl
+                            })
+                        },
+                    ))
+                    .push(Slider::new(
+                        hsl2,
+                        0.0..=1.0,
+                        hsl.saturation,
+                        move |saturation| {
+                            Message::HslColorChanged(palette::Hsl {
+                                saturation,
+                                ..hsl
+                            })
+                        },
+                    ))
+                    .push(Slider::new(
+                        hsl3,
+                        0.0..=1.0,
+                        hsl.lightness,
+                        move |lightness| {
+                            Message::HslColorChanged(palette::Hsl {
+                                lightness,
+                                ..hsl
+                            })
+                        },
+                    )),
+            )
+            .push(
+                Row::new()
+                    .spacing(10)
+                    .push(Text::new("HSV"))
+                    .push(Slider::new(
+                        hsv1,
+                        0.0..=360.0,
+                        hsv.hue.to_positive_degrees(),
+                        move |hue| {
+                            Message::HsvColorChanged(palette::Hsv {
+                                hue: palette::RgbHue::from_degrees(hue),
+                                ..hsv
+                            })
+                        },
+                    ))
+                    .push(Slider::new(
+                        hsv2,
+                        0.0..=1.0,
+                        hsv.saturation,
+                        move |saturation| {
+                            Message::HsvColorChanged(palette::Hsv {
+                                saturation,
+                                ..hsv
+                            })
+                        },
+                    ))
+                    .push(Slider::new(
+                        hsv3,
+                        0.0..=1.0,
+                        hsv.value,
+                        move |value| {
+                            Message::HsvColorChanged(palette::Hsv {
+                                value,
+                                ..hsv
+                            })
+                        },
+                    )),
+            )
+            .push(
+                Row::new()
+                    .spacing(10)
+                    .push(Text::new("HWB"))
+                    .push(Slider::new(
+                        hwb1,
+                        0.0..=360.0,
+                        hwb.hue.to_positive_degrees(),
+                        move |hue| {
+                            Message::HwbColorChanged(palette::Hwb {
+                                hue: palette::RgbHue::from_degrees(hue),
+                                ..hwb
+                            })
+                        },
+                    ))
+                    .push(Slider::new(
+                        hwb2,
+                        0.0..=1.0,
+                        hwb.whiteness,
+                        move |whiteness| {
+                            Message::HwbColorChanged(palette::Hwb {
+                                whiteness,
+                                ..hwb
+                            })
+                        },
+                    ))
+                    .push(Slider::new(
+                        hwb3,
+                        0.0..=1.0,
+                        hwb.blackness,
+                        move |blackness| {
+                            Message::HwbColorChanged(palette::Hwb {
+                                blackness,
+                                ..hwb
+                            })
+                        },
+                    )),
+            )
+            .push(
+                Row::new()
+                    .spacing(10)
+                    .push(Text::new("Lab"))
+                    .push(Slider::new(lab1, 0.0..=100.0, lab.l, move |l| {
+                        Message::LabColorChanged(palette::Lab { l, ..lab })
+                    }))
+                    .push(Slider::new(lab2, -128.0..=127.0, lab.a, move |a| {
+                        Message::LabColorChanged(palette::Lab { a, ..lab })
+                    }))
+                    .push(Slider::new(lab3, -128.0..=127.0, lab.b, move |b| {
+                        Message::LabColorChanged(palette::Lab { b, ..lab })
+                    })),
+            )
+            .push(
+                Row::new()
+                    .spacing(10)
+                    .push(Text::new("Lch"))
+                    .push(Slider::new(lch1, 0.0..=100.0, lch.l, move |l| {
+                        Message::LchColorChanged(palette::Lch { l, ..lch })
+                    }))
+                    .push(Slider::new(
+                        lch2,
+                        0.0..=128.0,
+                        lch.chroma,
+                        move |chroma| {
+                            Message::LchColorChanged(palette::Lch {
+                                chroma,
+                                ..lch
+                            })
+                        },
+                    ))
+                    .push(Slider::new(
+                        lch3,
+                        0.0..=360.0,
+                        lch.hue.to_positive_degrees(),
+                        move |hue| {
+                            Message::LchColorChanged(palette::Lch {
+                                hue: palette::LabHue::from_degrees(hue),
+                                ..lch
+                            })
+                        },
+                    )),
+            )
+            .into()
+    }
+}