＜Rust＞egui学习之小部件（七）：如何在窗口中添加颜色选择器colorpicker部件？

前言
本专栏是关于Rust的GUI库egui的部件讲解及应用实例分析，主要讲解egui的源代码、部件属性、如何应用。

环境配置
系统：windows
平台：visual studio code
语言：rust
库：egui、eframe

概述
本文是本专栏的第七篇博文，主要讲述颜色选择器部件colorpicker的使用。

事实上，类似于iced，egui都提供了示例程序，本专栏的博文都是建立在官方示例程序以及源代码的基础上，进行的实例讲解。
即，本专栏的文章并非只是简单的翻译egui的官方示例与文档，而是针对于官方代码进行的实际使用，会在官方的代码上进行修改，包括解决一些问题。

系列博客链接：
1、＜Rust＞egui学习之小部件（一）：如何在窗口及部件显示中文字符？
2、＜Rust＞egui学习之小部件（二）：如何在egui窗口中添加按钮button以及标签label部件？
3、＜Rust＞egui学习之小部件（三）：如何为窗口UI元件设置布局（间隔、水平、垂直排列）？
4、＜Rust＞egui学习之小部件（四）：如何在窗口中添加滑动条部件？
5、＜Rust＞egui学习之小部件（五）：如何在窗口中添加图像部件？
6、＜Rust＞egui学习之小部件（六）：如何在窗口中添加菜单栏部件？

部件属性

在egui中，也提供了颜色选择器这样的部件color_picker，且有多重颜色样式：

源代码中提供的可调用选项：

/// # Colors
impl Ui {
    /// Shows a button with the given color.
    /// If the user clicks the button, a full color picker is shown.
    pub fn color_edit_button_srgba(&mut self, srgba: &mut Color32) -> Response {
        color_picker::color_edit_button_srgba(self, srgba, color_picker::Alpha::BlendOrAdditive)
    }

    /// Shows a button with the given color.
    /// If the user clicks the button, a full color picker is shown.
    pub fn color_edit_button_hsva(&mut self, hsva: &mut Hsva) -> Response {
        color_picker::color_edit_button_hsva(self, hsva, color_picker::Alpha::BlendOrAdditive)
    }

    /// Shows a button with the given color.
    /// If the user clicks the button, a full color picker is shown.
    /// The given color is in `sRGB` space.
    pub fn color_edit_button_srgb(&mut self, srgb: &mut [u8; 3]) -> Response {
        color_picker::color_edit_button_srgb(self, srgb)
    }

    /// Shows a button with the given color.
    /// If the user clicks the button, a full color picker is shown.
    /// The given color is in linear RGB space.
    pub fn color_edit_button_rgb(&mut self, rgb: &mut [f32; 3]) -> Response {
        color_picker::color_edit_button_rgb(self, rgb)
    }

    /// Shows a button with the given color.
    /// If the user clicks the button, a full color picker is shown.
    /// The given color is in `sRGBA` space with premultiplied alpha
    pub fn color_edit_button_srgba_premultiplied(&mut self, srgba: &mut [u8; 4]) -> Response {
        let mut color = Color32::from_rgba_premultiplied(srgba[0], srgba[1], srgba[2], srgba[3]);
        let response = self.color_edit_button_srgba(&mut color);
        *srgba = color.to_array();
        response
    }

    /// Shows a button with the given color.
    /// If the user clicks the button, a full color picker is shown.
    /// The given color is in `sRGBA` space without premultiplied alpha.
    /// If unsure, what "premultiplied alpha" is, then this is probably the function you want to use.
    pub fn color_edit_button_srgba_unmultiplied(&mut self, srgba: &mut [u8; 4]) -> Response {
        let mut rgba = Rgba::from_srgba_unmultiplied(srgba[0], srgba[1], srgba[2], srgba[3]);
        let response =
            color_picker::color_edit_button_rgba(self, &mut rgba, color_picker::Alpha::OnlyBlend);
        *srgba = rgba.to_srgba_unmultiplied();
        response
    }

    /// Shows a button with the given color.
    /// If the user clicks the button, a full color picker is shown.
    /// The given color is in linear RGBA space with premultiplied alpha
    pub fn color_edit_button_rgba_premultiplied(&mut self, rgba_premul: &mut [f32; 4]) -> Response {
        let mut rgba = Rgba::from_rgba_premultiplied(
            rgba_premul[0],
            rgba_premul[1],
            rgba_premul[2],
            rgba_premul[3],
        );
        let response = color_picker::color_edit_button_rgba(
            self,
            &mut rgba,
            color_picker::Alpha::BlendOrAdditive,
        );
        *rgba_premul = rgba.to_array();
        response
    }

    /// Shows a button with the given color.
    /// If the user clicks the button, a full color picker is shown.
    /// The given color is in linear RGBA space without premultiplied alpha.
    /// If unsure, what "premultiplied alpha" is, then this is probably the function you want to use.
    pub fn color_edit_button_rgba_unmultiplied(&mut self, rgba_unmul: &mut [f32; 4]) -> Response {
        let mut rgba = Rgba::from_rgba_unmultiplied(
            rgba_unmul[0],
            rgba_unmul[1],
            rgba_unmul[2],
            rgba_unmul[3],
        );
        let response =
            color_picker::color_edit_button_rgba(self, &mut rgba, color_picker::Alpha::OnlyBlend);
        *rgba_unmul = rgba.to_rgba_unmultiplied();
        response
    }
}

我们选择rgb格式来看一下：

ui.color_edit_button_rgb(&mut self.color1);

color_edit_button提供一个按钮，当我们点击此按钮时，就会弹出颜色选择器，上图就是rgb格式下的选择器样式。
再看看其他选择器样式：

hsva

ui.color_edit_button_hsva(&mut self.color_hsva);

就不一一列举了。

需要注意的是，调用color_picker函数中添加的参数变量，最好不要是临时变量，因为updat是实时更新的，此区域的临时变量会一直被复位，你选择的颜色值一般会闪现，然后归零。

本例中的颜色值变量，是在结构体中提前添加的，直接调用即可。
这样就可以获取实时选择的颜色值了。

看一下实例演示：