From 8bd487dc11b420931ddf6b98d11a0147cc272a39 Mon Sep 17 00:00:00 2001
From: Francesco Magliocca <franciman12@gmail.com>
Date: Mon, 9 Nov 2020 17:18:00 +0100
Subject: [PATCH] Use a RadioGroup to show which canvas tool is active

---
 src/main.rs | 47 ++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 40 insertions(+), 7 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 5721e1e..607a727 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -16,10 +16,15 @@
 
 use druid::kurbo::{BezPath, Rect};
 use druid::widget::prelude::*;
-use druid::{AppLauncher, Color, Data, Event, LocalizedString, WindowDesc};
+use druid::{AppLauncher, Color, Data, Lens, Event, LocalizedString, WidgetExt, WindowDesc};
 
 use stiletto::{CanvasElement, VersionedCanvas, Canvas};
 
+#[derive(Clone, Data, PartialEq)]
+enum CanvasToolType {
+    Pen,
+    Eraser
+}
 
 // Tools that can be used to interact with the canvas
 #[derive(Clone, Data)]
@@ -35,6 +40,33 @@ impl CanvasTool {
     fn new_eraser() -> CanvasTool {
         CanvasTool::Eraser { eraser_rect: None }
     }
+
+    fn tool_type(&self) -> CanvasToolType {
+        match self {
+            CanvasTool::Pen { current_element: _ } => CanvasToolType::Pen,
+            CanvasTool::Eraser { eraser_rect: _ } => CanvasToolType::Eraser,
+        }
+    }
+}
+
+struct CanvasToolLens;
+
+impl Lens<CanvasData, CanvasToolType> for CanvasToolLens {
+    fn with<R, F: FnOnce(&CanvasToolType) -> R>(&self, data: &CanvasData, f: F) -> R {
+        f(&data.current_tool.tool_type())
+    }
+
+    fn with_mut<R, F: FnOnce(&mut CanvasToolType) -> R>(&self, data: &mut CanvasData, f: F) -> R {
+        let mut curr_type = data.current_tool.tool_type();
+        let result = f(&mut curr_type);
+
+        match curr_type {
+            CanvasToolType::Pen    => data.current_tool = CanvasTool::new_pen(),
+            CanvasToolType::Eraser => data.current_tool = CanvasTool::new_eraser(),
+        }
+
+        result
+    }
 }
 
 #[derive(Clone, Data)]
@@ -48,9 +80,7 @@ impl CanvasData {
         self.current_element.is_some()
     }*/
 
-    fn set_tool(&mut self, tool: CanvasTool) {
-        self.current_tool = tool;
-    }
+    const CURRENT_TOOL_LENS: CanvasToolLens = CanvasToolLens;
 
     fn perform_undo(&mut self) {
         self.elements.undo();
@@ -133,6 +163,7 @@ impl CanvasData {
     }
 }
 
+
 struct CanvasWidget;
 
 impl Widget<CanvasData> for CanvasWidget {
@@ -231,15 +262,17 @@ impl Widget<CanvasData> for CanvasWidget {
 }
 
 fn build_ui() -> impl Widget<CanvasData> {
-    use druid::widget::{Align, Button, CrossAxisAlignment, Flex, SizedBox};
+    use druid::widget::{Align, Button, RadioGroup, CrossAxisAlignment, Flex, SizedBox};
+
+    let radio_group = RadioGroup::new(vec![("Pen", CanvasToolType::Pen), ("Eraser", CanvasToolType::Eraser)]);
+        
 
     let toolbar = Flex::row()
         .cross_axis_alignment(CrossAxisAlignment::Center)
         .with_spacer(30.0)
         .with_child(Button::new("Undo").on_click(|_ctx, data: &mut CanvasData, _env| data.perform_undo()))
         .with_child(Button::new("Redo").on_click(|_ctx, data: &mut CanvasData, _env| data.perform_redo()))
-        .with_child(Button::new("Pen").on_click(|_ctx, data: &mut CanvasData, _env| data.set_tool(CanvasTool::new_pen())))
-        .with_child(Button::new("Eraser").on_click(|_ctx, data: &mut CanvasData, _env| data.set_tool(CanvasTool::new_eraser())));
+        .with_child(radio_group.lens(CanvasData::CURRENT_TOOL_LENS));
 
     Flex::column()
         .cross_axis_alignment(CrossAxisAlignment::Center)