Working finally

src/bin/canvas_tool_list.rs

@@ -18,61 +18,49 @@
 
 use druid::im::{vector, Vector};
 use druid::widget::prelude::*;
-use druid::widget::{Align, Label, Button, CrossAxisAlignment, Flex, List, ListGrowDirection, WidgetExt, SizedBox, Either};
+use druid::widget::{Align, Label, Button, CrossAxisAlignment, Flex, List, ListGrowDirection, WidgetExt, SizedBox, ViewSwitcher};
 use druid::{AppLauncher, Color, Data, LocalizedString, WindowDesc, Lens, UnitPoint};
 
 #[derive(Clone, Data)]
 enum CanvasToolState {
-    Pen { thickness: f64 },
+    Pen { thickness: f64, color: Color },
     Eraser,
 }
 
-trait CanvasToolBuilder {
-    fn default_state() -> CanvasToolState;
-    fn build_widget() -> Box<dyn Widget<CanvasToolState>>;
+#[derive(Clone, PartialEq)]
+enum CanvasToolType {
+    Pen,
+    Eraser,
 }
 
-struct PenBuilder;
-struct EraserBuilder;
+impl CanvasToolState {
+    fn tool_type(&self) -> CanvasToolType {
+        match self {
+            CanvasToolState::Pen { .. } => CanvasToolType::Pen,
+            CanvasToolState::Eraser => CanvasToolType::Eraser,
+        }
+    }
+}
 
-impl CanvasToolBuilder for PenBuilder {
-    fn default_state() -> CanvasToolState {
-        CanvasToolState::Pen {
-            thickness: 2.0
-        }
-    }
-    fn build_widget() -> Box<dyn Widget<CanvasToolState>> {
-        Box::new(SizedBox::new(
-            Label::new(|item: &CanvasToolState, _env: &_| format!("pen"))
+fn build_simple_tool_widget(tool_state: &CanvasToolState) -> Box<dyn Widget<CanvasToolState>> {
+    let (label_text, bg_color) = match tool_state {
+        CanvasToolState::Pen { thickness, color } =>
+            (format!("pen {}", thickness), color.clone()),
+        CanvasToolState::Eraser =>
+            (String::from("eraser"), Color::rgb(200, 200, 200))
+    };
+
+    Box::new(
+        SizedBox::new(
+            Label::new(label_text)
                 .align_horizontal(UnitPoint::CENTER)
-                .background(Color::rgb(19.0, 0.5, 0.5))
+                .background(bg_color)
                 .fix_width(100.0)
                 .fix_height(100.0)
         )
         .padding((10.0, 0.0)))
-    }
 }
 
-impl CanvasToolBuilder for EraserBuilder {
-    fn default_state() -> CanvasToolState {
-        CanvasToolState::Eraser {}
-    }
-    fn build_widget() -> Box<dyn Widget<CanvasToolState>> {
-        Box::new(SizedBox::new(
-            Label::new(|item: &CanvasToolState, _env: &_| format!("eraser"))
-                .align_horizontal(UnitPoint::CENTER)
-                .background(Color::rgb(0.5, 0.5, 0.5))
-                .fix_width(100.0)
-                .fix_height(100.0)
-        )
-        .padding((10.0, 0.0)))
-    }
-}
-
-enum CanvasTool {
-    Pen(PenBuilder),
-    Eraser(EraserBuilder)
-}
 
 #[derive(Clone, Data, Lens)]
 struct AppState {
@@ -89,7 +77,12 @@ fn build_ui() -> impl Widget<AppState> {
         .cross_axis_alignment(CrossAxisAlignment::Center)
     	.with_flex_child(
             List::new(|| {
-                PenBuilder::build_widget()
+                ViewSwitcher::<CanvasToolState, CanvasToolType>::new(
+                    |tool_state, _| tool_state.tool_type(),
+                    |_, tool_state, _| {
+                        build_simple_tool_widget(&tool_state)
+                    }
+                )
             })
             .grow(ListGrowDirection::Right)
             .lens(AppState::tools)
@@ -119,7 +112,7 @@ pub fn main() {
             LocalizedString::new("custom-widget-demo-window-title").with_placeholder("Tools"),
         );
     let app_state = AppState {
-        tools: vector![CanvasToolState::Eraser],
+        tools: vector![CanvasToolState::Eraser, CanvasToolState::Pen { thickness: 3.3, color: Color::rgb(30.0, 0.4, 0.4) }]
     };
 
     AppLauncher::with_window(window)