Mirror mirror of the wall, how the fuck do lens work?

Cargo.lock

@@ -257,7 +257,7 @@ checksum = "212d0f5754cb6769937f4501cc0e67f4f4483c8d2c3e1e922ee9edbe4ab4c7c0"
 [[package]]
 name = "druid"
 version = "0.6.0"
-source = "git+https://github.com/doppioandante/druid?branch=stylus_events_0.6.0#b0f9dc0268409a56b5066f569ad245e5df016166"
+source = "git+https://github.com/doppioandante/druid?branch=v0.6.0_stiletto#f8f8a566b77795cfa10caf7f2861f9240d159e90"
 dependencies = [
  "console_log",
  "druid-derive",
@@ -278,7 +278,7 @@ dependencies = [
 [[package]]
 name = "druid-derive"
 version = "0.3.1"
-source = "git+https://github.com/doppioandante/druid?branch=stylus_events_0.6.0#b0f9dc0268409a56b5066f569ad245e5df016166"
+source = "git+https://github.com/doppioandante/druid?branch=v0.6.0_stiletto#f8f8a566b77795cfa10caf7f2861f9240d159e90"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -288,7 +288,7 @@ dependencies = [
 [[package]]
 name = "druid-shell"
 version = "0.6.0"
-source = "git+https://github.com/doppioandante/druid?branch=stylus_events_0.6.0#b0f9dc0268409a56b5066f569ad245e5df016166"
+source = "git+https://github.com/doppioandante/druid?branch=v0.6.0_stiletto#f8f8a566b77795cfa10caf7f2861f9240d159e90"
 dependencies = [
  "anyhow",
  "bitflags",

src/bin/canvas_tool_list.rs

@@ -18,17 +18,68 @@
 
 use druid::im::{vector, Vector};
 use druid::widget::prelude::*;
-use druid::{AppLauncher, Color, Data, LocalizedString, WindowDesc, Lens};
+use druid::widget::{Align, Label, Button, CrossAxisAlignment, Flex, List, ListGrowDirection, WidgetExt, SizedBox};
+use druid::{AppLauncher, Color, Data, LocalizedString, WindowDesc, Lens, UnitPoint};
+
+#[derive(Clone, Data)]
+enum CanvasToolState {
+    Pen { thickness: f64 },
+    Eraser,
+}
+
+trait CanvasToolBuilder {
+    fn default_state() -> CanvasToolState;
+    fn build_widget(&self) -> Box<dyn Widget<CanvasToolState>>;
+}
+
+struct PenBuilder;
+struct EraserBuilder;
+
+impl CanvasToolBuilder for PenBuilder {
+    fn default_state() -> CanvasToolState {
+        CanvasToolState::Pen {
+            thickness: 2.0
+        }
+    }
+    fn build_widget(&self) -> Box<dyn Widget<CanvasToolState>> {
+        Box::new(SizedBox::new(
+            Label::new(|item: &CanvasToolState, _env: &_| format!("pen"))
+                .align_horizontal(UnitPoint::CENTER)
+                .background(Color::rgb(19.0, 0.5, 0.5))
+                .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(&self) -> 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 {
-    numbers: Vector<u32>,
+    tools: Vector<CanvasToolState>,
 }
 
 fn build_ui() -> impl Widget<AppState> {
-    use druid::UnitPoint;
-    use druid::widget::{Align, Label, Button, CrossAxisAlignment, Flex, List, ListGrowDirection, WidgetExt, SizedBox};
-
     let list_buttons = Flex::row()
         .cross_axis_alignment(CrossAxisAlignment::Center)
         .with_child(Button::new("Add"))
@@ -38,17 +89,10 @@ fn build_ui() -> impl Widget<AppState> {
         .cross_axis_alignment(CrossAxisAlignment::Center)
     	.with_flex_child(
             List::new(|| {
-                SizedBox::new(
+                //CanvasToolBuilder::build_widget ???
-                    Label::new(|item: &u32, _env: &_| format!("{}", item))
-                        .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))
             })
             .grow(ListGrowDirection::Right)
-            .lens(AppState::numbers)
+            .lens(AppState::tools)
     	, 1.0);
 
     let toolbar = Flex::row()
@@ -75,7 +119,7 @@ pub fn main() {
             LocalizedString::new("custom-widget-demo-window-title").with_placeholder("Tools"),
         );
     let app_state = AppState {
-        numbers: vector![1,2],
+        tools: vector![CanvasToolState::Eraser],
     };
 
     AppLauncher::with_window(window)