DisabledIf widget

CHANGELOG.md

@@ -33,7 +33,7 @@ You can find its changes [documented below](#070---2021-01-01).
 - `LifeCycle::DisabledChanged`, `InternalLifeCycle::RouteDisabledChanged` and the `set_disabled()` and `is_disabled()` 
   context-methods to implement disabled ([#1632] by [@xarvic])
 - `LifeCycle::BuildFocusChain` to update the focus-chain ([#1632] by [@xarvic])
-
+- `DisabledIf` widget wrapper to disable based on the state of Data and Env ([#1702] by [@xarvic])
 ### Changed
 
 - Warn on unhandled Commands ([#1533] by [@Maan2003])
@@ -672,8 +672,9 @@ Last release without a changelog :(
 [#1677]: https://github.com/linebender/druid/pull/1677
 [#1691]: https://github.com/linebender/druid/pull/1691
 [#1693]: https://github.com/linebender/druid/pull/1693
-[#1698]: https://github.com/linebender/druid/pull/1698
 [#1695]: https://github.com/linebender/druid/pull/1695
+[#1698]: https://github.com/linebender/druid/pull/1698
+[#1702]: https://github.com/linebender/druid/pull/1702
 
 [Unreleased]: https://github.com/linebender/druid/compare/v0.7.0...master
 [0.7.0]: https://github.com/linebender/druid/compare/v0.6.0...v0.7.0

druid/examples/disabled.rs

@@ -0,0 +1,93 @@
+use druid::widget::{Checkbox, CrossAxisAlignment, Flex, Label, Slider, Stepper, Switch, TextBox};
+use druid::{AppLauncher, Data, Lens, LocalizedString, UnitPoint, Widget, WidgetExt, WindowDesc};
+
+#[derive(Clone, Data, Lens)]
+struct AppData {
+    option: bool,
+    text: String,
+    value: f64,
+
+    disabled: bool,
+}
+
+fn named_child(name: &str, widget: impl Widget<AppData> + 'static) -> impl Widget<AppData> {
+    Flex::row()
+        .with_child(Label::new(name))
+        .with_default_spacer()
+        .with_child(widget)
+}
+
+fn main_widget() -> impl Widget<AppData> {
+    Flex::column()
+        .with_child(named_child("text:", TextBox::new().lens(AppData::text)))
+        .with_default_spacer()
+        .with_child(named_child(
+            "text (disabled):",
+            TextBox::new()
+                .lens(AppData::text)
+                .disabled_if(|data, _| data.disabled),
+        ))
+        .with_default_spacer()
+        .with_child(named_child("text:", TextBox::new().lens(AppData::text)))
+        .with_default_spacer()
+        .with_child(named_child(
+            "text (disabled):",
+            TextBox::new()
+                .lens(AppData::text)
+                .disabled_if(|data, _| data.disabled),
+        ))
+        .with_default_spacer()
+        .with_default_spacer()
+        .with_child(named_child(
+            "value (disabled):",
+            Slider::new()
+                .with_range(0.0, 10.0)
+                .lens(AppData::value)
+                .disabled_if(|data, _| data.disabled),
+        ))
+        .with_default_spacer()
+        .with_child(named_child(
+            "value (disabled):",
+            Stepper::new()
+                .with_range(0.0, 10.0)
+                .with_step(0.5)
+                .lens(AppData::value)
+                .disabled_if(|data, _| data.disabled),
+        ))
+        .with_default_spacer()
+        .with_child(named_child(
+            "option (disabled):",
+            Checkbox::new("option")
+                .lens(AppData::option)
+                .disabled_if(|data, _| data.disabled),
+        ))
+        .with_default_spacer()
+        .with_child(named_child(
+            "option (disabled):",
+            Switch::new()
+                .lens(AppData::option)
+                .disabled_if(|data, _| data.disabled),
+        ))
+        .with_default_spacer()
+        .with_default_spacer()
+        .with_default_spacer()
+        .with_child(Checkbox::new("disabled").lens(AppData::disabled))
+        .with_default_spacer()
+        .cross_axis_alignment(CrossAxisAlignment::End)
+        .align_horizontal(UnitPoint::CENTER)
+}
+
+pub fn main() {
+    let window = WindowDesc::new(main_widget()).title(
+        LocalizedString::new("disabled-demo-window-title").with_placeholder("Disabled demo"),
+    );
+    AppLauncher::with_window(window)
+        .log_to_console()
+        .launch(AppData {
+            option: true,
+            text: "a very important text!".to_string(),
+            value: 2.0,
+            disabled: false,
+        })
+        .expect("launch failed");
+}

druid/examples/web/src/lib.rs

@@ -58,6 +58,7 @@ impl_example!(anim);
 impl_example!(calc);
 impl_example!(cursor);
 impl_example!(custom_widget);
+impl_example!(disabled);
 impl_example!(either);
 impl_example!(event_viewer);
 impl_example!(flex);

druid/src/widget/disable_if.rs

@@ -0,0 +1,50 @@
+use crate::{
+    BoxConstraints, Data, Env, Event, EventCtx, LayoutCtx, LifeCycle, LifeCycleCtx, PaintCtx,
+    Point, Size, UpdateCtx, Widget, WidgetPod,
+};
+
+/// A widget wrapper which disables the inner widget if the provided closure return true.
+pub struct DisabledIf<T, W> {
+    inner: WidgetPod<T, W>,
+    disabled_if: Box<dyn Fn(&T, &Env) -> bool>,
+}
+
+impl<T: Data, W: Widget<T>> DisabledIf<T, W> {
+    /// Creates a new `DisabledIf` widget with the inner widget and the closure to decide if the
+    /// widget should be disabled.
+    pub fn new(widget: W, disabled_if: impl Fn(&T, &Env) -> bool + 'static) -> Self {
+        DisabledIf {
+            inner: WidgetPod::new(widget),
+            disabled_if: Box::new(disabled_if),
+        }
+    }
+}
+
+impl<T: Data, W: Widget<T>> Widget<T> for DisabledIf<T, W> {
+    fn event(&mut self, ctx: &mut EventCtx, event: &Event, data: &mut T, env: &Env) {
+        self.inner.event(ctx, event, data, env);
+    }
+
+    fn lifecycle(&mut self, ctx: &mut LifeCycleCtx, event: &LifeCycle, data: &T, env: &Env) {
+        if let LifeCycle::WidgetAdded = event {
+            ctx.set_disabled((self.disabled_if)(data, env));
+        }
+        self.inner.lifecycle(ctx, event, data, env);
+    }
+
+    fn update(&mut self, ctx: &mut UpdateCtx, _: &T, data: &T, env: &Env) {
+        ctx.set_disabled((self.disabled_if)(data, env));
+        self.inner.update(ctx, data, env);
+    }
+
+    fn layout(&mut self, ctx: &mut LayoutCtx, bc: &BoxConstraints, data: &T, env: &Env) -> Size {
+        let size = self.inner.layout(ctx, bc, data, env);
+        self.inner.set_origin(ctx, data, env, Point::ZERO);
+        ctx.set_baseline_offset(self.inner.baseline_offset());
+        size
+    }
+
+    fn paint(&mut self, ctx: &mut PaintCtx, data: &T, env: &Env) {
+        self.inner.paint(ctx, data, env);
+    }
+}

druid/src/widget/mod.rs

@@ -27,6 +27,7 @@ mod clip_box;
 mod common;
 mod container;
 mod controller;
+mod disable_if;
 mod either;
 mod env_scope;
 mod flex;
@@ -71,6 +72,7 @@ pub use clip_box::{ClipBox, Viewport};
 pub use common::FillStrat;
 pub use container::Container;
 pub use controller::{Controller, ControllerHost};
+pub use disable_if::DisabledIf;
 pub use either::Either;
 pub use env_scope::EnvScope;
 pub use flex::{Axis, CrossAxisAlignment, Flex, FlexParams, MainAxisAlignment};

druid/src/widget/widget_ext.rs

@@ -19,7 +19,7 @@ use super::{
     Added, Align, BackgroundBrush, Click, Container, Controller, ControllerHost, EnvScope,
     IdentityWrapper, LensWrap, Padding, Parse, SizedBox, WidgetId,
 };
-use crate::widget::Scroll;
+use crate::widget::{DisabledIf, Scroll};
 use crate::{
     Color, Data, Env, EventCtx, Insets, KeyOrValue, Lens, LifeCycleCtx, UnitPoint, Widget,
 };
@@ -273,6 +273,18 @@ pub trait WidgetExt<T: Data>: Widget<T> + Sized + 'static {
     fn scroll(self) -> Scroll<T, Self> {
         Scroll::new(self)
     }
+
+    /// Wrap this widget in a [`DisabledIf`] widget.
+    /// The provided closure will determine if the widget is disabled.
+    ///
+    /// See [`is_disabled`] or [`set_disabled`] for more info about the disabled state.
+    ///
+    /// [`is_disabled`]: struct.EventCtx.html#method.is_disabled
+    /// [`set_disabled`]: struct.EventCtx.html#method.set_disabled
+    /// [`DisabledIf`]: widget/struct.DisabledIf.html
+    fn disabled_if(self, disabled_if: impl Fn(&T, &Env) -> bool + 'static) -> DisabledIf<T, Self> {
+        DisabledIf::new(self, disabled_if)
+    }
 }
 
 impl<T: Data, W: Widget<T> + 'static> WidgetExt<T> for W {}