Add ui.add_enabled and ui.add_enabled_ui, and remove Button::enabled

CHANGELOG.md

@@ -11,6 +11,8 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui_w
 * Add horizontal scrolling support to `ScrollArea` and `Window` (opt-in).
 * `TextEdit::layouter`: Add custom text layout for e.g. syntax highlighting or WYSIWYG.
 * `Fonts::layout_job`: New text layout engine allowing mixing fonts, colors and styles, with underlining and strikethrough.
+* Add `ui.add_enabled(bool, widget)` to easily add a possibly disabled widget.
+* Add `ui.add_enabled_ui(bool, |ui| …)` to create a possibly disabled UI section.
 * Add feature `"serialize"` separatedly from `"persistence"`.
 * Add `egui::widgets::global_dark_light_mode_buttons` to easily add buttons for switching the egui theme.
 * `TextEdit` can now be used to show text which can be selectedd and copied, but not edited.
@@ -35,6 +37,9 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui_w
 * Show tooltips above widgets on touch screens.
 * Fix popups sometimes getting clipped by panels.
 
+### Removed 🔥
+* Replace `Button::enabled` with `ui.add_enabled`.
+
 
 ## 0.14.2 - 2021-08-28 - Window resize fix
 

egui/src/ui.rs

@@ -207,6 +207,11 @@ impl Ui {
     /// If `false`, the `Ui` does not allow any interaction and
     /// the widgets in it will draw with a gray look.
     #[inline(always)]
+    pub fn is_enabled(&self) -> bool {
+        self.enabled
+    }
+
+    #[deprecated = "Renamed to is_enabled"]
     pub fn enabled(&self) -> bool {
         self.enabled
     }
@@ -214,6 +219,8 @@ impl Ui {
     /// Calling `set_enabled(false)` will cause the `Ui` to deny all future interaction
     /// and all the widgets will draw with a gray look.
     ///
+    /// Usually it is more convenient to use [`Self::add_enabled_ui`] or [`Self::add_enabled`].
+    ///
     /// Calling `set_enabled(true)` has no effect - it will NOT re-enable the `Ui` once disabled.
     ///
     /// ### Example
@@ -926,6 +933,59 @@ impl Ui {
         .inner
     }
 
+    /// Add a  single[`Widget`] that is possibly disabled, i.e. greyed out and non-interactive.
+    ///
+    /// If you call `add_enabled` from within an already disabled UI,
+    /// the widget will always be disabled, even if the `enabled` argument is true.
+    ///
+    /// See also [`Self::add_enabled_ui`] and [`Self::is_enabled`].
+    ///
+    /// ```
+    /// # let ui = &mut egui::Ui::__test();
+    /// ui.add_enabled(false, egui::Button::new("Can't click this"));
+    /// ```
+    pub fn add_enabled(&mut self, enabled: bool, widget: impl Widget) -> Response {
+        if enabled || !self.is_enabled() {
+            self.add(widget)
+        } else {
+            let old_painter = self.painter.clone();
+            self.set_enabled(false);
+            let response = self.add(widget);
+            self.enabled = true;
+            self.painter = old_painter;
+            response
+        }
+    }
+
+    /// Add a section that is possibly disabled, i.e. greyed out and non-interactive.
+    ///
+    /// If you call `add_enabled_ui` from within an already disabled UI,
+    /// the result will always be disabled, even if the `enabled` argument is true.
+    ///
+    /// See also [`Self::add_enabled`] and [`Self::is_enabled`].
+    ///
+    /// ### Example
+    /// ```
+    /// # let ui = &mut egui::Ui::__test();
+    /// # let mut enabled = true;
+    /// ui.checkbox(&mut enabled, "Enable subsection");
+    /// ui.add_enabled_ui(enabled, |ui| {
+    ///     if ui.button("Button that is not always clickable").clicked() {
+    ///         /* … */
+    ///     }
+    /// });
+    /// ```
+    pub fn add_enabled_ui<R>(
+        &mut self,
+        enabled: bool,
+        add_contents: impl FnOnce(&mut Ui) -> R,
+    ) -> InnerResponse<R> {
+        self.scope(|ui| {
+            ui.set_enabled(enabled);
+            add_contents(ui)
+        })
+    }
+
     /// Add extra space before the next widget.
     ///
     /// The direction is dependent on the layout.

egui/src/widgets/button.rs

@@ -15,10 +15,16 @@ fn select<T>(b: bool, if_true: T, if_false: T) -> T {
 ///
 /// ```
 /// # let ui = &mut egui::Ui::__test();
+/// # fn do_stuff() {}
+///
 /// if ui.add(egui::Button::new("Click mew")).clicked() {
 ///     do_stuff();
 /// }
-/// # fn do_stuff() {}
+///
+/// // A greyed-out and non-interactive button:
+/// if ui.add_enabled(false, egui::Button::new("Can't click this")).clicked() {
+///     unreachable!();
+/// }
 /// ```
 #[must_use = "You should put this widget in an ui with `ui.add(widget);`"]
 pub struct Button {
@@ -103,17 +109,6 @@ impl Button {
         self
     }
 
-    /// If you set this to `false`, the button will be grayed out and un-clickable.
-    /// `enabled(false)` has the same effect as calling `sense(Sense::hover())`.
-    ///
-    /// This is a convenience for [`Ui::set_enabled`].
-    pub fn enabled(mut self, enabled: bool) -> Self {
-        if !enabled {
-            self.sense = Sense::hover();
-        }
-        self
-    }
-
     /// If `true`, the text will wrap at the `max_width`.
     /// By default [`Self::wrap`] will be true in vertical layouts
     /// and horizontal layouts with wrapping,
@@ -131,8 +126,8 @@ impl Button {
     }
 }
 
-impl Button {
+impl Widget for Button {
-    fn enabled_ui(self, ui: &mut Ui) -> Response {
+    fn ui(self, ui: &mut Ui) -> Response {
         let Button {
             text,
             text_color,
@@ -201,22 +196,6 @@ impl Button {
     }
 }
 
-impl Widget for Button {
-    fn ui(self, ui: &mut Ui) -> Response {
-        let button_enabled = self.sense != Sense::hover();
-        if button_enabled || !ui.enabled() {
-            self.enabled_ui(ui)
-        } else {
-            // We need get a temporary disabled `Ui` to get that grayed out look:
-            ui.scope(|ui| {
-                ui.set_enabled(false);
-                self.enabled_ui(ui)
-            })
-            .inner
-        }
-    }
-}
-
 // ----------------------------------------------------------------------------
 
 // TODO: allow checkbox without a text label

egui/src/widgets/mod.rs

@@ -91,7 +91,7 @@ pub fn reset_button<T: Default + PartialEq>(ui: &mut Ui, value: &mut T) {
 /// The button is only enabled if the value does not already have its original value.
 pub fn reset_button_with<T: PartialEq>(ui: &mut Ui, value: &mut T, reset_value: T) {
     if ui
-        .add(Button::new("Reset").enabled(*value != reset_value))
+        .add_enabled(*value != reset_value, Button::new("Reset"))
         .clicked()
     {
         *value = reset_value;

egui_demo_lib/src/apps/demo/widget_gallery.rs

@@ -53,9 +53,8 @@ impl super::Demo for WidgetGallery {
 
 impl super::View for WidgetGallery {
     fn ui(&mut self, ui: &mut egui::Ui) {
-        ui.scope(|ui| {
+        ui.add_enabled_ui(self.enabled, |ui| {
             ui.set_visible(self.visible);
-            ui.set_enabled(self.enabled);
 
             egui::Grid::new("my_grid")
                 .num_columns(2)

egui_demo_lib/src/backend_panel.rs

@@ -240,10 +240,9 @@ impl BackendPanel {
             )
             .on_hover_text("Physical pixels per point.");
             if let Some(native_pixels_per_point) = info.native_pixels_per_point {
-                let button = egui::Button::new("Reset")
+                let enabled = *pixels_per_point != native_pixels_per_point;
-                    .enabled(*pixels_per_point != native_pixels_per_point);
                 if ui
-                    .add(button)
+                    .add_enabled(enabled, egui::Button::new("Reset"))
                     .on_hover_text(format!(
                         "Reset scale to native value ({:.1})",
                         native_pixels_per_point

egui_demo_lib/src/syntax_highlighting.rs

@@ -262,7 +262,7 @@ impl CodeTheme {
                 };
 
                 if ui
-                    .add(egui::Button::new("Reset theme").enabled(*self != reset_value))
+                    .add_enabled(*self != reset_value, egui::Button::new("Reset theme"))
                     .clicked()
                 {
                     *self = reset_value;