Add accessibility to `ProgressBar` and `Spinner` (#4139)

- Introduces `WidgetType::ProgressIndicator` and maps it to the
corresponding AccessKit role.
- A `Spinner` is now exposed as a widget indicating a progress for which
a completion state is not known.
- On the other hand, a `ProgressBar` reports a completion state and can
possibly be labeled. Note that a label is not used if not explicitly
asked by the user, as it would be redundant information. Assistive
technologies prefer the numerical value so they can, for instance, emit
beeps of which the frequency rise as the completion state increase. I
had to call `floor` on the progression as it seems all the ATs I tested
would round the value, hence reporting something different than what is
displayed on the label.

crates/egui/src/data/output.rs

@@ -633,6 +633,7 @@ impl WidgetInfo {
             WidgetType::ColorButton => "color button",
             WidgetType::ImageButton => "image button",
             WidgetType::CollapsingHeader => "collapsing header",
+            WidgetType::ProgressIndicator => "progress indicator",
             WidgetType::Label | WidgetType::Other => "",
         };
 

crates/egui/src/lib.rs

@@ -643,6 +643,8 @@ pub enum WidgetType {
 
     CollapsingHeader,
 
+    ProgressIndicator,
+
     /// If you cannot fit any of the above slots.
     ///
     /// If this is something you think should be added, file an issue.

crates/egui/src/response.rs

@@ -783,6 +783,7 @@ impl Response {
             WidgetType::Slider => Role::Slider,
             WidgetType::DragValue => Role::SpinButton,
             WidgetType::ColorButton => Role::ColorWell,
+            WidgetType::ProgressIndicator => Role::ProgressIndicator,
             WidgetType::Other => Role::Unknown,
         });
         if let Some(label) = info.label {

crates/egui/src/widgets/progress_bar.rs

@@ -113,6 +113,17 @@ impl Widget for ProgressBar {
         let (outer_rect, response) =
             ui.allocate_exact_size(vec2(desired_width, height), Sense::hover());
 
+        response.widget_info(|| {
+            let mut info = if let Some(ProgressBarText::Custom(text)) = &text {
+                WidgetInfo::labeled(WidgetType::ProgressIndicator, text.text())
+            } else {
+                WidgetInfo::new(WidgetType::ProgressIndicator)
+            };
+            info.value = Some((progress as f64 * 100.0).floor());
+
+            info
+        });
+
         if ui.is_rect_visible(response.rect) {
             if animate {
                 ui.ctx().request_repaint();

crates/egui/src/widgets/spinner.rs

@@ -1,6 +1,6 @@
 use epaint::{emath::lerp, vec2, Color32, Pos2, Rect, Shape, Stroke};
 
-use crate::{Response, Sense, Ui, Widget};
+use crate::{Response, Sense, Ui, Widget, WidgetInfo, WidgetType};
 
 /// A spinner widget used to indicate loading.
 ///
@@ -66,6 +66,7 @@ impl Widget for Spinner {
             .size
             .unwrap_or_else(|| ui.style().spacing.interact_size.y);
         let (rect, response) = ui.allocate_exact_size(vec2(size, size), Sense::hover());
+        response.widget_info(|| WidgetInfo::new(WidgetType::ProgressIndicator));
         self.paint_at(ui, rect);
 
         response