Additional accessibility support (#412)

* Expose getter for currently focused widget.

* Remove a level of indirection, exposing the widget event on the top level.

* Align widget descriptions more closely with common screen reader conventions.

Note that this work isn't complete--I'll correct more cases as I add more widgets and become familiar with their structures.

* Add support for click and double-click events.

* Add `ValueChanged` events, with initial support for text.

* Add support for reporting cursor selection changes.

* Track enabled/disabled status.

* Move `prev_text` off of the widget struct.

* Get rid of `has_widget_info` and push events directly where it makes sense.

* Fix typo.

* s/text_value/current_text_value/

* Use a `RangeInclusive` for text selection.

* Invert parameters.

* Various fixes.

* Only dispatch `SelectionChanged` if the selection actually changes.
* Fix missing focus events.

* If values for `current_text` and `prev_text` are unchanged, filter out the previous value.

* No need to pass in `&mut prev_text` everywhere

* Appease Clippy.

* Mask password fields in generated events.

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

egui/src/data/output.rs

@@ -42,7 +42,11 @@ impl Output {
         // only describe last event:
         if let Some(event) = self.events.iter().rev().next() {
             match event {
-                OutputEvent::WidgetEvent(WidgetEvent::Focus, widget_info) => {
+                OutputEvent::Clicked(widget_info)
+                | OutputEvent::DoubleClicked(widget_info)
+                | OutputEvent::FocusGained(widget_info)
+                | OutputEvent::TextSelectionChanged(widget_info)
+                | OutputEvent::ValueChanged(widget_info) => {
                     return widget_info.description();
                 }
             }
@@ -206,60 +210,77 @@ impl Default for CursorIcon {
 /// In particular, these events may be useful for accessability, i.e. for screen readers.
 #[derive(Clone, PartialEq)]
 pub enum OutputEvent {
+    // A widget was clicked.
+    Clicked(WidgetInfo),
+    // A widget was double-clicked.
+    DoubleClicked(WidgetInfo),
     /// A widget gained keyboard focus (by tab key).
-    WidgetEvent(WidgetEvent, WidgetInfo),
+    FocusGained(WidgetInfo),
+    // Text selection was updated.
+    TextSelectionChanged(WidgetInfo),
+    // A widget's value changed.
+    ValueChanged(WidgetInfo),
 }
 
 impl std::fmt::Debug for OutputEvent {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            Self::WidgetEvent(we, wi) => write!(f, "{:?}: {:?}", we, wi),
+            Self::Clicked(wi) => write!(f, "Clicked({:?})", wi),
+            Self::DoubleClicked(wi) => write!(f, "DoubleClicked({:?})", wi),
+            Self::FocusGained(wi) => write!(f, "FocusGained({:?})", wi),
+            Self::TextSelectionChanged(wi) => write!(f, "TextSelectionChanged({:?})", wi),
+            Self::ValueChanged(wi) => write!(f, "ValueChanged({:?})", wi),
         }
     }
 }
 
-#[derive(Clone, Copy, Debug, PartialEq)]
-pub enum WidgetEvent {
-    /// Keyboard focused moved onto the widget.
-    Focus,
-    // /// Started hovering a new widget.
-    // Hover, // TODO: cursor hovered events
-}
-
 /// Describes a widget such as a [`crate::Button`] or a [`crate::TextEdit`].
 #[derive(Clone, PartialEq)]
 pub struct WidgetInfo {
     /// The type of widget this is.
     pub typ: WidgetType,
+    // Whether the widget is enabled.
+    pub enabled: bool,
     /// The text on labels, buttons, checkboxes etc.
     pub label: Option<String>,
     /// The contents of some editable text (for `TextEdit` fields).
-    pub edit_text: Option<String>,
+    pub current_text_value: Option<String>,
+    // The previous text value.
+    pub prev_text_value: Option<String>,
     /// The current value of checkboxes and radio buttons.
     pub selected: Option<bool>,
     /// The current value of sliders etc.
     pub value: Option<f64>,
+    // Selected range of characters in [`Self::current_text_value`].
+    pub text_selection: Option<std::ops::RangeInclusive<usize>>,
 }
 
 impl std::fmt::Debug for WidgetInfo {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let Self {
             typ,
+            enabled,
             label,
-            edit_text,
+            current_text_value: text_value,
+            prev_text_value,
             selected,
             value,
+            text_selection,
         } = self;
 
         let mut s = f.debug_struct("WidgetInfo");
 
         s.field("typ", typ);
+        s.field("enabled", enabled);
 
         if let Some(label) = label {
             s.field("label", label);
         }
-        if let Some(edit_text) = edit_text {
+        if let Some(text_value) = text_value {
-            s.field("edit_text", edit_text);
+            s.field("text_value", text_value);
+        }
+        if let Some(prev_text_value) = prev_text_value {
+            s.field("prev_text_value", prev_text_value);
         }
         if let Some(selected) = selected {
             s.field("selected", selected);
@@ -267,6 +288,9 @@ impl std::fmt::Debug for WidgetInfo {
         if let Some(value) = value {
             s.field("value", value);
         }
+        if let Some(text_selection) = text_selection {
+            s.field("text_selection", text_selection);
+        }
 
         s.finish()
     }
@@ -276,10 +300,13 @@ impl WidgetInfo {
     pub fn new(typ: WidgetType) -> Self {
         Self {
             typ,
+            enabled: true,
             label: None,
-            edit_text: None,
+            current_text_value: None,
+            prev_text_value: None,
             selected: None,
             value: None,
+            text_selection: None,
         }
     }
 
@@ -319,9 +346,29 @@ impl WidgetInfo {
     }
 
     #[allow(clippy::needless_pass_by_value)]
-    pub fn text_edit(edit_text: impl ToString) -> Self {
+    pub fn text_edit(prev_text_value: impl ToString, text_value: impl ToString) -> Self {
+        let text_value = text_value.to_string();
+        let prev_text_value = prev_text_value.to_string();
+        let prev_text_value = if text_value == prev_text_value {
+            None
+        } else {
+            Some(prev_text_value)
+        };
         Self {
-            edit_text: Some(edit_text.to_string()),
+            current_text_value: Some(text_value),
+            prev_text_value,
+            ..Self::new(WidgetType::TextEdit)
+        }
+    }
+
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn text_selection_changed(
+        text_selection: std::ops::RangeInclusive<usize>,
+        current_text_value: impl ToString,
+    ) -> Self {
+        Self {
+            text_selection: Some(text_selection),
+            current_text_value: Some(current_text_value.to_string()),
             ..Self::new(WidgetType::TextEdit)
         }
     }
@@ -330,14 +377,17 @@ impl WidgetInfo {
     pub fn description(&self) -> String {
         let Self {
             typ,
+            enabled,
             label,
-            edit_text,
+            current_text_value: text_value,
+            prev_text_value: _,
             selected,
             value,
+            text_selection: _,
         } = self;
 
         // TODO: localization
-        let widget_name = match typ {
+        let widget_type = match typ {
             WidgetType::Hyperlink => "link",
             WidgetType::TextEdit => "text edit",
             WidgetType::Button => "button",
@@ -353,25 +403,33 @@ impl WidgetInfo {
             WidgetType::Label | WidgetType::Other => "",
         };
 
-        let mut description = widget_name.to_owned();
+        let mut description = widget_type.to_owned();
 
         if let Some(selected) = selected {
             if *typ == WidgetType::Checkbox {
-                description += " ";
+                let state = if *selected { "checked" } else { "unchecked" };
-                description += if *selected { "checked" } else { "unchecked" };
+                description = format!("{} {}", state, description);
             } else {
                 description += if *selected { "selected" } else { "" };
             };
         }
 
         if let Some(label) = label {
-            description += " ";
+            description = format!("{}: {}", label, description);
-            description += label;
         }
 
-        if let Some(edit_text) = edit_text {
+        if typ == &WidgetType::TextEdit {
-            description += " ";
+            let text;
-            description += edit_text;
+            if let Some(text_value) = text_value {
+                if text_value.is_empty() {
+                    text = "blank".into();
+                } else {
+                    text = text_value.to_string();
+                }
+            } else {
+                text = "blank".into();
+            }
+            description = format!("{}: {}", text, description);
         }
 
         if let Some(value) = value {
@@ -379,6 +437,9 @@ impl WidgetInfo {
             description += &value.to_string();
         }
 
+        if !enabled {
+            description += ": disabled";
+        }
         description.trim().to_owned()
     }
 }

egui/src/memory.rs

@@ -315,6 +315,11 @@ impl Memory {
         self.interaction.focus.id == Some(id)
     }
 
+    /// Which widget has keyboard focus?
+    pub fn focus(&self) -> Option<Id> {
+        self.interaction.focus.id
+    }
+
     pub(crate) fn lock_focus(&mut self, id: Id, lock_focus: bool) {
         if self.had_focus_last_frame(id) && self.has_focus(id) {
             self.interaction.focus.is_focus_locked = lock_focus;

egui/src/response.rs

@@ -428,10 +428,19 @@ impl Response {
     ///
     /// Call after interacting and potential calls to [`Self::mark_changed`].
     pub fn widget_info(&self, make_info: impl Fn() -> crate::WidgetInfo) {
-        if self.gained_focus() {
+        use crate::output::OutputEvent;
-            use crate::output::{OutputEvent, WidgetEvent};
+        let event = if self.clicked() {
-            let widget_info = make_info();
+            Some(OutputEvent::Clicked(make_info()))
-            let event = OutputEvent::WidgetEvent(WidgetEvent::Focus, widget_info);
+        } else if self.double_clicked() {
+            Some(OutputEvent::DoubleClicked(make_info()))
+        } else if self.gained_focus() {
+            Some(OutputEvent::FocusGained(make_info()))
+        } else if self.changed {
+            Some(OutputEvent::ValueChanged(make_info()))
+        } else {
+            None
+        };
+        if let Some(event) = event {
             self.ctx.output().events.push(event);
         }
     }

egui/src/widgets/text_edit.rs

@@ -1,4 +1,4 @@
-use crate::{util::undoer::Undoer, *};
+use crate::{output::OutputEvent, util::undoer::Undoer, *};
 use epaint::{text::cursor::*, *};
 use std::ops::Range;
 
@@ -393,6 +393,7 @@ impl<'t, S: TextBuffer> TextEdit<'t, S> {
             lock_focus,
         } = self;
 
+        let prev_text = text.clone();
         let text_style = text_style
             .or(ui.style().override_text_style)
             .unwrap_or_else(|| ui.style().body_text_style);
@@ -496,6 +497,8 @@ impl<'t, S: TextBuffer> TextEdit<'t, S> {
             ui.output().cursor_icon = CursorIcon::Text;
         }
 
+        let mut text_cursor = None;
+        let prev_text_cursor = state.cursorp;
         if ui.memory().has_focus(id) && enabled {
             ui.memory().lock_focus(id, lock_focus);
 
@@ -554,7 +557,6 @@ impl<'t, S: TextBuffer> TextEdit<'t, S> {
                             && text_to_insert != "\r"
                         {
                             let mut ccursor = delete_selected(text, &cursorp);
-
                             insert_text(&mut ccursor, text, text_to_insert);
                             Some(CCursorPair::one(ccursor))
                         } else {
@@ -667,6 +669,7 @@ impl<'t, S: TextBuffer> TextEdit<'t, S> {
                 }
             }
             state.cursorp = Some(cursorp);
+            text_cursor = Some(cursorp);
 
             state
                 .undoer
@@ -709,7 +712,48 @@ impl<'t, S: TextBuffer> TextEdit<'t, S> {
 
         ui.memory().id_data.insert(id, state);
 
-        response.widget_info(|| WidgetInfo::text_edit(&*text));
+        let selection_changed = if let (Some(text_cursor), Some(prev_text_cursor)) =
+            (text_cursor, prev_text_cursor)
+        {
+            text_cursor.primary.ccursor.index != prev_text_cursor.primary.ccursor.index
+                || text_cursor.secondary.ccursor.index != prev_text_cursor.secondary.ccursor.index
+        } else {
+            false
+        };
+
+        let masked = if self.password {
+            let prev_text_len = prev_text.to_string().len();
+            let text_len = text.to_string().len();
+            Some(("*".repeat(prev_text_len), "*".repeat(text_len)))
+        } else {
+            None
+        };
+
+        if response.changed {
+            if let Some((prev_text, text)) = masked {
+                response.widget_info(|| WidgetInfo::text_edit(&prev_text, &text));
+            } else {
+                response.widget_info(|| WidgetInfo::text_edit(&prev_text, &text));
+            }
+        } else if selection_changed {
+            let text_cursor = text_cursor.unwrap();
+            let char_range =
+                text_cursor.primary.ccursor.index..=text_cursor.secondary.ccursor.index;
+            let info = if let Some((_, text)) = masked {
+                WidgetInfo::text_selection_changed(char_range, text)
+            } else {
+                WidgetInfo::text_selection_changed(char_range, &*text)
+            };
+            response
+                .ctx
+                .output()
+                .events
+                .push(OutputEvent::TextSelectionChanged(info));
+        } else if let Some((prev_text, text)) = masked {
+            response.widget_info(|| WidgetInfo::text_edit(&prev_text, &text));
+        } else {
+            response.widget_info(|| WidgetInfo::text_edit(&prev_text, &text));
+        }
         response
     }
 }