Add experimental screen_reader feature

Part of https://github.com/emilk/egui/issues/167

egui_glium/src/backend.rs

@@ -180,6 +180,8 @@ pub fn run(mut app: Box<dyn epi::App>) -> ! {
     #[cfg(feature = "http")]
     let http = std::sync::Arc::new(crate::http::GliumHttp {});
 
+    let mut screen_reader = crate::screen_reader::ScreenReader::default();
+
     if app.warm_up_enabled() {
         // let warm_up_start = Instant::now();
         input_state.raw.time = Some(0.0);
@@ -273,6 +275,7 @@ pub fn run(mut app: Box<dyn epi::App>) -> ! {
                 };
             }
 
+            screen_reader.speak(&egui_output.events_description());
             handle_output(egui_output, &display, clipboard.as_mut());
 
             #[cfg(feature = "persistence")]

egui_glium/src/lib.rs

@@ -15,6 +15,7 @@ pub mod http;
 mod painter;
 #[cfg(feature = "persistence")]
 pub mod persistence;
+pub mod screen_reader;
 pub mod window_settings;
 
 pub use backend::*;

egui_glium/src/screen_reader.rs

@@ -0,0 +1,44 @@
+pub struct ScreenReader {
+    #[cfg(feature = "screen_reader")]
+    tts: Option<tts::TTS>,
+}
+
+#[cfg(not(feature = "screen_reader"))]
+impl Default for ScreenReader {
+    fn default() -> Self {
+        Self {}
+    }
+}
+
+#[cfg(feature = "screen_reader")]
+impl Default for ScreenReader {
+    fn default() -> Self {
+        let tts = match tts::TTS::default() {
+            Ok(screen_reader) => {
+                eprintln!("Initialized screen reader.");
+                Some(screen_reader)
+            }
+            Err(err) => {
+                eprintln!("Failed to load screen reader: {}", err);
+                None
+            }
+        };
+        Self { tts }
+    }
+}
+
+impl ScreenReader {
+    #[cfg(not(feature = "screen_reader"))]
+    pub fn speak(&mut self, _text: &str) {}
+
+    #[cfg(feature = "screen_reader")]
+    pub fn speak(&mut self, text: &str) {
+        if let Some(tts) = &mut self.tts {
+            eprintln!("Speaking: {:?}", text);
+            let interrupt = true;
+            if let Err(err) = tts.speak(text, interrupt) {
+                eprintln!("Failed to read: {}", err);
+            }
+        }
+    }
+}