Only repaint on cursor movements of area, or if dragging outside (#4730)

* Closes https://github.com/emilk/egui/issues/4723

Also fix some small bugs in the touch input on web

crates/eframe/src/web/app_runner.rs

@@ -15,7 +15,6 @@ pub struct AppRunner {
     pub(crate) needs_repaint: std::sync::Arc<NeedRepaint>,
     last_save_time: f64,
     pub(crate) text_agent: TextAgent,
-    pub(crate) mutable_text_under_cursor: bool,
 
     // Output for the last run:
     textures_delta: TexturesDelta,
@@ -121,7 +120,6 @@ impl AppRunner {
             needs_repaint,
             last_save_time: now_sec(),
             text_agent,
-            mutable_text_under_cursor: false,
             textures_delta: Default::default(),
             clipped_primitives: None,
         };
@@ -275,7 +273,7 @@ impl AppRunner {
         #[cfg(not(web_sys_unstable_apis))]
         let _ = copied_text;
 
-        self.mutable_text_under_cursor = mutable_text_under_cursor;
+        self.text_agent.set_focus(mutable_text_under_cursor);
 
         if let Err(err) = self.text_agent.move_to(ime, self.canvas()) {
             log::error!(