opt: fetch rgba positively for sessions on flutter

flutter/lib/models/model.dart

@@ -1376,7 +1376,12 @@ class FFI {
             debugPrint('json.decode fail1(): $e, ${message.field0}');
           }
         } else if (message is EventToUI_Rgba) {
-          imageModel.onRgba(message.field0);
+          // Fetch the image buffer from rust codes.
+          bind.sessionGetRgba(id: id).then((rgba)  {
+            if (rgba != null) {
+              imageModel.onRgba(rgba);
+            }
+          });
         }
       }
     }();

src/flutter.rs

@@ -110,6 +110,7 @@ pub unsafe extern "C" fn free_c_args(ptr: *mut *mut c_char, len: c_int) {
 #[derive(Default, Clone)]
 pub struct FlutterHandler {
     pub event_stream: Arc<RwLock<Option<StreamSink<EventToUI>>>>,
+    pub rgba: Arc<RwLock<Option<Vec<u8>>>>
 }
 
 impl FlutterHandler {
@@ -290,7 +291,8 @@ impl InvokeUiSession for FlutterHandler {
 
     fn on_rgba(&self, data: &[u8]) {
         if let Some(stream) = &*self.event_stream.read().unwrap() {
-            stream.add(EventToUI::Rgba(ZeroCopyBuffer(data.to_owned())));
+            drop(self.rgba.write().unwrap().replace(data.to_owned()));
+            stream.add(EventToUI::Rgba);
         }
     }
 
@@ -409,6 +411,10 @@ impl InvokeUiSession for FlutterHandler {
     fn on_voice_call_incoming(&self) {
         self.push_event("on_voice_call_incoming", [].into());
     }
+
+    fn get_rgba(&self) -> Option<Vec<u8>> {
+        self.rgba.write().unwrap().take()
+    }
 }
 
 /// Create a new remote session with the given id.

src/flutter_ffi.rs

@@ -20,6 +20,7 @@ use std::{
     os::raw::c_char,
     str::FromStr,
 };
+use crate::ui_session_interface::InvokeUiSession;
 
 // use crate::hbbs_http::account::AuthResult;
 
@@ -47,7 +48,7 @@ fn initialize(app_dir: &str) {
 
 pub enum EventToUI {
     Event(String),
-    Rgba(ZeroCopyBuffer<Vec<u8>>),
+    Rgba,
 }
 
 pub fn start_global_event_stream(s: StreamSink<String>, app_type: String) -> ResultType<()> {
@@ -103,6 +104,16 @@ pub fn session_get_remember(id: String) -> Option<bool> {
     }
 }
 
+pub fn session_get_rgba(id: String) -> Option<ZeroCopyBuffer<Vec<u8>>> {
+    if let Some(session) = SESSIONS.read().unwrap().get(&id) {
+        return match session.get_rgba() {
+            Some(buf) => Some(ZeroCopyBuffer(buf)),
+            _ => None
+        };
+    }
+    None
+}
+
 pub fn session_get_toggle_option(id: String, arg: String) -> Option<bool> {
     if let Some(session) = SESSIONS.read().unwrap().get(&id) {
         Some(session.get_toggle_option(arg))

src/ui/remote.rs

@@ -282,6 +282,11 @@ impl InvokeUiSession for SciterHandler {
     fn on_voice_call_incoming(&self) {
         self.call("onVoiceCallIncoming", &make_args!());
     }
+
+    /// RGBA is directly rendered by [on_rgba]. No need to store the rgba for the sciter ui.
+    fn get_rgba(&self) -> Option<Vec<u8>> {
+        None
+    }
 }
 
 pub struct SciterSession(Session<SciterHandler>);

src/ui_session_interface.rs

@@ -722,6 +722,7 @@ pub trait InvokeUiSession: Send + Sync + Clone + 'static + Sized + Default {
     fn on_voice_call_closed(&self, reason: &str);
     fn on_voice_call_waiting(&self);
     fn on_voice_call_incoming(&self);
+    fn get_rgba(&self) -> Option<Vec<u8>>;
 }
 
 impl<T: InvokeUiSession> Deref for Session<T> {