feat: add general ui handler

flutter/lib/main.dart

@@ -13,6 +13,7 @@ import 'package:flutter_hbb/desktop/screen/desktop_port_forward_screen.dart';
 import 'package:flutter_hbb/desktop/screen/desktop_remote_screen.dart';
 import 'package:flutter_hbb/desktop/widgets/refresh_wrapper.dart';
 import 'package:flutter_hbb/models/state_model.dart';
+import 'package:flutter_hbb/plugin/handlers.dart';
 import 'package:flutter_hbb/utils/multi_window_manager.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:get/get.dart';
@@ -428,4 +429,10 @@ _registerEventHandler() {
       reloadAllWindows();
     });
   }
+  // Register native handlers.
+  if (isDesktop) {
+    platformFFI.registerEventHandler('native_ui', 'native_ui', (evt) async {
+      NativeUiHandler.instance.onEvent(evt);
+    });
+  }
 }

flutter/lib/plugin/handlers.dart

@@ -0,0 +1,43 @@
+import 'dart:ffi';
+
+abstract class NativeHandler {
+  bool onEvent(Map<String, dynamic> evt);
+}
+
+typedef OnSelectPeersCallback = Bool Function(Int returnCode,
+    Pointer<Void> data, Uint64 dataLength, Pointer<Void> userData);
+typedef OnSelectPeersCallbackDart = bool Function(
+    int returnCode, Pointer<Void> data, int dataLength, Pointer<Void> userData);
+
+class NativeUiHandler extends NativeHandler {
+  NativeUiHandler._();
+
+  static NativeUiHandler instance = NativeUiHandler._();
+
+  @override
+  bool onEvent(Map<String, dynamic> evt) {
+    final name = evt['name'];
+    final action = evt['action'];
+    if (name != "native_ui") {
+      return false;
+    }
+    switch (action) {
+      case "select_peers":
+        int cb = evt['cb'];
+        int userData = evt['user_data'] ?? 0;
+        final cbFuncNative = Pointer.fromAddress(cb)
+            .cast<NativeFunction<OnSelectPeersCallback>>();
+        final cbFuncDart = cbFuncNative.asFunction<OnSelectPeersCallbackDart>();
+        onSelectPeers(cbFuncDart, userData);
+        break;
+      default:
+        return false;
+    }
+    return true;
+  }
+
+  void onSelectPeers(OnSelectPeersCallbackDart cb, int userData) async {
+    // TODO: design a UI interface to pick peers.
+    cb(0, Pointer.fromAddress(0), 0, Pointer.fromAddress(userData));
+  }
+}

src/plugin/native_handlers/mod.rs

@@ -10,12 +10,13 @@ use serde_json::Map;
 
 use crate::return_if_not_method;
 
-use self::session::PluginNativeSessionHandler;
+use self::{session::PluginNativeSessionHandler, ui::PluginNativeUIHandler};
 
 use super::cstr_to_string;
 
 mod macros;
 pub mod session;
+pub mod ui;
 
 pub type NR = super::native::NativeReturnValue;
 pub type PluginNativeHandlerRegistrar = NativeHandlerRegistrar<Box<dyn Callable + Send + Sync>>;
@@ -33,10 +34,11 @@ pub struct NativeHandlerRegistrar<H> {
 impl Default for PluginNativeHandlerRegistrar {
     fn default() -> Self {
         Self {
-            handlers: Arc::new(RwLock::new(vec![Box::new(
+            handlers: Arc::new(RwLock::new(vec![
                 // Add prebuilt native handlers here.
-                PluginNativeSessionHandler::default(),
-            )])),
+                Box::new(PluginNativeSessionHandler::default()),
+                Box::new(PluginNativeUIHandler::default()),
+            ])),
         }
     }
 }

src/plugin/native_handlers/ui.rs

@@ -0,0 +1,100 @@
+use std::{collections::HashMap, ffi::c_void, os::raw::c_int};
+
+use serde_json::json;
+
+use crate::{
+    define_method_prefix,
+    flutter::{APP_TYPE_MAIN},
+};
+
+use super::PluginNativeHandler;
+
+#[derive(Default)]
+pub struct PluginNativeUIHandler;
+
+/// Callback for UI interface.
+///
+/// [Note]
+/// We will transfer the native callback to u64 and post it to flutter.
+/// The flutter thread will directly call this method.
+///
+/// an example of `data` is:
+/// ```
+/// {
+///     "cb": 0x1234567890
+/// }
+/// ```
+/// [Safety]
+/// Please make sure the callback u provided is VALID, or memory or calling issues may occur to cause the program crash!
+pub type OnUIReturnCallback = extern "C" fn(return_code: c_int, data: *const c_void, data_len: u64, user_data: *const c_void);
+
+impl PluginNativeHandler for PluginNativeUIHandler {
+    define_method_prefix!("ui_");
+
+    fn on_message(
+        &self,
+        method: &str,
+        data: &serde_json::Map<String, serde_json::Value>,
+    ) -> Option<super::NR> {
+        match method {
+            "select_peers_async" => {
+                if let Some(cb) = data.get("cb") {
+                    if let Some(cb) = cb.as_u64() {
+                        let user_data = match data.get("user_data") {
+                            Some(user_data) => {
+                                user_data.as_u64().unwrap_or(0)
+                            },
+                            None => 0,
+                        };
+                        self.select_peers_async(cb, user_data);
+                        return Some(super::NR {
+                            return_type: 0,
+                            data: std::ptr::null(),
+                        });
+                    }
+                }
+                return Some(super::NR {
+                    return_type: -1,
+                    data: "missing cb field message".as_ptr() as _,
+                });
+            }
+            _ => {}
+        }
+        None
+    }
+
+    fn on_message_raw(
+        &self,
+        method: &str,
+        data: &serde_json::Map<String, serde_json::Value>,
+        raw: *const std::ffi::c_void,
+        _raw_len: usize,
+    ) -> Option<super::NR> {
+        None
+    }
+}
+
+impl PluginNativeUIHandler {
+    /// Call with method `select_peers_async` and the following json:
+    /// ```json
+    /// {
+    ///     "cb": 0, // The function address
+    ///     "user_data": 0 // An opaque pointer value passed to the callback.
+    /// }
+    /// ```
+    /// 
+    /// [Arguments] 
+    /// @param cb: the function address with type [OnUIReturnCallback].
+    /// @param user_data: the function will be called with this value. 
+    fn select_peers_async(&self, cb: u64, user_data: u64) {
+        let mut param = HashMap::new();
+        param.insert("name", json!("native_ui"));
+        param.insert("action", json!("select_peers"));
+        param.insert("cb", json!(cb));
+        param.insert("user_data", json!(user_data));
+        crate::flutter::push_global_event(
+            APP_TYPE_MAIN,
+            serde_json::to_string(&param).unwrap_or("".to_string()),
+        );
+    }
+}