cxx-qt-lib: use cxx_qt::bridge and #[qsignal] in QQmlEngine

This allows for us to declare a signal and listen to it.

Author: ahayzen-kdab

crates/cxx-qt-lib-headers/include/qml/qqmlapplicationengine.h

@@ -11,13 +11,17 @@
 #include <memory>
 
 #include <QtQml/QQmlApplicationEngine>
+#include <QtQml/QQmlEngine>
 
 namespace rust {
 namespace cxxqtlib1 {
 
 ::std::unique_ptr<QQmlApplicationEngine>
 qqmlapplicationengineNew();
 
+QQmlEngine&
+qqmlapplicationengineAsQQmlEngine(QQmlApplicationEngine&);
+
 }
 }
 

crates/cxx-qt-lib/src/qml/qqmlapplicationengine.cpp

@@ -16,5 +16,11 @@ qqmlapplicationengineNew()
   return ::std::make_unique<QQmlApplicationEngine>();
 }
 
+QQmlEngine&
+qqmlapplicationengineAsQQmlEngine(QQmlApplicationEngine& engine)
+{
+  return static_cast<QQmlEngine&>(engine);
+}
+
 }
 }

crates/cxx-qt-lib/src/qml/qqmlapplicationengine.rs

@@ -61,11 +61,22 @@ mod ffi {
         fn setOfflineStoragePath(self: Pin<&mut QQmlApplicationEngine>, dir: &QString);
     }
 
+    unsafe extern "C++" {
+        include!("cxx-qt-lib/qqmlengine.h");
+        type QQmlEngine = crate::QQmlEngine;
+    }
+
     #[namespace = "rust::cxxqtlib1"]
     unsafe extern "C++" {
         #[doc(hidden)]
         #[rust_name = "qqmlapplicationengine_new"]
         fn qqmlapplicationengineNew() -> UniquePtr<QQmlApplicationEngine>;
+
+        #[doc(hidden)]
+        #[rust_name = "qqmlapplicationengine_as_qqmlengine"]
+        fn qqmlapplicationengineAsQQmlEngine(
+            ptr: Pin<&mut QQmlApplicationEngine>,
+        ) -> Pin<&mut QQmlEngine>;
     }
 
     // QQmlApplicationEngine is not a trivial to CXX and is not relocatable in Qt
@@ -75,9 +86,17 @@ mod ffi {
     impl UniquePtr<QQmlApplicationEngine> {}
 }
 
+use crate::QQmlEngine;
+use core::pin::Pin;
+
 pub use ffi::QQmlApplicationEngine;
 
 impl QQmlApplicationEngine {
+    /// Convert the existing [QQmlApplicationEngine] to a [QQmlEngine]
+    pub fn as_qqmlengine<'a>(self: Pin<&'a mut Self>) -> Pin<&'a mut QQmlEngine> {
+        ffi::qqmlapplicationengine_as_qqmlengine(self)
+    }
+
     /// Create a new QQmlApplicationEngine
     pub fn new() -> cxx::UniquePtr<Self> {
         ffi::qqmlapplicationengine_new()

crates/cxx-qt-lib/src/qml/qqmlengine.rs

@@ -3,8 +3,21 @@
 //
 // SPDX-License-Identifier: MIT OR Apache-2.0
 
-#[cxx::bridge]
+#[cxx_qt::bridge(cxx_file_stem = "qqmlengine")]
 mod ffi {
+    unsafe extern "C++Qt" {
+        include!("cxx-qt-lib/qqmlengine.h");
+        type QQmlEngine;
+
+        /// This signal is emitted when the QML loaded by the engine would like to exit from the event loop with the specified return code ret_code.
+        #[qsignal]
+        fn exit(self: Pin<&mut QQmlEngine>, ret_code: i32);
+
+        /// This signal is emitted when the QML loaded by the engine would like to quit.
+        #[qsignal]
+        fn quit(self: Pin<&mut QQmlEngine>);
+    }
+
     unsafe extern "C++" {
         include!("cxx-qt-lib/qstring.h");
         type QString = crate::QString;
@@ -13,9 +26,6 @@ mod ffi {
         include!("cxx-qt-lib/qurl.h");
         type QUrl = crate::QUrl;
 
-        include!("cxx-qt-lib/qqmlengine.h");
-        type QQmlEngine;
-
         /// Adds path as a directory where the engine searches for installed modules in a URL-based directory structure.
         #[rust_name = "add_import_path"]
         fn addImportPath(self: Pin<&mut QQmlEngine>, path: &QString);

examples/cargo_without_cmake/src/main.rs

@@ -28,6 +28,13 @@ fn main() {
         engine.load(&QUrl::from("qrc:/qt/qml/com/kdab/cxx_qt/demo/qml/main.qml"));
     }
 
+    if let Some(engine) = engine.as_mut() {
+        // Listen to a signal from the QML Engine
+        engine.as_qqmlengine().on_quit(|_| {
+            println!("QML Quit!");
+        });
+    }
+
     // Start the app
     if let Some(app) = app.as_mut() {
         app.exec();

examples/qml_minimal/qml/main.qml

@@ -51,6 +51,12 @@ Window {
 
             onClicked: myObject.sayHi(myObject.string, myObject.number)
         }
+
+        Button {
+            text: qsTr("Quit")
+
+            onClicked: Qt.quit()
+        }
     }
 }
 // ANCHOR_END: book_main_qml