cxx-qt-gen: add support for choosing a custom parent class

This then allows you to create a QQuickItem such as a QQuickPaintedItem.

Closes #474

CHANGELOG.md

@@ -19,6 +19,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Allow associated constants, types and macro invocations within `impl qobject::T` blocks
 - Ensure that generated Rust code works when `#![deny(missing_docs)]` is enabled
 
+### Added
+
+- Support for choosing a custom parent class, this allows for deriving from `QQuickItem` classes
+
 ### Changed
 
 - Pretty-print errors messages when build script fails

crates/cxx-qt-gen/src/generator/cpp/qobject.rs

@@ -65,6 +65,8 @@ pub struct GeneratedCppQObject {
     pub namespace_internals: String,
     /// Base class of the QObject
     pub base_class: String,
+    /// Parent class of the QObject
+    pub parent_class: String,
     /// The blocks of the QObject
     pub blocks: GeneratedCppQObjectBlocks,
 }
@@ -86,6 +88,10 @@ impl GeneratedCppQObject {
                 .base_class
                 .clone()
                 .unwrap_or_else(|| "QObject".to_string()),
+            parent_class: qobject
+                .parent_class
+                .clone()
+                .unwrap_or_else(|| "QObject".to_string()),
             blocks: GeneratedCppQObjectBlocks::from(qobject),
         };
 
@@ -145,6 +151,7 @@ mod tests {
         assert_eq!(cpp.cxx_qt_thread_ident, "MyObjectCxxQtThread");
         assert_eq!(cpp.namespace_internals, "cxx_qt_my_object");
         assert_eq!(cpp.base_class, "QObject");
+        assert_eq!(cpp.parent_class, "QObject");
         assert_eq!(cpp.blocks.metaobjects.len(), 0);
     }
 
@@ -153,7 +160,7 @@ mod tests {
         let module: ItemMod = parse_quote! {
             #[cxx_qt::bridge(namespace = "cxx_qt")]
             mod ffi {
-                #[cxx_qt::qobject(base = "QStringListModel")]
+                #[cxx_qt::qobject(base = "QStringListModel", parent = "QQuickItem")]
                 pub struct MyObject;
             }
         };
@@ -166,6 +173,7 @@ mod tests {
         .unwrap();
         assert_eq!(cpp.namespace_internals, "cxx_qt::cxx_qt_my_object");
         assert_eq!(cpp.base_class, "QStringListModel");
+        assert_eq!(cpp.parent_class, "QQuickItem");
         assert_eq!(cpp.blocks.metaobjects.len(), 0);
     }
 

crates/cxx-qt-gen/src/parser/qobject.rs

@@ -36,6 +36,8 @@ pub struct QmlElementMetadata {
 pub struct ParsedQObject {
     /// The base class of the struct
     pub base_class: Option<String>,
+    /// The parent class of the struct
+    pub parent_class: Option<String>,
     /// QObject struct that stores the invokables for the QObject
     pub qobject_struct: ItemStruct,
     /// The namespace of the QObject. If one isn't specified for the QObject,
@@ -81,6 +83,11 @@ impl ParsedQObject {
             .get(&quote::format_ident!("base"))
             .map(|base| base.value());
 
+        // Find if there is any parent class
+        let parent_class = attrs_map
+            .get(&quote::format_ident!("parent"))
+            .map(|parent| parent.value());
+
         // Load the namespace, if it is empty then the ParsedCxxQtData will inject any global namespace
         let namespace = attrs_map
             .get(&quote::format_ident!("namespace"))
@@ -105,6 +112,7 @@ impl ParsedQObject {
 
         Ok(Self {
             base_class,
+            parent_class,
             qobject_struct,
             namespace,
             signals: None,
@@ -278,18 +286,20 @@ pub mod tests {
 
         let qobject = ParsedQObject::from_struct(&qobject_struct, 0).unwrap();
         assert!(qobject.base_class.is_none());
+        assert!(qobject.parent_class.is_none());
         assert!(qobject.qml_metadata.is_none());
     }
 
     #[test]
     fn test_from_struct_base_class() {
         let qobject_struct: ItemStruct = parse_quote! {
-            #[cxx_qt::qobject(base = "QStringListModel")]
+            #[cxx_qt::qobject(base = "QStringListModel", parent = "QQuickItem")]
             pub struct MyObject;
         };
 
         let qobject = ParsedQObject::from_struct(&qobject_struct, 0).unwrap();
         assert_eq!(qobject.base_class.as_ref().unwrap(), "QStringListModel");
+        assert_eq!(qobject.parent_class.as_ref().unwrap(), "QQuickItem");
     }
 
     #[test]

crates/cxx-qt-gen/src/writer/cpp/header.rs

@@ -74,7 +74,7 @@ fn qobjects_header(generated: &GeneratedCppBlocks) -> Vec<String> {
               {metaobjects}
 
             public:
-              explicit {ident}(QObject* parent = nullptr);
+              explicit {ident}({parent_class}* parent = nullptr);
               ~{ident}();
               {rust_ident} const& unsafeRust() const;
               {rust_ident}& unsafeRustMut();
@@ -104,6 +104,7 @@ fn qobjects_header(generated: &GeneratedCppBlocks) -> Vec<String> {
         namespace_internals = qobject.namespace_internals,
         rust_ident = qobject.rust_ident,
         base_class = qobject.base_class,
+        parent_class = qobject.parent_class,
         metaobjects = qobject.blocks.metaobjects.join("\n  "),
         methods = create_block("public", &qobject.blocks.methods.iter().filter_map(pair_as_header).collect::<Vec<&str>>()),
         metatype = if generated.namespace.is_empty() {

crates/cxx-qt-gen/src/writer/cpp/mod.rs

@@ -60,6 +60,7 @@ mod tests {
                     cxx_qt_thread_ident: "MyObjectCxxQtThread".to_owned(),
                     namespace_internals: "cxx_qt::my_object::cxx_qt_my_object".to_owned(),
                     base_class: "QStringListModel".to_owned(),
+                    parent_class: "QObject".to_owned(),
                     blocks: GeneratedCppQObjectBlocks {
                         metaobjects: vec![
                             "Q_PROPERTY(int count READ count WRITE setCount NOTIFY countChanged)".to_owned(),
@@ -158,6 +159,7 @@ mod tests {
                     cxx_qt_thread_ident: "FirstObjectCxxQtThread".to_owned(),
                     namespace_internals: "cxx_qt::cxx_qt_first_object".to_owned(),
                     base_class: "QStringListModel".to_owned(),
+                    parent_class: "QObject".to_owned(),
                     blocks: GeneratedCppQObjectBlocks {
                         metaobjects: vec![
                             "Q_PROPERTY(int longPropertyNameThatWrapsInClangFormat READ count WRITE setCount NOTIFY countChanged)"
@@ -195,6 +197,7 @@ mod tests {
                     cxx_qt_thread_ident: "SecondObjectCxxQtThread".to_owned(),
                     namespace_internals: "cxx_qt::cxx_qt_second_object".to_owned(),
                     base_class: "QStringListModel".to_owned(),
+                    parent_class: "QQuickItem".to_owned(),
                     blocks: GeneratedCppQObjectBlocks {
                         metaobjects: vec![
                             "Q_PROPERTY(int count READ count WRITE setCount NOTIFY countChanged)"
@@ -367,7 +370,7 @@ mod tests {
           Q_PROPERTY(int count READ count WRITE setCount NOTIFY countChanged)
 
         public:
-          explicit SecondObject(QObject* parent = nullptr);
+          explicit SecondObject(QQuickItem* parent = nullptr);
           ~SecondObject();
           SecondObjectRust const& unsafeRust() const;
           SecondObjectRust& unsafeRustMut();
@@ -611,7 +614,7 @@ mod tests {
 
         namespace cxx_qt {
 
-        SecondObject::SecondObject(QObject* parent)
+        SecondObject::SecondObject(QQuickItem* parent)
           : QStringListModel(parent)
           , m_rustObj(cxx_qt::cxx_qt_second_object::createRs())
           , m_rustObjMutex(::std::make_shared<::std::recursive_mutex>())

crates/cxx-qt-gen/src/writer/cpp/source.rs

@@ -24,7 +24,7 @@ fn qobjects_source(generated: &GeneratedCppBlocks) -> Vec<String> {
         formatdoc! { r#"
             {namespace_start}
 
-            {ident}::{ident}(QObject* parent)
+            {ident}::{ident}({parent_class}* parent)
               : {base_class}(parent)
               , m_rustObj({namespace_internals}::createRs())
               , m_rustObjMutex(::std::make_shared<::std::recursive_mutex>())
@@ -73,6 +73,7 @@ fn qobjects_source(generated: &GeneratedCppBlocks) -> Vec<String> {
         namespace_end = namespace_end,
         namespace_internals = qobject.namespace_internals,
         base_class = qobject.base_class,
+        parent_class = qobject.parent_class,
         rust_ident = qobject.rust_ident,
         methods = qobject.blocks.methods.iter().filter_map(pair_as_source).collect::<Vec<String>>().join("\n"),
         }

crates/cxx-qt-gen/test_inputs/passthrough_and_naming.rs

@@ -79,7 +79,7 @@ pub mod ffi {
         include!(<QtCore/QStringListModel>);
     }
 
-    #[cxx_qt::qobject(base = "QStringListModel")]
+    #[cxx_qt::qobject(base = "QStringListModel", parent = "QQuickItem")]
     pub struct MyObject {
         #[qproperty]
         property_name: i32,

crates/cxx-qt-gen/test_outputs/passthrough_and_naming.cpp

@@ -2,7 +2,7 @@
 
 namespace cxx_qt::multi_object {
 
-MyObject::MyObject(QObject* parent)
+MyObject::MyObject(QQuickItem* parent)
   : QStringListModel(parent)
   , m_rustObj(cxx_qt::multi_object::cxx_qt_my_object::createRs())
   , m_rustObjMutex(::std::make_shared<::std::recursive_mutex>())

crates/cxx-qt-gen/test_outputs/passthrough_and_naming.h

@@ -28,7 +28,7 @@ class MyObject : public QStringListModel
                setPropertyName NOTIFY propertyNameChanged)
 
 public:
-  explicit MyObject(QObject* parent = nullptr);
+  explicit MyObject(QQuickItem* parent = nullptr);
   ~MyObject();
   MyObjectRust const& unsafeRust() const;
   MyObjectRust& unsafeRustMut();

examples/qml_features/CMakeLists.txt

@@ -15,10 +15,10 @@ set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 if(NOT USE_QT5)
-    find_package(Qt6 COMPONENTS Core Gui Qml QuickControls2 QmlImportScanner QuickTest Test)
+    find_package(Qt6 COMPONENTS Core Gui Qml Quick QuickControls2 QmlImportScanner QuickTest Test)
 endif()
 if(NOT Qt6_FOUND)
-    find_package(Qt5 5.15 COMPONENTS Core Gui Qml QuickControls2 QmlImportScanner QuickTest Test REQUIRED)
+    find_package(Qt5 5.15 COMPONENTS Core Gui Qml Quick QuickControls2 QmlImportScanner QuickTest Test REQUIRED)
 endif()
 get_target_property(QMAKE Qt::qmake IMPORTED_LOCATION)
 
@@ -48,6 +48,7 @@ target_link_libraries(${APP_NAME}_lib INTERFACE
     Qt::Core
     Qt::Gui
     Qt::Qml
+    Qt::Quick
     Qt::QuickControls2
 )
 

examples/qml_features/qml/main.qml

@@ -112,6 +112,10 @@ ApplicationWindow {
                     name: "Singleton"
                     source: "qrc:/pages/SingletonPage.qml"
                 }
+                ListElement {
+                    name: "Custom Parent Class"
+                    source: "qrc:/pages/CustomParentClassPage.qml"
+                }
             }
         }
     }

examples/qml_features/qml/pages/CustomParentClassPage.qml

@@ -0,0 +1,64 @@
+// SPDX-FileCopyrightText: 2023 Klarälvdalens Datakonsult AB, a KDAB Group company <[email protected]>
+// SPDX-FileContributor: Andrew Hayzen <[email protected]>
+//
+// SPDX-License-Identifier: MIT OR Apache-2.0
+import QtQuick 2.12
+import QtQuick.Controls 2.12
+import QtQuick.Layouts 1.12
+
+import com.kdab.cxx_qt.demo 1.0
+
+Page {
+    header: ToolBar {
+        RowLayout {
+            anchors.fill: parent
+
+            ToolButton {
+                text: qsTr("Red")
+
+                onClicked: customPainter.color = "red"
+            }
+
+            ToolButton {
+                text: qsTr("Green")
+
+                onClicked: customPainter.color = "green"
+            }
+
+            ToolButton {
+                text: qsTr("Blue")
+
+                onClicked: customPainter.color = "blue"
+            }
+
+            Item {
+                Layout.fillWidth: true
+            }
+        }
+    }
+
+
+    ColumnLayout {
+        anchors.left: parent.left
+        anchors.right: parent.right
+        anchors.verticalCenter: parent.verticalCenter
+
+        CustomParentClass {
+            id: customPainter
+            color: "red"
+            Layout.alignment: Qt.AlignHCenter
+            height: 200
+            width: 200
+
+            // TODO: once we can connect to signals on the Rust side, this could be done there
+            onColorChanged: update()
+        }
+
+        Label {
+            Layout.fillWidth: true
+            horizontalAlignment: Text.AlignHCenter
+            text: qsTr("In this demo the Rectangle is rendered in Rust by implementing a QQuickPaintedItem.")
+            wrapMode: Text.Wrap
+        }
+    }
+}

examples/qml_features/qml/qml.qrc

@@ -11,6 +11,7 @@ SPDX-License-Identifier: MIT OR Apache-2.0
         <file>main.qml</file>
         <file>pages/ContainersPage.qml</file>
         <file>pages/CustomBaseClassPage.qml</file>
+        <file>pages/CustomParentClassPage.qml</file>
         <file>pages/InvokablesPage.qml</file>
         <file>pages/MultipleQObjectsPage.qml</file>
         <file>pages/NestedQObjectsPage.qml</file>

examples/qml_features/rust/build.rs

@@ -11,6 +11,7 @@ fn main() {
     CxxQtBuilder::new()
         .file("src/containers.rs")
         .file("src/custom_base_class.rs")
+        .file("src/custom_parent_class.rs")
         .file("src/invokables.rs")
         .file("src/multiple_qobjects.rs")
         .file("src/nested_qobjects.rs")
@@ -28,6 +29,9 @@ fn main() {
             cc.file("../cpp/custom_object.cpp");
         })
         .qobject_header("../cpp/custom_object.h")
+        // Ensure that Quick module is linked, so that cargo test can work.
+        // In a CMake project this isn't required as the linking happens in CMake.
+        .qt_module("Quick")
         .build();
 }
 // ANCHOR_END: book_build_rs