Add access to internalPointer to QModelIndex

Unfortunately this currently requires the use of our own c_void type.
See: dtolnay/cxx#1049

Closes #719

Author: LeonMatthesKDAB

crates/cxx-qt-lib-headers/include/common.h

@@ -14,6 +14,8 @@
 namespace rust {
 namespace cxxqtlib1 {
 
+using c_void = void;
+
 template<typename T, typename... Args>
 T
 construct(Args... args)

crates/cxx-qt-lib/src/core/mod.rs

@@ -95,3 +95,33 @@ pub use qvariant::{QVariant, QVariantValue};
 
 mod qvector;
 pub use qvector::{QVector, QVectorElement};
+
+#[cxx::bridge]
+mod ffi {
+    #[namespace = "rust::cxxqtlib1"]
+    unsafe extern "C++" {
+        include!("cxx-qt-lib/common.h");
+        type c_void;
+    }
+}
+
+/// This is a workaround for CXX missing support for `*mut c_void`/`*const c_void` types.
+///
+/// To use this type add this to your bridge:
+/// ```rust
+/// # #[cxx::bridge]
+/// # mod ffi {
+/// #
+/// #[namespace = "rust::cxxqtlib1"]
+/// unsafe extern "C++" {
+///     include!("cxx-qt-lib/common.h");
+///     type c_void = cxx_qt_lib::c_void;
+/// }
+/// #
+/// # }
+/// #
+/// # fn main() {}
+/// ```
+///
+/// See: <https://github.com/dtolnay/cxx/issues/1049>
+pub use ffi::c_void;

crates/cxx-qt-lib/src/core/qmodelindex.rs

@@ -34,11 +34,16 @@ mod ffi {
         /// Returns the sibling at row for the current column. If there is no sibling at this position, an invalid QModelIndex is returned.
         #[rust_name = "sibling_at_row"]
         fn siblingAtRow(self: &QModelIndex, row: i32) -> QModelIndex;
+
+        /// Returns a `*mut c_void` pointer used by the model to associate the index with the internal data structure.
+        #[rust_name = "internal_pointer_mut"]
+        fn internalPointer(self: &QModelIndex) -> *mut c_void;
     }
 
     #[namespace = "rust::cxxqtlib1"]
     unsafe extern "C++" {
         include!("cxx-qt-lib/common.h");
+        type c_void = crate::c_void;
 
         #[doc(hidden)]
         #[rust_name = "qmodelindex_init_default"]

tests/qt_types_standalone/cpp/qmodelindex.h

@@ -6,16 +6,31 @@
 // SPDX-License-Identifier: MIT OR Apache-2.0
 #pragma once
 
+#include <QtCore/QAbstractListModel>
 #include <QtCore/QModelIndex>
 #include <QtCore/QStringListModel>
 #include <QtTest/QTest>
 
 #include "cxx-qt-gen/qmodelindex_cxx.cxx.h"
 
-class QModelIndexTest : public QObject
+// We subclass from QAbstractListModel to have a valid model to use for
+// access to createIndex();
+class QModelIndexTest : public QAbstractListModel
 {
   Q_OBJECT
 
+public:
+  int rowCount(const QModelIndex& parent = QModelIndex()) const override
+  {
+    return 0;
+  }
+
+  QVariant data(const QModelIndex& index,
+                int role = Qt::DisplayRole) const override
+  {
+    return QVariant();
+  }
+
 private Q_SLOTS:
   void construct()
   {
@@ -38,4 +53,23 @@ private Q_SLOTS:
     QCOMPARE(c.isValid(), true);
     QCOMPARE(c.row(), 0);
   }
+
+  void internalPointer()
+  {
+    const auto index = createIndex(0, 0, (void*)&my_data);
+
+    auto pointer = internal_pointer_qmodelindex(index);
+    QCOMPARE((int*)pointer, &my_data);
+  }
+
+  void internalId()
+  {
+    const auto index = createIndex(0, 0, (quintptr)1234);
+
+    auto id = internal_id_qmodelindex(index);
+    QCOMPARE(id, 1234);
+  }
+
+private:
+  int my_data = 42;
 };

tests/qt_types_standalone/rust/src/qmodelindex.rs

@@ -12,10 +12,18 @@ mod qmodelindex_cxx {
         type QModelIndex = cxx_qt_lib::QModelIndex;
     }
 
+    #[namespace = "rust::cxxqtlib1"]
+    unsafe extern "C++" {
+        include!("cxx-qt-lib/common.h");
+        type c_void = cxx_qt_lib::c_void;
+    }
+
     extern "Rust" {
         fn construct_qmodelindex() -> QModelIndex;
         fn read_qmodelindex(i: &QModelIndex) -> bool;
         fn clone_qmodelindex(i: &QModelIndex) -> QModelIndex;
+        fn internal_pointer_qmodelindex(i: &QModelIndex) -> *mut c_void;
+        fn internal_id_qmodelindex(i: &QModelIndex) -> usize;
     }
 }
 
@@ -30,3 +38,11 @@ fn read_qmodelindex(i: &QModelIndex) -> bool {
 fn clone_qmodelindex(i: &QModelIndex) -> QModelIndex {
     i.clone()
 }
+
+fn internal_pointer_qmodelindex(i: &QModelIndex) -> *mut qmodelindex_cxx::c_void {
+    i.internal_pointer_mut()
+}
+
+fn internal_id_qmodelindex(i: &QModelIndex) -> usize {
+    i.internal_id()
+}