Rename PySide2 to PySide6

Adapt CMake files, build scripts, tests and examples.

Task-number: PYSIDE-904
Change-Id: I845f7b006e9ad274fed5444ec4c1f9dbe176ff88
Reviewed-by: Christian Tismer <[email protected]>

1 files changed, 766 insertions, 0 deletions

diff --git a/sources/pyside6/libpyside/feature_select.cpp b/sources/pyside6/libpyside/feature_select.cpp
new file mode 100644
index 000000000..d6d77a530
--- /dev/null
+++ b/sources/pyside6/libpyside/feature_select.cpp
@@ -0,0 +1,766 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt for Python.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "feature_select.h"
+#include "pyside.h"
+#include "pysidestaticstrings.h"
+#include "class_property.h"
+
+#include <shiboken.h>
+#include <sbkstaticstrings.h>
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// PYSIDE-1019: Support switchable extensions
+//
+// This functionality is no longer implemented in the signature module, since
+// the PyCFunction getsets do not have to be modified any longer.
+// Instead, we simply exchange the complete class dicts. This is done in the
+// basewrapper.cpp file and in every generated `tp_(get|set)attro`.
+//
+// This is the general framework of the switchable extensions.
+// A maximum of eight features is planned so far. This seems to be enough.
+// More features are possible, but then we must somehow register the
+// extra `select_id`s above 255.
+//
+
+/*****************************************************************************
+
+    How Does This Feature Selection Work?
+    -------------------------------------
+
+The basic idea is to replace the `tp_dict` of a QObject derived type.
+This way, we can replace the methods of the class in no time.
+
+The crucial point to understand is how the `tp_dict` is actually accessed:
+When you type "QObject.__dict__", the descriptor of `SbkObjectType_Type`
+is called. This descriptor is per default unassigned, so the base class
+PyType_Type provides the tp_getset method `type_dict`:
+
+    static PyObject *
+    type_dict(PyTypeObject *type, void *context)
+    {
+        if (type->tp_dict == NULL) {
+            Py_RETURN_NONE;
+        }
+        return PyDictProxy_New(type->tp_dict);
+    }
+
+In order to change that, we need to insert our own version into SbkObjectType:
+
+    static PyObject *Sbk_TypeGet___dict__(PyTypeObject *type, void *context)
+    {
+        auto dict = type->tp_dict;
+        if (dict == NULL)
+            Py_RETURN_NONE;
+        if (SelectFeatureSet != nullptr)
+            dict = SelectFeatureSet(type);
+        return PyDictProxy_New(dict);
+    }
+
+This way, the Python function `type_ready()` does not fill in the default,
+but uses our modified version. It a similar way, we overwrite type_getattro
+with our own version, again in SbkObjectType, replacing the default of
+PyType_Type.
+
+Now we can exchange the dict with a customized version.
+We have our own derived type `ChameleonDict` with additional attributes.
+These allow us to create a ring of dicts which can be rotated to the actual
+needed dict version:
+
+Every dict has a field `select_id` which is selected by the `from __feature__`
+import. The dicts are cyclic connected by the `dict_ring` field.
+
+When a class dict is required, now always `SelectFeatureSet` is called, which
+looks into the `__name__` attribute of the active module and decides which
+version of `tp_dict` is needed. Then the right dict is searched in the ring
+and created if not already there.
+
+Furthermore, we need to overwrite every `tp_(get|set)attro`  with a version
+that switches dicts right before looking up methods.
+The dict changing must walk the whole `tp_mro` in order to change all names.
+
+This is everything that the following code does.
+
+*****************************************************************************/
+
+
+namespace PySide { namespace Feature {
+
+using namespace Shiboken;
+
+typedef bool(*FeatureProc)(PyTypeObject *type, PyObject *prev_dict, int id);
+
+static FeatureProc *featurePointer = nullptr;
+
+static PyObject *cached_globals = nullptr;
+static PyObject *last_select_id = nullptr;
+
+static PyObject *_fast_id_array[1 + 256] = {};
+// this will point to element 1 to allow indexing from -1
+static PyObject **fast_id_array;
+
+static inline PyObject *getFeatureSelectId()
+{
+    static PyObject *undef = fast_id_array[-1];
+    static PyObject *feature_dict = GetFeatureDict();
+    // these things are all borrowed
+    PyObject *globals = PyEval_GetGlobals();
+    if (   globals == nullptr
+        || globals == cached_globals)
+        return last_select_id;
+
+    PyObject *modname = PyDict_GetItem(globals, PyMagicName::name());
+    if (modname == nullptr)
+        return last_select_id;
+
+    PyObject *select_id = PyDict_GetItem(feature_dict, modname);
+    if (   select_id == nullptr
+        || !PyInt_Check(select_id)  // int/long cheating
+        || select_id == undef)
+        return last_select_id;
+
+    cached_globals = globals;
+    last_select_id = select_id;
+    assert(PyInt_AsSsize_t(select_id) >= 0);
+    return select_id;
+}
+
+// Create a derived dict class
+static PyTypeObject *
+createDerivedDictType()
+{
+    // It is not easy to create a compatible dict object with the
+    // limited API. Easier is to use Python to create a derived
+    // type and to modify that a bit from the C code.
+    PyObject *ChameleonDict = PepRun_GetResult(R"CPP(if True:
+
+        class ChameleonDict(dict):
+            __slots__ = ("dict_ring", "select_id")
+
+        result = ChameleonDict
+
+        )CPP");
+    return reinterpret_cast<PyTypeObject *>(ChameleonDict);
+}
+
+static PyTypeObject *new_dict_type = nullptr;
+
+static void ensureNewDictType()
+{
+    if (new_dict_type == nullptr) {
+        new_dict_type = createDerivedDictType();
+        if (new_dict_type == nullptr)
+            Py_FatalError("PySide6: Problem creating ChameleonDict");
+    }
+}
+
+static inline PyObject *nextInCircle(PyObject *dict)
+{
+    // returns a borrowed ref
+    AutoDecRef next_dict(PyObject_GetAttr(dict, PyName::dict_ring()));
+    return next_dict;
+}
+
+static inline void setNextDict(PyObject *dict, PyObject *next_dict)
+{
+    PyObject_SetAttr(dict, PyName::dict_ring(), next_dict);
+}
+
+static inline void setSelectId(PyObject *dict, PyObject *select_id)
+{
+    PyObject_SetAttr(dict, PyName::select_id(), select_id);
+}
+
+static inline PyObject *getSelectId(PyObject *dict)
+{
+    auto select_id = PyObject_GetAttr(dict, PyName::select_id());
+    return select_id;
+}
+
+static inline void setCurrentSelectId(PyTypeObject *type, PyObject *select_id)
+{
+    SbkObjectType_SetReserved(type, PyInt_AsSsize_t(select_id));    // int/long cheating
+}
+
+static inline void setCurrentSelectId(PyTypeObject *type, int id)
+{
+    SbkObjectType_SetReserved(type, id);
+}
+
+static inline PyObject *getCurrentSelectId(PyTypeObject *type)
+{
+    int id = SbkObjectType_GetReserved(type);
+    // This can be too early.
+    if (id < 0)
+        id = 0;
+    return fast_id_array[id];
+}
+
+static bool replaceClassDict(PyTypeObject *type)
+{
+    /*
+     * Replace the type dict by the derived ChameleonDict.
+     * This is mandatory for all type dicts when they are touched.
+     */
+    ensureNewDictType();
+    PyObject *dict = type->tp_dict;
+    auto ob_ndt = reinterpret_cast<PyObject *>(new_dict_type);
+    PyObject *new_dict = PyObject_CallObject(ob_ndt, nullptr);
+    if (new_dict == nullptr || PyDict_Update(new_dict, dict) < 0)
+        return false;
+    // Insert the default id. Cannot fail for small numbers.
+    AutoDecRef select_id(PyInt_FromLong(0));
+    setSelectId(new_dict, select_id);
+    // insert the dict into itself as ring
+    setNextDict(new_dict, new_dict);
+    // We have now an exact copy of the dict with a new type.
+    // Replace `__dict__` which usually has refcount 1 (but see cyclic_test.py)
+    Py_DECREF(type->tp_dict);
+    type->tp_dict = new_dict;
+    return true;
+}
+
+static bool addNewDict(PyTypeObject *type, PyObject *select_id)
+{
+    /*
+     * Add a new dict to the ring and set it as `type->tp_dict`.
+     * A 'false' return is fatal.
+     */
+    auto dict = type->tp_dict;
+    auto ob_ndt = reinterpret_cast<PyObject *>(new_dict_type);
+    auto new_dict = PyObject_CallObject(ob_ndt, nullptr);
+    if (new_dict == nullptr)
+        return false;
+    setSelectId(new_dict, select_id);
+    // insert the dict into the ring
+    auto next_dict = nextInCircle(dict);
+    setNextDict(dict, new_dict);
+    setNextDict(new_dict, next_dict);
+    type->tp_dict = new_dict;
+    return true;
+}
+
+static bool moveToFeatureSet(PyTypeObject *type, PyObject *select_id)
+{
+    /*
+     * Rotate the ring to the given `select_id` and return `true`.
+     * If not found, stay at the current position and return `false`.
+     */
+    auto initial_dict = type->tp_dict;
+    auto dict = initial_dict;
+    do {
+        dict = nextInCircle(dict);
+        AutoDecRef current_id(getSelectId(dict));
+        // This works because small numbers are singleton objects.
+        if (current_id == select_id) {
+            type->tp_dict = dict;
+            setCurrentSelectId(type, select_id);
+            return true;
+        }
+    } while (dict != initial_dict);
+    type->tp_dict = initial_dict;
+    return false;
+}
+
+static bool createNewFeatureSet(PyTypeObject *type, PyObject *select_id)
+{
+    /*
+     * Create a new feature set.
+     * A `false` return value is a fatal error.
+     *
+     * A FeatureProc sees an empty `type->tp_dict` and the previous dict
+     * content in `prev_dict`. It is responsible of filling `type->tp_dict`
+     * with modified content.
+     */
+    static auto small_1 = PyInt_FromLong(255);
+    Q_UNUSED(small_1);
+    static auto small_2 = PyInt_FromLong(255);
+    Q_UNUSED(small_2);
+    // make sure that small integers are cached
+    assert(small_1 != nullptr && small_1 == small_2);
+
+    static auto zero = fast_id_array[0];
+    bool ok = moveToFeatureSet(type, zero);
+    Q_UNUSED(ok);
+    assert(ok);
+
+    AutoDecRef prev_dict(type->tp_dict);
+    Py_INCREF(prev_dict);   // keep the first ref unchanged
+    if (!addNewDict(type, select_id))
+        return false;
+    auto id = PyInt_AsSsize_t(select_id);   // int/long cheating
+    if (id == -1)
+        return false;
+    setCurrentSelectId(type, id);
+    FeatureProc *proc = featurePointer;
+    for (int idx = id; *proc != nullptr; ++proc, idx >>= 1) {
+        if (idx & 1) {
+            // clear the tp_dict that will get new content
+            PyDict_Clear(type->tp_dict);
+            // let the proc re-fill the tp_dict
+            if (!(*proc)(type, prev_dict, id))
+                return false;
+            // if there is still a step, prepare `prev_dict`
+            if (idx >> 1) {
+                prev_dict.reset(PyDict_Copy(type->tp_dict));
+                if (prev_dict.isNull())
+                    return false;
+            }
+        }
+    }
+    return true;
+}
+
+static bool SelectFeatureSetSubtype(PyTypeObject *type, PyObject *select_id)
+{
+    /*
+     * This is the selector for one sublass. We need to call this for
+     * every subclass until no more subclasses or reaching the wanted id.
+     */
+    if (Py_TYPE(type->tp_dict) == Py_TYPE(PyType_Type.tp_dict)) {
+        // On first touch, we initialize the dynamic naming.
+        // The dict type will be replaced after the first call.
+        if (!replaceClassDict(type)) {
+            Py_FatalError("failed to replace class dict!");
+            return false;
+        }
+    }
+    if (!moveToFeatureSet(type, select_id)) {
+        if (!createNewFeatureSet(type, select_id)) {
+            Py_FatalError("failed to create a new feature set!");
+            return false;
+        }
+    }
+    return true;
+}
+
+static inline PyObject *SelectFeatureSet(PyTypeObject *type)
+{
+    /*
+     * This is the main function of the module.
+     * The purpose of this function is to switch the dict of a class right
+     * before a (get|set)attro call is performed.
+     *
+     * Generated functions call this directly.
+     * Shiboken will assign it via a public hook of `basewrapper.cpp`.
+     */
+    if (Py_TYPE(type->tp_dict) == Py_TYPE(PyType_Type.tp_dict)) {
+        // We initialize the dynamic features by using our own dict type.
+        if (!replaceClassDict(type))
+            return nullptr;
+    }
+    PyObject *select_id = getFeatureSelectId();         // borrowed
+    PyObject *current_id = getCurrentSelectId(type);    // borrowed
+    static PyObject *undef = fast_id_array[-1];
+
+    // PYSIDE-1019: During import PepType_SOTP is still zero.
+    if (current_id == undef)
+        current_id = select_id = fast_id_array[0];
+
+    if (select_id != current_id) {
+        PyObject *mro = type->tp_mro;
+        Py_ssize_t idx, n = PyTuple_GET_SIZE(mro);
+        // We leave 'Shiboken.Object' and 'object' alone, therefore "n - 2".
+        for (idx = 0; idx < n - 2; idx++) {
+            auto *sub_type = reinterpret_cast<PyTypeObject *>(PyTuple_GET_ITEM(mro, idx));
+            // When any subtype is already resolved (false), we can stop.
+            if (!SelectFeatureSetSubtype(sub_type, select_id))
+                break;
+        }
+    }
+    return type->tp_dict;
+}
+
+// For cppgenerator:
+void Select(PyObject *obj)
+{
+    if (featurePointer == nullptr)
+        return;
+    auto type = Py_TYPE(obj);
+    type->tp_dict = SelectFeatureSet(type);
+}
+
+PyObject *Select(PyTypeObject *type)
+{
+    if (featurePointer != nullptr)
+        type->tp_dict = SelectFeatureSet(type);
+    return type->tp_dict;
+}
+
+static bool feature_01_addLowerNames(PyTypeObject *type, PyObject *prev_dict, int id);
+static bool feature_02_true_property(PyTypeObject *type, PyObject *prev_dict, int id);
+static bool feature_04_addDummyNames(PyTypeObject *type, PyObject *prev_dict, int id);
+static bool feature_08_addDummyNames(PyTypeObject *type, PyObject *prev_dict, int id);
+static bool feature_10_addDummyNames(PyTypeObject *type, PyObject *prev_dict, int id);
+static bool feature_20_addDummyNames(PyTypeObject *type, PyObject *prev_dict, int id);
+static bool feature_40_addDummyNames(PyTypeObject *type, PyObject *prev_dict, int id);
+static bool feature_80_addDummyNames(PyTypeObject *type, PyObject *prev_dict, int id);
+
+static FeatureProc featureProcArray[] = {
+    feature_01_addLowerNames,
+    feature_02_true_property,
+    feature_04_addDummyNames,
+    feature_08_addDummyNames,
+    feature_10_addDummyNames,
+    feature_20_addDummyNames,
+    feature_40_addDummyNames,
+    feature_80_addDummyNames,
+    nullptr
+};
+
+void finalize()
+{
+    for (int idx = -1; idx < 256; ++idx)
+        Py_DECREF(fast_id_array[idx]);
+}
+
+static bool patch_property_impl();
+
+void init()
+{
+    // This function can be called multiple times.
+    static bool is_initialized = false;
+    if (!is_initialized) {
+        fast_id_array = &_fast_id_array[1];
+        for (int idx = -1; idx < 256; ++idx)
+            fast_id_array[idx] = PyInt_FromLong(idx);
+        last_select_id = fast_id_array[0];
+        featurePointer = featureProcArray;
+        initSelectableFeature(SelectFeatureSet);
+        registerCleanupFunction(finalize);
+        patch_property_impl();
+        PySide::ClassProperty::init();
+        is_initialized = true;
+    }
+    // Reset the cache. This is called at any "from __feature__ import".
+    cached_globals = nullptr;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// PYSIDE-1019: Support switchable extensions
+//
+//     Feature 0x01: Allow snake_case instead of camelCase
+//
+// This functionality is no longer implemented in the signature module, since
+// the PyCFunction getsets do not have to be modified any longer.
+// Instead, we simply exchange the complete class dicts. This is done in the
+// basewrapper.cpp file.
+//
+
+static PyObject *methodWithNewName(PyTypeObject *type,
+                                   PyMethodDef *meth,
+                                   const char *new_name)
+{
+    /*
+     * Create a method with a lower case name.
+     */
+    auto obtype = reinterpret_cast<PyObject *>(type);
+    int len = strlen(new_name);
+    auto name = new char[len + 1];
+    strcpy(name, new_name);
+    auto new_meth = new PyMethodDef;
+    new_meth->ml_name = name;
+    new_meth->ml_meth = meth->ml_meth;
+    new_meth->ml_flags = meth->ml_flags;
+    new_meth->ml_doc = meth->ml_doc;
+    PyObject *descr = nullptr;
+    if (new_meth->ml_flags & METH_STATIC) {
+        AutoDecRef cfunc(PyCFunction_NewEx(new_meth, obtype, nullptr));
+        if (cfunc.isNull())
+            return nullptr;
+        descr = PyStaticMethod_New(cfunc);
+    }
+    else {
+        descr = PyDescr_NewMethod(type, new_meth);
+    }
+    return descr;
+}
+
+static bool feature_01_addLowerNames(PyTypeObject *type, PyObject *prev_dict, int id)
+{
+    /*
+     * Add objects with lower names to `type->tp_dict` from 'prev_dict`.
+     */
+    PyObject *lower_dict = type->tp_dict;
+    PyObject *key, *value;
+    Py_ssize_t pos = 0;
+
+    // We first copy the things over which will not be changed:
+    while (PyDict_Next(prev_dict, &pos, &key, &value)) {
+        if (   Py_TYPE(value) != PepMethodDescr_TypePtr
+            && Py_TYPE(value) != PepStaticMethod_TypePtr) {
+            if (PyDict_SetItem(lower_dict, key, value))
+                return false;
+            continue;
+        }
+    }
+    // Then we walk over the tp_methods to get all methods and insert
+    // them with changed names.
+    PyMethodDef *meth = type->tp_methods;
+    if (!meth)
+        return true;
+
+    for (; meth != nullptr && meth->ml_name != nullptr; ++meth) {
+        const char *name = String::toCString(String::getSnakeCaseName(meth->ml_name, true));
+        AutoDecRef new_method(methodWithNewName(type, meth, name));
+        if (new_method.isNull())
+            return false;
+        if (PyDict_SetItemString(lower_dict, name, new_method) < 0)
+            return false;
+    }
+    return true;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// PYSIDE-1019: Support switchable extensions
+//
+//     Feature 0x02: Use true properties instead of getters and setters
+//
+
+// This is the Python 2 version for inspection of m_ml, only.
+// The actual Python 3 version is larget.
+
+typedef struct {
+    PyObject_HEAD
+    PyMethodDef *m_ml; /* Description of the C function to call */
+    PyObject    *m_self; /* Passed as 'self' arg to the C func, can be NULL */
+    PyObject    *m_module; /* The __module__ attribute, can be anything */
+} PyCFunctionObject;
+
+static PyObject *modifyStaticToClassMethod(PyTypeObject *type, PyObject *sm)
+{
+    AutoDecRef func_ob(PyObject_GetAttr(sm, PyMagicName::func()));
+    if (func_ob.isNull())
+        return nullptr;
+    auto func = reinterpret_cast<PyCFunctionObject *>(func_ob.object());
+    auto new_func = new PyMethodDef;
+    new_func->ml_name = func->m_ml->ml_name;
+    new_func->ml_meth = func->m_ml->ml_meth;
+    new_func->ml_flags = (func->m_ml->ml_flags & ~METH_STATIC) | METH_CLASS;
+    new_func->ml_doc = func->m_ml->ml_doc;
+    auto cfunc = PyCFunction_NewEx(new_func, nullptr, nullptr);
+    cfunc = PyDescr_NewClassMethod(type, new_func);
+    return cfunc;
+}
+
+static PyObject *createProperty(PyTypeObject *type, PyObject *getter, PyObject *setter)
+{
+    bool chassprop = false;
+    assert(getter != nullptr);
+    if (setter == nullptr)
+        setter = Py_None;
+    auto ptype = &PyProperty_Type;
+    if (Py_TYPE(getter) == PepStaticMethod_TypePtr) {
+        ptype = PyClassPropertyTypeF();
+        chassprop = true;
+        getter = modifyStaticToClassMethod(type, getter);
+        if (setter != Py_None)
+            setter = modifyStaticToClassMethod(type, setter);
+    }
+    auto obtype = reinterpret_cast<PyObject *>(ptype);
+    PyObject *prop = PyObject_CallFunctionObjArgs(obtype, getter, setter, nullptr);
+    return prop;
+}
+
+static QStringList parseFields(const char *propstr)
+{
+    /*
+     * Break the string into subfields at ':' and add defaults.
+     */
+    QString s = QString(QLatin1String(propstr));
+    auto list = s.split(QLatin1Char(':'));
+    assert(list.size() == 2 || list.size() == 3);
+    auto name = list[0];
+    auto read = list[1];
+    if (read.size() == 0)
+        list[1] = name;
+    if (list.size() == 2)
+        return list;
+    auto write = list[2];
+    if (write.size() == 0) {
+        list[2] = QLatin1String("set") + name;
+        list[2][3] = list[2][3].toUpper();
+    }
+    return list;
+}
+
+static PyObject *make_snake_case(QString s, bool lower)
+{
+    if (s.isNull())
+        return nullptr;
+    return String::getSnakeCaseName(s.toLatin1().data(), lower);
+}
+
+static bool feature_02_true_property(PyTypeObject *type, PyObject *prev_dict, int id)
+{
+    /*
+     * Use the property info to create true Python property objects.
+     */
+
+    // The empty `tp_dict` gets populated by the previous dict.
+    PyObject *prop_dict = type->tp_dict;
+    if (PyDict_Update(prop_dict, prev_dict) < 0)
+        return false;
+
+    // We then replace methods by properties.
+    bool lower = (id & 0x01) != 0;
+    auto props = SbkObjectType_GetPropertyStrings(type);
+    if (props == nullptr || *props == nullptr)
+        return true;
+    for (; *props != nullptr; ++props) {
+        auto propstr = *props;
+        auto fields = parseFields(propstr);
+        bool haveWrite = fields.size() == 3;
+        PyObject *name = make_snake_case(fields[0], lower);
+        PyObject *read = make_snake_case(fields[1], lower);
+        PyObject *write = haveWrite ? make_snake_case(fields[2], lower) : nullptr;
+        PyObject *getter = PyDict_GetItem(prev_dict, read);
+        if (getter == nullptr || !(Py_TYPE(getter) == PepMethodDescr_TypePtr ||
+                                   Py_TYPE(getter) == PepStaticMethod_TypePtr))
+            continue;
+        PyObject *setter = haveWrite ? PyDict_GetItem(prev_dict, write) : nullptr;
+
+        AutoDecRef PyProperty(createProperty(type, getter, setter));
+        if (PyProperty.isNull())
+            return false;
+        if (PyDict_SetItem(prop_dict, name, PyProperty) < 0)
+            return false;
+        if (fields[0] != fields[1] && PyDict_GetItem(prop_dict, read))
+            if (PyDict_DelItem(prop_dict, read) < 0)
+                return false;
+        // Theoretically, we need to check for multiple signatures to be exact.
+        // But we don't do so intentionally because it would be confusing.
+        if (haveWrite && PyDict_GetItem(prop_dict, write))
+            if (PyDict_DelItem(prop_dict, write) < 0)
+                return false;
+    }
+    return true;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// These are a number of patches to make Python's property object better
+// suitable for us.
+// We turn `__doc__` into a lazy attribute saving signature initialization.
+//
+// There is now also a class property implementation which inherits
+// from this one.
+//
+
+static PyObject *property_doc_get(PyObject *self, void *)
+{
+    auto po = reinterpret_cast<propertyobject *>(self);
+
+    if (po->prop_doc != nullptr && po->prop_doc != Py_None) {
+        Py_INCREF(po->prop_doc);
+        return po->prop_doc;
+    }
+    if (po->prop_get) {
+        // PYSIDE-1019: Fetch the default `__doc__` from fget. We do it late.
+        auto txt = PyObject_GetAttr(po->prop_get, PyMagicName::doc());
+        if (txt != nullptr) {
+            Py_INCREF(txt);
+            po->prop_doc = txt;
+            Py_INCREF(txt);
+            return txt;
+        }
+        PyErr_Clear();
+    }
+    Py_RETURN_NONE;
+}
+
+static int property_doc_set(PyObject *self, PyObject *value, void *)
+{
+    auto po = reinterpret_cast<propertyobject *>(self);
+
+    Py_INCREF(value);
+    po->prop_doc = value;
+    return 0;
+}
+
+static PyGetSetDef property_getset[] = {
+    // This gets added to the existing getsets
+    {const_cast<char *>("__doc__"), property_doc_get, property_doc_set, nullptr, nullptr},
+    {nullptr, nullptr, nullptr, nullptr, nullptr}
+};
+
+static bool patch_property_impl()
+{
+    // Turn `__doc__` into a computed attribute without changing writability.
+    auto gsp = property_getset;
+    auto type = &PyProperty_Type;
+    auto dict = type->tp_dict;
+    AutoDecRef descr(PyDescr_NewGetSet(type, gsp));
+    if (descr.isNull())
+        return false;
+    if (PyDict_SetItemString(dict, gsp->name, descr) < 0)
+        return false;
+    return true;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// PYSIDE-1019: Support switchable extensions
+//
+//     Feature 0x04..0x40: A fake switchable option for testing
+//
+
+#define SIMILAR_FEATURE(xx)  \
+static bool feature_##xx##_addDummyNames(PyTypeObject *type, PyObject *prev_dict, int id) \
+{ \
+    PyObject *dict = type->tp_dict; \
+    if (PyDict_Update(dict, prev_dict) < 0) \
+        return false; \
+    if (PyDict_SetItemString(dict, "fake_feature_" #xx, Py_None) < 0) \
+        return false; \
+    return true; \
+}
+
+SIMILAR_FEATURE(04)
+SIMILAR_FEATURE(08)
+SIMILAR_FEATURE(10)
+SIMILAR_FEATURE(20)
+SIMILAR_FEATURE(40)
+SIMILAR_FEATURE(80)
+
+} // namespace PySide
+} // namespace Feature