Make bindings introspectable through moc

Add a new BINDABLE declaration to the Q_PROPERTY() macro that tells moc
where to find the QBindable for the property.

Add a QUntypedBindable base class to QBindable<T> that gives access to
generic functionality and checks argument compatibility at runtime.
QBindable<T> will still do static checking at compile time.

Add QMetaProperty::isBindable() and QMetaProperty::bindable()
to be able to dynamically access the binding functionality.

Change-Id: Ic7b08ae2cde83fd43e627d813a886e1de01fa3dc
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

3 files changed, 23 insertions, 68 deletions

diff --git a/src/tools/moc/generator.cpp b/src/tools/moc/generator.cpp
index 1d2fa5d1d7..155a98209d 100644
--- a/src/tools/moc/generator.cpp
+++ b/src/tools/moc/generator.cpp
@@ -906,8 +906,8 @@ void Generator::generateProperties()
         if (p.required)
             flags |= Required;
 
-        if (p.isQProperty)
-            flags |= IsQProperty;
+        if (!p.bind.isEmpty())
+            flags |= Bindable;
 
         fprintf(out, "    %4d, ", stridx(p.name));
         generateTypeInfo(p.type);
@@ -1025,9 +1025,8 @@ void Generator::generateMetacall()
             fprintf(out, "else ");
         fprintf(out,
             "if (_c == QMetaObject::ReadProperty || _c == QMetaObject::WriteProperty\n"
-            "            || _c == QMetaObject::ResetProperty || _c == QMetaObject::RegisterPropertyMetaType\n"
-            "            || _c == QMetaObject::RegisterQPropertyObserver\n"
-            "            || _c == QMetaObject::SetQPropertyBinding) {\n"
+            "            || _c == QMetaObject::ResetProperty || _c == QMetaObject::BindableProperty\n"
+            "            || _c == QMetaObject::RegisterPropertyMetaType) {\n"
             "        qt_static_metacall(this, _c, _id, _a);\n"
             "        _id -= %d;\n    }", int(cdef->propertyList.count()));
         fprintf(out, "\n#endif // QT_NO_PROPERTIES");
@@ -1268,7 +1267,7 @@ void Generator::generateStaticMetacall()
         bool needTempVarForGet = false;
         bool needSet = false;
         bool needReset = false;
-        bool haveQProperties = false;
+        bool hasBindableProperties = false;
         for (int i = 0; i < cdef->propertyList.size(); ++i) {
             const PropertyDef &p = cdef->propertyList.at(i);
             needGet |= !p.read.isEmpty() || !p.member.isEmpty();
@@ -1278,7 +1277,7 @@ void Generator::generateStaticMetacall()
 
             needSet |= !p.write.isEmpty() || (!p.member.isEmpty() && !p.constant);
             needReset |= !p.reset.isEmpty();
-            haveQProperties |= p.isQProperty;
+            hasBindableProperties |= !p.bind.isEmpty();
         }
         fprintf(out, "\n#ifndef QT_NO_PROPERTIES\n    ");
 
@@ -1404,59 +1403,21 @@ void Generator::generateStaticMetacall()
         }
         fprintf(out, "    }");
 
-#if 0
         fprintf(out, " else ");
-        fprintf(out, "if (_c == QMetaObject::RegisterQPropertyObserver) {\n");
-        if (haveQProperties) {
+        fprintf(out, "if (_c == QMetaObject::BindableProperty) {\n");
+        if (hasBindableProperties) {
             setupMemberAccess();
-            fprintf(out, "        QPropertyObserver *observer = reinterpret_cast<QPropertyObserver *>(_a[0]);\n");
             fprintf(out, "        switch (_id) {\n");
             for (int propindex = 0; propindex < cdef->propertyList.size(); ++propindex) {
                 const PropertyDef &p = cdef->propertyList.at(propindex);
-                if (!p.isQProperty)
+                if (p.bind.isEmpty())
                     continue;
-                QByteArray prefix = "_t->";
-                if (p.qpropertyname.isEmpty() || p.stored == "true") {
-                    fprintf(out, "        case %d: observer->setSource(%s%s); break;\n",
-                            propindex, prefix.constData(), p.bindingAccessor.constData());
-                } else {
-                    fprintf(out, "        case %d: if (auto *source = %s%s) observer->setSource(*source); break; \n",
-                            propindex, prefix.constData(), p.bindingAccessor.constData());
-                }
+                fprintf(out, "        case %d: *static_cast<QUntypedBindable *>(_a[0]) = _t->%s(); break;\n", propindex, p.bind.constData());
             }
             fprintf(out, "        default: break;\n");
             fprintf(out, "        }\n");
         }
         fprintf(out, "    }");
-
-        fprintf(out, " else ");
-        fprintf(out, "if (_c == QMetaObject::SetQPropertyBinding) {\n");
-        if (haveQProperties) {
-            setupMemberAccess();
-            fprintf(out, "        switch (_id) {\n");
-            for (int propindex = 0; propindex < cdef->propertyList.size(); ++propindex) {
-                const PropertyDef &p = cdef->propertyList.at(propindex);
-                if (!p.isQProperty)
-                    continue;
-                QByteArray prefix = "_t->";
-
-                if (p.qpropertyname.isEmpty() || p.stored == "true") {
-                    fprintf(out, "        case %d: %s%s.setBinding(*reinterpret_cast<QPropertyBinding<%s> *>(_a[0])); break;\n",
-                            propindex, prefix.constData(),
-                            p.bindingAccessor.constData(),
-                            p.type.constData());
-                } else {
-                    fprintf(out, "        case %d: if (auto *source = %s%s) source->setBinding(*reinterpret_cast<QPropertyBinding<%s> *>(_a[0])); break;\n",
-                            propindex, prefix.constData(), p.bindingAccessor.constData(),
-                            p.type.constData());
-                }
-
-            }
-            fprintf(out, "        default: break;\n");
-            fprintf(out, "        }\n");
-        }
-        fprintf(out, "    }");
-#endif
         fprintf(out, "\n#endif // QT_NO_PROPERTIES");
         needElse = true;
     }
diff --git a/src/tools/moc/moc.cpp b/src/tools/moc/moc.cpp
index 1a20d32d7c..516b231cd5 100644
--- a/src/tools/moc/moc.cpp
+++ b/src/tools/moc/moc.cpp
@@ -1022,7 +1022,7 @@ static QByteArrayList requiredQtContainers(const QList<ClassDef> &classes)
 
         for (const auto &c : classes) {
             for (const auto &p : c.propertyList)
-                needsQProperty |= p.isQProperty;
+                needsQProperty |= !p.bind.isEmpty();
             if (any_type_contains(c.propertyList, pattern) ||
                     any_arg_contains(c.slotList, pattern) ||
                     any_arg_contains(c.signalList, pattern) ||
@@ -1219,23 +1219,9 @@ void Moc::createPropertyDef(PropertyDef &propDef)
 {
     propDef.location = index;
 
-    const bool isPrivateProperty = !propDef.inPrivateClass.isEmpty();
-    bool typeWrappedInQProperty = false;
-    if (isPrivateProperty) {
-        const int rewind = index;
-        if (test(IDENTIFIER) && lexem() == "QProperty" && test(LANGLE)) {
-            typeWrappedInQProperty = true;
-            propDef.isQProperty = true;
-        } else {
-            index = rewind;
-        }
-    }
-
     QByteArray type = parseType().name;
     if (type.isEmpty())
         error();
-    if (typeWrappedInQProperty)
-        next(RANGLE);
     propDef.designable = propDef.scriptable = propDef.stored = "true";
     propDef.user = "false";
     /*
@@ -1346,6 +1332,9 @@ void Moc::parsePropertyAttributes(PropertyDef &propDef)
         case 'W': if (l != "WRITE") error(2);
             propDef.write = v;
             break;
+        case 'B': if (l != "BINDABLE") error(2);
+            propDef.bind = v;
+            break;
         case 'D': if (l != "DESIGNABLE") error(2);
             propDef.designable = v + v2;
             checkIsFunction(propDef.designable, "DESIGNABLE");
@@ -1373,6 +1362,12 @@ void Moc::parsePropertyAttributes(PropertyDef &propDef)
         propDef.constant = false;
         warning(msg.constData());
     }
+    if (propDef.constant && !propDef.bind.isNull()) {
+        const QByteArray msg = "Property declaration " + propDef.name
+                + " is both BINDable and CONSTANT. CONSTANT will be ignored.";
+        propDef.constant = false;
+        warning(msg.constData());
+    }
 }
 
 void Moc::parseProperty(ClassDef *def)
@@ -1808,7 +1803,7 @@ void Moc::checkProperties(ClassDef *cdef)
             warning(msg.constData());
         }
 
-        if (p.read.isEmpty() && p.member.isEmpty() && !p.isQProperty) {
+        if (p.read.isEmpty() && p.member.isEmpty() && p.bind.isEmpty()) {
             const int rewind = index;
             if (p.location >= 0)
                 index = p.location;
@@ -2012,6 +2007,7 @@ QJsonObject PropertyDef::toJson() const
     jsonify("member", member);
     jsonify("read", read);
     jsonify("write", write);
+    jsonify("bindable", bind);
     jsonify("reset", reset);
     jsonify("notify", notify);
     jsonify("privateClass", inPrivateClass);
@@ -2035,7 +2031,6 @@ QJsonObject PropertyDef::toJson() const
     prop[QLatin1String("constant")] = constant;
     prop[QLatin1String("final")] = final;
     prop[QLatin1String("required")] = required;
-    prop[QLatin1String("isQProperty")] = isQProperty;
 
     if (revision > 0)
         prop[QLatin1String("revision")] = revision;
diff --git a/src/tools/moc/moc.h b/src/tools/moc/moc.h
index def5a8e82d..7f63402aca 100644
--- a/src/tools/moc/moc.h
+++ b/src/tools/moc/moc.h
@@ -132,7 +132,7 @@ struct PropertyDef
         return (s == write);
     }
 
-    QByteArray name, type, member, read, write, reset, designable, scriptable, stored, user, notify, inPrivateClass;
+    QByteArray name, type, member, read, write, bind, reset, designable, scriptable, stored, user, notify, inPrivateClass;
     int notifyId = -1; // -1 means no notifyId, >= 0 means signal defined in this class, < -1 means signal not defined in this class
     enum Specification  { ValueSpec, ReferenceSpec, PointerSpec };
     Specification gspec = ValueSpec;
@@ -140,7 +140,6 @@ struct PropertyDef
     bool constant = false;
     bool final = false;
     bool required = false;
-    bool isQProperty = false;
 
     int location = -1; // token index, used for error reporting