From 238752495267c3d65c19898dfc8f8d702caffb8b Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Tue, 10 Sep 2024 14:49:34 -0700
Subject: [PATCH] moc: add a helper function to set member properties

There is one minor difference: we now use operator== instead of
operator!= now, so some defective types may start working (but may break
some other, defective types).

Simplifies the emitted code, from

        case 6:
            if (_t->sMember != *reinterpret_cast< QString*>(_v)) {
                _t->sMember = *reinterpret_cast< QString*>(_v);
                Q_EMIT _t->member5Changed(_t->sMember);
            }
            break;
        case 8:
            if (_t->sub.m_string != *reinterpret_cast< QString*>(_v)) {
                _t->sub.m_string = *reinterpret_cast< QString*>(_v);
            }
            break;

to:

        case 6:
            if (QtMocHelpers::setProperty(_t->sMember, *reinterpret_cast<QString*>(_v)))
                Q_EMIT _t->member5Changed(_t->sMember);
            break;
        case 8: QtMocHelpers::setProperty(_t->sub.m_string, *reinterpret_cast<QString*>(_v)); break;

The second parameter to setProperty() helper is passed as an rvalue
reference and forwarded to the assignment, making this ready for move
semantics when moc generates code for it.

Change-Id: I45ad4a236d38f6c8f994fffd701d4193504d985a
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
---
 src/corelib/kernel/qtmochelpers.h             |  8 +++++
 src/tools/moc/generator.cpp                   | 31 +++++++++----------
 .../qmetaproperty/tst_qmetaproperty.cpp       |  4 +--
 3 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/src/corelib/kernel/qtmochelpers.h b/src/corelib/kernel/qtmochelpers.h
index 38c028d5291..a09f0d44014 100644
--- a/src/corelib/kernel/qtmochelpers.h
+++ b/src/corelib/kernel/qtmochelpers.h
@@ -88,6 +88,14 @@ template <typename FuncType> inline bool indexOfMethod(void **_a, FuncType f, in
     return true;
 }
 
+template <typename Prop, typename Value> inline bool setProperty(Prop &property, Value &&value)
+{
+    if (property == value)
+        return false;
+    property = std::forward<Value>(value);
+    return true;
+}
+
 struct NoType {};
 template <typename T> struct ForceCompleteMetaTypes {};
 
diff --git a/src/tools/moc/generator.cpp b/src/tools/moc/generator.cpp
index 84f0d3f45e6..0b8b9c05226 100644
--- a/src/tools/moc/generator.cpp
+++ b/src/tools/moc/generator.cpp
@@ -1195,23 +1195,22 @@ void Generator::generateStaticMetacall()
                     fprintf(out, "        case %d: %s%s(*reinterpret_cast< %s*>(_v)); break;\n",
                             propindex, prefix.constData(), p.write.constData(), p.type.constData());
                 } else {
-                    fprintf(out, "        case %d:\n", propindex);
-                    fprintf(out, "            if (%s%s != *reinterpret_cast< %s*>(_v)) {\n",
-                            prefix.constData(), p.member.constData(), p.type.constData());
-                    fprintf(out, "                %s%s = *reinterpret_cast< %s*>(_v);\n",
-                            prefix.constData(), p.member.constData(), p.type.constData());
-                    if (!p.notify.isEmpty() && p.notifyId > -1) {
-                        const FunctionDef &f = cdef->signalList.at(p.notifyId);
-                        if (f.arguments.size() == 0)
-                            fprintf(out, "                Q_EMIT _t->%s();\n", p.notify.constData());
-                        else if (f.arguments.size() == 1 && f.arguments.at(0).normalizedType == p.type)
-                            fprintf(out, "                Q_EMIT _t->%s(%s%s);\n",
-                                    p.notify.constData(), prefix.constData(), p.member.constData());
-                    } else if (!p.notify.isEmpty() && p.notifyId < -1) {
-                        fprintf(out, "                Q_EMIT _t->%s();\n", p.notify.constData());
+                    fprintf(out, "        case %d:", propindex);
+                    if (p.notify.isEmpty()) {
+                        fprintf(out, " QtMocHelpers::setProperty(%s%s, *reinterpret_cast<%s*>(_v)); break;\n",
+                                prefix.constData(), p.member.constData(), p.type.constData());
+                    } else {
+                        fprintf(out, "\n            if (QtMocHelpers::setProperty(%s%s, *reinterpret_cast<%s*>(_v)))\n",
+                                prefix.constData(), p.member.constData(), p.type.constData());
+                        fprintf(out, "                Q_EMIT _t->%s(", p.notify.constData());
+                        if (p.notifyId > -1) {
+                            const FunctionDef &f = cdef->signalList.at(p.notifyId);
+                            if (f.arguments.size() == 1 && f.arguments.at(0).normalizedType == p.type)
+                                fprintf(out, "%s%s", prefix.constData(), p.member.constData());
+                        }
+                        fprintf(out, ");\n");
+                        fprintf(out, "            break;\n");
                     }
-                    fprintf(out, "            }\n");
-                    fprintf(out, "            break;\n");
                 }
             }
             fprintf(out, "        default: break;\n");
diff --git a/tests/auto/corelib/kernel/qmetaproperty/tst_qmetaproperty.cpp b/tests/auto/corelib/kernel/qmetaproperty/tst_qmetaproperty.cpp
index 00cd4c0446f..bde70e32233 100644
--- a/tests/auto/corelib/kernel/qmetaproperty/tst_qmetaproperty.cpp
+++ b/tests/auto/corelib/kernel/qmetaproperty/tst_qmetaproperty.cpp
@@ -16,8 +16,8 @@ struct CustomType
     QString str;
     CustomType(const QString &str = QString()) : str(str) {}
     operator QString() const { return str; }
-    friend bool operator!=(const CustomType &a, const CustomType &b)
-    { return a.str != b.str; }
+    friend bool operator==(const CustomType &a, const CustomType &b)
+    { return a.str == b.str; }
 };
 
 Q_DECLARE_METATYPE(CustomType)