moc: Allow writing properties through bindables

BINDABLE should generally behave the same as MEMBER if "WRITE default",
except where it cannot. In particular we cannot know if any NOTIFY
signal should be sent from the synthetic WRITE accessor.

[ChangeLog][QtCore] moc will now synthesize WRITE accessors for
properties with BINDABLE if you specify "WRITE default".

Task-number: QTBUG-97249
Change-Id: I883c40ba0dda7989c840971860addaeaa75a8c83
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

3 files changed, 19 insertions, 2 deletions

diff --git a/src/corelib/doc/src/objectmodel/properties.qdoc b/src/corelib/doc/src/objectmodel/properties.qdoc
index 7276e8d86a..7ca3e25b00 100644
--- a/src/corelib/doc/src/objectmodel/properties.qdoc
+++ b/src/corelib/doc/src/objectmodel/properties.qdoc
@@ -53,7 +53,12 @@
     argument, either of the property's type or a pointer or reference
     to that type. e.g., QWidget::enabled has the \c WRITE function
     QWidget::setEnabled().  Read-only properties do not need \c WRITE
-    functions. e.g., QWidget::focus has no \c WRITE function.
+    functions. e.g., QWidget::focus has no \c WRITE function. If you specify
+    both a \c BINDABLE and \c{WRITE default}, a \c WRITE accessor will be
+    generated from the \c BINDABLE. The generated \c WRITE accessor will \e not
+    explicitly emit any signal declared with \c NOTIFY. You should register
+    the signal as change handler to the \c BINDABLE, for example using
+    \l{Q_OBJECT_BINDABLE_PROPERTY}.
 
     \li A \c MEMBER variable association is required if no \c READ accessor
     function is specified. This makes the given member variable
diff --git a/src/tools/moc/generator.cpp b/src/tools/moc/generator.cpp
index f030bc8918..0e8ba0bb72 100644
--- a/src/tools/moc/generator.cpp
+++ b/src/tools/moc/generator.cpp
@@ -1315,6 +1315,12 @@ void Generator::generateStaticMetacall()
                 if (cdef->enumDeclarations.value(p.type, false)) {
                     fprintf(out, "        case %d: %s%s(QFlag(*reinterpret_cast<int*>(_v))); break;\n",
                             propindex, prefix.constData(), p.write.constData());
+                } else if (p.write == "default") {
+                    fprintf(out, "        case %d: {\n", propindex);
+                    fprintf(out, "            %s%s().setValue(*reinterpret_cast< %s*>(_v));\n",
+                            prefix.constData(), p.bind.constData(), p.type.constData());
+                    fprintf(out, "            break;\n");
+                    fprintf(out, "        }\n");
                 } else if (!p.write.isEmpty()) {
                     fprintf(out, "        case %d: %s%s(*reinterpret_cast< %s*>(_v)); break;\n",
                             propindex, prefix.constData(), p.write.constData(), p.type.constData());
diff --git a/src/tools/moc/moc.cpp b/src/tools/moc/moc.cpp
index a14f0c1ccd..8a5abd3020 100644
--- a/src/tools/moc/moc.cpp
+++ b/src/tools/moc/moc.cpp
@@ -1301,7 +1301,7 @@ void Moc::parsePropertyAttributes(PropertyDef &propDef)
                 error(1);
         } else if (test(DEFAULT)) {
             v = lexem();
-            if (l != "READ")
+            if (l != "READ" && l != "WRITE")
                 error(1);
         } else {
             next(IDENTIFIER);
@@ -1387,6 +1387,12 @@ void Moc::parsePropertyAttributes(PropertyDef &propDef)
         propDef.read = "";
         warning(msg.constData());
     }
+    if (propDef.write == "default" && propDef.bind.isNull()) {
+        const QByteArray msg = "Property declaration " + propDef.name
+                + " is not BINDable but default-WRITEable. WRITE will be ignored.";
+        propDef.write = "";
+        warning(msg.constData());
+    }
 }
 
 void Moc::parseProperty(ClassDef *def)