Handle function expressions as signal handlers

There are two ways to use function expressions on the right-hand side
of bindings:

  property var somethingPressed
  somethingPressed: function() { /* ..press something else.. */ }

  signal buttonPressed
  onButtonPressed: function() { /* ..handle buttonPress.. */ }

In the former case, it declares a property that holds a function. So on
initialization, the right-hand side of the binding returns a closure
that gets assigned to the property 'somethingPressed'.

In the latter case, the signal handler is explicitly marked as a
function for clarity. So, the handler should not be returning the
closure, but the handler should *be* the closure.

In general, it is not possible to detect if the left-hand side is a
property or a signal handler when generating QML cache files ahead of
time. So for this case, we mark the function as only returning a
closure. Then when instantiating the object, we check if it is a signal
handler, and if the handler is marked as only returning a closure. If
so, we set that closure to be the signal handler.

Task-number: QTBUG-57043
Task-number: QTBUG-50328
Change-Id: I3008ddd847e30b7d0adef07344a326f84d85f1ba
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/qml/jsruntime/qv4function_p.h b/src/qml/jsruntime/qv4function_p.h
index 4c8c790ca7..59a94e5dde 100644
--- a/src/qml/jsruntime/qv4function_p.h
+++ b/src/qml/jsruntime/qv4function_p.h
@@ -105,6 +105,13 @@ struct Q_QML_EXPORT Function {
     {
         return QQmlSourceLocation(sourceFile(), compiledFunction->location.line, compiledFunction->location.column);
     }
+
+    Function *nestedFunction() const
+    {
+        if (compiledFunction->nestedFunctionIndex == std::numeric_limits<uint32_t>::max())
+            return nullptr;
+        return compilationUnit->runtimeFunctions[compiledFunction->nestedFunctionIndex];
+    }
 };
 
 }