Overview

For QML, the existing QObject metasystem requires an order of magnitude performance improvement in the following areas:

• QObject construction and destruction time
• Assigning a QObject parent
• Making a by-index (ie. QMetaObject::connect()) signal/slot connection
• Emitting an unconnected signal
• Emitting a connected signal

QML itself does not require improvements in any of these areas. Any improvements here will only very marginally improve overall performance.

• QObject::connect() performance
• QMetaObject::indexOf*() performance

Unnecessary features

QML does not use, and would thus prefer not to pay for, the following QObject features:

• Object thread-affinity
• Thread-safe connections
• Object name
• QEvent's and event filters

Memory Allocation

The two major costs in the current QObject implementation are threading support, and excessive memory allocation. QML can help reduce memory allocation in several ways:

• QML knows ahead of time the number of objects, their types and their in-memory size it is going to allocate. QML can allocate memory for these objects in one operation, instead of the current n allocations.
• If required, QML can provide additional pooled memory to most QObject operations it uses. For example, QML can batch allocate the internal Connection structures.
• All QML objects currently require a QDeclarativeData allocation to store QML specific information. This structure should be merged with QObjectPrivate.