Useful Java System Properties for QtJambi

Following system properties are accepted by QtJambi. You can specify Java system properties as start argument -Dproperty=value or in Java code System.setProperty("property", "value").

Logging

  • io.qt.log-messages - By specifying any combination of ALL, CRITICAL, DEBUG, WARNING, FATAL, INFO and SYSTEM you can install a message handler forwarding messages of given types to Java logging. In combination with this use following properties to define logging levels. All specified values have to be parsable by Level.parse(String):
    • io.qt.log.debug.level - Specify level value to define the log level for QtDebugMsg (defaults to FINEST)
    • io.qt.log.critical.level - Specify level value to define the log level for QtCriticalMsg (defaults to SEVERE)
    • io.qt.log.fatal.level - Specify level value to define the log level for QtFatalMsg (defaults to SEVERE)
    • io.qt.log.info.level - Specify level value to define the log level for QtInfoMsg (defaults to INFO)
    • io.qt.log.warning.level - Specify level value to define the log level for QtWarningMsg (defaults to WARNING)
  • io.qt.exceptions-for-messages - By specifying any combination of ALL, CRITICAL, DEBUG, WARNING, FATAL, INFO and SYSTEM you can install a message handler causing exceptions to be thrown in the event of a message of given type.

Runtime Diagnostics

  • io.qt.enable-event-logs - Specify true to activate logging of all handled events with their receivers.
  • io.qt.enable-method-logs - Specify true to activate method logging. Caution! This highly decreases performance especially in combination with io.qt.log-messages or custom message handlers.
  • io.qt.enable-cleanup-logs - Specify true to log native object cleanup after GC.
  • io.qt.enable-metaobject-logs - Specify true to log metaobject analysis results.
  • io.qt.enable-dangling-pointer-check - Specify true to activate dangling pointer checks.
  • io.qt.enable-signal-argument-check - Specify true to activate signal argument checks where applicable.
  • io.qt.enable-signal-emit-thread-check - Specify true to activate thread checks on signal emits. If a signal is emitted from a foreign thread a warning is given. Install custom handler with QtUtilities.installSignalEmitThreadCheckHandler to change this behavior.
  • io.qt.enable-concurrent-container-modification-check - Specify true to activate concurrent modification checks during container iteration.
  • io.qt.enable-thread-affinity-check - Specify true to activate thread affinity checks when calling certain thread-affine methods.
  • io.qt.enable-event-thread-affinity-check - ...the same applying to access checks during event handling.
  • io.qt.disable-thread-affinity-check - check is disabled by default since QtJambi 6.5.1.
  • io.qt.disable-event-thread-affinity-check - check is disabled by default since QtJambi 6.5.1.

Library Management

  • io.qt.library-path-override - Use this property if you want to force Java to load Qt and QtJambi libraries from other paths than given by java.library.path.
  • io.qt.debug - Specify debug to force Java using debug libraries of Qt and QtJambi.
  • io.qt.pluginpath - Specify list of paths added as plugin search path.

If you don't specify QtJambi's native location in library path QtJambi will extract libraries from native bundles to temporary directory each time at program startup. Typically, it is a process specific directory purged at program termination. This behavior can be adapted with following properties:

  • io.qt.deploymentdir - Specify temp to let QtJambi extract libraries to temporary directory (default), user for user's application data directory and common for common program data directory. Specify a target directory (io.qt.deploymentdir=<path>) to let them be extracted at the specified location.
  • io.qt.keep-temp-deployment - Specify true to avoid library deletion at program termination. The libraries remain in temporary directory instead.
  • io.qt.no-native-deployment - Specify true if you want to inhibit the search for native library bundles at all and load QtJambi from library path instead.

Library extraction only takes place if QtJambi does not detect the required libraries elsewhere (e.g. in io.qt.library-path-override, java.library.path or system's library path).

Debugging

When using a native debugger to debug your application you need to provide debuginfo along with the native Qtjambi libraries. This information is available in specific bundles corresponding to native bundles. QtJambi will extract the debug info files if you enable it with io.qt.provide-debuginfo=true. The extraction behavior can be adapted by following properties:

  • io.qt.provide-debuginfo - Specify true to let QtJambi extract debuginfo files.

Along with debuginfo files, source code files could be extracted. However, this is not done unless you specify a target sources directory:

  • io.qt.sourcesdir - Specify temp to let QtJambi extract source code files to temporary directory, user for user's application data directory and common for common program data directory. Specify a target directory (io.qt.sourcesdir=<path>) to let them be extracted at the specified location.

Development

For development purpose it is possible to let QtJambi extract header files from native bundles.

  • io.qt.headersdir - Specify user to let QtJambi extract header files to user's application data directory. Specify common to let them be extracted to common program data directory. Specify a target directory to let them be extracted there.

QtJambi Runtime

  • io.qt.allow-nonfinal-signals - Specify true to avoid exception to be thrown when detecting non-final signal declarations.
  • io.qt.allow-nonfinal-qproperties - Specify true to avoid exception to be thrown when detecting non-final QProperty declarations.
  • io.qt.no-library-shutdown-hook - Specify true to avoid library shutdown at program termination.
  • io.qt.no-app-deletion - Specify true if you combine native code with Java code and your QCoreApplication instance has been created elsewhere than inside Java.
  • io.qt.no-exception-forwarding-from-meta-calls - Specify true to avoid QMetaObject calls (like method invocation and property access) forwarding exceptions to the Qt caller in any case (it is avoided by default in case of Qml-related QObjects).
  • io.qt.no-exception-forwarding-from-virtual-calls - Specify true to avoid virtual calls (i.e. Java overrides) forwarding exceptions to the Qt caller in any case.
  • io.qt.avoid-jni-global-references - Specify true to avoid using JNI global references. Instead, QtJambi will use a Java HashMap to manage references. (default on Android)
  • io.qt.use-jni-global-references - Only on Android: Specify true to let QtJambi use JNI global references instead of HashMap to manage references.
  • io.qt.disable-thread-purger - Specify true to not starting a watcher thread for purging Java-related thread data.
  • io.qt.resourcepath - (semi)colon-separated list of jar files or directories to be added as Qt resource path at initialization. Skips classpath from being used.
  • io.qt.no-classpath-to-resourcepath - Specify true to not adding Java classpath to Qt resource path. You may neeed to do this manually by using QResource.addClassPath.
  • io.qt.no-directories-to-resourcepath - Specify true to not adding Java classpath directories to Qt resource path (jar files only). This has no effect on QResource.addClassPath.
  • io.qt.allow-classfiles-as-resource - Specify true to allow .class files in jar bundles to be found by Qt resources.
  • io.qt.allow-meta-inf-as-resource - Specify true to add the META-INF of jar files to Qt resource path (legacy option).
  • io.qt.resource-cache-timeout - Specify the amount of time in milliseconds a resource is kept alive in cache.

QML

  • io.qt.enable-qml-debugging - Specify true to allow QML debugging for the entire runtime of the application.
  • io.qt.enabled-qml-debugging - Specify true to allow QML debugging for the entire runtime of the application.
  • io.qt.enable-qml-debugging-nowarn - ...also inhibits a security warning.
  • io.qt.enabled-qml-debugging-nowarn - ...also inhibits a security warning.

Along with this use program argument -qmljsdebugger=... to enable QML debugging for Qt.

Experimental Features

  • io.qt.experimental.fast-jni - Specify true to enable improved gathering of JNI environment during native calls
  • io.qt.experimental.fast-jni-for-overrides - Specify true to enable improved gathering of JNI environment during native virtual calls

Following properties deal with the improvement of item model performance:

  • io.qt.experimental.item-model-cached-virtuals - Specify true to cache the return values of item model's rowCount() and columnCount() to improve performance of item views.
  • io.qt.experimental.enable-invalid-modelindex-singleton - Specify true to use one single Java object to represent invalid QModelIndex instead of copies.
  • io.qt.experimental.enable-ephemeral-modelindexes - Specify true to call virtual Java methods with an alias for QModelIndex arguments instead of submitting a copies. These alias objects are invalidated after use.