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# QNPlugin Class Reference

The plugin central factory.

This class is part of the Qt NSPlugin Extension. More...

`#include <qnp.h>`

List of all member functions.

## Public Members

- virtual ~QNPlugin ()
- void getVersionInfo ( int & plugin_major, int & plugin_minor, int & browser_major, int & browser_minor )
- virtual QNPInstance* newInstance ()
- virtual const char* getMIMEDescription () const
- virtual const char* getPluginNameString () const
- virtual const char* getPluginDescriptionString () const
- virtual void* getJavaClass ()
- virtual void unuseJavaClass ()
- void* getJavaEnv () const

## Static Public Members

- QNPlugin* create ()
- QNPlugin* actual ()

## Protected Members

- QNPlugin ()

## Detailed Description

This class is defined in the Qt NSPlugin Extension, which can be found in the `qt/extensions` directory. It is not included in the main Qt API.

The plugin central factory.

This class is the heart of the plugin. One instance of this object is created when the plugin is first needed, by calling QNPlugin::create(), which must be implemented in your plugin code to return some derived class of QNPlugin. The one QNPlugin object creates all instances for a single running Web-browser process.

Additionally, if Qt is linked to the plugin as a dynamic library, only one instance of QApplication will exist across all plugins that have been made with Qt. So, your plugin should tread lightly on global settings - do not for example, use QApplication::setFont() - that will change the font in every widget of every Qt-based plugin currently loaded!.

Examples: qtimage/qtimage.cpp grapher/grapher.cpp trivial/trivial.cpp

## Member Function Documentation

### QNPlugin::QNPlugin () `[protected]`

Creates a QNPlugin. This may only be used by the constructor derived class returned by plugin's implementation of the QNPlugin::create() function.

### QNPlugin::~QNPlugin () `[virtual]`

Destroys the QNPlugin. This is called by the plugin binding code just before the plugin is about to be unloaded from memory. If newWindow() has been called, a QApplication will still exist at this time, but will be deleted shortly after before the plugin is deleted.

### QNPlugin* QNPlugin::actual () `[static]`

Returns the plugin most recently returns by QNPlugin::create().

### QNPlugin* QNPlugin::create () `[static]`

This must be implemented by your plugin code. It should return a derived class of QNPlugin.

### void* QNPlugin::getJavaClass () `[virtual]`

Override to return a reference to the Java class that represents the plugin. The default returns 0, indicating no class.

If you override this class, you must also override QNPlugin::unuseJavaClass().

The return value is actually a `jref` we use `void*` so as to avoid burdening plugins which do not require Java.

See also getJavaEnv() and QNPInstance::getJavaPeer().

### void* QNPlugin::getJavaEnv () const

Returns a pointer to the Java execution environment, or 0 if Java is disabled or an error occurred.

The return value is actually a `JRIEnv*` we use `void*` so as to avoid burdening plugins which do not require Java.

See also getJavaClass() and QNPInstance::getJavaPeer().

### const char* QNPlugin::getMIMEDescription () const `[virtual]`

Override this to return the MIME description of the data formats supported by your plugin. The format of this string is described by the following example:

        const char* getMIMEDescription() const
        {
            return "image/x-png:png:PNG Image;"
                   "image/png:png:PNG Image;"
                   "image/x-portable-bitmap:pbm:PBM Image;"
                   "image/x-portable-graymap:pgm:PGM Image;"
                   "image/x-portable-pixmap:ppm:PPM Image;"
                   "image/bmp:bmp:BMP Image;"
                   "image/x-ms-bmp:bmp:BMP Image;"
                   "image/x-xpixmap:xpm:XPM Image;"
                   "image/xpm:xpm:XPM Image";
        }

### const char* QNPlugin::getPluginDescriptionString () const `[virtual]`

Returns a plain-text description of the plugin.

### const char* QNPlugin::getPluginNameString () const `[virtual]`

Returns the plain-text name of the plugin.

### void QNPlugin::getVersionInfo ( int & plugin_major, int & plugin_minor, int & browser_major, int & browser_minor )

Returns the version information - the version of the plugin API, and the version of the browser.

### QNPInstance* QNPlugin::newInstance () `[virtual]`

Override this to return an appropriate derived class of QNPInstance.

### void QNPlugin::unuseJavaClass () `[virtual]`

This function is called when the plugin is shutting down, with jc set to the value returned earlier by getJavaClass(). The function should unuse the Java class and return 0.

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