Extending components

The Browser Extension

If the KXMLTreePart component is meant to be used by Konqueror to display a certain type of file when clicking on it in the file manager, better integration with Konqueror can be provided by creating a BrowserExtension for the part.

This allows, for example, the component to save and restore its state when the user navigates using the back and forward actions in Konqueror, or for session management purposes. It also allows the component to request that a URL be opened by Konqueror. For example, this is used when clicking on a link in the HTML component.

To provide a browser extension for a better integration of a read-only part into Konqueror, the component usually needs to define a class that inherits from KParts::BrowserExtension. An instance of that class must be created by the part's constructor, with the part itself as the parent object. Konqueror will detect it and use it automatically.

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The BrowserExtension-derived class

The BrowserExtension-derived class should re-implement xOffset() and yOffset() if the component's widget has scrollbars, as in the case of it inheriting QScrollView. Reimplementing saveState and restoreState allows the component to store additional information in memory, such as when navigating in Konqueror using the back and forward actions.

The browser extension's signals (which are public, unlike usual signals) also allow a component, among other things, to open a URL (openURLRequest), to open a window (createNewWindow), to show a standard popupmenu for a set of files (popupMenu), and to change the URL shown in the location bar (setLocationBarURL).

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Developing a read-write part

A read-write part must inherit KParts::ReadWritePart and implement saveFile(). It must also implement the read-only status in setReadWrite(bool rw), usually disabling some actions when rw is false and enabling them when rw is true. Any action that modifies the data must be prevented when the part is in read-only mode.

When the user modifies the data in the part, it must call setModified(). This usually updates the caption bar to show modified, and enables the confirmation when closing without saving.

Make sure to specify that the part is read-write in the .desktop file, using ServiceTypes=KParts/ReadWritePart, and adapt the factory if using KDE 2 code (see Factory code to create the part) so that setReadWrite is called right after creating the component.

This is how to provide read-write functionality in a KParts component. Note that Konqueror can't use the read-write functionality: it is a design decision that Konqueror only uses read-only components. A separate application is needed to take advantage of the read-write functionality of the component.

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Table of contents

• About this tutorial
• Read-only and read-write parts
• Writing a basic KParts component
• Deploying a KParts component
• Adding actions to the component
• Extending components
• Resources
• About the author

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