Accessibility/Plugins
<< Back to Accessibility Home Page
Introduction
This page is designed to provide draft specification of Mozilla plugins accessibility. In the meantime plugins authors are forced to care about accessibility itself. They need to implement AT API interfaces for UI interfaces used in their plugins for each platform plugins are intended to work. That means if plugin is assumed to be supported on all platform Mozilla works on then plugin authors must implement MSAA/IA2 on Windows, AT/AT-SPI on Linux, Universal Access on OS X. So it's getting hard to share common accessibility code between platforms, need to learn different APIs for each platform. This article subject is getting specification to allow plugin authors to embed their plugins into accessibility hierarchy and write common accessibility code for each platform the plugin is indented to work on.
Benefits are
- plugins are embedded into Mozilla accessibility hierarchy
- plugins have crossplatform accessibility code
Disadvantages are
- learning specific Mozilla accessibility API
Implementation
Interfaces
nsIAccessibleTreeNode
This interface is intended to assign accessible parent, children and siblings.
interface nsIAccessibleTreeNode : public nsISupports
{
setParent(nsIAccessibleTreeNode *aNode);
setFirstChild(nsIAccessibleTreeNode *aNode);
setNextSibling(nsIAccessibleTreeNode *aNode);
};
nsIAccessibleTree
This interface is intended to create accessible objects
interface nsIAccessibleTree : public nsISupports
{
nsIAccessibleTreeNode *createAccessible();
nsIAccessibleTreeNode *createTextAccessible();
};
Embedding plugin hierarchy to Mozilla hierarchy
Extend plugin API to provide accessible object implementing nsIAccessible interfaces created for element embedding the plugin.
NPError NPN_GetPluginAccessible(NPP aInstance, nsIAccessibleTreeNode **aNode);
Create crossplatfrom code
Base classes
Plugin SDK provides set of accessible base classes. You can inherit your accessible classes from these base classes to get some accessible functionality for free.
In the meantime there are available two base accessible classes. The set of base classes can be extended on demand.
class npnAccessible : public nsIAccessible {};
class npnTextAccessible : public nsIAccessibleText,
public nsIAccessibleEditableText {};
Interfaces
Here's the list of interfaces you might want to implement in your accessible objects.