Virtual keyboards

The virtual keyboard classes allow you to create new keyboard layouts to add to the system.

Each virtual keyboard maintains a set of mapping rules between a virtual key code, or a combination of modifier keys and a virtual key code, and either a single Unicode character or multiple Unicode characters. You create these mappings independently of the layout of the physical keyboard. These virtual keyboards are nonmodal. To provide dead-key functionality, use the transliteration classes.

The following classes provide the mechanism for creating and modifying
virtual keyboards:

TVirtualKeyboard is the abstract base class providing the protocol for virtual keyboards, including:

Basic mapping functions for converting keyboard input to text (generally these are called by the corresponding functions in the typing configuration)
A mechanism for representing command key combinations with text strings

Each keyboard can also have localizable names for use with the locale mechanism.

TStandardEditableVirtualKeyboard provides the concrete implementation of TVirtualKeyboard, including functions for accessing and editing the keyboard mapping rules. This class is responsible for managing the storage of keyboard mapping rules.

TVirtualKeyboardHandle provides a lightweight mechanism for accessing a specific virtual keyboard. Because a TStandardEditableVirtualKeyboard encapsulates a very large amount of data, you should reference a virtual keyboard with a handle unless you need to edit the keyboard data.

NOTE In a future release, the Typing framework will provide an editor for viewing, modifying, and creating virtual keyboards. This editor will use the interfaces described in this section. In the meantime, use the classes described here to create and modify virtual keyboards programmatically through text file representations.

Exception handling

The keyboard classes also include an exception class, TVirtualKeyboardException. This class, derived from TStandardException, defines the following exception conditions:

Exception Description

kNoVirtualKeyboards No keyboards are installed.

kKeyboardNotInstalled The specified keyboard is not installed.

kDefaultKeyboardNotInstalled A default global keyboard has not been installed.

kKeyboardInstantiationFailed The data for the keyboard could not be streamed in.

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	Exception	Description
	kNoVirtualKeyboards	No keyboards are installed.
	kKeyboardNotInstalled	The specified keyboard is not installed.
	kDefaultKeyboardNotInstalled	A default global keyboard has not been installed.
	kKeyboardInstantiationFailed	The data for the keyboard could not be streamed in.