Xlib Geometry Management

In most input method architectures (OnTheSpot being the notable exception), the input method performs the display of its own data. To provide better visual locality, it is often desirable to have the input method areas embedded within a client. To do this, the client may need to allocate space for an input method. Xlib provides support that allows the client to provide the size and position of input method areas. The input method areas that are supported for geometry management are the status area and the preedit area.

The fundamental concept on which geometry management for input method windows is based is the proper division of responsibilities between the client (or toolkit) and the input method. The division of responsibilities is the following:

• The client is responsible for the geometry of the input method window.

• The input method is responsible for the contents of the input method window. It is also responsible for creating the input method window per the geometry constraints given to it by the client.

An input method can suggest a size to the client, but it cannot suggest a placement. The input method can only suggest a size: it does not determine the size, and it must accept the size it is given.

Before a client provides geometry management for an input method, it must determine if geometry management is needed. The input method indicates the need for geometry management by setting the XIMPreeditArea() or XIMStatusArea() function in its XIMStyles value returned by the XGetIMValues() function. When a client decides to provide geometry management for an input method, it indicates that decision by setting the XNInputStyle value in the XIC.

After a client has established with the input method that it will do geometry management, the client must negotiate the geometry with the input method. The geometry is negotiated by the following steps:

• The client suggests an area to the input method by setting the XNAreaNeeded value for that area. If the client has no constraints for the input method, it either does not suggest an area or sets the width and height to 0 (zero). Otherwise, it sets one of the values.

• The client gets the XIC XNAreaNeeded value. The input method returns its suggested size in this value. The input method should pay attention to any constraints suggested by the client.

• The client sets the XIC XNArea value to inform the input method of the geometry of the input method's window. The client should try to honor the geometry requested by the input method. The input method must accept this geometry.

Clients performing geometry management must be aware that setting other IC values may affect the geometry desired by an input method. For example, the XNFontSet and XNLineSpacing values may change the geometry desired by the input method. It is the responsibility of the client to renegotiate the geometry of the input method window when it is needed.

In addition, a geometry management callback is provided by which an input method can initiate a geometry change.