Input for localized
text is typically done by using either the local input method or
the network-based input method.
The local input method means that the
input method is built in the Xlib. It is typically used for a language
that can be composed using simple rules and that does not require
language-specific features. The network-based input
method means that the actual input method is provided
as separate servers, and Xlib communicates with them through the
XIM protocol to do the language-specific composition.
Basic Prompts and Dialogs |
 |
It is strongly
recommended that applications use the Text
widget to do all text input.
Input within a DrawingArea
Widget |
|
Many applications do their own drawing within a widget based
on input. To provide consistency within the desktop environment,
XmIm functions
are recommended because the style and geometry management needed
for an input method is managed by the VendorShell
widget class. The application need only worry about handling key
events, focus, and communicating the current input location within
the drawing area. Using these functions requires some basic knowledge
of the underlying Xlib input method architecture, but a developer
need only be concerned with the XmIm
pieces of information.
Application-Specific and Language-Specific
Intermediate Feedbacks |
|
Some applications may need to
directly display intermediate feedback during preediting, such as
when an application exceeds the functions supplied by Xlib. Examples
of this include for PostScriptTM rendering
or using vertical writing.
The core Xlib provides the common set of interfaces that allow
an application to display intermediate feedback during preediting.
By registering the application's callbacks and setting the preediting
style to XNPreeditCallbacks,
an application can get the intermediate preediting data from the
input method and can draw whatever it needs. This means using the
OnTheSpot input method style.
Applications intended to do sophisticated language processing
may recognize extensions within a specific XIM implementation and
its input method engines. Such applications are on the leading edge
and will require familiarity with details of the XIM functions.
Text and TextField Widget |
|
For basic prompts and dialogs, the Text
or TextField
widget is recommended. Besides resources, all of the XmTextField
and XmText functions
are available for getting and for setting localized text inside
a Text[Field]
widget.
Most XmText
functions are based on the number of characters, not on the number of bytes. For example,
all XmTextPosition()
function positions are character positions, not byte positions.
The XmTextGetMaxLength()
function returns the number of bytes. When in doubt, remember that
positions are always in character units.
The width of a Text
or TextField
widget is determined by the resource value of XmNcolumns.
But, this value means the number of the widest characters in the
font set, not the number of bytes or columns. For example, suppose
that you have selected a variable-width font for the Text
widget. The character i may have
a width of 1 pixel, while the character W may
have a width of 7 pixels. When a value of 10 is set for XmNcolumns,
this is considered a request to make the Text
widget wide enough to be able to display at least 10 characters.
So the Text widget
must use the width of the widest character to determine the pixel
width of its core widget. With this example, it may be able to display
10 W characters in the widget, or 70 i
characters. This structure for XmNcolumns
may cause problems in locales whose code set is a multibyte and
a multicolumn encoding. As such, this value should be set within
a localized resource.
The following section identifies the set of functions available
for applications that are used to manage input methods. For applications
that use the Text
and TextField
widgets, refer to “Input
Method (Keyboards)”
Character Input within Customized
Widgets Not Using Text[Field]
Widgets |
|
In some cases, an application may obtain character input from
the user but does not use a TextField
or Text widget
to do so. For example, an application using a DrawingArea
widget may allow the user to type in text directly into the DrawingArea.
In this case, the application could use the Xlib XIM functions as
described in later sections, or alternatively, the application may
use the XmIm
functions of Motif. The XmIm
functions allow an application to connect to and interact with an
input method with a minimum of code. Further, it allows the Motif
VendorShell widget
to take care of geometry management for the input method on the
application's behalf. For more information on XmIm functions, refer
to Motif Programmer's Guide.
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