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Common Desktop Environment: Internationalization Programmer's Guide

Interclient Communications Conventions for Localized Text

The following information explains how components use Interclient Communications Conventions (ICCC) to communicate text data and is offered as a guideline to understand how ICCC selections are performed. The XmText widget, XmTextField widget, and the dtterm command adhere to these guidelines.

The toolkit is enhanced for internationalized ICCC compliance. The selection mechanism of XmText, XmTextField, and dtterm is enhanced to ensure proper matching of data and data encoding in any selection transaction. This includes standard cut-and-paste operations.

For developers who use the toolkit to write their applications, the toolkit enables the application to be ICCC-compliant. However, for developers who may use another non-ICCC-compliant toolkit to develop applications that communicate with toolkit-based applications, the following may be helpful.

Owner of Selection

Any owner returns at least the following atom list when XA_TARGETS is requested on some localized text:

When XA_TEXT is requested, the owner returns its text as is with the encoding type of the property set to the code set of the current locale (no data conversion). An atom is created, representing the name of the code set of the locale.

When COMPOUND_TEXT is requested, the owner converts its localized text to compound text and passes it with the property type of COMPOUND_TEXT.

When XA_STRING is requested, the owner attempts to convert the localized text to XA_STRING. If the text string contains characters that cannot be converted to XA_STRING, the operation is unsuccessful.

Note -

XA_STRING is defined to be ISO8859-1.

Requester of Selection

A requester first requests XA_TARGET when text data is to be communicated with the selection owner.

The requester then searches for one of the following atoms in priority order:

If the code set of the requester's locale matches one of the targets, the requester makes a request using the atom representing that code set. The XA_TEXT atom is used only if none of the other atoms is found. Because the owner returns a property with a type representing its encoding, the requester attempts to convert to the code set of its locale.

If the type COMPOUND_TEXT or XA_STRING is requested, the requester attempts to convert the text property to the code set of its current locale by using the XmbTextPropertyToTextList() or XwcTextPropertyToTextList() functions. These are used when the owner client and requester client are running under different code sets.

When converting from COMPOUND_TEXT or XA_STRING, not all text data is guaranteed to be converted; only those characters that are in common between the owner and the requester will be converted.

XmClipboard

XmClipboard is also enhanced to be ICCC-compliant in conjunction with the XmText and XmTextField widgets. When text is being put on the clipboard by way of the XmText and XmTextField widgets, the following ICCC protocol is implemented:

When text is being retrieved from the clipboard by way of the XmText and XmTextField widgets, the text from the clipboard is converted to encoding of the current locale from either COMPOUND_TEXT or XA_STRING. All text on the clipboard is assumed to be in either the compound text format or the string format.

Note -

If text is put directly on the clipboard, the application needs to specify the format, or encoding type in the form of an atom, along with the text to put on the clipboard. Similarly, if text is retrieved directly from the clipboard, the retrieving application needs to check the format to see what encoding the data on the clipboard is encoded in and take the appropriate action.

Passing Window Title and Icon Name to Window Managers

The default of the XtNtitleEncoding and XtNiconNameEncoding resources for the VendorShell class is set to None. This is done only when using the libXm.a library. The libXt.a library still retains XA_STRING as the default for the resources.

This is done so that, as a default case, the XmNtitle and XmNiconName resources are converted to a standard ICCC interchange, such as compound text, based on the assumption the text (title and icon name) is localized text.

It is recommended that the user not set the XtNtitleEncoding and XtNiconNameEncoding resources. Instead, ensure that the XtNtitle and XtNiconName resources are strings encoded in the encoding of the currently active locale of the running client. If the None value is used, the toolkit converts the localized text to the standard ICCC style. (The encoding communicated is COMPOUND_TEXT or XA_STRING.) If the XtNtitleEncoding and XtNiconNameEncoding resources are set, the XtNtitle and XtNiconName resources are not converted in any way and are communicated to the Window Manager with the encoding specified.

Assuming the Window Manager being communicated with is ICCC-compliant, that Window Manager is able to use the encoding type of COMPOUND_TEXT or XA_STRING, or both.

When setting the XmNdialogTitle resource of the XmBulletinBoard widget class, remember that there is a restriction on the charset segment. For charsets that are not X Consortium-standard compound text encodings or XmFONTLIST_DEFAULT_TAG-associated, the text segment is treated as localized text. Localized text is converted to either compound text or ISO8859-1 before being communicated to the Window Manager.

The Window Manager is enhanced so that it always converts the client title and icon name passed from clients to the encoding of its current locale, and an XmString is created using the XmFONTLIST_DEFAULT_TAG identifier. Thus, the client title and icon name are always drawn with the default font list entry of the Window Manager font list.

Note -

This allows clients running with different code sets but with similar character sets to communicate their titles to the Window Manager. For example, both a PC code client and an ISO8859-1 client can display their titles regardless of the code set of the Window Manager.