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XtDisplayInitialize

Section: XT FUNCTIONS (3)
Updated: libXt 1.1.5
Index Return to Main Contents

NAME

XtDisplayInitialize, XtOpenDisplay, XtDatabase, XtScreenDatabase, XtCloseDisplay - initialize, open, or close a display

SYNTAX

: void XtDisplayInitialize(XtAppContext app_context, Display *display, String application_name, String application_class, XrmOptionDescRec *options, Cardinal num_options, int *argc, String *argv);
: Display *XtOpenDisplay(XtAppContext app_context, String display_string, String application_name, String application_class, XrmOptionDescRec *options, Cardinal num_options, int *argc, String *argv);
: void XtCloseDisplay(Display *display);
: XrmDatabase XtDatabase(Display *display);
: XrmDatabase XtScreenDatabase(Screen* screen);

ARGUMENTS

argc: Specifies a pointer to the number of command line parameters.
argv: Specifies the command line parameters.
app_context: Specifies the application context.
application_class: Specifies the class name of this application, which usually is the generic name for all instances of this application.
application_name: Specifies the name of the application instance.
display: Specifies the display. Note that a display can be in at most one application context.
num_options: Specifies the number of entries in the options list.
options: Specifies how to parse the command line for any application-specific resources. The options argument is passed as a parameter to XrmParseCommand. For further information, see Xlib - C Language X Interface.
screen: Specifies the screen whose resource database is to be returned.

DESCRIPTION

The XtDisplayInitialize function builds the resource database, calls the Xlib XrmParseCommand function to parse the command line, and performs other per display initialization. After XrmParseCommand has been called, argc and argv contain only those parameters that were not in the standard option table or in the table specified by the options argument. If the modified argc is not zero, most applications simply print out the modified argv along with a message listing the allowable options. On UNIX-based systems, the application name is usually the final component of argv[0]. If the synchronize resource is True for the specified application, XtDisplayInitialize calls the Xlib XSynchronize function to put Xlib into synchronous mode for this display connection. If the reverseVideo resource is True, the Intrinsics exchange XtDefaultForeground and XtDefaultBackground for widgets created on this display. (See Section 9.6.1).

The XtOpenDisplay function calls XOpenDisplay the specified display name. If display_string is NULL, XtOpenDisplay uses the current value of the -display option specified in argv and if no display is specified in argv, uses the user's default display (on UNIX-based systems, this is the value of the DISPLAY environment variable).

If this succeeds, it then calls XtDisplayInitialize and pass it the opened display and the value of the -name option specified in argv as the application name. If no name option is specified, it uses the application name passed to XtOpenDisplay. If the application name is NULL, it uses the last component of argv[0]. XtOpenDisplay returns the newly opened display or NULL if it failed.

XtOpenDisplay is provided as a convenience to the application programmer.

The XtCloseDisplay function closes the specified display as soon as it is safe to do so. If called from within an event dispatch (for example, a callback procedure), XtCloseDisplay does not close the display until the dispatch is complete. Note that applications need only call XtCloseDisplay if they are to continue executing after closing the display; otherwise, they should call XtDestroyApplicationContext or just exit.

The XtDatabase function returns the fully merged resource database that was built by XtDisplayInitialize associated with the display that was passed in. If this display has not been initialized by XtDisplayInitialize, the results are not defined.

The XtScreenDatabase function returns the fully merged resource database associated with the specified screen. If the screen does not belong to a Display initialized by XtDisplayInitialize, the results are undefined.