DISPLAY_SEGMENT(3G)

NAME

display_segment − display a segment network on specified graphics display device

SYNOPSIS

C Syntax:

void display_segment(fildes,segno,devdes)
int fildes,segno,devdes;

void display_segment_hsr(fildes,segno,devdes)
int fildes,segno,devdes;

FORTRAN77 Syntax:

subroutine display_segment(fildes,segno,devdes)
integer*4 fildes,segno,devdes

subroutine display_segment_hsr(fildes,segno,devdes)
integer*4 fildes,segno,devdes

Pascal Syntax:

procedure display_segment(fildes,segno,devdes:integer);

procedure display_segment_hsr(fildes,segno,devdes:integer);

DESCRIPTION

Input Parameters

fildes Integer file descriptor returned by gopen when an I/O path to a graphics output device is opened. This file descriptor identifies the display list device.

segno Segment name.

devdes Integer file descriptor returned by gopen when an I/O path to a graphics output device is opened. This file descriptor identifies the graphics display device on which the specified segment network will be displayed.

Discussion

Display_segment displays the specified segment network from the display list of the specified display list device on the specified graphics display device.

If a segment is open on graphics display device devdes, the displayed elements of the segment network are copied to the open segment. Call_segment elements are expanded, flattening the segment network as it is copied.

Display_segment_hsr displays the specified segment network from the specified display list device on the associated graphics display device, removing hidden surfaces. For correct results from strip-zbuffer hidden-surface removal, the specified segment network should represent the complete image being displayed. Hidden surface removal must be enabled before making this call (see hidden_surface(3G)). This call applies appropriate zbuffer switching (see zbuffer_switch(3G)).

Display_segment_hsr should not be called if any segment is currently open on the specified graphics output device. Otherwise, multiple copies of the segment network and zbuffer_switch elements could be placed in the open segment.

An error is generated if:

• Fildes does not identify a display list device.

• The segment identified by segno does not exist.

Set_traversal_depth(3G) can be used to limit traversal depth. The default maximum traversal depth limits traversal processing to 42 call_segment elements. If a call_segment element would exceed the maximum traversal depth, a warning is generated and the call_segment element is not traversed.

Segment network traversal can also be limited by display traversal control elements (see set_disp_traversal_control(3G)).

Output from the display traversal process is subject to buffering (see buffer_mode(3G)). If buffering is enabled, output from the display traversal process may not be displayed until the buffer is flushed. Calling make_picture_current(3G) will make sure that the buffers have been flushed.

ERRORS

1 Graphics device is not initialized for this operation.

39 Specified segment does not exist.

40 Fildes is not a display list device.

1042 Warning: Traversal attempted beyond specified maximum traversal depth.

HARDWARE DEPENDENCIES

For bit-mapped displays, display traversal performance can be improved by using traversal_lock(3G). This call gains exclusive access to the display during display traversal, postponing all other display updates (such as printing in terminal emulator windows) while display traversal is in progress.

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