seg_control(3G)

NAME

seg_control − set or clear segment control flags of a segment.

SYNOPSIS

C Syntax:

void seg_control ( fildes, segno, control, on )
int fildes, segno, control, on;

FORTRAN77 Syntax:

subroutine seg_control ( fildes, segno, control, on )
integer*4 fildes, segno, control, on

Pascal Syntax:

procedure seg_control ( fildes, segno, control, on: integer );

DESCRIPTION

Input Parameters

fildes Integer file descriptor returned by gopen when an I/O path to a graphics device is opened.

segno Segment name.

control Indicates which segment control flags are to be affected.

on TRUE (1) if the given segment control flags should be set for the segment, or FALSE (0) if they should be cleared.

Discussion

Seg_control affects how display list traversals process the given segment of the given fildes. This can be useful for "commenting out" a display list segment without actually removing it, or for highlighting an entire segment.

Control must be a bitwise combination (i.e., bitwise OR or arithmetic sum) of the constants

DISP_IGNORE to affect whether the segment is ignored during segment display traversal,

PICK_IGNORE to affect whether the segment is ignored during segment pick traversal, or

HIGHLIGHT to affect whether the segment is highlighted during segment display traversal.

If on is TRUE (1), the segment will be processed differently during the specified segment traversals. If the DISP_IGNORE or PICK_IGNORE flags are turned on, the segment will be ignored during segment display traversals or segment pick traversals, respectively. If the HIGHLIGHT flag is turned on, the segment will be highlighted during segment display traversals, as if by highlight_on(3G).

If on is FALSE (0), normal processing will take place on the segment during the specified segment traversal(s).

A "segment traversal" is a traversal initiated by a call to display_segment(3G), display_segment_hsr(3G), refresh_segment(3G), refresh_segment_hsr(3G), or pick_from_segment(3G), or by a call to display_element(3G) or refresh_element(3G) when the current element of the currently open segment is a call_segment(3G), execute_segment(3G), cond_call_segment(3G), or cond_execute_segment(3G). Other calls to display_element(3G) or refresh_element(3G) are not affected by the owning segment’s control flags.

WARNING

Mixing highlighting calls from seg_control, set_highlighting_filter, and highlight_on is not recommended. If they are mixed, they behave independently. Primitives are then highlighted if any of the three indicates they should be. For example, if segment 1 contains the following elements:

highlight_on(fildes, FALSE)
polygon2d(fildes,...)

and the segment has been marked HIGHLIGHT with seg_control, the polygon will be highlighted, because the highlight_on call cannot turn off seg_control highlighting.

When a segment is being copied, the segment control flags are ignored since only its elements are being copied.

ERRORS

1 Graphics device is not initialized for this operation.

6 Improper parameter value: control is not a bitwise OR of the defined constants.

39 Specified segment does not exist.

DEFAULTS

When a segment is created with open_segment, its segment control flags are all off. This results in normal display and pick traversal and no highlighting.

Museum

Related Articles