push_state(3G)

NAME

push_state, pop_state − save and restore the state of the graphics device

SYNOPSIS

C Syntax:

void push_state(fildes)
int fildes;

void pop_state(fildes)
int fildes;

FORTRAN77 Syntax:

subroutine push_state(fildes)
integer*4 fildes

subroutine pop_state(fildes)
integer*4 fildes

Pascal Syntax:

procedure push_state(fildes:integer);

procedure pop_state(fildes:integer);

DESCRIPTION

Input Parameters

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

Discussion

Push_state causes a subset of the current state of the specified graphics device to be saved for subsequent restoration with pop_state. The graphics state stored and restored consists of modal attribute settings, such as line_color_index(3G), and device control settings, such as drawing_mode(3G).

See sbdl(3G) for a complete list of the functions that contribute to the current state. Modelling transforms on the matrix stack are not saved and restored by push_state and pop_state. The state of the matrix stack can be saved and restored as appropriate by use of push_matrix(3G) and pop_matrix(3G).

The required state is saved on a stack so that push_state and pop_state pairs can be nested. The common usage of pushing the state at the start of a segment and popping the state at the end of a segment is provided implicitly by execute_segment(3G) and cond_execute_segment(3G).

EXAMPLE

In the following C program segment, fildes is assumed to hold a a file descriptor returned by a call to gopen(3G). The change to line_color_index following the push_state does not affect the color of the polyline following the pop_state.

open_segment(fildes,1,FALSE,FALSE);	/* build segment 1 */
line_color_index(fildes, 1);	/* set line color to index 1 */
polyline(fd, ...);	/* this polyline is drawn with color 1 */
push_state(fildes);	/* save the current state */
line_color_index(fildes,3);	/* set line color index to 3 */
polyline(fd, ...);	/* this polyline is drawn with color 3 */
pop_state(fildes);	/* restore the state */
polyline(fd, ...);	/* this polyline is drawn with color 1 */
close_segment(fildes);	/* segment 1 is now closed */

ERRORS

1 Graphics device is not initialized for this operation.

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