display_enable(3G)

NAME

display_enable − select which planes of a raster device are to be displayed

SYNOPSIS

C Syntax:

void display_enable ( fildes, plane_mask );
int fildes, plane_mask;

FORTRAN77 Syntax:

subroutine display_enable ( fildes, plane_mask )
integer*4 fildes, plane_mask

Pascal Syntax:

procedure display_enable ( fildes, plane_mask:integer );

DESCRIPTION

Input Parameters

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

plane_mask Mask used to determine which planes are enabled to drive the visual output. Each bit is interpreted as the plane enable of that respective plane. In other words, if the least significant bit is 0, then plane 1 is disabled. If the second bit is 1, then plane 2 is enabled, etc. Range is 0x00 to 0xFF.

Discussion

Disabled frame buffer device planes drive the visual output as if they were zeros. For example, if the background_color_index is set to 170 (hex AA) and the display is cleared then: for plane_mask = 255 (hex FF), the color seen is the color at color table index 170. For plane_mask = 15 (hex 0F), the color seen is the color at color table index 10 (hex 0A), etc. This procedure, along with write_enable is very useful for writing into undisplayed bit-planes while leaving the displayed planes unaltered (double-buffering).

For multi-bank graphics devices, plane_mask is a byte quantity that affects the planes of all displayed banks simultaneously. See the Starbase Device Drivers Manual for details.

Double-buffering with 12 planes or with fewer than 6 planes uses display_enable and write_enable to select buffers (other values use bank_switch). During double-buffering, display_enable and write_enable are applied to only the displayed and written planes as determined by double_buffer.

Some devices may not support this operation. See Starbase Graphics Techniques for more information about using this routine.

DEFAULTS

plane_index = 255: All planes (in first bank, if multi-bank) enabled.

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