DBUFFER_SWITCH(3G)

NAME

dbuffer_switch − switch buffers when double buffering

SYNOPSIS

C Syntax:

void dbuffer_switch(fildes,buffer);
int fildes,buffer;

FORTRAN77 Syntax:

subroutine dbuffer_switch(fildes,buffer)
integer *4 fildes,buffer

Pascal Syntax:

procedure dbuffer_switch(fildes,buffer:integer);

DESCRIPTION

Input Parameters

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

buffer Least significant bit of this integer determines which buffer (odd or even) to use.

Discussion

dbuffer_switch switches between output buffers when double buffering is enabled. Besides the device file descriptor, this function takes one parameter: buffer, the least significant bit of which is used to select the output buffer used when writing to the graphics output device.

When dbuffer_switch is called:

1. Starbase waits (if necessary for visual continuity) for the graphics device to enter its vertical retrace period.

2. Either write_enable/display_enable or bank_select is used to activate the selected buffer from the double buffer pair.

3. The newly enabled write buffer is cleared using clear_view_surface, unless suppressed by the SUPPRESS_CLEAR mode in double_buffer.

If double buffering is disabled and dbuffer_switch is called, dbuffer_switch simply calls clear_view_surface, unless suppressed by the SUPPRESS_CLEAR mode in dbuffer_switch.

Make_picture_current is not called from dbuffer_switch. In general, it need not be called from the application program, since all preceding buffered primitives will be drawn before dbuffer_switch is performed.

DEFAULTS

buffer = 0:Enable lowest buffer for writing.

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