xil_get_active_buffer(3)

NAME

xil_get_active_buffer, xil_set_active_buffer - get or set the active buffer on a double-buffered device image

SYNOPSIS

#include <xil/xil.h>

XilBufferId xil_get_active_buffer ( XilImage image);

void xil_set_active_buffer ( XilImage image,

XilBufferId id);

DESCRIPTION

The active buffer of a double-buffered device image represents the buffer that will be affected when an operation uses the double-buffered image. At creation of a double-buffered image, the back buffer is the active buffer.

xil_get_active_buffer () returns the current XilBufferId for the active buffer of a double-buffered device image. The XilBufferId is an enumeration type that can be one of the following enumeration constants :

XIL_FRONT_BUFFER
XIL_BACK_BUFFER

If this function is called on an image that is either not a device image or not a double-buffered image, an error is generated and the value XIL_BACK_BUFFER is returned to the user.

xil_set_active_buffer () sets the active buffer for the double-buffered device image to either XIL_FRONT_BUFFER or XIL_BACK_BUFFER. If this function is called on an image that is either not a device image or not a double-buffered device image, an error is generated.

EXAMPLES

    XilSystemState State;
    XilImage display_image;
    XilImage image0, image1;
    Display∗ display;
    Window window;
     /∗ Create an XIL display image from existing X display and window ∗/
    if(display_image = xil_create_double_buffered_window(State,
                                              display,window) == NULL) {

        /∗ return with error ∗/
    }
     /∗ We know that this device image is double buffered ∗/
     /∗ Copy image0 to the back buffer of display ∗/
    xil_copy(image0, display_image);
     /∗ Move the back buffers contents to the front buffer ∗/
    xil_swap_buffers(display_image);
     /∗ Set the active buffer of the display image to the front buffer ∗/
    xil_set_active_buffer(display_image, XIL_FRONT_BUFFER);

    /∗ overwrite the contents of the front buffer directly ∗/
    xil_copy(image1, display_image);

ERRORS

For a complete list of XIL error messages by number, consult Appendix B of the XIL Programmer’s Guide.

NOTES

Changing the active buffer to the XIL_FRONT_BUFFER does not change the fact that xil_swap_buffers(3) swaps the contents of the back buffer to the front buffer.

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