WFD_QNX_destination_acquire_image

Description

Examples

The following is an example of how to configure writeback:

/**
* This is the preferred way to get data generated by port writeback.
*
* It depends on the following extensions:
*  - @c WFD_QNX_destination
*  - @c WFD_QNX_port_writeback
*
* The following code shows how writeback could be configured:
* @anchor sample_writeback @code{.c}
#define WFD_WFDEXT_PROTOTYPES
#include <WF/wfd.h>
#include <WF/wfdext.h>
#include <assert.h>
#include <stddef.h>
#include <stdio.h>
#include <time.h>
    
struct wb_arg {
    WFDDevice devhdl;
    WFDPort porthdl;
    WFDint width, height;
    WFDEGLImage images[3];
};
                        
void *writeback_thread(void *arg)
{
    struct wb_arg *wb = arg;
    WFDDestinationQNX desthdl;
    __errno_t err;
    WFDErrorCode wfderr;
    
    //TODO: check for necessary extensions:
    //          - WFD_QNX_destination_create_from_images
    //          - WFD_QNX_port_writeback
    //          - WFD_QNX_destination
    //          - WFD_QNX_destination_acquire_image
    //      verify that the writeback is enabled on the port:
    //          - eg. wfdGetPortAttribi(device, port, WFD_PORT_WRITEBACK_SUPPORT_QNX)
    //      allocate image buffers
    //      fill the 'images' array
    
    err = wfdCreateDestinationFromImagesQNX(wb->devhdl, 3, &wb-&gt;images[0], NULL, &desthdl);
    if (err) { goto fail; }
    
    wfderr = wfdBindDestinationToPortQNX(wb->devhdl, wb->porthdl, desthdl, WFD_TRANSITION_AT_VSYNC);
    if (wfderr) { goto fail; }

    wfdSetPortAttribiv(wb->devhdl, wb->porthdl, WFD_PORT_WRITEBACK_SOURCE_RECTANGLE_QNX,
        4, (const WFDint[]){0, 0, wb->width, wb->height});
    wfdSetPortAttribiv(wb->devhdl, wb->porthdl, WFD_PORT_WRITEBACK_DESTINATION_RECTANGLE_QNX,
        4, (const WFDint[]){0, 0, wb->width, wb->height});

    wfdDeviceCommit(wb->devhdl, WFD_COMMIT_ENTIRE_PORT, wb->porthdl);
    wfderr = wfdGetError(wb->devhdl);
    if (wfderr) { goto fail; }
                        
    for(;;) {
        WFDint image_idx;
        struct timespec endtime;
        unsigned seqno;
        
        if (0 != clock_gettime(CLOCK_MONOTONIC, &endtime)) { goto fail; }
        endtime.tv_sec += 1;
        
        // wait for the driver to write an image buffer
        err = wfdAcquireDestinationImageQNX(wb->devhdl, desthdl, (const intptr_t[]){
            WFD_TIMEOUT_ABS_MONOTONIC_QNX, (intptr_t)&endtime,
            WFD_WRITEBACK_SEQUENCE_NUMBER_QNX, (intptr_t)&seqno,
            WFD_NONE
        }, &image_idx);
                        
        if (err) {
            goto fail;
        }

        printf("got frame #%u from writeback\n", seqno);
        //TODO: look for sequence number gaps, to detect missed frames
        //TODO: use images[image_idx], possibly via WFD_QNX_egl_image_attrib
        
        // release the buffer back to the driver, so it can write new
        // data there if necessary
        err = wfdReleaseDestinationImageQNX(wb->devhdl, desthdl, image_idx);
        assert(!err);
    }
                        
    // unbind the destination
    wfderr = wfdBindDestinationToPortQNX(wb->devhdl, wb->porthdl, WFD_INVALID_HANDLE, WFD_TRANSITION_AT_VSYNC);
    if (wfderr) { goto fail; }
                        
    wfdDeviceCommit(wb->devhdl, WFD_COMMIT_ENTIRE_PORT, wb->porthdl);
    wfderr = wfdGetError(wb->devhdl);
    if (wfderr) { goto fail; }
    
    wfdDestroyDestinationQNX(wb->devhdl, desthdl);
    return NULL;
    fail:
        ; //TODO
    }
* @endcode
*/