hyperion.ng/libsrc/grabber/x11/X11Grabber.cpp

// STL includes
#include <iostream>
#include <cstdint>

// X11 includes
#include <X11/Xutil.h>

// X11Grabber includes
#include <grabber/X11Grabber.h>

X11Grabber::X11Grabber(int cropLeft, int cropRight, int cropTop, int cropBottom, int horizontalPixelDecimation, int verticalPixelDecimation) :
    _imageResampler(),
    _cropLeft(cropLeft),
    _cropRight(cropRight),
    _cropTop(cropTop),
    _cropBottom(cropBottom),
    _x11Display(nullptr),
    _screenWidth(0),
    _screenHeight(0),
    _image(0,0)
{
    _imageResampler.setHorizontalPixelDecimation(horizontalPixelDecimation);
    _imageResampler.setVerticalPixelDecimation(verticalPixelDecimation);
    _imageResampler.setCropping(0, 0, 0, 0); // cropping is performed by XGetImage
}

X11Grabber::~X11Grabber()
{
    if (_x11Display != nullptr)
    {
        XCloseDisplay(_x11Display);
    }
}

int X11Grabber::open()
{
    const char * display_name = nullptr;
    _x11Display = XOpenDisplay(display_name);

    if (_x11Display == nullptr)
    {
        std::cerr << "Failed to open the default X11-display" << std::endl;
        return -1;
    }

    return 0;
}

Image<ColorRgb> & X11Grabber::grab()
{
    if (_x11Display == nullptr)
    {
        open();
    }

    updateScreenDimensions();
    
    Xscreen = DefaultScreenOfDisplay(_x11Display);

    const unsigned croppedWidth  = _screenWidth - _cropLeft - _cropRight;
    const unsigned croppedHeight = _screenHeight - _cropTop - _cropBottom;
    
    xImage = XShmCreateImage(_x11Display,   DefaultVisualOfScreen(Xscreen),
				  DefaultDepthOfScreen(Xscreen),
				  ZPixmap, NULL, &shminfo,
				  croppedWidth, croppedHeight);
    
    shminfo.shmid = shmget(IPC_PRIVATE, xImage->bytes_per_line * xImage->height, IPC_CREAT|0777);
    shminfo.shmaddr = xImage->data = (char*)shmat(shminfo.shmid,0,0);
    shminfo.readOnly = False;
    
    XShmAttach(_x11Display, &shminfo);

    // Capture the current screen
    XShmGetImage(_x11Display, DefaultRootWindow(_x11Display), xImage, _cropLeft, _cropTop, 0x00FFFFFF);
    if (xImage == nullptr)
    {
        std::cerr << "Grab failed" << std::endl;
        return _image;
    }

    _imageResampler.processImage(reinterpret_cast<const uint8_t *>(xImage->data), xImage->width, xImage->height, xImage->bytes_per_line, PIXELFORMAT_BGR32, _image);

    // Cleanup allocated resources of the X11 grab
    XShmDetach(_x11Display, &shminfo);
    XDestroyImage(xImage);
    shmdt (shminfo.shmaddr);
    shmctl(shminfo.shmid, IPC_RMID, 0);

    return _image;
}

int X11Grabber::updateScreenDimensions()
{
    XWindowAttributes window_attributes_return;
    const Status status = XGetWindowAttributes(_x11Display, DefaultRootWindow(_x11Display), &window_attributes_return);
    if (status == 0)
    {
        std::cerr << "Failed to obtain window attributes" << std::endl;
        return -1;
    }

    if (_screenWidth == unsigned(window_attributes_return.width) && _screenHeight == unsigned(window_attributes_return.height))
    {
        // No update required
        return 0;
    }
    std::cout << "Update of screen resolution: [" << _screenWidth << "x" << _screenHeight <<"] => ";
    _screenWidth  = window_attributes_return.width;
    _screenHeight = window_attributes_return.height;
    std::cout << "[" << _screenWidth << "x" << _screenHeight <<"]" << std::endl;

    return 0;
}